Photocatalysis and the origin of life: synthesis of nucleoside bases from formamide on TiO2(001) single surfaces.

PubMed

Senanayake, S D; Idriss, H

2006-01-31

We report the conversion of a large fraction of formamide (NH(2)CHO) to high-molecular-weight compounds attributed to nucleoside bases on the surface of a TiO(2) (001) single crystal in ultra-high vacuum conditions. If true, we present previously unreported evidence for making biologically relevant molecules from a C1 compound on any single crystal surface in high vacuum and in dry conditions. An UV light of 3.2 eV was necessary to make the reaction. This UV light excites the semiconductor surface but not directly the adsorbed formamide molecules or the reaction products. There thus is no need to use high energy in the form of photons or electrical discharge to make the carbon-carbon and carbon-nitrogen bonds necessary for life. Consequently, the reaction products may accumulate with time and may not be subject to decomposition by the excitation source. The formation of these molecules, by surface reaction of formamide, is proof that some minerals in the form of oxide semiconductors are active materials for making high-molecular-weight organic molecules that may have acted as precursors for biological compounds required for life in the universe.

Shedding light on the formation of the pre-biotic molecule formamide with ASAI

NASA Astrophysics Data System (ADS)

López-Sepulcre, A.; Jaber, Ali A.; Mendoza, E.; Lefloch, B.; Ceccarelli, C.; Vastel, C.; Bachiller, R.; Cernicharo, J.; Codella, C.; Kahane, C.; Kama, M.; Tafalla, M.

2015-05-01

Formamide (NH2CHO) has been proposed as a pre-biotic precursor with a key role in the emergence of life on Earth. While this molecule has been observed in space, most of its detections correspond to high-mass star-forming regions. Motivated by this lack of investigation in the low-mass regime, we searched for formamide, as well as isocyanic acid (HNCO), in 10 low- and intermediate-mass pre-stellar and protostellar objects. The present work is part of the IRAM Large Programme ASAI (Astrochemical Surveys At IRAM), which makes use of unbiased broad-band spectral surveys at millimetre wavelengths. We detected HNCO in all the sources and NH2CHO in five of them. We derived their abundances and analysed them together with those reported in the literature for high-mass sources. For those sources with formamide detection, we found a tight and almost linear correlation between HNCO and NH2CHO abundances, with their ratio being roughly constant - between 3 and 10 - across 6 orders of magnitude in luminosity. This suggests the two species are chemically related. The sources without formamide detection, which are also the coldest and devoid of hot corinos, fall well off the correlation, displaying a much larger amount of HNCO relative to NH2CHO. Our results suggest that, while HNCO can be formed in the gas-phase during the cold stages of star formation, NH2CHO forms most efficiently on the mantles of dust grains at these temperatures, where it remains frozen until the temperature rises enough to sublimate the icy grain mantles. We propose hydrogenation of HNCO as a likely formation route leading to NH2CHO.

Synthesis of formamide and isocyanic acid after ion irradiation of frozen gas mixtures

NASA Astrophysics Data System (ADS)

Kaňuchová, Z.; Urso, R. G.; Baratta, G. A.; Brucato, J. R.; Palumbo, M. E.; Strazzulla, G.

2016-01-01

Context. Formamide (NH2HCO) and isocyanic acid (HNCO) have been observed as gaseous species in several astronomical environments such as cometary comae and pre- and proto-stellar objects. A debate is open on the formation route of those molecules, in particular if they are formed by chemical reactions in the gas phase and/or on grains. In this latter case it is relevant to understand if the formation occurs through surface reactions or is induced by energetic processing. Aims: We present arguments that support the formation of formamide in the solid phase by cosmic-ion-induced energetic processing of ices present as mantles of interstellar grains and on comets. Formamides, along with other molecules, are expelled in the gas phase when the physical parameters are appropriate to induce the desorption of ices. Methods: We have performed several laboratory experiments in which ice mixtures (H2O:CH4:N2, H2O:CH4:NH3, and CH3OH:N2) were bombarded with energetic (30-200 keV) ions (H+ or He+). FTIR spectroscopy was performed before, during, and after ion bombardment. In particular, the formation of HNCO and NH2HCO was measured quantiatively. Results: Energetic processing of ice can quantitatively reproduce the amount of NH2HCO observed in cometary comae and in many circumstellar regions. HNCO is also formed, but additional formation mechanisms are requested to quantitatively account for the astronomical observations. Conclusions: We suggest that energetic processing of ices in the pre- and proto-stellar regions and in comets is the main mechanism to produce formamide, which, once it is released in the gas phase because of desorption of ices, is observed in the gas phase in these astrophysical environments.

The Roles of TGF-Beta and TGF-Beta Signaling Receptors in Breast Carcinogenesis.

DTIC Science & Technology

1996-07-01

hybridization was at 42°C in 45% antipain, aprotinin, leupeptin, and trypsin inhibitor; 0.5 .giml formamide, 5x standard saline phosphate/EDTA ( SSPE ; 0.18...for 16-20 hr at 42°C in 50% formamide. 5x SSPE , 5x Denhardt’s solution, 0.5% SDS, and 100 Mg/ml Cloning of Dwarfin-A and Dwarfin-C. Full-length cDNAs

Catalytic Role of Manganese Oxides in Prebiotic Nucleobases Synthesis from Formamide.

PubMed

Bhushan, Brij; Nayak, Arunima; Kamaluddin

2016-06-01

Origin of life processes might have begun with the formation of important biomonomers, such as amino acids and nucleotides, from simple molecules present in the prebiotic environment and their subsequent condensation to biopolymers. While studying the prebiotic synthesis of naturally occurring purine and pyrimidine derivatives from formamide, the manganese oxides demonstrated not only good binding for formamide but demonstrated novel catalytic activity. A novel one pot manganese oxide catalyzed synthesis of pyrimidine nucleobases like thymine is reported along with the formation of other nucleobases like purine, 9-(hydroxyacetyl) purine, cytosine, 4(3 H)-pyrimidinone and adenine in acceptable amounts. The work reported is significant in the sense that the synthesis of thymine has exhibited difficulties especially under one pot conditions and also such has been reported only under the catalytic activity of TiO2. The lower oxides of manganese were reported to show higher potential as catalysts and their existence were favored by the reducing atmospheric conditions prevalent on early Earth; thereby confirming the hypothesis that mineral having metals in reduced form might have been more active during the course of chemical evolution. Our results further confirm the role of formamide as a probable precursor for the formation of purine and pyrimidine bases during the course of chemical evolution and origin of life.

Model for the partition of neutral compounds between n-heptane and formamide.

PubMed

Karunasekara, Thushara; Poole, Colin F

2010-04-01

Partition coefficients for 84 varied compounds were determined for n-heptane-formamide biphasic partition system and used to derive a model for the distribution of neutral compounds between the n-heptane-rich and formamide-rich layers. The partition coefficients, log K(p), were correlated through the solvation parameter model giving log K(p)=0.083+0.559E-2.244S-3.250A-1.614B+2.387V with a multiple correlation coefficient of 0.996, standard error of the estimate 0.139, and Fisher statistic 1791. In the model, the solute descriptors are excess molar refraction, E, dipolarity/polarizability, S, overall hydrogen-bond acidity, A, overall hydrogen-bond basicity, B, and McGowan's characteristic volume, V. The model is expected to be able to estimate further values of the partition coefficient to about 0.13 log units for the same descriptor space covered by the calibration compounds (E=-0.26-2.29, S=0-1.93, A=0-1.25, B=0.02-1.58, and V=0.78-2.50). The n-heptane-formamide partition system is shown to have different selectivity to other totally organic biphasic systems and to be suitable for estimating descriptor values for compounds of low water solubility and/or stability.

Preferential solvation of Brooker's merocyanine in binary solvent mixtures composed of formamides and hydroxylic solvents.

PubMed

Bevilaqua, Tharly; da Silva, Domingas C; Machado, Vanderlei G

2004-03-01

The ET polarity values of 4-[(1-methyl-4(1H)-pyridinylidene)-ethylidene]-2,5-cyclohexadien-1-one (Brooker's merocyanine) were collected in mixed-solvent systems comprising a formamide [N,N-dimethylformamide (DMF), N-methylformamide (NMF) or formamide (FA)] and a hydroxylic (water, methanol, ethanol, propan-2-ol or butan-1-ol) solvent. Binary mixtures involving DMF and the other formamides (NMF and FA) as well as NMF and FA were also studied. These data were employed in the investigation of the preferential solvation (PS) of the probe. Each solvent system was analyzed in terms of both solute-solvent and solvent-solvent interactions. These latter interactions were responsible for the synergism observed in many binary mixtures. This synergistic behaviour was observed for DMF-propan-2-ol, DMF-butan-1-ol, FA-methanol, FA-ethanol and for the mixtures of the alcohols with NMF. All data were successfully fitted to a model based on solvent-exchange equilibria, which allowed the separation of the different contributions of the solvent species in the solvation shell of the dye. The results suggest that both hydrogen bonding and solvophobic interactions contribute to the formation of the solvent complexes responsible for the observed synergistic effects in the PS of the dye.

Fast and Non-Toxic In Situ Hybridization without Blocking of Repetitive Sequences

PubMed Central

Matthiesen, Steen H.; Hansen, Charles M.

2012-01-01

Formamide is the preferred solvent to lower the melting point and annealing temperature of nucleic acid strands in in situ hybridization (ISH). A key benefit of formamide is better preservation of morphology due to a lower incubation temperature. However, in fluorescence in situ hybridization (FISH), against unique DNA targets in tissue sections, an overnight hybridization is required to obtain sufficient signal intensity. Here, we identified alternative solvents and developed a new hybridization buffer that reduces the required hybridization time to one hour (IQFISH method). Remarkably, denaturation and blocking against repetitive DNA sequences to prevent non-specific binding is not required. Furthermore, the new hybridization buffer is less hazardous than formamide containing buffers. The results demonstrate a significant increased hybridization rate at a lowered denaturation and hybridization temperature for both DNA and PNA (peptide nucleic acid) probes. We anticipate that these formamide substituting solvents will become the foundation for changes in the understanding and performance of denaturation and hybridization of nucleic acids. For example, the process time for tissue-based ISH for gene aberration tests in cancer diagnostics can be reduced from days to a few hours. Furthermore, the understanding of the interactions and duplex formation of nucleic acid strands may benefit from the properties of these solvents. PMID:22911704

Meteorite-catalyzed syntheses of nucleosides and of other prebiotic compounds from formamide under proton irradiation

PubMed Central

Saladino, Raffaele; Carota, Eleonora; Botta, Giorgia; Kapralov, Mikhail; Timoshenko, Gennady N.; Rozanov, Alexei Y.; Krasavin, Eugene; Di Mauro, Ernesto

2015-01-01

Liquid formamide has been irradiated by high-energy proton beams in the presence of powdered meteorites, and the products of the catalyzed resulting syntheses were analyzed by mass spectrometry. Relative to the controls (no radiation, or no formamide, or no catalyst), an extremely rich, variegate, and prebiotically relevant panel of compounds was observed. The meteorites tested were representative of the four major classes: iron, stony iron, chondrites, and achondrites. The products obtained were amino acids, carboxylic acids, nucleobases, sugars, and, most notably, four nucleosides: cytidine, uridine, adenosine, and thymidine. In accordance with theoretical studies, the detection of HCN oligomers suggests the occurrence of mechanisms based on the generation of radical cyanide species (CN·) for the synthesis of nucleobases. Given that many of the compounds obtained are key components of extant organisms, these observations contribute to outline plausible exogenous high-energy–based prebiotic scenarios and their possible boundary conditions, as discussed. PMID:25870268

Di-μ3-chlorido-tetra-μ2-chlorido-dichloridobis(dimethyl­formamide-κO)hexa­kis­(1H-imidazole-κN 3)tetra­cadmium

PubMed Central

Zhu, Run-Qiang

2011-01-01

The centrosymmetric mol­ecule of the title complex, [Cd4Cl8(C3H4N2)6(C3H7NO)2], contains four CdII atoms, six imidazole, two dimethyl­formamide and eight chloride ligands. The structure shows a novel chloride-bridged tetra­nuclear cadmium quasi-cubane cluster. The coordination geometry of all CdII atoms is distorted octa­hedral, with the two metal atoms in the asymmetric unit in different coordination environments. One of the Cd2+ ions is coordinated by five Cl− ions and by one N atom from an imidazole ligand, while the second is coordinated by three chloride ligands, two N atoms from two imidazole ligands and one O atom from a dimethyl­formamide mol­ecule. Inter­molecular N—H⋯Cl hydrogen bonds link the mol­ecules into a two-dimensional polymeric structure parallel to the ab plane. PMID:22058708

Nitrosation of amides involves a pseudopericyclic 1,3-sigmatropic rearrangement.

PubMed

Birney, David M

2004-03-04

Two possible pathways for the nitrosation of formamide and N-methyl formamide by nitrosonium ion (NO(+)) have been investigated at the B3LYP/6-31G(d,p) level. The key steps are pseudopericyclic 1,3-sigmatropic rearrangements to give the observed N-nitrosamides. The transition structures (8a and 8b) are close to planar on the amide moiety and have remarkably low barriers of only 6.6 and 4.8 kcal/mol from the lowest energy conformations of 6a and 6b, respectively. [reaction: see text

High-resolution far-infrared synchrotron FTIR spectrum of the ν12 band of formamide-d1 (DCONH2)

NASA Astrophysics Data System (ADS)

Tan, T. L.; Wu, Q. Y.; Ng, L. L.; Appadoo, Dominique R. T.; McNaughton, Don

2018-05-01

The spectrum of the ν12 band of formamide-d1 (DCONH2) was recorded using a synchrotron Fourier transform infrared (FTIR) spectrometer coupled to the Australian Synchrotron THz/Far-IR beamline, with an unapodized resolution of 0.00096 cm-1 in the 350-210 cm-1 region. For the first time, rovibrational constants up to five quartic and two sextic terms were derived for the v12 = 1 state through the fitting of a total of 2072 far-infrared transitions using Watson's A-reduced Hamiltonian in the Ir representation with a root-mean-square (rms) deviation of 0.000073 cm-1. The band centre of the ν12 band of DCONH2 was found to be 289.3327553(47) cm-1 although the experimental uncertainty was limited to ±0.0002 cm-1. Ground state rovibrational constants of DCONH2 up to five quartic and two sextic constants were derived from a fit of 847 ground state combination differences (GSCDs) obtained from the infrared transitions of the ν12 band, together with 6 previously reported microwave transitions, with a rms deviation of 0.000108 cm-1. The ground state rotational constants (A, B, and C) of DCONH2 were improved while the ground state centrifugal distortion constants were accurately obtained for the first time. The uncertainty of the measured infrared lines was estimated to be ±0.0002 cm-1. From the ground state rotational constants, the inertial defect of DCONH2 was calculated to be 0.0169412(11) uÅ2.

Catalytic Formylation of Primary and Secondary Amines with CO2 and H2 Using Abundant-Metal Catalysts.

PubMed

Affan, Mohammad A; Jessop, Philip G

2017-06-19

Catalytic hydrogenation of CO 2 is an efficient and selective way to prepare formic acid derivatives, but most of the highly active catalysts used for this purpose require precious metals. In this study, in situ abundant-metal complexes have been evaluated as potential catalysts for CO 2 hydrogenation to prepare formamides, including N-formylmorpholine, 2-ethylhexylformamide, and dimethylformamide, from the corresponding amines. From these initial screening results, the most active catalysts for these reactions were found to be MX 2 /dmpe in situ catalysts (M = Fe(II), Ni(II); X = Cl - , CH 3 CO 2 - , acac - ; dmpe = 1,2-bis(dimethylphosphino)ethane) in DMSO. The optimal reaction conditions were found to be 100-135 °C and a total pressure of 100 bar. Morpholine was formylated with a TON value of up to 18000, which is the highest TON for the hydrogenation of CO 2 to formamides using any abundant-metal-phosphine complex. With an appropriate selection of catalyst and reaction conditions, >90-98% conversion of amine to formamide could be achieved.

Hexakis(N,N-dimethyl­formamide-κO)cobalt(II) bis­(perchlorate)

PubMed Central

Eissmann, Frank; Böhle, Tony; Mertens, Florian O. R. L.; Weber, Edwin

2010-01-01

The asymmetric unit of the title complex, [Co(DMF)6](ClO4)2 (DMF = N,N-dimethyl­formamide, C3H7NO), consists of two half complex cations with the Co2+ metal ions located on centers of inversion and two perchlorate anions. In the crystal packing, each Co2+ ion is coordinated by six mol­ecules of DMF in a slightly distorted octa­hedral geometry. The crystal structure is mainly stabilized by coordinative, ionic and C—H⋯O hydrogen-bonding inter­actions. PMID:21580225

Two-state model based on the block-localized wave function method

NASA Astrophysics Data System (ADS)

Mo, Yirong

2007-06-01

The block-localized wave function (BLW) method is a variant of ab initio valence bond method but retains the efficiency of molecular orbital methods. It can derive the wave function for a diabatic (resonance) state self-consistently and is available at the Hartree-Fock (HF) and density functional theory (DFT) levels. In this work we present a two-state model based on the BLW method. Although numerous empirical and semiempirical two-state models, such as the Marcus-Hush two-state model, have been proposed to describe a chemical reaction process, the advantage of this BLW-based two-state model is that no empirical parameter is required. Important quantities such as the electronic coupling energy, structural weights of two diabatic states, and excitation energy can be uniquely derived from the energies of two diabatic states and the adiabatic state at the same HF or DFT level. Two simple examples of formamide and thioformamide in the gas phase and aqueous solution were presented and discussed. The solvation of formamide and thioformamide was studied with the combined ab initio quantum mechanical and molecular mechanical Monte Carlo simulations, together with the BLW-DFT calculations and analyses. Due to the favorable solute-solvent electrostatic interaction, the contribution of the ionic resonance structure to the ground state of formamide and thioformamide significantly increases, and for thioformamide the ionic form is even more stable than the covalent form. Thus, thioformamide in aqueous solution is essentially ionic rather than covalent. Although our two-state model in general underestimates the electronic excitation energies, it can predict relative solvatochromic shifts well. For instance, the intense π →π* transition for formamide upon solvation undergoes a redshift of 0.3eV, compared with the experimental data (0.40-0.5eV).

Single-base-pair discrimination of terminal mismatches by using oligonucleotide microarrays and neural network analyses

NASA Technical Reports Server (NTRS)

Urakawa, Hidetoshi; Noble, Peter A.; El Fantroussi, Said; Kelly, John J.; Stahl, David A.

2002-01-01

The effects of single-base-pair near-terminal and terminal mismatches on the dissociation temperature (T(d)) and signal intensity of short DNA duplexes were determined by using oligonucleotide microarrays and neural network (NN) analyses. Two perfect-match probes and 29 probes having a single-base-pair mismatch at positions 1 to 5 from the 5' terminus of the probe were designed to target one of two short sequences representing 16S rRNA. Nonequilibrium dissociation rates (i.e., melting profiles) of all probe-target duplexes were determined simultaneously. Analysis of variance revealed that position of the mismatch, type of mismatch, and formamide concentration significantly affected the T(d) and signal intensity. Increasing the concentration of formamide in the washing buffer decreased the T(d) and signal intensity, and it decreased the variability of the signal. Although T(d)s of probe-target duplexes with mismatches in the first or second position were not significantly different from one another, duplexes with mismatches in the third to fifth positions had significantly lower T(d)s than those with mismatches in the first or second position. The trained NNs predicted the T(d) with high accuracies (R(2) = 0.93). However, the NNs predicted the signal intensity only moderately accurately (R(2) = 0.67), presumably due to increased noise in the signal intensity at low formamide concentrations. Sensitivity analysis revealed that the concentration of formamide explained most (75%) of the variability in T(d)s, followed by position of the mismatch (19%) and type of mismatch (6%). The results suggest that position of the mismatch at or near the 5' terminus plays a greater role in determining the T(d) and signal intensity of duplexes than the type of mismatch.

Providing theoretical data for detection of four formamidic acid isomers in astrophysical media

NASA Astrophysics Data System (ADS)

Vichietti, R. M.; da Silva, A. B. F.; Haiduke, R. L. A.

2018-03-01

We present a theoretical study, so that molecular data (geometrical parameters, vibrational frequencies, infrared intensities, electronic energies, enthalpies, and Gibbs energies) of four formamidic acid (FA) isomers (labeled here as FA1, FA2, FA3, and FA4) and formamide (HCONH2) are obtained from CCSD/cc-pVTZ, CCSD/aug-cc-pVTZ, CCSD/cc-pVQZ, and CCSD(T)/cc-pVTZ calculations. Furthermore, on the basis of insufficient or even lacking theoretical and experimental results in the literature, we employed the aforementioned theory levels to determine benchmark values of dipole moments and rotational constants for these four FA isomers in order to contribute for their detection in astrophysical environments. Besides, we provide for the first time data about forward and reverse rate constants (200-4000 K) and Arrhenius' parameters for each interconversion reaction between pairs of FA isomers as well as for the tautomeric process involving FA4 and formamide, which were calculated from a Complete Basis Set (CBS) extrapolation equation obtained at CCSD/cc-pVTZ optimized geometries. Our kinetic analysis indicated a faster interconversion between the FA structures in comparison with the FA4 ↔ HCONH2 process, suggesting that these isomers could co-exist in astrophysical media. Finally, we estimated that these isomers may be detected with relative abundances, [FAx]/[HCONH2] (x = 1, 2, 3, and 4), between ∼0.01 and ∼0.1% in astrophysical sources at chemical equilibrium conditions and temperatures around 1000 K. However, these ratios can become as high as ∼1, ∼3, and ∼5%, respectively, in hotter regions with temperatures around 2000, 3000, and 4000 K (expected, for example, in massive star-forming regions).

Elastic electron scattering from formamide

NASA Astrophysics Data System (ADS)

Buk, M. V.; Bardela, F. P.; da Silva, L. A.; Iga, I.; Homem, M. G. P.

2018-05-01

Differential cross sections for elastic electron scattering by formamide (NH2CHO) were measured in the 30–800 eV and 10°–120° ranges. The angular distribution of scattered electrons was obtained using a crossed electron beam-molecular beam geometry. The relative flow technique was applied to normalize our data. Integral and momentum-transfer cross sections were derived from the measured differential cross sections. Theoretical results in the framework of the independent-atom model at the static-exchange-polarization plus absorption level of approximation are also given. The present measured and calculated results are compared with those available in the literature showing a generally good agreement.

Theoretical studies of weak interactions of formamide with methanol and its derivates

NASA Astrophysics Data System (ADS)

Zheng, Xiao-Wen; Wang, Lu; Han, Shu-Min; Cui, Xiang-Yang; Du, Chong-Yang; Liu, Tao

2015-08-01

Theoretical calculations have been performed for the complexes of formamide (FA) with methanol and its derivates (MAX, X = F, Cl, Br, NO2, H, OH, CH3, and NH2) to study their structures and properties. Substituent effects on the hydrogen bond (H-bond) strength and cooperative effect by using water and its derivatives (HOZ, Z = H, NH2, and Br) as weak interaction probe were also explored. The calculation results show that electron-donating groups strengthen the weak interaction between formamide with methanol whereas electron-withdrawing groups weaken it. The cooperativity is present for the N-HïO H-bond in MAX-FA-HOZ and the cooperative effect increases in a series HONH2, HOH, and HOBr. In addition, we investigated the interaction between FA with hypohalous acids HOY (Y = F, Cl, and Br). It was found that the weak interaction between FA and HOY became stronger with the increase of the size of halogen atom. The nature of the halogen atom has negligible impact on the strength of the H-bond in MAX-FA (X = F, Cl, and Br), whereas it has an obvious influence on the strength of the H-bond in HOY-FA (Y = F, Cl, and Br).

Glycerol as a Building Block for Prochiral Aminoketone, N-Formamide, and N-Methyl Amine Synthesis.

PubMed

Dai, Xingchao; Rabeah, Jabor; Yuan, Hangkong; Brückner, Angelika; Cui, Xinjiang; Shi, Feng

2016-11-23

Prochiral aminoketones are key intermediates for the synthesis of optically active amino alcohols, and glycerol is one of the main biomass-based alcohols available in industry. In this work, glycerol was catalytically activated and purposefully converted with amines to generate highly valuable prochiral aminoketones, as well as N-formamides and N-methyl amines, over CuNiAlO x catalyst. The catalyst structure can be anticipated as nano-Ni species on or in CuAlO x via the formation of nano- Cu-Ni alloy particles. This concept may present a novel and valuable methodology for glycerol utilization. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultraviolet-gas phase and -photocatalytic synthesis from CO and NH3. [photolysis products

NASA Technical Reports Server (NTRS)

Hubbard, J. S.; Voecks, G. E.; Hobby, G. L.; Ferris, J. P.; Williams, E. A.; Nicodem, D. E.

1975-01-01

Ammonium cyanate is identified as the major product of the photolysis of gaseous NH3-CO mixtures at 206.2 or 184.9 nm. Lesser amounts of urea, biurea, biuret semicarbazide, formamide and cyanide are observed. A series of 18 reactions underlying the formation of photolysis products is presented and discussed. Photocatalytic syntheses of C-14-urea, -formamide, and -formaldehyde are carried out through irradiation of (C-14)O and NH3 in the presence of Vycor, silica gel, or volcanic ash shale surfaces. The possible contributions of the relevant reactions to the abiotic synthesis of organic nitrogen compounds on Mars, the primitive earth, and in interstellar space are examined.

Adsorption of poly(vinyl formamide-co-vinyl amine) (PVFA-co-PVAm) polymers on zinc, zinc oxide, iron, and iron oxide surfaces.

PubMed

Seifert, Susan; Simon, Frank; Baumann, Giesela; Hietschold, Michael; Seifert, Andreas; Spange, Stefan

2011-12-06

The adsorption of poly(vinyl formamide) (PVFA) and the statistic copolymers poly(vinyl formamide-co-vinyl amine) (PVFA-co-PVAm) onto zinc and iron metal particles as well as their oxides was investigated. The adsorbates were characterized by means of XPS, DRIFT spectroscopy, wet chemical analysis, and solvatochromic probes. Dicyano-bis-(1,10-phenanthroline)-iron(II) (1), 3-(4-amino-3-methylphenyl)-7-phenyl-benzo-[1,2-b:4,5-b']difuran-2,6-dione (2), and 4-tert-butyl-2-(dicyano-methylene)-5-[4-(diethylamino)-benzylidene]-Δ(3)-thiazoline (3) as solvatochromic probes were coadsorbed onto zinc oxide to measure various effects of surface polarity. The experimental findings showed that the adsorption mechanism of PVFA and PVFA-co-PVAm strongly depends on the degree of hydrolysis of PVFA and pH values and also on the kind of metal or metal oxide surfaces that were employed as adsorbents. The adsorption mechanism of PVFA/PVFA-co-PVAm onto zinc oxide and iron oxide surfaces is mainly affected by electrostatic interactions. Particularly in the region of pH 5, the adsorption of PVFA/PVFA-co-PVAm onto zinc and iron metal particles is additionally influenced by redox processes, dissolution, and complexation reactions. © 2011 American Chemical Society

Matrix Isolation and ab initio study of the noncovalent complexes between formamide and acetylene.

PubMed

Mardyukov, Artur; Sánchez-García, Elsa; Sander, Wolfram

2009-02-12

Matrix isolation spectroscopy in combination with ab initio calculations is a powerful technique for the identification of weakly bound intermolecular complexes. Here, weak complexes between formamide and acetylene are studied, and three 1:1 complexes with binding energies of -2.96, -2.46, and -1.79 kcal/mol have been found at the MP2 level of theory (MP2/cc-pVTZ + ZPE + BSSE). The two most stable dimers A and B are identified in argon and nitrogen matrices by comparison between the experimental and calculated infrared frequencies. Both complexes are stabilized by the formamide C=O...HC acetylene and H...pi interactions. Large shifts have been observed experimentally for the C-H stretching vibrations of the acetylene molecule, in very good agreement with the calculated values. Eight 1:2 FMA-acetylene trimers (T-A to T-H) with binding energies between -5.44 and -2.62 kcal/mol (MP2/aug-cc-pVDZ + ZPE + BSSE) were calculated. The two most stable trimers T-A and T-B are very close in energy and have similar infrared spectra. Several weak bands that are in agreement with the calculated frequencies of the trimers T-A and T-B are observed under matrix isolation conditions. However, the differences are too small for a definitive assignment.

Complex organic molecules in comets C/2012 F6 (Lemmon) and C/2013 R1 (Lovejoy): detection of ethylene glycol and formamide

NASA Astrophysics Data System (ADS)

Biver, N.; Bockelée-Morvan, D.; Debout, V.; Crovisier, J.; Boissier, J.; Lis, D. C.; Dello Russo, N.; Moreno, R.; Colom, P.; Paubert, G.; Vervack, R.; Weaver, H. A.

2014-06-01

A spectral survey in the 1 mm wavelength range was undertaken in the long-period comets C/2012 F6 (Lemmon) and C/2013 R1 (Lovejoy) using the 30 m telescope of the Institut de radioastronomie millimétrique (IRAM) in April and November-December 2013. We report the detection of ethylene glycol (CH2OH)2 (aGg' conformer) and formamide (NH2CHO) in the two comets. The abundances relative to water of ethylene glycol and formamide are 0.2-0.3% and 0.02% in the two comets, similar to the values measured in comet C/1995 O1 (Hale-Bopp). We also report the detection of HCOOH and CH3CHO in comet C/2013 R1 (Lovejoy), and a search for other complex species (methyl formate, glycolaldehyde). Based on observations carried out with the IRAM 30 m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).Tables 4 and 5 are available in electronic form at http://www.aanda.orgThe IRAM dataset is available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/566/L5

Effect of solvents on the fluorescence spectra of bacterial luciferase

NASA Astrophysics Data System (ADS)

Sukovataya, Irina E.; Tyulkova, Natalya A.; Kaykova, Elisaveta V.

2006-08-01

Bacteria luciferases catalyze the oxidation reaction of the long-chain aliphatic aldehyde and reduced flavinmononucleotide involving molecular oxygen to a respective fatty acid emitting light quanta in the visible spectrum. Fluorescence emission of luciferases from Photobacterium leiognathi dissolved in organic solvent-water mixtures was investigated. Methanol, acetone, dimethyl sulfoxide and formamide were used as organic solvents. As the methanol and acetone concentration is increased the emission maximum peak is decrease. In contrast, with dimethyl sulfoxide and formamide addition induced a increasing of the emission maximum intensity. The values of wavelength maximum (λ max) at the addition of this solvent can shows the spectra shifted to the red by about 12 nm. These increasing in the fluorescence intensity and in the λ max may be due to luciferase denaturation, resulting from the more intensive contact of chromospheres of luciferase with the solvent. At all used concentrations of methanol, acetone and formamide the shape of the fluorescence spectra was not changed. These studies demonstrate that the luciferase tryptophan fluorescence is sensitive to changes of physical-chemical property of enzyme environment. A comparison of activation/inactivation and fluorescence spectra of luciferase in methanol or acetone solutions shows that the extent of inactivation is larger than the extent of fluorescence changes at the same methanol or acetone concentration.

Separation of nitrogen heterocyclic compounds from model coal tar fraction by solvent extraction

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

Kim, S.J.; Chun, Y.J.

2005-07-01

The separation of four kinds of nitrogen heterocyclic compounds (NHCs) from a model mixture comprising NHCs (indole (In), quinoline (Q), iso-quinoline (iQ), quinaldine (Qu)), three kinds of bicyclic aromatic compounds (BACs; 1-methyl-naphthalene (IMN), 2-methyl naphthalene (2MN), dimethylnaphthalene (DMN)), biphenyl (Bp) and phenyl ether (Pe) was examined by a solvent extraction. The model mixture used as a raw material of this work was prepared according to the components and compositions contained in coal tar fraction (the temperature ranges of fraction: 240-265{sup o}C). An aqueous solution of methanol, ethanol, iso-propyl alcohol, N,N-dimethyl acetamide, DMF, formamide, N-methylformamide/methanol, and formamide/methanol were used as solvents.more » An aqueous solution of formamide was found suitable for separating NHCs contained in coal tar fraction based on distribution coefficient and selectivity. The effect of operation factors on separating NHCs was investigated by the distribution equilibrium using an aqueous solution of formamide. Increasing the operation temperature and the volume ratio of solvent to feed at initial (S/F)(o) resulted in improving the distribution coefficients of each NHC, but increasing the volume fraction of water in the solvent at initial (y(w,O)) resulted in deteriorating the distribution coefficients of each NHC. With increasing y(w,O) and (S/F)(o), the selectivities of each NHC in reference to DMN increased. Increase in operation temperature resulted in decrease in selectivities of each NHC in reference to DMN. At an experimental condition fixed, the sequence of the distribution coefficient and selectivity in reference to DMN for each NHC was In {gt} iQ {gt} Q {gt} Qu, and also the sequence of the distribution coefficient for each BAC was IMN {gt} 2MN {gt} DMN. The sequence of the distribution coefficient for entire compounds analyzed by this work was In {gt} iQ {gt} Q {gt} Qu {gt} BP {gt} 1MN {gt} 2MN {gt} Pe {gt} DMN.« less

Thermal desorption of formamide and methylamine from graphite and amorphous water ice surfaces

NASA Astrophysics Data System (ADS)

Chaabouni, H.; Diana, S.; Nguyen, T.; Dulieu, F.

2018-04-01

Context. Formamide (NH2CHO) and methylamine (CH3NH2) are known to be the most abundant amine-containing molecules in many astrophysical environments. The presence of these molecules in the gas phase may result from thermal desorption of interstellar ices. Aims: The aim of this work is to determine the values of the desorption energies of formamide and methylamine from analogues of interstellar dust grain surfaces and to understand their interaction with water ice. Methods: Temperature programmed desorption (TPD) experiments of formamide and methylamine ices were performed in the sub-monolayer and monolayer regimes on graphite (HOPG) and non-porous amorphous solid water (np-ASW) ice surfaces at temperatures 40-240 K. The desorption energy distributions of these two molecules were calculated from TPD measurements using a set of independent Polanyi-Wigner equations. Results: The maximum of the desorption of formamide from both graphite and ASW ice surfaces occurs at 176 K after the desorption of H2O molecules, whereas the desorption profile of methylamine depends strongly on the substrate. Solid methylamine starts to desorb below 100 K from the graphite surface. Its desorption from the water ice surface occurs after 120 K and stops during the water ice sublimation around 150 K. It continues to desorb from the graphite surface at temperatures higher than160 K. Conclusions: More than 95% of solid NH2CHO diffuses through the np-ASW ice surface towards the graphitic substrate and is released into the gas phase with a desorption energy distribution Edes = 7460-9380 K, which is measured with the best-fit pre-exponential factor A = 1018 s-1. However, the desorption energy distribution of methylamine from the np-ASW ice surface (Edes = 3850-8420 K) is measured with the best-fit pre-exponential factor A = 1012 s-1. A fraction of solid methylamine monolayer of roughly 0.15 diffuses through the water ice surface towards the HOPG substrate. This small amount of methylamine desorbs later with higher binding energies (5050-8420 K) that exceed that of the crystalline water ice (Edes = 4930 K), which is calculated with the same pre-exponential factor A = 1012 s-1. The best wetting ability of methylamine compared to H2O molecules makes CH3NH2 molecules a refractory species for low coverage. Other binding energies of astrophysical relevant molecules are gathered and compared, but we could not link the chemical functional groups (amino, methyl, hydroxyl, and carbonyl) with the binding energy properties. Implications of these high binding energies are discussed.

Synthesis and characterization of poly (benzyl trimethyl ammonium chloride) ionic polymer

NASA Astrophysics Data System (ADS)

Mathew, Manjusha Elizabeth; Ahmad, Ishak; Thomas, Sabu; Daik, Rusli; Kassim, Muhammad

2018-04-01

Poly vinyl benzyl chloride (PVBC) was synthesized by free radical polymerization of 4-vinyl benzyl chloride (VBC) using benzoyl peroxide initiator at 80°C. Amine functionalised polymer prepared by treatment of PVBC with trimethyl amine in different solvents such as water, ethanol, tetra hydro furan(THF) and dimethyl formamide(DMF). The polymers characterized structurally by nuclear magnetic resonance and infrared spectroscopic techniques. The thermal decomposition of the polymer is studied by Thermo Gravimetric Analysis(TGA) and found that the polymer has stability up to 230°C. The nitrogen content of the aminated polymer determined by elemental analysis. The nitrogen content obtained from tetra hydro furan and dimethyl formamide solvents are 20.1% and 19.9% respectively.

Accurate Induction Energies for Small Organic Molecules. 2. Development and Testing of Distributed Polarizability Models against SAPT(DFT) Energies.

PubMed

Misquitta, Alston J; Stone, Anthony J; Price, Sarah L

2008-01-01

In part 1 of this two-part investigation we set out the theoretical basis for constructing accurate models of the induction energy of clusters of moderately sized organic molecules. In this paper we use these techniques to develop a variety of accurate distributed polarizability models for a set of representative molecules that include formamide, N-methyl propanamide, benzene, and 3-azabicyclo[3.3.1]nonane-2,4-dione. We have also explored damping, penetration, and basis set effects. In particular, we have provided a way to treat the damping of the induction expansion. Different approximations to the induction energy are evaluated against accurate SAPT(DFT) energies, and we demonstrate the accuracy of our induction models on the formamide-water dimer.

Surface Nanobubbles in Nonaqueous Media: Looking for Nanobubbles in DMSO, Formamide, Propylene Carbonate, Ethylammonium Nitrate, and Propylammonium Nitrate.

PubMed

An, Hongjie; Liu, Guangming; Atkin, Rob; Craig, Vincent S J

2015-07-28

Surface nanobubbles produced by supersaturation during the exchange of ethanol for water are routinely observed on hydrophobic surfaces, are stable for days, and have contact angles that are very much greater than observed macroscopically. Here, we test the hypothesis that nanobubbles can also be observed in nonaqueous solvents in order to ascertain if their anomalous lifetimes and contact angles are related to properties of the solvent. Nanobubbles were seen in the protic solvents formamide, ethylammonium nitrate, and propylammonium nitrate, but not in propylene carbonate or dimethyl sulfoxide. Solvents in which nanobubbles were observed exhibit a three-dimensional hydrogen-bonding network. Like in aqueous systems, the nanobubbles were stable for days and exhibited high contact angles (∼165°).

First Evidence on the Role of Heavy Ion Irradiation of Meteorites and Formamide in the Origin of Biomolecules

NASA Astrophysics Data System (ADS)

Saladino, Raffaele; Carota, Eleonora; Botta, Giorgia; Kapralov, Michail; Timoshenko, Gennady N.; Rozanov, Alexei; Krasavin, Eugene; Di Mauro, Ernesto

2016-11-01

Formamide (NH2CHO) has been irradiated in condensed phase at 273 K by 11B-boron beams in the presence of powdered meteorites of the chondrite and stony-iron types. Relative to the controls (no radiation or no catalysis), a variegate panel of compounds was observed, including purine and pyrimidine nucleobases (uracil, cytosine, adenine, and guanine), nucleobase analogues, heterocycles, and carboxylic acids involved in metabolic pathways. The presence of amino imidazole carbonitrile (AICN), 4,6-diamino purine (4,6-DAP) and 2,4-diamino pyrimidine (2,4-DAPy) among the observed products suggests the occurrence of an unified mechanism based on the generation of radical cyanide species (•CN). These observations contribute to outline plausible prebiotic scenarios involving 11B-boron as energy source.

21 CFR 177.2440 - Polyethersulfone resins.

Code of Federal Regulations, 2014 CFR

2014-04-01

... determined by reduced viscosity in dimethyl formamide in accordance with ASTM method D2857-70 (Reapproved 1977), “Standard Test Method for Dilute Solution Viscosity of Polymers,” which is incorporated by...

21 CFR 177.2440 - Polyethersulfone resins.

Code of Federal Regulations, 2013 CFR

2013-04-01

... molecular weight is determined by reduced viscosity in dimethyl formamide in accordance with ASTM method D2857-70 (Reapproved 1977), “Standard Test Method for Dilute Solution Viscosity of Polymers,” which is...

21 CFR 177.2440 - Polyethersulfone resins.

Code of Federal Regulations, 2012 CFR

2012-04-01

... molecular weight is determined by reduced viscosity in dimethyl formamide in accordance with ASTM method D2857-70 (Reapproved 1977), “Standard Test Method for Dilute Solution Viscosity of Polymers,” which is...

21 CFR 177.2440 - Polyethersulfone resins.

Code of Federal Regulations, 2011 CFR

2011-04-01

... molecular weight is determined by reduced viscosity in dimethyl formamide in accordance with ASTM method D2857-70 (Reapproved 1977), “Standard Test Method for Dilute Solution Viscosity of Polymers,” which is...

Cryochemistry: freezing effect on peptide coupling in different organic solutions.

PubMed

Vajda, T; Szókán, G; Hollósi, M

1998-06-01

The freezing effect on peptide coupling in organic solutions of different polarity has been investigated and compared with the results obtained in liquid phase. The model reaction of DCC-activated coupling of Boc-Ala-Phe-OH with H-Ala-OBu(t) has been carried out in dioxane, dimethylsulfoxide and formamide, as well as in mixtures (90%/10%, v/v) of dioxane with acetonitrile, dimethylformamide, dimethylsulfoxide and formamide. The reactions have been traced and evaluated by RP-HPLC analysis. Freezing the reaction mixture resulted in all cases in a significant suppression of the N-dipeptidylurea side-product formation together with a slight decrease of tripeptide epimerization. The coupling yields and the side effects depended on the solvent, with the dioxane and dioxane/acetonitrile mixture produced the best results. The role of freezing and solvent in the improved results is discussed.

A quantum mechanical strategy to investigate the structure of liquids: the cases of acetonitrile, formamide, and their mixture.

PubMed

Mennucci, Benedetta; da Silva, Clarissa O

2008-06-05

A computational strategy based on quantum mechanical (QM) calculations and continuum solvation models is used to investigate the structure of liquids (either neat liquids or mixtures). The strategy is based on the comparison of calculated and experimental spectroscopic properties (IR-Raman vibrational frequencies and Raman intensities). In particular, neat formamide, neat acetonitrile, and their equimolar mixture are studied comparing isolated and solvated clusters of different nature and size. In all cases, the study seems to indicate that liquids, even when strongly associated, can be effectively modeled in terms of a shell-like system in which clusters of strongly interacting molecules (the microenvironments) are solvated by a polarizable macroenvironment represented by the rest of the molecules. Only taking into proper account both these effects can a correct picture of the liquid structure be achieved.

Probing the Hofmeister series beyond water: Specific-ion effects in non-aqueous solvents

NASA Astrophysics Data System (ADS)

Mazzini, Virginia; Liu, Guangming; Craig, Vincent S. J.

2018-06-01

We present an experimental investigation of specific-ion effects in non-aqueous solvents, with the aim of elucidating the role of the solvent in perturbing the fundamental ion-specific trend. The focus is on the anions: CH3COO->F->Cl->Br->I->ClO4 ->SCN- in the solvents water, methanol, formamide, dimethyl sulfoxide (DMSO), and propylene carbonate (PC). Two types of experiments are presented. The first experiment employs the technique of size exclusion chromatography to evaluate the elution times of electrolytes in the different solvents. We observe that the fundamental (Hofmeister) series is observed in water and methanol, whilst the series is reversed in DMSO and PC. No clear series is observed for formamide. The second experiment uses the quartz crystal microbalance technique to follow the ion-induced swelling and collapse of a polyelectrolyte brush. Here the fundamental series is observed in the protic solvents water, methanol, and formamide, and the series is once again reversed in DMSO and PC. These behaviours are not attributed to the protic/aprotic nature of the solvents, but rather to the polarisability of the solvents and are due to the competition between the interaction of ions with the solvent and the surface. A rule of thumb is proposed for ion specificity in non-aqueous solvents. In weakly polarisable solvents, the trends in specific-ion effects will follow those in water, whereas in strongly polarisable solvents the reverse trend will be observed. Solvents of intermediate polarisability will give weak specific-ion effects.

Microwave spectrum and structural parameters for the formamide-formic acid dimer.

PubMed

Daly, Adam M; Sargus, Bryan A; Kukolich, Stephen G

2010-11-07

The rotational spectra for six isotopologues of the complex formed between formamide and formic acid have been measured using a pulsed-beam Fourier transform microwave spectrometer and analyzed to obtain rotational constants and quadrupole coupling parameters. The rotational constants and quadrupole coupling strengths obtained for H  (12)COOH-H(2)  (14)NCOH are A = 5889.465(2), B = 2148.7409(7), 1575.1234(6), eQq(aa) = 1.014(5), eQq(bb) = 1.99(1), and eQq(cc) = -3.00(1) MHz. Using the 15 rotational constants obtained for the H  (13)COOH, HCOOD, DCOOH, and H(2)  (15)NCHO isotopologues, key structural parameters were obtained from a least-squares structure fit. Hydrogen bond distances of 1.78 Å for R(O3⋯H1) and 1.79 Å for R(H4⋯O1) were obtained. The "best fit" value for the angle(C-O-H) of formic acid is significantly larger than the monomer value of 106.9° with an optimum value of 121.7(3)°. The complex is nearly planar with inertial defect Δ = -0.158 amu  Å(2). The formamide proton is moved out of the molecular plane by 15(3)° for the best fit structure. Density functional theory using B3PW91, HCTH407, and TPSS as well as MP2 and CCSD calculations were performed using 6-311++G(d,p) and the results were compared to experimentally determined parameters.

Probing the Hofmeister series beyond water: Specific-ion effects in non-aqueous solvents.

PubMed

Mazzini, Virginia; Liu, Guangming; Craig, Vincent S J

2018-06-14

We present an experimental investigation of specific-ion effects in non-aqueous solvents, with the aim of elucidating the role of the solvent in perturbing the fundamental ion-specific trend. The focus is on the anions: CH 3 COO - >F - >Cl - >Br - >I - >ClO 4 - >SCN - in the solvents water, methanol, formamide, dimethyl sulfoxide (DMSO), and propylene carbonate (PC). Two types of experiments are presented. The first experiment employs the technique of size exclusion chromatography to evaluate the elution times of electrolytes in the different solvents. We observe that the fundamental (Hofmeister) series is observed in water and methanol, whilst the series is reversed in DMSO and PC. No clear series is observed for formamide. The second experiment uses the quartz crystal microbalance technique to follow the ion-induced swelling and collapse of a polyelectrolyte brush. Here the fundamental series is observed in the protic solvents water, methanol, and formamide, and the series is once again reversed in DMSO and PC. These behaviours are not attributed to the protic/aprotic nature of the solvents, but rather to the polarisability of the solvents and are due to the competition between the interaction of ions with the solvent and the surface. A rule of thumb is proposed for ion specificity in non-aqueous solvents. In weakly polarisable solvents, the trends in specific-ion effects will follow those in water, whereas in strongly polarisable solvents the reverse trend will be observed. Solvents of intermediate polarisability will give weak specific-ion effects.

40 CFR 180.673 - Triforine; tolerances for residues.

Code of Federal Regulations, 2014 CFR

2014-07-01

...-trichloroehylidene)]bis[formamide]), in or on the following commodities. Commodity Parts permillion Blueberry 1 1.0 Tomato 1 0.5 1 There are no U.S. registrations for blueberry and tomato. (b) Section 18 emergency...

40 CFR 180.673 - Triforine; tolerances for residues.

Code of Federal Regulations, 2013 CFR

2013-07-01

...-trichloroehylidene)]bis[formamide]), in or on the following commodities. Commodity Parts permillion Blueberry 1 1.0 Tomato 1 0.5 1 There are no U.S. registrations for blueberry and tomato. (b) Section 18 emergency...

Enthalpy characteristics of the dissolution of L-valine in water/formamide mixtures at 298.15 K

NASA Astrophysics Data System (ADS)

Smirnov, V. I.; Badelin, V. G.

2016-11-01

The thermochemical dissolution of L-valine in solvent mixtures H2O + (formamide, N-methylformamide, and N, N-dimethylformamide) is studied at an organic component concentration of x 2 = 0-0.35 molar fractions and a temperature of 298.15 K. The experimental data are used to calculate standard enthalpies of dissolution, the transferring of L-valine from water to a mixed solvent, and the enthalpy coefficients of pairwise interactions ( h xy ) with organic solvent molecules. The correlation between the enthalpy characteristics of the dissolution of L-valine with the composition of aqueous organic mixtures and the nature of the organic solvent (its physicochemical properties) is determined. A comparative analysis of the values of h xy of a number of aliphatic L-amino acids in similar solvent mixtures with the hydrophobicity parameters of their side chains is performed.

Exploratory studies on some electrochemical cell systems

NASA Astrophysics Data System (ADS)

Chaudhuri, Srikumar; Guha, D.

Exploratory studies were conducted on cell systems with different metal anodes, and iodine and sulphur mixed with graphite powder in a polymer matrix as cathodes, using different electrolytes in non-aqueous and aqueous media as ionic charge carriers. The electrical conductance of the electrolyte solutions in aqueous and non-aqueous solvents, the open circuit voltage (OCV) and short circuit current (SCC) for the different cell systems were measured. To date, the non-aqueous solvents used in our studies were dimethylformamide, formamide, dioxan, and nitrobenzene, and the electrolytes used were potassium iodide, caustic potash, cetyltrimethylammonium bromide (CTAB), sodium lauryl sulphate (SLS) and calcium chloride. These electrolytes were used in both non-aqueous and aqueous media. In general, aqueous electrolyte solutions gave a better performance than non-aqueous electrolyte solutions. Of the aqueous electrolytes, the highest conductance was shown by potassium chloride solution in water (conductance=0.0334 mho). However, the best OCV and SCC were shown by aluminium as anode and iodine as cathode with a saturated solution of caustic potash in water. The OCV was 1.85 V and the SCC was 290 mA cm -2. The highest conductance among the non-aqueous systems was shown by caustic potash in formamide. (Conductance=0.013 mho.) The best OCV and SCC, however, were shown by a zinc anode and iodine cathode with saturated potassium chloride in formamide, having an OCV of 1.55 V and an SCC of 150 mA cm -2. Further studies are in progress to obtain detailed performance data and recharging characteristics of some of the more promising systems reported here.

A New Synthetic Route to N-Benzyl Carboxamides through the Reverse Reaction of N-Substituted Formamide Deformylase

PubMed Central

Hashimoto, Yoshiteru; Sakashita, Toshihide; Fukatsu, Hiroshi; Sato, Hiroyoshi

2014-01-01

Previously, we isolated a new enzyme, N-substituted formamide deformylase, that catalyzes the hydrolysis of N-substituted formamide to the corresponding amine and formate (H. Fukatsu, Y. Hashimoto, M. Goda, H. Higashibata, and M. Kobayashi, Proc. Natl. Acad. Sci. U. S. A. 101:13726–13731, 2004, doi:10.1073/pnas.0405082101). Here, we discovered that this enzyme catalyzed the reverse reaction, synthesizing N-benzylformamide (NBFA) from benzylamine and formate. The reverse reaction proceeded only in the presence of high substrate concentrations. The effects of pH and inhibitors on the reverse reaction were almost the same as those on the forward reaction, suggesting that the forward and reverse reactions are both catalyzed at the same catalytic site. Bisubstrate kinetic analysis using formate and benzylamine and dead-end inhibition studies using a benzylamine analogue, aniline, revealed that the reverse reaction of this enzyme proceeds via an ordered two-substrate, two-product (bi-bi) mechanism in which formate binds first to the enzyme active site, followed by benzylamine binding and the subsequent release of NBFA. To our knowledge, this is the first report of the reverse reaction of an amine-forming deformylase. Surprisingly, analysis of the substrate specificity for acids demonstrated that not only formate, but also acetate and propionate (namely, acids with numbers of carbon atoms ranging from C1 to C3), were active as acid substrates for the reverse reaction. Through this reaction, N-substituted carboxamides, such as NBFA, N-benzylacetamide, and N-benzylpropionamide, were synthesized from benzylamine and the corresponding acid substrates. PMID:24123742

Lineage Analysis in Pulmonary Arterial Hypertension

DTIC Science & Technology

2011-06-01

later by intravenous injection of monocrotaline pyrrole . The fate of GFP-expressing cells of endothelial lineage will be correlated with...vein injection of monocrotaline pyrrole in dimethyl formamide. At day 35, mice demonstrated pulmonary hypertension with RVSP increased from 22 + 3

14N Quadrupole Coupling in the Microwave Spectra of N-Vinylformamide

NASA Astrophysics Data System (ADS)

Kannengießer, Raphaela; Stahl, Wolfgang; Nguyen, Ha Vinh Lam; Bailey, William C.

2016-06-01

The microwave spectra of two conformers, trans and cis, of the title compound were recorded using two molecular beam Fourier transform microwave spectrometers operating in the frequency range 2 GHz to 40 GHz, and aimed at analysis of their 14N quadrupole hyperfine structures. Rotational constants, centrifugal distortion constants, and nuclear quadrupole coupling constants (NQCCs) χaa and χbb - χcc, were all determined with very high accuracy. Two fits including 176 and 117 hyperfine transitions were performed for the trans and cis conformers, respectively. Standard deviations of both fits are close to the measurement accuracy of 2 kHz. The NQCCs of the two conformers are almost exactly the same, and are compared with values found for other saturated and unsaturated formamides. Complementary quantum chemical calculations - MP2/6-311++G(d,p) rotational constants, MP2/cc-pVTZ centrifugal distortion constants, and B3PW91/6-311+G(d,p)//MP2/6-311++G(d,p) nuclear quadrupole coupling constants - give spectroscopic parameters in excellent agreement with the experimental parameters. B3PW91/6-311+G(d,p) calculated electric field gradients, in conjunction with eQ/h = 4.599(12) MHz/a.u., yields more reliable NQCCs for formamides possessing conjugated π-electron systems than does the B3PW91/6-311+G(df,pd) model recommended in Ref., whereas this latter performs better for aliphatic formamides. We conclude from this that f-polarization functions on heavy atoms hinder rather than help with modeling of conjugated π-electron systems. W. C. Bailey, Chem. Phys., 2000, 252, 57 W. C. Bailey, Calculation of Nuclear Quadrupole Coupling Constants in Gaseous State Molecules, http://nqcc.wcbailey.net/index.html.

Supramolecular aromaticity

NASA Astrophysics Data System (ADS)

Karabıyık, Hande; Sevinçek, Resul; Karabıyık, Hasan

2014-05-01

We report experimental and theoretical evidences for supramolecular aromaticity as a new concept to be widely used in researches about molecular crystals. CSD survey regarding frequently encountered resonance-assisted H-bonds (RAHBs) in formic acid, formamide, formimidamide, formic acid-formamide, and formamide-formimidamide dimers shows that supramolecular quasirings formed by RAHBs have remarkable electronic delocalization within themselves, which is reminiscent of aromaticity at supramolecular level. This study criticizes and reevaluates the validity of conventional judgment which states that ring systems formed by intermolecular H-bonds cannot be aromatic. Thus, the term aromaticity can be extended to supramolecular systems formed by RAHBs. Supramolecular aromaticity has a multi-fold nature involving both σ- and π-delocalization, and σ-delocalization through RAHBs takes on a task of compensating σ-deficiency within quasirings. Atomic composition in donor-acceptor set of the dimers is descriptive for supramolecular aromaticity. We revised bond-valence parameters for RAHBs and they suggest that hypervalent character of H atoms is more pronounced than their hypovalent character in RAHBs. The σ-delocalized bonding within H-bonded quasirings necessitates hypervalent character of H atoms. Quantum chemical calculations based on adiabatic Hydrogen Atom Transfer (HAT) between the monomers reveal that topological parameters at ring critical points (RCPs) of the quasirings correlate well with Shannon's entropic aromaticity index. The presence of additional LP orbital on O atoms implying more diffused LP-orbitals in donor-acceptor set leads to the formation of resonance-disabling states reducing supramolecular aromaticity of a quasiring and energetic cost of the electron transfer between the monomers. There is a nonignorable electron transfer between the monomers even in the cases where H atoms are close to donor or acceptor atom. NBO analyses have revealed that formally vacant LP* orbitals on H-atoms in TS geometries mediate intermolecular electron transfer as a result of the hyperconjugative stereoelectronic interactions.

Silicate-Promoted Phosphorylation of Glycerol in Non-Aqueous Solvents: A Prebiotically Plausible Route to Organophosphates

PubMed Central

Gull, Maheen; Cafferty, Brian J.; Hud, Nicholas V.; Pasek, Matthew A.

2017-01-01

Phosphorylation reactions of glycerol were studied using different inorganic phosphates such as sodium phosphate, trimetaphosphate (a condensed phosphate), and struvite. The reactions were carried out in two non-aqueous solvents: formamide and a eutectic solvent consisting of choline-chloride and glycerol in a ratio of 1:2.5. The glycerol reacted in formamide and in the eutectic solvent with phosphate to yield its phosphorylated derivatives in the presence of silicates such as quartz sand and kaolinite clay. The reactions were carried out by heating glycerol with a phosphate source at 85 °C for one week and were analyzed by 31P-nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). The yield of the phosphorylated glycerol was improved by the presence of silicates, and reached 90% in some experiments. Our findings further support the proposal that non-aqueous solvents are advantageous for the prebiotic synthesis of biomolecules, and suggest that silicates may have aided in the formation of organophosphates on the prebiotic earth. PMID:28661422

Iron-catalyzed urea synthesis: dehydrogenative coupling of methanol and amines† †Electronic supplementary information (ESI) available: Experimental details, characterization data, and select NMR spectra. See DOI: 10.1039/c8sc00775f

PubMed Central

Lane, Elizabeth M.; Hazari, Nilay

2018-01-01

Substituted ureas have numerous applications but their synthesis typically requires the use of highly toxic starting materials. Herein we describe the first base-metal catalyst for the selective synthesis of symmetric ureas via the dehydrogenative coupling of methanol with primary amines. Using a pincer supported iron catalyst, a range of ureas was generated with isolated yields of up to 80% (corresponding to a catalytic turnover of up to 160) and with H2 as the sole byproduct. Mechanistic studies indicate a stepwise pathway beginning with methanol dehydrogenation to give formaldehyde, which is trapped by amine to afford a formamide. The formamide is then dehydrogenated to produce a transient isocyanate, which reacts with another equivalent of amine to form a urea. These mechanistic insights enabled the development of an iron-catalyzed method for the synthesis of unsymmetric ureas from amides and amines. PMID:29780531

Diaqua­bis­(5-carb­oxy-2-propyl-1H-imidazole-4-carboxyl­ato-κ2 N 3,O 4)cadmium N,N-dimethyl­formamide disolvate

PubMed Central

Tong, Shao-Wei; Li, Shi-Jie; Song, Wen-Dong; Miao, Dong-Liang; An, Jing-Bo

2011-01-01

In the title complex, [Cd(C8H9N2O4)2(H2O)2]·2C3H7NO, the six-coordinate CdII ion is in a slightly distorted octa­hedral environment, defined by two O atoms from two coordinated water mol­ecules and two carboxyl­ate O atoms and two N atoms from two N,O-bidentate 5-carb­oxy-2-propyl-1H-imidazole-4-carboxyl­ate ligands. In the crystal, complex mol­ecules and dimethyl­formamide solvent mol­ecules are linked by O—H⋯O and N—H⋯O hydrogen bonds into a two-dimensional supra­molecular structure. The propyl groups of the ligands are disordered over two conformations with refined occupancies of 0.680 (7) and 0.320 (7). PMID:22199635

Stone-Ice Bodies as Possible Incubators of a Primary Life

NASA Astrophysics Data System (ADS)

Busarev, V. V.

2014-10-01

Widespread in the interstellar medium three-atomic molecules of HCN and H2O and derivative formamid (NH2COH) are the basis for the origin of life. It is shown that irradiation of formamid by protons in the presence of terrestrial mineral and meteoritic catalysts in conditions compatible with terrestrial leads to simultaneous synthesis of a wide range of compounds (amino acids, heterocycles, alcohols, amides, sugars, etc.) having potential to develop as genetics (based on RNA and DNA), and metabolism underlying terrestrial life forms [1, 2]. However, the intended path of extraterrestrial origin of life in the open interstellar medium could not reach its logical end. The subsequent stages of the assumed biological synthesis needed protection from the harsh cosmic factors and presence of liquid water, catalysts, etc. (e.g., [3]). Such conditions could be realized only on planetary bodies and/or in their interiors. On the basis of observations and calculations, the author sug! gested that the objects were in the early Solar system. Such could be stone-ice bodies.

Poly(ethylene oxide) surfactant polymers.

PubMed

Vacheethasanee, Katanchalee; Wang, Shuwu; Qiu, Yongxing; Marchant, Roger E

2004-01-01

We report on a series of structurally well-defined surfactant polymers that undergo surface-induced self-assembly on hydrophobic biomaterial surfaces. The surfactant polymers consist of a poly(vinyl amine) backbone with poly(ethylene oxide) and hexanal pendant groups. The poly(vinyl amine) (PVAm) was synthesized by hydrolysis of poly(N-vinyl formamide) following free radical polymerization of N-vinyl formamide. Hexanal and aldehyde-terminated poly(ethylene oxide) (PEO) were simultaneously attached to PVAm via reductive amination. Surfactant polymers with different PEO:hexanal ratios and hydrophilic/hydrophobic balances were prepared, and characterized by FT-IR, 1H-NMR and XPS spectroscopies. Surface active properties at the air/water interface were determined by surface tension measurements. Surface activity at a solid surface/water interface was demonstrated by atomic force microscopy, showing epitaxially molecular alignment for surfactant polymers adsorbed on highly oriented pyrolytic graphite. The surfactant polymers described in this report can be adapted for simple non-covalent surface modification of biomaterials and hydrophobic surfaces to provide highly hydrated interfaces.

Silica metal-oxide vesicles catalyze comprehensive prebiotic chemistry.

PubMed

Bizzarri, Bruno Mattia; Botta, Lorenzo; Pérez-Valverde, Maritza Iveth; Saladino, Raffaele; Di Mauro, Ernesto; Garcia Ruiz, Juan Manuel

2018-03-30

It has recently been demonstrated that mineral self-assembled structures catalyzing prebiotic chemical reactions may form in natural waters derived from serpentinization, a geological process widespread in the early stages of Earth-like planets. We have synthesized self-assembled membranes by mixing microdrops of metal solutions with alkaline silicate solutions in the presence of formamide (NH2CHO), a single carbon molecule, at 80ºC. We found that these bilayer membranes, made of amorphous silica and metal oxide-hydroxide nanocrystals, catalyze the condensation of formamide, yielding the four nucleobases of RNA, three aminoacids and several carboxylic acids in a single pot experiment. Besides manganese, iron and magnesium, two abundant elements in the earliest Earth crust that are key in serpentinization reactions, are enough to produce all these biochemical compounds. These results suggest that the transition from inorganic geochemistry to prebiotic organic chemistry is common on a universal scale and, most probably, earlier than ever thought for our planet. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

N-formylation of amines via the aerobic oxidation of methanol over supported gold nanoparticles.

PubMed

Ishida, Tamao; Haruta, Masatake

2009-01-01

Dress code: formyl. Gold nanoparticles supported on NiO catalyze the one-pot N-formylation of amines with methanol and molecular oxygen to produce formamide at a selectivity of 90 %. This process generates methyl formate in situ, followed by reaction with amines.

The Two Faces of Sulfinates: Illustrating Umpolung Reactivity

ERIC Educational Resources Information Center

Tapia-Pineda, Adabelia; Perez-Arrieta, Carlos; Silva-Cuevas, Carolina; Paleo, Ehecatl; Lujan-Montelongo, J. Armando

2016-01-01

A simple, microscale experiment was developed with the aim of demonstrating the concept of umpolung in synthetic organic chemistry. Starting from a common alkyl sulfinate, students perform a polarity inversion by performing a Grignard-based sulfoxide synthesis and a Mannich-type formamide synthesis. The products are purified without chromatography…

Synthesis of Formate Esters and Formamides Using an Au/TiO2-Catalyzed Aerobic Oxidative Coupling of Paraformaldehyde

PubMed Central

Metaxas, Ioannis; Vasilikogiannaki, Eleni

2017-01-01

A simple method for the synthesis of formate esters and formamides is presented based on the Au/TiO2-catalyzed aerobic oxidative coupling between alcohols or amines and formaldehyde. The suitable form of formaldehyde is paraformaldehyde, as cyclic trimeric 1,3,5-trioxane is inactive. The reaction proceeds via the formation of an intermediate hemiacetal or hemiaminal, respectively, followed by the Au nanoparticle-catalyzed aerobic oxidation of the intermediate. Typically, the oxidative coupling between formaldehyde (2 equiv) and amines occurs quantitatively at room temperature within 4 h, and there is no need to add a base as in analogous coupling reactions. The oxidative coupling between formaldehyde (typically 3 equiv) and alcohols is unprecedented and occurs more slowly, yet in good to excellent yields and selectivity. Minor side-products (2–12%) from the acetalization of formaldehyde by the alcohol are also formed. The catalyst is recyclable and can be reused after a simple filtration in five consecutive runs with a small loss of activity. PMID:29231853

Extraction of Structural Extracellular Polymeric Substances from Aerobic Granular Sludge

PubMed Central

Felz, Simon; Al-Zuhairy, Salah; Aarstad, Olav Andreas; van Loosdrecht, Mark C.M.; Lin, Yue Mei

2016-01-01

To evaluate and develop methodologies for the extraction of gel-forming extracellular polymeric substances (EPS), EPS from aerobic granular sludge (AGS) was extracted using six different methods (centrifugation, sonication, ethylenediaminetetraacetic acid (EDTA), formamide with sodium hydroxide (NaOH), formaldehyde with NaOH and sodium carbonate (Na2CO3) with heat and constant mixing). AGS was collected from a pilot wastewater treatment reactor. The ionic gel-forming property of the extracted EPS of the six different extraction methods was tested with calcium ions (Ca2+). From the six extraction methods used, only the Na2CO3 extraction could solubilize the hydrogel matrix of AGS. The alginate-like extracellular polymers (ALE) recovered with this method formed ionic gel beads with Ca2+. The Ca2+-ALE beads were stable in EDTA, formamide with NaOH and formaldehyde with NaOH, indicating that ALE are one part of the structural polymers in EPS. It is recommended to use an extraction method that combines physical and chemical treatment to solubilize AGS and extract structural EPS. PMID:27768085

State-of-the-art thermochemical and kinetic computations for astrochemical complex organic molecules: formamide formation in cold interstellar clouds as a case study

PubMed Central

Vazart, Fanny; Calderini, Danilo; Puzzarini, Cristina; Skouteris, Dimitrios

2017-01-01

We propose an integrated computational strategy aimed at providing reliable thermochemical and kinetic information on the formation processes of astrochemical complex organic molecules. The approach involves state-of-the-art quantum-mechanical computations, second-order vibrational perturbation theory, and kinetic models based on capture and transition state theory together with the master equation approach. Notably, tunneling, quantum reflection, and leading anharmonic contributions are accounted for in our model. Formamide has been selected as a case study in view of its interest as a precursor in the abiotic amino acid synthesis. After validation of the level of theory chosen for describing the potential energy surface, we have investigated several pathways of the OH+CH2NH and NH2+HCHO reaction channels. Our results indicate that both reaction channels are essentially barrier-less (in the sense that all relevant transition states lie below or only marginally above the reactants) and can, therefore, occur under the low temperature conditions of interstellar objects provided that tunneling is taken into the proper account. PMID:27689448

ON THE FORMATION OF AMIDE POLYMERS VIA CARBONYL–AMINO GROUP LINKAGES IN ENERGETICALLY PROCESSED ICES OF ASTROPHYSICAL RELEVANCE

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

Förstel, Marko; Maksyutenko, Pavlo; Jones, Brant M.

2016-04-01

We report on the formation of organic amide polymers via carbonyl–amino group linkages in carbon monoxide and ammonia bearing energetically processed ices of astrophysical relevance. The first group comprises molecules with one carboxyl group and an increasing number of amine moieties starting with formamide (45 u), urea (60 u), and hydrazine carboxamide (75 u). The second group consists of species with two carboxyl (58 u) and up to three amine groups (73 u, 88 u, and 103 u). The formation and polymerization of these linkages from simple inorganic molecules via formamide und urea toward amide polymers is discussed in anmore » astrophysical and astrobiological context. Our results show that long chain molecules, which are closely related to polypeptides, easily form by energetically processing simple, inorganic ices at very low temperatures and can be released into the gas phase by sublimation of the ices in star-forming regions. Our experimental results were obtained by employing reflectron time-of-flight mass spectroscopy, coupled with soft, single photon vacuum ultraviolet photoionization; they are complemented by theoretical calculations.« less

Polyacrylonitrile nanofiber as polar solvent N,N-dimethyl formamide sensor based on quartz crystal microbalance technique

NASA Astrophysics Data System (ADS)

Rianjanu, A.; Julian, T.; Hidayat, S. N.; Suyono, E. A.; Kusumaatmaja, A.; Triyana, K.

2018-04-01

Here, we describe an N,N-dimethyl formamide (DMF) vapour sensor fabricated by coating polyacrylonitrile (PAN) nanofiber structured on quartz crystal microbalance (QCM). The PAN nanofiber sensors with an average diameter of 225 nm to 310 nm were fabricated via electrospinning process with different mass deposition on QCM substrate. The nanostructured of PAN nanofiber offers a high specific surface area that improved the sensing performance of nanofiber sensors. Benefiting from that fine structure, and high polymer-solvent affinity between PAN and DMF, the development of DMF sensors presented good response at ambient temperature. Since there is no chemical reaction between PAN nanofiber and DMF vapour, weak physical interaction such absorption and swelling were responsible for the sensing behavior. The results are indicating that the response of PAN nanofiber sensors has more dependency on the nanofiber structure (specific surface area) rather than its mass deposition. The sensor also showed good stability after a few days sensing. These findings have significant implications for developing DMF vapour sensor based on QCM coated polymer nanofibers.

Effect of Collagen Matrix Saturation on the Surface Free Energy of Dentin using Different Agents.

PubMed

de Almeida, Leopoldina de Fátima Dantas; Souza, Samilly Evangelista; Sampaio, Aline Araújo; Cavalcanti, Yuri Wanderley; da Silva, Wander José; Del Bel Cur, Altair A; Hebling, Josimeri

2015-07-01

The surface free energy of conditioned-dentin is one of the factors that interfere with monomeric infiltration of the interfibrillar spaces. Saturation of the tooth matrix with different substances may modulate this energy and, consequently, the wettability of the dentin. To evaluate the influence of different substances used to saturate conditioned-dentin on surface free energy (SFE) of this substrate. Dentin blocks (4 × 7 × 1 mm, n = 6/ group), obtained from the roots of bovine incisors, were etched using phosphoric acid for 15 seconds, rinsed and gently dried. The surfaces were treated for 60 seconds with: ultra-purified water (H20-control); ethanol (EtOH), acetone (ACT), chlorhexidine (CHX), ethylenediaminetetraacetic acid (EDTA); or sodium hypochlorite (NaOCl). The tooth surfaces were once again dried with absorbent paper and prepared for SFE evaluation using three standards: water, formamide and bromonaphthalene. Analysis of variance (ANOVA) and Dunnet's tests (a = 0.05) were applied to the data. Ethylenediaminetetraacetic acid was the only substance that caused a change to the contact angle for the standards water and formamide, while only EtOH influenced the angles formed between formamide and the dentin surface. None of the substances exerted a significant effect for bromonaphtha-lene. In comparison to the control, only EDTA and NaOCl altered both polar components of the SFE. Total SFE was increased by saturation of the collagen matrix by EDTA and reduced when NaOCl was used. Saturation of the collagen matrix by EDTA and EtOH changed the surface free energy of the dentin. In addition, the use of NaOCl negatively interfered with the properties evaluated. The increase of surface free energy and wettability of the dentin surface would allow higher penetration of the the adhesive system, which would be of importance to the clinical success of resin-dentin union.

Experimental and theoretical understanding of the gas phase oxidation of atmospheric amides with OH radicals: kinetics, products, and mechanisms.

PubMed

Borduas, Nadine; da Silva, Gabriel; Murphy, Jennifer G; Abbatt, Jonathan P D

2015-05-14

Atmospheric amides have primary and secondary sources and are present in ambient air at low pptv levels. To better assess the fate of amides in the atmosphere, the room temperature (298 ± 3 K) rate coefficients of five different amides with OH radicals were determined in a 1 m(3) smog chamber using online proton-transfer-reaction mass spectrometry (PTR-MS). Formamide, the simplest amide, has a rate coefficient of (4.44 ± 0.46) × 10(-12) cm(3) molec(-1) s(-1) against OH, translating to an atmospheric lifetime of ∼1 day. N-methylformamide, N-methylacetamide and propanamide, alkyl versions of formamide, have rate coefficients of (10.1 ± 0.6) × 10(-12), (5.42 ± 0.19) × 10(-12), and (1.78 ± 0.43) × 10(-12) cm(3) molec(-1) s(-1), respectively. Acetamide was also investigated, but due to its slow oxidation kinetics, we report a range of (0.4-1.1) × 10(-12) cm(3) molec(-1) s(-1) for its rate coefficient with OH radicals. Oxidation products were monitored and quantified and their time traces were fitted using a simple kinetic box model. To further probe the mechanism, ab initio calculations are used to identify the initial radical products of the amide reactions with OH. Our results indicate that N-H abstractions are negligible in all cases, in contrast to what is predicted by structure-activity relationships. Instead, the reactions proceed via C-H abstraction from alkyl groups and from formyl C(O)-H bonds when available. The latter process leads to radicals that can readily react with O2 to form isocyanates, explaining the detection of toxic compounds such as isocyanic acid (HNCO) and methyl isocyanate (CH3NCO). These contaminants of significant interest are primary oxidation products in the photochemical oxidation of formamide and N-methylformamide, respectively.

Biosynthesis of pteridines. Reaction mechanism of GTP cyclohydrolase I.

PubMed

Rebelo, Jorge; Auerbach, Günter; Bader, Gerd; Bracher, Andreas; Nar, Herbert; Hösl, Cornelia; Schramek, Nicholas; Kaiser, Johannes; Bacher, Adelbert; Huber, Robert; Fischer, Markus

2003-02-14

GTP cyclohydrolase I catalyses the hydrolytic release of formate from GTP followed by cyclization to dihydroneopterin triphosphate. The enzymes from bacteria and animals are homodecamers containing one zinc ion per subunit. Replacement of Cys110, Cys181, His112 or His113 of the enzyme from Escherichia coli by serine affords catalytically inactive mutant proteins with reduced capacity to bind zinc. These mutant proteins are unable to convert GTP or the committed reaction intermediate, 2-amino-5-formylamino-6-(beta-ribosylamino)-4(3H)-pyrimidinone 5'-triphosphate, to dihydroneopterin triphosphate. The crystal structures of GTP complexes of the His113Ser, His112Ser and Cys181Ser mutant proteins determined at resolutions of 2.5A, 2.8A and 3.2A, respectively, revealed the conformation of substrate GTP in the active site cavity. The carboxylic group of the highly conserved residue Glu152 anchors the substrate GTP, by hydrogen bonding to N-3 and to the position 2 amino group. Several basic amino acid residues interact with the triphosphate moiety of the substrate. The structure of the His112Ser mutant in complex with an undefined mixture of nucleotides determined at a resolution of 2.1A afforded additional details of the peptide folding. Comparison between the wild-type and mutant enzyme structures indicates that the catalytically active zinc ion is directly coordinated to Cys110, Cys181 and His113. Moreover, the zinc ion is complexed to a water molecule, which is in close hydrogen bond contact to His112. In close analogy to zinc proteases, the zinc-coordinated water molecule is suggested to attack C-8 of the substrate affording a zinc-bound 8R hydrate of GTP. Opening of the hydrated imidazole ring affords a formamide derivative, which remains coordinated to zinc. The subsequent hydrolysis of the formamide motif has an absolute requirement for zinc ion catalysis. The hydrolysis of the formamide bond shows close mechanistic similarity with peptide hydrolysis by zinc proteases.

A safer, urea-based in situ hybridization method improves detection of gene expression in diverse animal species.

PubMed

Sinigaglia, Chiara; Thiel, Daniel; Hejnol, Andreas; Houliston, Evelyn; Leclère, Lucas

2018-02-01

In situ hybridization is a widely employed technique allowing spatial visualization of gene expression in fixed specimens. It has greatly advanced our understanding of biological processes, including developmental regulation. In situ protocols are today routinely followed in numerous laboratories, and although details might change, they all include a hybridization step, where specific antisense RNA or DNA probes anneal to the target nucleic acid sequence. This step is generally carried out at high temperatures and in a denaturing solution, called hybridization buffer, commonly containing 50% (v/v) formamide - a hazardous chemical. When applied to the soft-bodied hydrozoan medusa Clytia hemisphaerica, we found that this traditional hybridization approach was not fully satisfactory, causing extensive deterioration of morphology and tissue texture which compromised our observation and interpretation of results. We thus tested alternative solutions for in situ detection of gene expression and, inspired by optimized protocols for Northern and Southern blot analysis, we substituted the 50% formamide with an equal volume of 8M urea solution in the hybridization buffer. Our new protocol not only yielded better morphologies and tissue consistency, but also notably improved the resolution of the signal, allowing more precise localization of gene expression and reducing aspecific staining associated with problematic areas. Given the improved results and reduced manipulation risks, we tested the urea protocol on other metazoans, two brachiopod species (Novocrania anomala and Terebratalia transversa) and the priapulid worm Priapulus caudatus, obtaining a similar reduction of aspecific probe binding. Overall, substitution of formamide by urea during in situ hybridization offers a safer alternative, potentially of widespread use in research, medical and teaching contexts. We encourage other workers to test this approach on their study organisms, and hope that they will also obtain better sample preservation, more precise expression patterns and fewer problems due to aspecific staining, as we report here for Clytia medusae and Novocrania and Terebratalia developing larvae. Copyright © 2017 Elsevier Inc. All rights reserved.

In situ one-pot preparation of superparamagnetic hydrophilic porous microspheres for covalently immobilizing penicillin G acylase to synthesize amoxicillin

NASA Astrophysics Data System (ADS)

Xue, Ping; Gu, Yaohua; Su, Weiguang; Shuai, Huihui; Wang, Julan

2016-01-01

Magnetic hydrophilic porous microspheres were successfully one-pot synthesized for the first time via in situ inverse suspension polymerization of glycidyl methacrylate, N,N‧-methylene bisacrylamide and 2-hydroxyethyl methacrylate in the presence of Fe3+ and Fe2+ dispersed in formamide, which were denoted as magnetic Fe3O4-GMH microspheres. The morphology and properties of magnetic Fe3O4-GMH microspheres were characterized by SEM, VSM, XRD, FTIR, and so on. The formamide content had an important influence on the morphology of Fe3O4-GMH, and nearly perfectly spherical Fe3O4-GMH particles were formed when the amount of formamide was 15 ml. The diameters of the microspheres were in the range of 100-200 μm and Fe3O4-GMH exhibited superparamagnetic behavior with the saturation magnetization of 5.44 emu/g. The specific surface area of microspheres was 138.7 m2/g, the average pore diameter and pore volume were 15.1 nm and 0.60 cm3/g, respectively. The content of oxirane groups on Fe3O4-GMH was 0.40 mmol/g. After penicillin G acylase (PGA) was covalently immobilized on Fe3O4-GMH microspheres, the catalytic performance for amoxicillin synthesis by 6-aminopenicillanic acid and D-hydroxyphenylglycine methyl ester was largely improved. As a result, 90.1% amoxicillin yield and 1.18 of the synthesis/hydrolysis (S/H) ratio were achieved on PGA/Fe3O4-GMH with ethylene glycol as solvent, but only 62.6% amoxicillin yield and 0.37 of the S/H ratio were obtained on free PGA under the same reaction conditions. Furthermore, the amoxicillin yield and S/H ratio were still kept at 88.2% and 1.06, respectively after the immobilized PGA was magnetically separated and recycled for 10 times, indicating that PGA/Fe3O4-GMH had a very good reusability.

Femtosecond dynamics in hydrogen-bonded solvents

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

Castner, E.W. Jr.; Chang, Y.J.

1993-09-01

We present results on the ultrafast dynamics of pure hydrogen-bonding solvents, obtained using femtosecond Fourier-transform optical-heterodyne-detected, Raman-induced Kerr effect spectroscopy. Solvent systems we have studied include the formamides, water, ethylene glycol, and acetic acid. Inertial and diffusive motions are clearly resolved. We comment on the effect that such ultrafast solvent motions have on chemical reactions in solution.

46 CFR Table I to Part 150 - Alphabetical List of Cargoes

Code of Federal Regulations, 2014 CFR

2014-10-01

... (C17+) alkanoic acid 34 CUS CFT Corn syrup 43 CSY Cottonseed oil, fatty acid 34 CFY Creosote 21 2 CCT... tar 33 COR OCT Coal tar distillate 33 CDL Coal tar, high temperature 33 CHH Coal tar pitch 33 CTP... MTM Formaldehyde solution 19 2 FMS Formamide 10 FAM Formic acid 4 2 FMA Fructose solution 43 Fumaric...

46 CFR Table I to Part 150 - Alphabetical List of Cargoes

Code of Federal Regulations, 2013 CFR

2013-10-01

... (C17+) alkanoic acid 34 CUS CFT Corn syrup 43 CSY Cottonseed oil, fatty acid 34 CFY Creosote 21 2 CCT... tar 33 COR OCT Coal tar distillate 33 CDL Coal tar, high temperature 33 CHH Coal tar pitch 33 CTP... MTM Formaldehyde solution 19 2 FMS Formamide 10 FAM Formic acid 4 2 FMA Fructose solution 43 Fumaric...

46 CFR Table I to Part 150 - Alphabetical List of Cargoes

Code of Federal Regulations, 2010 CFR

2010-10-01

... (C17+) alkanoic acid 34 CUS CFT Corn syrup 43 CSY Cottonseed oil, fatty acid 34 CFY Creosote 21 2 CCT... tar 33 COR OCT Coal tar distillate 33 CDL Coal tar, high temperature 33 CHH Coal tar pitch 33 CTP... MTM Formaldehyde solution 19 2 FMS Formamide 10 FAM Formic acid 4 2 FMA Fructose solution 43 Fumaric...

46 CFR Table I to Part 150 - Alphabetical List of Cargoes

Code of Federal Regulations, 2011 CFR

2011-10-01

... (C17+) alkanoic acid 34 CUS CFT Corn syrup 43 CSY Cottonseed oil, fatty acid 34 CFY Creosote 21 2 CCT... tar 33 COR OCT Coal tar distillate 33 CDL Coal tar, high temperature 33 CHH Coal tar pitch 33 CTP... MTM Formaldehyde solution 19 2 FMS Formamide 10 FAM Formic acid 4 2 FMA Fructose solution 43 Fumaric...

46 CFR Table I to Part 150 - Alphabetical List of Cargoes

Code of Federal Regulations, 2012 CFR

2012-10-01

... (C17+) alkanoic acid 34 CUS CFT Corn syrup 43 CSY Cottonseed oil, fatty acid 34 CFY Creosote 21 2 CCT... tar 33 COR OCT Coal tar distillate 33 CDL Coal tar, high temperature 33 CHH Coal tar pitch 33 CTP... MTM Formaldehyde solution 19 2 FMS Formamide 10 FAM Formic acid 4 2 FMA Fructose solution 43 Fumaric...

Synergistic induction of the heat shock response in Escherichia coli by simultaneous treatment with chemical inducers.

PubMed Central

Van Dyk, T K; Reed, T R; Vollmer, A C; LaRossa, R A

1995-01-01

Escherichia coli strains carrying transcriptional fusions of four sigma 32-controlled E. coli heat shock promoters to luxCDABE or lacZ reporter genes were stressed by chemicals added singly or in pairs. Much more than additive induction resulted from combinations of cadmium chloride, copper sulfate, ethanol, formamide, 4-nitrophenol, and pentachlorophenol. PMID:7592357

Antibacterial Efficacy of Tender Coconut Water (Cocos nucifera L) on Streptococcus mutans: An In-Vitro Study

PubMed Central

Rukmini, J. N.; Manasa, Sunkari; Rohini, Chenna; Sireesha, Lavanya Putchla; Ritu, Sachan; Umashankar, G. K.

2017-01-01

Objective: The antibacterial property of coconut, the presence of lauric acid, and the ability to extract antimicrobial peptides Cn-AMP (1, 2, and 3) from tender coconut water has drawn attention on its effectiveness in normal consumption. An in-vitro experimental study was conducted to evaluate the antimicrobial efficacy of tender coconut water in its natural state on Streptococcus mutans. Materials and Methods: Fresh tender coconut water and pasteurized tender coconut water were taken as test samples, dimethyl formamide was used as the negative control, and 0.2% chlorhexidine was used as the positive control. Pure strain of S. mutans (MTCC 890) was used for determining the antibacterial effects. The test samples along with the controls were subjected to antimicrobial sensitivity test procedure and the zone of inhibition was examined. Kruskal–Wallis test was used to check for any significant differences in the antibacterial efficacy between the samples. Result: There was no zone of inhibition with the tender coconut water, fresh and pasteurised, and negative control (dimethyl formamide). Zone of inhibition was seen in positive control (0.2% Chlorhexidine). Conclusion: No antimicrobial activity was demonstrated with tender coconut water in its normal state (in vitro). PMID:28462183

Antibacterial Efficacy of Tender Coconut Water (Cocos nucifera L) on Streptococcus mutans: An In-Vitro Study.

PubMed

Rukmini, J N; Manasa, Sunkari; Rohini, Chenna; Sireesha, Lavanya Putchla; Ritu, Sachan; Umashankar, G K

2017-01-01

The antibacterial property of coconut, the presence of lauric acid, and the ability to extract antimicrobial peptides Cn-AMP (1, 2, and 3) from tender coconut water has drawn attention on its effectiveness in normal consumption. An in-vitro experimental study was conducted to evaluate the antimicrobial efficacy of tender coconut water in its natural state on Streptococcus mutans . Fresh tender coconut water and pasteurized tender coconut water were taken as test samples, dimethyl formamide was used as the negative control, and 0.2% chlorhexidine was used as the positive control. Pure strain of S. mutans (MTCC 890) was used for determining the antibacterial effects. The test samples along with the controls were subjected to antimicrobial sensitivity test procedure and the zone of inhibition was examined. Kruskal-Wallis test was used to check for any significant differences in the antibacterial efficacy between the samples. There was no zone of inhibition with the tender coconut water, fresh and pasteurised, and negative control (dimethyl formamide). Zone of inhibition was seen in positive control (0.2% Chlorhexidine). No antimicrobial activity was demonstrated with tender coconut water in its normal state ( in vitro ).

Synthesis of ethylene maleic anhydride copolymer containing fungicides and evaluation of their effect for wood decay resistance

Treesearch

George C. Chen

2008-01-01

The aim of the present study was to combat wood decay based on the approach controlled-release biocides from polymers. The possibility of introducing polymer-bonded fungicides into the cell lumens was investigated. The synthesis of ethylene maleic anhydride copolymer containing pentachlorophenol (penta) and 8-hydroxy quinoline (8HQ) in N, N dimethyl formamide is...

Lineage Analysis in Pulmonary Arterial Hypertension

DTIC Science & Technology

2012-06-01

undergo pneunomectomy followed one week later by intravenous injection of monocrotaline pyrrole . The fate of GFP-expressing cells of endothelial lineage...pneumonectomy followed one week later by jugular vein injection of monocrotaline pyrrole in dimethyl formamide. Expression of smooth muscle alpha actin in...cells. We induced experimental pulmonary hypertension in SM22 Cre x mT/mG mice, by injecting monocrotaline pyrrole into the pulmonary circulation of

Formamide and the origin of life

NASA Astrophysics Data System (ADS)

Saladino, Raffaele; Crestini, Claudia; Pino, Samanta; Costanzo, Giovanna; Di Mauro, Ernesto

2012-03-01

The complexity of life boils down to the definition: “self-sustained chemical system capable of undergoing Darwinian evolution” (Joyce, 1994) [1]. The term “self-sustained” implies a set of chemical reactions capable of harnessing energy from the environment, using it to carry out programmed anabolic and catabolic functions. We briefly present our opinion on the general validity of this definition. Running anabolic and catabolic functions entails complex chemical information whose stability, reproducibility and evolution constitute the core of what is dubbed genetics. Life as-we-know-it is made of the intimate interaction of metabolism and genetics, both built around the chemistry of the most common elements of the Universe (hydrogen, oxygen, nitrogen, carbon). Other elements like phosphorus and sulphur play important but ancillary and potentially replaceable roles. The reproducible interaction of metabolic and genetic cycles results in the hypercycles of organization and de-organization of chemical information that we consider living entities. In order to approach the problem of the origin of life it is therefore reasonable to start from the assumption that both metabolism and genetics had a common origin, shared a common chemical frame, were embedded in physical-chemical conditions favourable for the onset of both. The most abundant three-atoms organic compound in interstellar environment is hydrogen cyanide HCN, the most abundant three-atoms inorganic compound is water H2O. The combination of the two results in the formation of formamide H2NCOH. We have explored the chemistry of formamide in conditions compatible with the synthesis and the stability of compounds of potential pre-genetic and pre-metabolic interest. We discuss evidence showing (i) that all the compounds necessary for the build-up of nucleic acids are easily obtained abiotically, (ii) that essentially all the steps leading to the spontaneous generation of RNA are abiotically possible, (iii) that the key compounds of extant metabolic cycles are obtained in the same chemical frame, often in the same test tube. How close are these observations to a plausible scenario for the origin of life?

Mesoporous imine-based organic polymer: catalyst-free synthesis in water and application in CO2 conversion.

PubMed

Yu, Xiaoxiao; Yang, Zhenzhen; Guo, Shien; Liu, Zhenghui; Zhang, Hongye; Yu, Bo; Zhao, Yanfei; Liu, Zhimin

2018-06-22

A mesoporous imine-functionalized organic polymer (Imine-POP) was prepared based on the reaction of an aryl ammonium salt with an aromatic aldehyde in water without any catalyst and template. The Pd coordinated Imine-POP exhibited high catalytic activity for the N-formylation of amines with CO2/H2 at 100 °C, affording a series of formamides in high yields.

Double positive effect of adding hexaethyelene glycol when optimizing the hybridization efficiency of a microring DNA detection assay

NASA Astrophysics Data System (ADS)

Van Eeghem, Anabelle; Werquin, Sam; Hoste, Jan-Willem; Goes, Arne; Vanderleyden, Els; Bienstman, Peter; Dubruel, Peter

2017-05-01

In this paper, a method for detection of DNA molecules using silicon-on-insulator (SOI) microring resonators is described. The influence of temperature and the use of formamide on the hybridization efficiency were studied. It was shown that 50 v/v% of formamide in the hybridization buffer can ensure hybridization when working close to physiological temperature. Furthermore, the use of hexaethylene glycol (HEG) as backfilling agent was studied in order to resolve issues of non-specific adsorption to the surface. The results indicated that not only non-specific binding was reduced significantly but also that HEG improves the orientation of the DNA probes on the surface. This led to a 4-fold increase in hybridization efficiency and thus in an equal decrease in the detection limit, compared to hybridization without the use of HEG. An improvement in robustness of the assay was also observed. This DNA reorientation hypothesis was confirmed by studying the thickness and density of the layers by using dual polarization microring sensing. Finally, the different steps in the sensing experiment were characterized in more detail by static contact angle (SCA) and X-ray photoelectron spectroscopy (XPS) analysis. The results showed quantitatively that the surface modifications were successful.

Dimethyl sulfoxide and dimethyl formamide increase lifespan of C. elegans in liquid.

PubMed

Frankowski, Harald; Alavez, Silvestre; Spilman, Patricia; Mark, Karla A; Nelson, Joel D; Mollahan, Pamela; Rao, Rammohan V; Chen, Sylvia F; Lithgow, Gordon J; Ellerby, H Michael

2013-03-01

Lifespan extension through pharmacological intervention may provide valuable tools to understanding the mechanisms of aging and could uncover new therapeutic approaches for the treatment of age-related disease. Although the nematode Caenorhabditis elegans is well known as a particularly suitable model for genetic manipulations, it has been recently used in a number of pharmacological studies searching for compounds with anti-aging activity. These compound screens are regularly performed in amphipathic solvents like dimethyl sulfoxide (DMSO), the solvent of choice for high-throughput drug screening experiments performed throughout the world. In this work, we report that exposing C. elegans to DMSO in liquid extends lifespan up to 20%. Interestingly, another popular amphipathic solvent, dimethyl formamide (DMF), produces a robust 50% increase in lifespan. These compounds work through a mechanism independent of insulin-like signaling and dietary restriction (DR). Additionally, the mechanism does not involve an increased resistance to free radicals or heat shock suggesting that stress resistance does not play a major role in the lifespan extension elicited by these compounds. Interestingly, we found that DMSO and DMF are able to decrease the paralysis associated with amyloid-β3-42 aggregation, suggesting a role of protein homeostasis for the mechanism elicited by these molecules to increase lifespan. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Computational study of the process of hydrogen bond breaking: the case of the formamide-formic acid complex.

PubMed

Pacios, Luis F

2006-11-15

MP2/6-311++G(d,p) and B3LYP/6-311++G(d,p) quantum calculations are used to study the formamide-formic acid complex (FFAC), a system bound by two hydrogen bonds, N--H...O and O--H...O, that forms a bond ring at equilibrium. When the intermolecular separation between monomers R increases, this ring opens at a distance for which the weaker N--H...O bond breaks remaining the stronger O--H...O bond. The computational study characterizes that process addressing changes of interaction energy DeltaE, structure and properties of the electron density rho(r) as well as spatial distributions of rho(r), the electrostatic potential U(r), and the electron localization function eta(r). It is shown that the spatial derivatives of DeltaE, the topology of rho(r), and qualitative changes noticed in U(r) = 0 isocontours allow to identify a precise distance R for which one can say the N--H...O hydrogen bond has broken. Both levels of theory predict essentially the same changes of structure and electron properties associated to the process of breaking and virtually identical distances at which it takes place. (c) 2006 Wiley Periodicals, Inc. J Comput Chem, 2006.

Optimization of RT-PCR reactions in studies with genes of lignin biosynthetic route in Saccharum spontaneum.

PubMed

Llerena, Juan P P; Araújo, Pedro; Mazzafera, Paulo

2018-01-01

Saccharum spontaneum has been used for the development of energy cane a crop aimed to be used for the production of second-generation ethanol, or lignocellulosic ethanol. Lignin is a main challenge in the conversion of cell wall sugars into ethanol. In our studies to isolate the genes the lignin biosynthesis in S. spontaneum we have had great difficulty in RT-PCR reactions. Thus, we evaluated the effectiveness of different additives in the amplification of these genes. While COMT and CCoAOMT genes did not need any additives for other genes there was no amplification (HCT, F5H, 4CL and CCR) or the yield was very low (CAD and C4H). The application of supplementary cDNA was enough to overcome the non-specificity and low yield for C4H and C3H, while the addition of 0.04% BSA + 2% formamide was effective to amplify 4CL, CCR, F5H and CCR. HCT was amplified only by addition of 0.04% BSA + 2% formamide + 0.1 M trehalose and amplification of PAL was possible with addition of 2% of DMSO. Besides optimization of expression assays, the results show that additives can act independently or synergistically.

Abundance of complex organic molecules in comets

NASA Astrophysics Data System (ADS)

Biver, N.; Bockelée-Morvan, D.; Debout, V.; Crovisier, J.; Moreno, R.; Boissier, J.; Lis, D.; Colom, P.; Paubert, G.; Dello Russo, N.; Vervack, R.; Weaver, H.

2014-07-01

The IRAM-30m submillimetre radio telescope has now an improved sensitivity and versality thanks to its wide-band EMIR receivers and high-resolution FFT spectrometer. Since 2012, we have undertaken ~70 GHz wide spectral surveys in the 1-mm band in several comets: C/2009 P1 (Garradd), C/2011 L4 (PanSTARRS), C/2012 F6 (Lemmon), C/2012 S1 (ISON), and C/2013 R1 (Lovejoy). Since their discovery in comet C/1995 O1 (Hale-Bopp) in 1997 (Bockelée-Morvan et al. 2000, Crovisier et al. 2004a, 2004b), we have detected complex CHO(N)-molecules such as formic acid (HCOOH), formamide (NH_2CHO), acetaldehyde (CH_3CHO), and ethylene glycol ((CH_2OH)_2) in several other comets. HCOOH has now been detected in 6 other comets since 2004, and formamide, ethylene glycol, and acetaldehyde were re-detected for the first time in comets Lemmon or Lovejoy in 2013 (Biver et al. 2014). We will present the abundances relative to water we derive for these species, and the sensitive upper limits we obtain for other complex CHO-bearing molecules. We will discuss the implication of these findings on the origin of cometary material in comparison with observations of such molecules in the interstellar medium.

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.

A Theoretical Study of the Mechanism of the Alkylation of Guanine by N- Nitroso Compounds.

DTIC Science & Technology

1992-01-01

Later, Loveless isolated an 0 6 - methylated product from treatment with MNU and was the first to suggest a relevance of O6 alkylation 11 to the...replication. The ultimate metabolite involved in the alkylation reaction has generally been thought to be an alkyldiazonium ion or, its decomposition... Methylation of Formamide by the Methyldiazonium Ion .................... 60 Table 3.10: Intrinsic Barriers for Degenerate SN 2 Reactions .......... 66 Table

Synthesis and evaluation of aminoborates derived from boric acid and diols for protecting wood against fungal and thermal degradation

Treesearch

George C. Chen

2008-01-01

N-methyl amino catechol borate (1), N-methyl amino-4-methyl catechol borate (2), N-methyl amino-4-t-butyl catechol borate (3), and N-methyl amino-2, 3-naphthyl borate (4) were synthesized by reflux of boric acid with a diol in solvent N,N-dimethyl formamide. The aminoborates were characterized by proton nuclear magnetic resonance spectroscopy, FTIR spectroscopy and...

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.

Chemical and Photochemical Reactivity in Microemulsions and Waterless Microemulsions.

DTIC Science & Technology

1988-02-10

virtually the same as that found in the alcohol rich microemulsion A. This value is also close to that found in pure butanol (= 5.0 - table I). It would...formamide or alcohol rich). RESEARCH PATTERN -Supplementing the physical chemical study of the microemulsion medium involving ionic surfactants with density...SAMII (1/02/1988) Ii&N 3 Part II - OXYDATIONS BY HYDROPEROXIDES IN MICROEMULSIONS E. OLIVEROS and M.T. MAURETTE During the past six months, the financial

METAL PHTHALOCYANINES

DOEpatents

Frigerio, N.A.

1962-03-27

A process is given for preparing heavy metal phthalocyanines, sulfonated or not. The process comprises mixing an inorganic metal salt with dimethyl formamide or methyl sulfoxide; separating the metal complex formed from the solution; mixing the complex with an equimolar amount of sodium, potassium, lithium, magnesium, or beryllium sulfonated or unsulfonated phthalocyanine whereby heavy-metal phthalocyanine crystals are formed; and separating the crystals from the solution. Uranyl, thorium, lead, hafnium, and lanthanide rare earth phthalocyanines can be produced by the process. (AEC)

Barbier Continuous Flow Preparation and Reactions of Carbamoyllithiums for Nucleophilic Amidation.

PubMed

Ganiek, Maximilian A; Becker, Matthias R; Berionni, Guillaume; Zipse, Hendrik; Knochel, Paul

2017-08-01

An ambient temperature continuous flow method for nucleophilic amidation and thioamidation is described. Deprotonation of formamides by lithium diisopropylamine (LDA) affords carbamoyllithium intermediates that are quenched in situ with various electrophiles such as ketones, allyl bromides, Weinreb and morpholino amides. The nature of the reactive lithium intermediates and the thermodynamics of the metalation were further investigated by ab initio calculations and kinetic experiments. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Density functional theory study on the ionization potentials and electron affinities of thymine-formamide complexes

NASA Astrophysics Data System (ADS)

Sun, Haitao; Tang, Ke; Li, Yanmin; Su, Chunfang; Zhou, Zhengyu; Wang, Zhizhong

The effect of hydrogen bond interactions on ionization potentials (IPs) and electron affinities (EAs) of thymine-formamide complexes (T-F) have been investigated employing the density functional theory B3LYP at 6-311++G(d, p) basis set level. All complexes experience a geometrical change on either electron detachment or attachment, and the change might be facilitated or hindered according to the strength of the hydrogen-bonding interaction involved. The strength of hydrogen bonds presents an opposite changing trend on the two processes. A more important role that H-bonding interaction plays in the process of electron attachment than in the process of electron detachment can be seen by a comparison of the IPs and EAs of complexes with that of isolated thymine. Futhermore, the EAs of isolated thymine are in good agreement with the experimental values (AEA is 0.79 eV, VEA is -0.29 eV [Wetmore et al., Chem Phys Lett 2000, 322, 129]). The calculated total NPA charge distributions reveal that nearly all the negative charges locate on thymine monomer in the anions and even in the cationic states, there are a few negative charges on thymine monomer. An analysis of dissociation energies predicts the processes T-F+→ T++ F and T-F- → T- + F to be the most energetically favorable for T-F+ and T-F-, respectively. Content:text/plain; charset="UTF-8"

Reactions of the melatonin metabolite N(1)-acetyl-5-methoxykynuramine with carbamoyl phosphate and related compounds.

PubMed

Kuesel, Jana T; Hardeland, Rüdiger; Pfoertner, Henrike; Aeckerle, Nelia

2010-01-01

N-[2-(6-methoxyquinazolin-4-yl)-ethyl] acetamide (MQA) is a compound formed from the melatonin metabolite N(1)-acetyl-5-methoxykynuramine (AMK). We followed MQA production in reaction systems containing various putative reaction partners, in the absence and presence of hydrogen peroxide and/or copper(II). Although MQA may be formally described as a condensation product of either N(1)-acetyl-N(2)-formyl-5-methoxykynuramine (AFMK) with ammonia, or AMK with formamide, none of these combinations led to substantial quantities of MQA. However, MQA formation was observed in mixtures containing AMK, hydrogen peroxide, hydrogen carbonate and ammonia, or AMK, hydrogen peroxide, copper(II) and potentially carbamoylating agents, such as potassium cyanate or, more efficiently, carbamoyl phosphate. In the presence of hydrogen peroxide, copper(II) and carbamoyl phosphate, MQA was the major product obtained from AMK, but the omission of copper(II) mainly led to another metabolite, 3-acetamidomethyl-6-methoxycinnolinone (AMMC). This was caused by nitric oxide (NO) generated under oxidative conditions from carbamoyl phosphate, as shown by an NO spin trap. MQA formation with carbamoyl phosphate was not due to the possible decomposition product, formamide. The reaction of AMK with carbamoyl phosphate under oxidative conditions, in which inorganic phosphate and water are released and which differs from the typical process of carbamoylation via isocyanate, may be considered as a new physiological route of MQA formation.

Amide-Catalyzed Phase-Selective Crystallization Reduces Defect Density in Wide-Bandgap Perovskites.

PubMed

Kim, Junghwan; Saidaminov, Makhsud I; Tan, Hairen; Zhao, Yicheng; Kim, Younghoon; Choi, Jongmin; Jo, Jea Woong; Fan, James; Quintero-Bermudez, Rafael; Yang, Zhenyu; Quan, Li Na; Wei, Mingyang; Voznyy, Oleksandr; Sargent, Edward H

2018-03-01

Wide-bandgap (WBG) formamidinium-cesium (FA-Cs) lead iodide-bromide mixed perovskites are promising materials for front cells well-matched with crystalline silicon to form tandem solar cells. They offer avenues to augment the performance of widely deployed commercial solar cells. However, phase instability, high open-circuit voltage (V oc ) deficit, and large hysteresis limit this otherwise promising technology. Here, by controlling the crystallization of FA-Cs WBG perovskite with the aid of a formamide cosolvent, light-induced phase segregation and hysteresis in perovskite solar cells are suppressed. The highly polar solvent additive formamide induces direct formation of the black perovskite phase, bypassing the yellow phases, thereby reducing the density of defects in films. As a result, the optimized WBG perovskite solar cells (PSCs) (E g ≈ 1.75 eV) exhibit a high V oc of 1.23 V, reduced hysteresis, and a power conversion efficiency (PCE) of 17.8%. A PCE of 15.2% on 1.1 cm 2 solar cells, the highest among the reported efficiencies for large-area PSCs having this bandgap is also demonstrated. These perovskites show excellent phase stability and thermal stability, as well as long-term air stability. They maintain ≈95% of their initial PCE after 1300 h of storage in dry air without encapsulation. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Layered zinc hydroxide salts: delamination, preferred orientation of hydroxide lamellae, and formation of ZnO nanodiscs.

PubMed

Demel, Jan; Pleštil, Josef; Bezdička, Petr; Janda, Pavel; Klementová, Mariana; Lang, Kamil

2011-08-15

Delamination of layered zinc hydroxide salts (LZH) into hydroxide layers provides nanobuilding blocs of a two-dimensional anisotropy. The methodology, extent of delamination, the size and stability of hydroxide lamellae are described in detail. The ability of lamellae to restack to form oriented hydroxide films depends on the solvent, original LZH salt, and conditions used for delamination. The most interesting results were obtained using LZH intercalated with dodecyl sulfate anions and LZH nitrate delaminated in butanol at 60 °C and in formamide at room temperature, respectively. The former method produces hydroxide lamellae of a lateral size of ca. 10-20 nm. The inner structure of the hydroxide layers is conserved and separated lamellae restack to the original layered structure of LZH dodecyl sulfate. The latter method yields lamellae with a size decreasing from 73.3 nm to 10 nm after a 2-week aging, while their thickness is nearly constant (2.6-3.8 nm). However, the use of formamide is complicated by the formation of Zn(II) formate. The major part of LZH intercalated with dodecyl sulfate anions is transformed during the delamination procedure to anisotropic ZnO nanoparticles, either needle-like particles prolonged in the [0 0 1] direction or disc-like particles flattened along the (0 0 1) plane. Copyright © 2011 Elsevier Inc. All rights reserved.

Thermally stable booster explosive and process for manufacture

DOEpatents

Quinlin, William T [Amarillo, TX; Thorpe, Raymond [Amarillo, TX; Lightfoot, James M [Amarillo, TX

2006-03-21

A thermally stable booster explosive and process for the manufacture of the explosive. The product explosive is 2,4,7,9-tetranitro-10H-benzo[4,5]furo[3,2-b]indole (TNBFI). A reactant/solvent such as n-methylpyrrolidone (NMP) or dimethyl formamide (DMF) is made slightly basic. The solution is heated to reduce the water content. The solution is cooled and hexanitrostilbene is added. The solution is heated to a predetermined temperature for a specific time period, cooled, and the product is collected by filtration.

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

Synthesis and evaluation of borates derived from boric acid and diols for the protection of wood against fungal decay and thermal degradation

Treesearch

George C. Chen

2004-01-01

N,N-dimethyl amino carbinol catechol borate(1). N,N-dimethyl amino carbinol-4-methyl catechol borate(2), N,N-dimethyl amino carbinol-4-t- butyl catechol borate(3). N,N-dimethyl amino carbinol-2,3-naphthyl borate 4) were synthesized by refluxing boric acid and diol in DMF(N,N-dimethyl formamide). The borates were characterized by NMR. Wood impregnated with borate 1,2 or...

AFOSR (Air Force Office of Scientific Research) Chemical & Atmospheric Sciences Program Review (28th).

DTIC Science & Technology

1983-06-01

the study of " hydrothermal " reaction of gels as the minimum energy route to ceramic consolidation. Ultra Low Thermal Expansion Ceramics - Dr. H. A...requirements can be accommodated. A series of OCCA’s, in particular, formamide and oxalic acid, and their use in making 100% S102, alkali-silicates, alkali...IIIB glass surface was proposed. The mechanisms of hydrothermal attach of two phase lithia-silicate glass-ceramics were identified and related to the

Transport characteristics of urea transporter-B.

PubMed

Yang, Baoxue

2014-01-01

UT-B represents the major urea transporter in erythrocytes, in addition to being expressed in kidney descending vasa recta, brain, spleen, ureter, bladder, and testis. Expression of urea transporter UT-B confers high urea permeability to mammalian erythrocytes. Erythrocyte membranes are also permeable to various urea analogues, suggesting common transport pathways for urea and structurally similar solutes. UT-B is highly permeable to urea and the chemical analogues formamide, acetamide, methylurea, methylformamide, ammonium carbamate, and acrylamide, each with a Ps > 5.0 × 10(-6) cm/s at 10 °C. The amides formamide, acetamide, acrylamide, and butyramide efficiently diffuse across lipid bilayers. The urea analogues dimethylurea, acryalmide, methylurea, thiourea, and methylformamide inhibit UT-B-mediated urea transport by >60 % by a pore-blocking mechanism. UT-B is also a water channel in erythrocytes and has a single-channel water permeability that is similar to aquaporin-1. Whether UT-B is an NH3 channel still needs further study. Urea permeability (Purea) in erythrocytes differs between different mammals. Carnivores (dog, fox, cat) exhibit high Purea. In contrast, herbivores (cow, donkey, sheep) show much lower Purea. Erythrocyte Purea in human and pig (omnivores) was intermediate. Rodents and lagomorphs (mouse, rat, rabbit) have Purea intermediate between carnivores and omnivores. Birds that do not excrete urea and do not express UT-B in their erythrocytes have very low values. In contrast to Purea, water permeability is relatively similar in all mammals studied. This chapter will provide information about the transporter characteristics of UT-B.

Cyanide Degradation under Alkaline Conditions by a Strain of Fusarium solani Isolated from Contaminated Soils

PubMed Central

Dumestre, A.; Chone, T.; Portal, J.; Gerard, M.; Berthelin, J.

1997-01-01

Several cyanide-tolerant microorganisms have been selected from alkaline wastes and soils contaminated with cyanide. Among them, a fungus identified as Fusarium solani IHEM 8026 shows a good potential for cyanide biodegradation under alkaline conditions (pH 9.2 to 10.7). Results of K(sup14)CN biodegradation studies show that fungal metabolism seems to proceed by a two-step hydrolytic mechanism: (i) the first reaction involves the conversion of cyanide to formamide by a cyanide-hydrolyzing enzyme, cyanide hydratase (EC 4.2.1.66); and (ii) the second reaction consists of the conversion of formamide to formate, which is associated with fungal growth. No growth occurred during the first step of cyanide degradation, suggesting that cyanide is toxic to some degree even in cyanide-degrading microorganisms, such as F. solani. The presence of organic nutrients in the medium has a major influence on the occurrence of the second step. Addition of small amounts of yeast extract led to fungal growth, whereas no growth was observed in media containing cyanide as the sole source of carbon and nitrogen. The simple hydrolytic detoxification pathway identified in the present study could be used for the treatment of many industrial alkaline effluents and wastes containing free cyanide without a prior acidification step, thus limiting the risk of cyanhydric acid volatilization; this should be of great interest from an environmental and health point of view. PMID:16535647

Hemin-utilizing G-quadruplex DNAzymes are strongly active in organic co-solvents.

PubMed

Canale, Thomas D; Sen, Dipankar

2017-05-01

The widespread use of organic solvents in industrial processes has focused in recent years on the utility of "green" solvents - those with less harmful environmental, health, and safety properties - such as methanol and formamide. However, protein enzymes, regarded as green catalysts, are often incompatible with organic solvents. Herein, we have explored the oxidative properties of a Fe(III)-heme, or hemin, utilizing catalytic DNA (heme·DNAzyme) in different green solvent-water mixtures. We find that the peroxidase and peroxygenase activities of the heme·DNAzyme are strongly enhanced in 20-30% v/v methanol or formamide, relative to water alone. Protic solvent content of >30% v/v gradually diminishes heme·DNAzyme catalytic activity; however, the heme·DNAzyme is still active in as high as 80% v/v methanol. In contrast to protic solvents, aqueous dimethylformamide solutions largely inhibit heme·DNAzyme activity. In view of the strong catalytic activity of heme·DNAzyme in aqueous methanol, we were able to determine that a 60% v/v methanol-water mixture gives the most optimal yield of the dibenzothiophene sulfoxide (DBTO) oxidation product of petroleum-derived dibenzothiophene (DBT). The high product yield reflects both DNAzyme catalysis and a high substrate availability. Overall, these results emphasize the excellent promise of G-quadruplex forming DNA catalysts in application to "greener" industrial chemistry. This article is part of a Special Issue entitled "G-quadruplex" Guest Editor: Dr. Concetta Giancola and Dr. Daniela Montesarchio. Copyright © 2016 Elsevier B.V. All rights reserved.

Interaction of Metal Oxides with Biomolecules: Implication in Astrobiology

NASA Astrophysics Data System (ADS)

Kamaluddin; Iqubal, Md. Asif

2014-08-01

Steps of chemical evolution have been designated as formation of biomonomers followed by their polymerization and then to modify in an organized structure leading to the formation of first living cell. Polymerization of biomonomers could have required some catalyst. In addition to clay, role of metal ions and metal complexes as prebiotic catalyst in the synthesis and polymerization of biomonomers cannot be ruled out. Metal oxides are important constituents of Earth crust and that of other planets. These oxides might have adsorbed organic molecules and catalyzed the condensation processes, which may have led to the formation of first living cell. Different studies were performed in order to investigate the role of metal oxides (especially oxides of iron and manganese) in chemical evolution. Iron oxides (goethite, akaganeite and hematite) as well as manganese oxides (MnO, Mn2O3, Mn3O4 and MnO2) were synthesized and their characterization was done using IR, powder XRD, FE-SEM and TEM. Role of above oxides was studied in the adsorption of ribose nucleotides, formation of nucleobases from formamide and oligomerization of amino acids. Above oxides of iron and manganese were found to have good adsorption affinity towards ribose nucleotides, high catalytic activity in the formation of several nucleobases from formamide and oligomerization of glycine and alanine. Characterization of products was performed using UV, IR, HPLC and ESI-MS techniques. Presence of hematite-water system on Mars has been suggested to be a positive indicator in the chemical evolution on Mars.

Penning ionization and ion fragmentation of formamide HCONH2 by He∗, Ne∗, and Ar∗ in molecular beams

NASA Astrophysics Data System (ADS)

Madison, Tamika A.; Siska, P. E.

2009-10-01

Mass spectra from Penning ionization by metastable atom bombardment (MAB) in the title system at kinetic energies near 1 kcal/mol are reported. The experiments employ a supersonic excited noble gas beam crossing an effusive beam of formamide vapor. Product ions are extracted perpendicular to the plane of the beams, analyzed by a quadrupole mass filter, and counted by a scintillation-type ion counter. Relative to 70 eV electron impact, the He∗ and Ne∗ spectra show more extensive breakage of C-N and C-H bonds despite the smaller available energy, while the Ar∗ spectrum shows only the molecular ion (m /z 45), H atom elimination (44), and the decarbonylation products CO+NH3+ (17). Fragmentation in the latter system has been analyzed using a combination of ab initio calculations and Rice-Ramsperger-Kassel-Marcus theory with tunneling correction; good agreement with the experimental 45/44/17 intensity ratio 100/6.8±0.7/6.2±1.7 is obtained. 15% of m/z 17 and 50% of m /z 44 is attributed to tunneling. The ab initio decarbonylation reaction path yields a hydrogen bonded H2N-HCO+ transition state, which transfers a proton while proceeding downhill to the observed products, while both the path and the energetics support the earlier conclusion that the lowest lying electronically excited state of the ion (2π or 2a″) crosses the ground state early along the reaction path, thereby dominating the dynamics of decarbonylation.

Computer-aided rational design of novel EBF analogues with an aromatic ring.

PubMed

Wang, Shanshan; Sun, Yufeng; Du, Shaoqing; Qin, Yaoguo; Duan, Hongxia; Yang, Xinling

2016-06-01

Odorant binding proteins (OBPs) are important in insect olfactory recognition. These proteins bind specifically to insect semiochemicals and induce their seeking, mating, and alarm behaviors. Molecular docking and molecular dynamics simulations were performed to provide computational insight into the interaction mode between AgamOBP7 and novel (E)-β-farnesene (EBF) analogues with an aromatic ring. The ligand-binding cavity in OBP7 was found to be mostly hydrophobic due to the presence of several nonpolar residues. The interactions between the EBF analogues and the hydrophobic residues in the binding cavity increased in strength as the distance between them decreased. The EBF analogues with an N-methyl formamide or ester linkage had higher docking scores than those with an amide linkage. Moreover, delocalized π-π and electrostatic interactions were found to contribute significantly to the binding between the ligand benzene ring and nearby protein residues. To design new compounds with higher activity, four EBF analogues D1-D4 with a benzene ring were synthesized and evaluated based on their docking scores and binding affinities. D2, which had an N-methyl formamide group linkage, exhibited stronger binding than D1, which had an amide linkage. D4 exhibited particularly strong binding due to multiple hydrophobic interactions with the protein. This study provides crucial foundations for designing novel EBF analogues based on the OBP structure. Graphical abstract The design strategy of new EBF analogues based on the OBP7 structure.

Theoretical insight into the solvent effect of H2O and formamide on the cooperativity effect in HMX complex.

PubMed

Meng, Rui-Hong; Cao, Xiong; Hu, Shuang-Qi; Hu, Li-Shuang

2017-08-01

The cooperativity effects of the H-bonding interactions in HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane)∙∙∙HMX∙∙∙FA (formamide), HMX∙∙∙HMX∙∙∙H 2 O and HMX∙∙∙HMX∙∙∙HMX complexes involving the chair and chair-chair HMX are investigated by using the ONIOM2 (CAM-B3LYP/6-31++G(d,p):PM3) and ONIOM2 (M06-2X/6-31++G(d,p):PM3) methods. The solvent effect of FA or H 2 O on the cooperativity effect in HMX∙∙∙HMX∙∙∙HMX are evaluated by the integral equation formalism polarized continuum model. The results show that the cooperativity and anti-cooperativity effects are not notable in all the systems. Although the effect of solvation on the binding energy of ternary system HMX∙∙∙HMX∙∙∙HMX is not large, that on the cooperativity of H-bonds is notable, which leads to the mutually strengthened H-bonding interaction in solution. This is perhaps the reason for the formation of different conformation of HMX in different solvent. Surface electrostatic potential and reduced density gradient are used to reveal the nature of the solvent effect on cooperativity effect in HMX∙∙∙HMX∙∙∙HMX. Graphical abstract RDG isosurface and electrostatic potential surface of HMX∙∙∙HMX∙∙∙HMX.

Transport of water in proximal kidney tubules from whole tubules to single channels: length and section of the selectivity filter of aquaporin-1.

PubMed

Whittembury, G; González, E; Hernández, C S; Gutiérrez, A M; Echevarría, M

1997-06-27

Proximal straight tubule (PST) were dissected from rabbit kidneys, held with crimping pipettes in a chamber bathed in a buffered mannitol isosmotic solution (MBS, 295 mOsm/kg). Tubule cell volume changes with time (dV/Adt) after steps in MBS osmolality (delta Cs) were monitored on line with an inverted microscope, a TV camera and an image processor. Reflection coefficients sigma and osmotic permeability coefficients, Pos, for several solutes were measured using two methods. Method 1: sigma was calculated from the delta Csiso of impermeant and permeant solutes at which (dV/Adt)t-->0 = 0 (i.e., by a null point method). It is denoted as sigma 1. sigma 1 = 1.00 for mannitol (M), raffinose (R), sucrose (S), glycerol (G), acetamide (A) and urea (U). With formamide (F), sigma 1, Formamide = 0.62 +/- 0.05. These findings confirm our previous value of dp = 4.5 A for the diameter of the selectivity filter of the basolateral PST cell membrane water channel AQP1. Method 2: PST were exposed for 20 s to MBS made hyperosmotic by addition of a delta Cs of 35 mOsm/kg of R, S, M, G, A and U. Cells shrunk within 500 ms of t = 0 to their osmometric volume and remained shrunk for the 20 s of the osmotic challenge. Pos was measured from the shrinking curves. P(os) = 3000 +/- 25 microns/s with R, S, M, G, A and U. Method 2 also allowed to calculate sigma, denoted as sigma 2. sigma 2 = 1.00 for R, S, M, G, A and U. By contrast, the shrinking curve produced by a delta Cs of 35 mOsm/kg F was 1/5th to 1/6th slower and smaller (i.e., subosmometric) than that produced by a delta Cs of 35 mOsm/kg R, S, M, G, A and U. Furthermore, with F cells did not remain shrunk but recovered their original volume within 3 s. P(os) (measured with F) is denoted as P(os)*, P(os)* = 480 +/- 30 microns/s. sigma 2, Formamide = 0.16 +/- 0.01. Use of sigma 1, sigma 2 and P(os)* values in Hill's equations for the bimodal theory of osmosis leads to n = 2-9. Where n is the number of water molecules single filling within the channel selectivity filter, whose length must lie within 6 to 27 A, a value significantly lower than our previous value calculated from the P(os)/Pd* ratio.

Reliability of high strain ionomeric polymer transducers fabricated using the direct assembly process

NASA Astrophysics Data System (ADS)

Akle, Barbar; Nawshin, Saila; Leo, Donald

2007-04-01

Ionomeric polymer transducers have received considerable attention in the past several years. These actuators, sometimes referred to as artificial muscles, have the ability to generate large bending strain and moderate stress at low applied voltages. As sensors, ionic polymer transducers generate an electric response due to mechanical strain. Typically, ionic polymer transducers are composed of Nafion-117 membranes with platinum electrodes and are saturated with water diluents. Recently the authors have developed a novel fabrication technique called the direct assembly process (DAP), which allowed improved control of the electrode morphology and composition. The DAP consists of spraying two high surface area metal-ionomer electrodes on a Nafion membrane. The benefits of the DAP process over previous methods is the ability to control the thickness of the electrode, the ability to control the composition of the electrode layer of the transducer, and the ability for it to be used with a wide variety of diluents. In past work we have demonstrated that platinum, ruthenium dioxide, and single-walled carbon nanotubes can be used as electrode material with diluents such as water, formamide, and ionic liquids. In this work we will present a reliability study of transducers fabricated using the DAP. Water-hydrated transducers dehydrate and stop moving within 5 min while operating in air under the application of ± 2 V. Ionic liquid based transducers are demonstrated to operate in air for over 400 000 cycles with little loss in performance, and are reliable up to 1 million cycles with a performance loss of less than 43%. The main source of degradation is the adhesion of the conductive surface to the high surface area electrode. This is enhanced in this study by using a PUU linking polymer that has good adhesion properties to gold. Large voltage and large strain are proven to decrease the life of the transducer. Formamide based samples are stable for 3 days under a 1 V actuation signal, while they are only reliable for 3-4 h under a 2 V actuation signal. Solvent evaporation is the main reason for degradation in formamide samples and it is increased at 2 V, indicating some electrochemical activity at such high voltages. Finally the initial drop in performance and the fluctuation in the generated strain are shown to be due to the loss of humidity absorbed from ambient air and the fluctuation in this ambient humidity, respectively.

Generation of RNA in abiotic conditions.

NASA Astrophysics Data System (ADS)

di Mauro, Ernesto

Generation of RNA in abiotic conditions. Ernesto Di Mauro Dipartimento di Genetica Bi-ologia Molecolare, Universit` "Sapienza" Roma, Italy. a At least four conditions must be satisfied for the spontaneous generation of (pre)-genetic poly-mers: 1) availability of precursors that are activated enough to spontaneously polymerize. Preliminary studies showed that (a) nucleic bases and acyclonucleosides can be synthesized from formamide H2NCOH by simply heating with prebiotically available mineral catalysts [last reviewed in (1)], and that b) nucleic bases can be phosphorylated in every possible posi-tion [2'; 3'; 5'; cyclic 2',3'; cyclic 3',5' (2)]. The higher stability of the cyclic forms allows their accumulation. 2) A polymerization mechanism. A reaction showing the formation of RNA polymers starting from prebiotically plausible precursors (3',5' cyclic GMP and 3', 5'cyclic AMP) was recently reported (3). Polymerization in these conditions is thermodynamically up-hill and an equilibrium is attained that limits the maximum length of the polymer produced to about 40 nucleotides for polyG and 100 nucleotides for polyA. 3) Ligation of the synthesized oligomers. If this type of reaction could occur according to a terminal-joining mechanism and could generate canonical 3',5' phosphodiester bonds, exponential growth would be obtained of the generated oligomers. This type of reaction has been reported (4) , limited to homogeneous polyA sequences and leading to the production of polyA dimers and tetramers. What is still missing are: 4) mechanisms that provide the proof of principle for the generation of sequence complexity. We will show evidence for two mechanisms providing this proof of principle for simple complementary sequences. Namely: abiotic sequence complementary-driven terminal ligation and sequence-complementary terminal growth. In conclusion: all the steps leading to the generation of RNA in abiotic conditions are satisfied. (1) R Saladino, C Crestini, F. Ciciriello, S. Pino, G. Costanzo, E. Di Mauro. From formamide to RNA: the roles of formamide and water in the evolution of chemical information. Research In Microbiology, Special Issue on The Origin of life and Microbiology (2009) 160:441-448. (2) Costanzo, G., Saladino, R., Crestini, C., Ciciriello, F., and Di Mauro, E. Nucleoside phos-phorylation by phosphate minerals. J. Biol. Chem. (2007) 282: 16729-16735. (3) Samanta Pino, Fabiana Ciciriello, Giovanna Costanzo and E. Di Mauro, Nonenzymatic RNA Ligation in Water J. Biol. Chem. (2008), 283: 36494-36503 (4) Costanzo, G., Pino, S., Ciciriello, F., and Di Mauro, E. Generation of long RNA chains in water. J Biol Chem. (2009) 284:33206-33216.

Nucleoside phosphorylation in amide solutions

NASA Technical Reports Server (NTRS)

Schoffstall, A. M.; Kokko, B.

1978-01-01

The paper deals with phosphorylation in possible prebiotic nonaqueous solvents. To this end, phosphorylation of nucleosides using inorganic phosphates in amide solutions is studied at room and elevated temperatures. Reaction proceeds most readily in formamide and N-methylformamide. Products obtained at elevated temperature are nucleotides, nucleoside 2',3'-cyclic phosphates, and when the phosphate concentration is high, nucleoside diphosphates. At room temperature, adenosine afforded a mixture of nucleotides, but none of the cyclic nucleotide. Conditions leading to the highest relative percentage of cyclic nucleotide involve the use of low concentrations of phosphate and an excess of nucleoside.

VizieR Online Data Catalog: C/2012 F6 (Lemmon) and C/2013 R1 (Lovejoy) spectra (Biver+, 2014)

NASA Astrophysics Data System (ADS)

Biver, N.; Bockelee-Morvan, D.; Debout, V.; Crovisier, J.; Boissier, J.; Lis, D. C.; Dello Russo, N.; Moreno, R.; Colom, P.; Paubert, G.; Vervack, R.; Weaver, H. A.

2014-06-01

Sum spectra of the lines of formamide and ethylene-glycol which intensities are listed in Tables 4 and 5. One fits file per spectrum, fits output from class (http://www.iram.fr/IRAMFR/GILDAS/). object.dat : -------------------------------------------------------------------------------- Code Name Elem q e i H1 d AU deg mag -------------------------------------------------------------------------------- C/2012 F6 Lemmon 2456375.5 0.7312461 0.9985125 82.607966 7.96 C/2013 R1 Lovejoy 2456651.5 0.8118182 0.9983297 64.040457 11.66 (2 data files).

The Shiga and Shiga-Like Cytotoxins: Gene Regulation and Functional Analysis of the Binding Subunits

DTIC Science & Technology

1989-05-05

SLT-I and SLT-II operons, designated slt-I and slt-II respectively, have been cloned from toxin-converting coliphage (Newland et al. 1985; Willshaw...The plasmid bands were removed through the sides of the tubes with a 20-gauge needle, the EtBr was extracted with water -saturated butanol, and the...pBluescript vectors were spread on LB agar plates with 50 ~1 Bluo-gal (BRL; 2% in dimethyl formamide) and 25 ~1 IPTG (BRL; lOOmM in water ) on LB agar

Diaminophosphine oxide ligand enabled asymmetric nickel-catalyzed hydrocarbamoylations of alkenes.

PubMed

Donets, Pavel A; Cramer, Nicolai

2013-08-14

Chiral trivalent phosphorus species are the dominant class of ligands and the key controlling element in asymmetric homogeneous transition-metal catalysis. Here, novel chiral diaminophosphine oxide ligands are described. The arising catalyst system with nickel(0) and trimethylaluminum efficiently activates formamide C-H bonds under mild conditions providing pyrrolidones via intramolecular hydrocarbamoylation in a highly enantioselective manner with as little as 0.25% mol catalyst loading. Mechanistically, the secondary phosphine oxides behave as bridging ligands for the nickel center and the Lewis acidic organoaluminum center to give a heterobimetallic catalyst with superior reactivity.

Poly[[tetra-μ-cyanido-κ8 C:N-dodeca-cyanido-κ12 C-tris­(N,N-di­methyl­formamide-κO)tris­(methanol-κO)tris­(3,4,7,8-tetra­methyl-1,10-phenanthroline-κ2 N,N′)trimanganese(II)ditungstate(V)] dihydrate

PubMed Central

Yang, Fei-Lin; Yang, Dan

2014-01-01

The asymmetric unit of the title compound, {[Mn3{W(CN)8}2(C16H16N2)3(C3H7NO)3(CH3OH)3]·2H2O}n, consists of three [Mn(N,N-di­methyl­formamide)(methanol)(3,4,7,8-tetra­methyl-1,10-phenanthroline)]2+ cations, two [W(CN)8]3− anions and two water mol­ecules. Each water mol­ecule is disordered over three sets of sites, with a refined occupancy ratio of 0.310 (9):0.275 (9):0.415 (9) for one mol­ecule and 0.335 (9):0.288 (9):0.377 (9) for the other mol­ecule. The MnII atoms exhibit a distorted octa­hedral geometry, while the WV atoms adopt a distorted square-anti­prismatic geometry. The MnII and WV atoms are linked alternatively through cyanide groups, forming a tetra­nuclear 12-atom rhombic metallacycle. Adjacent metallacycles are further connected by μ2-bridging cyanide anions, generating a 3,2-chain structure running parallel to [101]. Inter­chain π–π inter­actions are observed [centroid–centroid distances = 3.763 (3) and 3.620 (2) Å]. PMID:24860305

Formation of the prebiotic molecule NH2CHO on astronomical amorphous solid water surfaces: accurate tunneling rate calculations.

PubMed

Song, Lei; Kästner, Johannes

2016-10-26

Investigating how formamide forms in the interstellar medium is a hot topic in astrochemistry, which can contribute to our understanding of the origin of life on Earth. We have constructed a QM/MM model to simulate the hydrogenation of isocyanic acid on amorphous solid water surfaces to form formamide. The binding energy of HNCO on the ASW surface varies significantly between different binding sites, we found values between ∼0 and 100 kJ mol -1 . The barrier for the hydrogenation reaction is almost independent of the binding energy, though. We calculated tunneling rate constants of H + HNCO → NH 2 CO at temperatures down to 103 K combining QM/MM with instanton theory. Tunneling dominates the reaction at such low temperatures. The tunneling reaction is hardly accelerated by the amorphous solid water surface compared to the gas phase for this system, even though the activation energy of the surface reaction is lower than the one of the gas-phase reaction. Both the height and width of the barrier affect the tunneling rate in practice. Strong kinetic isotope effects were observed by comparing to rate constants of D + HNCO → NHDCO. At 103 K we found a KIE of 231 on the surface and 146 in the gas phase. Furthermore, we investigated the gas-phase reaction NH 2 + H 2 CO → NH 2 CHO + H and found it unlikely to occur at cryogenic temperatures. The data of our tunneling rate constants are expected to significantly influence astrochemical models.

Hydrophilic porous magnetic poly(GMA-MBAA-NVP) composite microspheres containing oxirane groups: An efficient carrier for immobilizing penicillin G acylase

NASA Astrophysics Data System (ADS)

Xue, Ping; Su, Weiguang; Gu, Yaohua; Liu, Haifeng; Wang, Julan

2015-03-01

Magnetic hydrophilic polymeric microspheres containing oxirane groups were prepared by inverse suspension polymerization of glycidyl methacrylate (GMA), N, N‧-methylene bisacrylamide (MBAA) and N-vinyl pyrrolidone (NVP) in the existence of formamide, which were denoted as magnetic poly(GMA-MBAA-NVP) microspheres. The magnetic poly(GMA-MBAA-NVP) microspheres were characterized by scanning electron microscopy (SEM), FT-IR spectroscopy, X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and so on. The results showed that poly(GMA-MBAA-NVP) microspheres possessed well spherical shape, narrow size distribution, abundant porous structure, reactive oxirane groups and superparamagnetic properties. Formamide used in the present work served as a modifier, a dispersant and a porogen to form final porous polymer microspheres. The penicillin G acylase (PGA) was covalently immobilized onto the magnetic microspheres through the reaction between the amino groups of enzyme and the oxirane groups on the microspheres for producing 6-aminopenicillanic acid (6-APA). The effects of GMA/NVP ratio and crosslink density on the activity of immobilized PGA were investigated. The highest apparent activity, enzyme loading and coupling yield of immobilized PGA were 821 IU/g, 65.3 mg/g and 42.3% respectively when the mass ratio of GMA/NVP was 1:1 and crosslink density was 60%. Compared with the free PGA, immobilized PGA showed a wider range of pH value and reaction temperature. The relative activity and reaction rate of immobilized PGA remained almost constant after 20 recycles. The magnetic poly(GMA-MBAA-NVP) microspheres would be very promising carriers for immobilizing enzymes in industrial application.

Electrochemical reduction of nitrate in the presence of an amide

DOEpatents

Dziewinski, Jacek J.; Marczak, Stanislaw

2002-01-01

The electrochemical reduction of nitrates in aqueous solutions thereof in the presence of amides to gaseous nitrogen (N.sub.2) is described. Generally, electrochemical reduction of NO.sub.3 proceeds stepwise, from NO.sub.3 to N.sub.2, and subsequently in several consecutive steps to ammonia (NH.sub.3) as a final product. Addition of at least one amide to the solution being electrolyzed suppresses ammonia generation, since suitable amides react with NO.sub.2 to generate N.sub.2. This permits nitrate reduction to gaseous nitrogen to proceed by electrolysis. Suitable amides include urea, sulfamic acid, formamide, and acetamide.

Purification of N-Acetylgalactosaminidase by Isoelectric Focusing.

DTIC Science & Technology

1986-08-01

Ole 1406H)Bok 0i~w,.s reR..t %- ~.T&os docmen hasPLbeenNapproved iS% l. K EY lO (Cmntt n mo"re. eide If ne Ir n Pub l.Ati Ic r lock i tbs) Type A human...ammonia saturated methanol was prepared by bubbling ammonia through methanol cooled in a dry ice/ethanol bath for 2 ’t.. hrs. The washed precipitate...amino hexanoic acid (7.95g) in 50 ml - of dry dimethyl formamide. After stirring for 20 min at -5 °, the mixture P was filtered and the filtrate added

Asphalt, water, and the prebiotic synthesis of ribose, ribonucleosides, and RNA.

PubMed

Benner, Steven A; Kim, Hyo-Joong; Carrigan, Matthew A

2012-12-18

RNA has been called a "prebiotic chemist's nightmare" because of its combination of large size, carbohydrate building blocks, bonds that are thermodynamically unstable in water, and overall intrinsic instability. However, a discontinuous synthesis model is well-supported by experimental work that might produce RNA from atmospheric CO(2), H(2)O, and N(2). For example, electrical discharge in such atmospheres gives formaldehyde (HCHO) in large amounts and glycolaldehyde (HOCH(2)CHO) in small amounts. When rained into alkaline aquifers generated by serpentinizing rocks, these substances were undoubtedly converted to carbohydrates including ribose. Likewise, atmospherically generated HCN was undoubtedly converted in these aquifers to formamide and ammonium formate, precursors for RNA nucleobases. Finally, high reduction potentials maintained by mantle-derived rocks and minerals would allow phosphite to be present in equilibrium with phosphate, mobilizing otherwise insoluble phosphorus for the prebiotic synthesis of phosphite and phosphate esters after oxidation. So why does the community not view this discontinuous synthesis model as compelling evidence for the RNA-first hypothesis for the origin of life? In part, the model is deficient because no experiments have joined together those steps without human intervention. Further, many steps in the model have problems. Some are successful only if reactive compounds are presented in a specific order in large amounts. Failing controlled addition, the result produces complex mixtures that are inauspicious precursors for biology, a situation described as the "asphalt problem". Many bonds in RNA are thermodynamically unstable with respect to hydrolysis in water, creating a "water problem". Finally, some bonds in RNA appear to be "impossible" to form under any conditions considered plausible for early Earth. To get a community-acceptable "RNA first" model for the origin of life, the discontinuous synthesis model must be developed. In particular, the model must be refined so that it yields oligomeric RNA from CO(2), H(2)O, and N(2) without human intervention. This Account describes our efforts in this direction. Our hypothesis centers on a geological model that synthesizes RNA in a prebiotic intermountain dry valley (not in a marine environment). This valley receives high pH run-off from a watershed rich in serpentinizing olivines and eroding borate minerals. The runoff contains borate-stabilized carbohydrates, formamide, and ammonium formate. As atmospheric CO(2) dissolves in the subaerial aquifer, the pH of the aquifer is lowered. In the desert valley, evaporation of water, a solvent with a nucleophilic "background reactivity", leaves behind formamide, a solvent with an electrophilic "background reactivity". As a result, nucleobases, formylated nucleobases, and formylated carbohydrates, including formylated ribose, can form. Well-known chemistry transforms these structures into nucleosides, nucleotides, and partially formylated oligomeric RNA.

In situ evaluation of a new silorane-based composite resin's bioadhesion properties.

PubMed

Claro-Pereira, Diogo; Sampaio-Maia, Benedita; Ferreira, Carla; Rodrigues, Andreia; Melo, Luís F; Vasconcelos, Mário R

2011-12-01

The aim of the present study was to compare, in situ, the initial dental plaque formation on a recently developed silorane-based composite resin, Filtek Silorane, and on a widely used methacrylate-based composite resin, Synergy D6, and to relate possible differences to surface free energy, hydrophobicity and type of organic matrix. Discs of Filtek Silorane and Synergy D6 were prepared and polished equally in order to attain the same surface roughness. Water, formamide and 1-bromonaphthalene contact angles were determined and the surface free energy and the hydrophobicity of the materials calculated. Two discs of each material were mounted in individual oral splints and exposed to the oral cavity of 20 participants for 4h. After this period the microbial adhesion to both materials' surface was measured by two different approaches, the DAPI staining and the plate count. Statistical analysis was performed using non-parametric tests. The surface roughness (R(a) parameter) was similar between the two materials and lower than 0.2μm. Mean water and formamide contact angles were significantly higher for Filtek Silorane, which presented significantly lower surface free energy and greater degree of hydrophobicity in comparison to Synergy D6. The bioadhesion potential evaluated by either DAPI staining or plate count did not differ between the two materials. In contrast to previous in vitro studies, the present in situ study found no statistically significant differences with respect to bacterial adhesion between Filtek Silorane and Synergy D6, despite the differences found for surface free energy and hydrophobicity. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Production, purification, and properties of a lipase from a bacterium (Pseudomonas aeruginosa YS-7) capable of growing in water-restricted environments.

PubMed Central

Shabtai, Y; Daya-Mishne, N

1992-01-01

An extracellular lipase from the low-water-tolerant bacterium P. aeruginosa YS-7 was produced, purified, and characterized with respect to its functional properties in aqueous solutions and organic solvents. The enzyme was partially released from the cells during fermentation in defined medium with 5% (wt/vol) soybean oil. Approximately one-half of the total culture activity remained in solution after removal of cells. More than 95% of the activity was found in culture supernatant after mild detergent treatment (10 mM sodium deoxycholate) or after shifting the carbon source during the fermentation from triglyceride to a free fatty acid. The enzyme was recovered from an acetone precipitate of the whole culture and purified by hydrophobic interaction chromatography, yielding a preparation having a specific activity of about 1,300 mumol of fatty acid mg-1 h-1. The lipase (molecular size, approximately 40 kDa) hydrolyzes a variety of fatty acid esters and has an optimum pH of about 7. The enzyme retained its full activity at 20 to 55 degrees C, even after prolonged exposure (more than 30 days) to different concentrations of water-miscible organic solvents such as alcohols, glycols, pyridine, acetonitrile, dimethyl formamide, and dimethyl sulfoxide. The hydrolysis of 4-nitrophenyl laurate ester and of triglyceride emulsified in water was slightly accelerated with increasing concentrations of alcohols and glycols up to about 20% but was abolished with a further increase in alcohol concentration or in the presence of acetonitrile. In contrast, the rate of hydrolysis of these substrates in concentrated solutions of dimethyl formamide or dimethyl sulfoxide was markedly increased, by more than twofold and more than fivefold, respectively.(ABSTRACT TRUNCATED AT 250 WORDS) Images PMID:1539972

Solvent-induced dimensional changes in EDTA-demineralized dentin matrix.

PubMed

Pashley, D H; Agee, K A; Nakajima, M; Tay, F R; Carvalho, R M; Terada, R S; Harmon, F J; Lee, W K; Rueggeberg, F A

2001-08-01

The purpose of this study was to test the null hypothesis that the re-expansion of dried matrix and the shrinkage of moist, demineralized dentin is not influenced by polar solvents. Dentin disks were prepared from midcoronal dentin of extracted human third molars. After complete demineralization in 0.5M of EDTA (pH 7), the specimens were placed in the well of a device that measures changes in matrix height in real time. Dry, collapsed matrices were created by blowing dry N(2) on the specimens until they shrank to a stable plateau. Polar solvents [water, methanol, ethanol, n-propanol, n-butanol, formamide, ethylene glycol, hydroxyethyl methacrylate (HEMA), or mixtures of water-HEMA] as model primers then were added and the degree of re-expansion measured. These same solvents also were applied to moist, expanded matrices and the solvent-induced shrinkages measured. Regression analysis was used to test the correlations between matrix height and Hansen's dispersive, polar, hydrogen bonding, and total solubility parameters (delta(d), delta(p), delta(h), delta(t)). The results indicate that water-free polar solvents of low hydrogen bonding (H-bond) ability (e.g., neat HEMA) do not re-expand dried matrices and that they shrink moist matrices. When HEMA was mixed with progressively higher water concentrations, the model water-HEMA primers expanded the dried matrix in proportion to their water concentrations and they produced less shrinkage of moist matrices. Solvents with higher H-bonding capacities (methanol, ethanol, ethylene glycol, formamide, and water) re-expanded the dried matrix in proportion to their solubility parameters for H-bonding (delta(h)). They also induced small transient shrinkages of moist matrices, which slowly re-expanded. The results require rejection of the null hypothesis. Copyright 2001 John Wiley & Sons, Inc. J Biomed Mater Res 56: 273-281, 2001

[Secondary metabolites of halotolerant fungus Penicillium chrysogenum HK14-01 from the Yellow River Delta area].

PubMed

Qu, Peng; Liu, Peipei; Fu, Peng; Wang, Yi; Zhu, Weiming

2012-09-04

To search for structurally novel and biologically active compounds from the secondary metabolites of halotolerant fungi from the Yellow River Delta area. We screened halotolerant fungi with rich chemical diversity and antitumor or antimicrobial activity by means of integrated chemical and biological method. We cultured halotolerant fungi under different conditions at first. Then we investigated the chemical diversity and the bioactivity of the EtOAc extracts of the fermentation broth by HPLC and TLC, and cytotoxic assay or antimicrobial assay. We selected Penicillium chrysogenum HK14-01 to further study for the large yield, producing alkaloids and cytotoxicity on P388 cells in YMDP culture medium containing 10% NaCl. We fermented P. chrysogenum HK14-01 on a large scale; we isolated and purified the compounds by column chromatography over silica gel, Sephadex LH-20, and semipreparative HPLC; and we identified the structures by spectroscopic analysis, X-ray diffraction (Mo-Kalpha), CD spectra and the time-dependent density functional theory electronic circular dichroism (TDDFT ECD) calculation. We isolated and identified a halotolerant fungal strain, P. chrysogenum HK14-01, from the sediments collected in the Yellow River Delta area. From the fermentation broth of P. chrysogenum HK14-01, we isolated and identified eight compounds, i.e. (2S,3R)-oxaline (1, a major product), (3R, 4R)-3,4,8-trihydroxy-3,4-dihydronaphthalen-1 (2H)-one (2), (Z)-N-(4-hydroxy styryl) formamide (3), (E)-N-(4-hydroxystyryl) formamide (4), emodin (5), 4-(2-hydroxyethyl) benzene-1,2-diol (6), methyl 2-(4-hydroxyphenyl) acetate (7), and 2-(4-hydroxyphenyl) acetonitrile (8). Bioactive compounds can be obtained from the secondary metabolites of halotolerant microorganisms from the Yellow River Delta area.

The census of complex organic molecules in the solar-type protostar IRAS16293-2422

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

Jaber, Ali A.; Ceccarelli, C.; Kahane, C.

2014-08-10

Complex organic molecules (COMs) are considered to be crucial molecules, since they are connected with organic chemistry, at the basis of terrestrial life. More pragmatically, they are molecules which in principle are difficult to synthesize in harsh interstellar environments and, therefore, are a crucial test for astrochemical models. Current models assume that several COMs are synthesized on lukewarm grain surfaces (≳30-40 K) and released in the gas phase at dust temperatures of ≳100 K. However, recent detections of COMs in ≲20 K gas demonstrate that we still need important pieces to complete the puzzle of COMs formation. Here, we presentmore » a complete census of the oxygen- and nitrogen-bearing COMs, previously detected in different Interstellar Medium (ISM) regions, toward the solar-type protostar IRAS16293-2422. The census was obtained from the millimeter-submillimeter unbiased spectral survey TIMASSS. Of the 29 COMs searched for, 6 were detected: methyl cyanide, ketene, acetaldehyde, formamide, dimethyl ether, and methyl formate. Multifrequency analysis of the last five COMs provides clear evidence that they are present in the cold (≲30 K) envelope of IRAS16293-2422, with abundances of 0.03-2 × 10{sup –10}. Our data do not allow us to support the hypothesis that the COMs abundance increases with increasing dust temperature in the cold envelope, as expected if COMs were predominately formed on lukewarm grain surfaces. Finally, when also considering other ISM sources, we find a strong correlation over five orders of magnitude between methyl formate and dimethyl ether, and methyl formate and formamide abundances, which may point to a link between these two couples of species in cold and warm gas.« less

The Census of Complex Organic Molecules in the Solar-type Protostar IRAS16293-2422

NASA Astrophysics Data System (ADS)

Jaber, Ali A.; Ceccarelli, C.; Kahane, C.; Caux, E.

2014-08-01

Complex organic molecules (COMs) are considered to be crucial molecules, since they are connected with organic chemistry, at the basis of terrestrial life. More pragmatically, they are molecules which in principle are difficult to synthesize in harsh interstellar environments and, therefore, are a crucial test for astrochemical models. Current models assume that several COMs are synthesized on lukewarm grain surfaces (gsim30-40 K) and released in the gas phase at dust temperatures of gsim100 K. However, recent detections of COMs in lsim20 K gas demonstrate that we still need important pieces to complete the puzzle of COMs formation. Here, we present a complete census of the oxygen- and nitrogen-bearing COMs, previously detected in different Interstellar Medium (ISM) regions, toward the solar-type protostar IRAS16293-2422. The census was obtained from the millimeter-submillimeter unbiased spectral survey TIMASSS. Of the 29 COMs searched for, 6 were detected: methyl cyanide, ketene, acetaldehyde, formamide, dimethyl ether, and methyl formate. Multifrequency analysis of the last five COMs provides clear evidence that they are present in the cold (lsim30 K) envelope of IRAS16293-2422, with abundances of 0.03-2 × 10-10. Our data do not allow us to support the hypothesis that the COMs abundance increases with increasing dust temperature in the cold envelope, as expected if COMs were predominately formed on lukewarm grain surfaces. Finally, when also considering other ISM sources, we find a strong correlation over five orders of magnitude between methyl formate and dimethyl ether, and methyl formate and formamide abundances, which may point to a link between these two couples of species in cold and warm gas.

Investigation of hydrogen bonding and self-association in neat HCONH 2 and the binary mixture (HCONH 2+CH 3OH) by concentration dependent Raman study and ab initio calculations

NASA Astrophysics Data System (ADS)

Ojha, Animesh K.; Srivastava, Sunil K.; Koster, J.; Shukla, M. K.; Leszczynski, J.; Asthana, B. P.; Kiefer, W.

2004-02-01

Raman spectra of neat formamide (HCONH 2) and its binary mixture (HCONH 2+CH 3OH) with hydrogen donor solvent, methanol (CH 3OH) were investigated using a sensitive scanning multichannel detection scheme, which is simultaneously more precise also, especially when the observed Raman line profile has multiple component bands. The spectra in the two regions, namely 1200-1500 and 1500-1800 cm -1 were recorded with varying mole fractions of the reference molecule, HCONH 2, from 0.1 to 0.9. The spectra in the region 1200-1500 cm -1 show a broad band at ˜1312 cm -1, which shows a peculiar concentration dependence, and a relatively sharp peak at ˜1392 cm -1, whose peak position is not influenced by concentration. The spectra in the region 1500-1800 cm -1 also show two peaks, one at ˜1593 cm -1 and the other one at ˜1668 cm -1 which are assigned to NH 2 bending and ν(CO) stretching vibrations, respectively. Both these Raman bands show an appreciable upshift of ˜15-20 cm -1 and the one at ˜1668 cm -1 has also a distinct asymmetry towards higher wavenumber. The optimized geometries and vibrational wavenumbers of various normal modes for neat formamide as well as its hydrogen-bonded complexes were also calculated using ab initio theory at the MP2 level. The results have been used to understand and explain the concentration dependent changes in the spectral features in terms of hydrogen bonding and self-association.

Emissions of amides (N,N-dimethylformamide and formamide) and other obnoxious volatile organic compounds from different mattress textile products.

PubMed

Kim, Ki-Hyun; Pandey, Sudhir K; Kim, Yong-Hyun; Sohn, Jong Ryeul; Oh, J-M

2015-04-01

The emission rates of N,N-dimethylformamide (DMF), formamide (FAd), and certain hazardous volatile organic compounds (VOCs) were measured from seventeen mattress textile samples with four different raw material types: polyurethane (PU: n=3), polyester/polyethylene (PE: n=7), ethylene vinyl acetate (EV: n=3), and polyvinyl chloride (PC: n=4). To simulate the emissions in a heated room during winter season, measurements were made under temperature-controlled conditions, i.e., 50°C by using a mini-chamber system made of a midget impinger. Comparison of the data indicates that the patterns were greatly distinguished between DMF and FAd. PU products yielded the highest mean emission rates of DMF (2940 μg m(-2)h(-1): n=3) followed by PE (325 μg m(-2)h(-1): n=7), although its emission was not seen from other materials (EV and PC). In contrast, the pattern of FAd emission was moderately reversed from that of DMF: EV>PC>PE>PU. The results of our analysis confirm that most materials used for mattress production have the strong potential to emit either DMF or FAd in relatively large quantities while in use in children׳s care facilities, especially in winter months. Moreover, it was also observed that an increase in temperature (25°C to 50°C) had a significant impact on the emission rate of FAd and other hazardous VOCs. In addition to the aforementioned amides, the study revealed significant emissions of a number of hazardous VOCs, such as aromatic and carbonyl compounds. Copyright © 2014 Elsevier Inc. All rights reserved.

Role of metal oxides in chemical evolution

NASA Astrophysics Data System (ADS)

Kamaluddin

2013-06-01

Steps of chemical evolution have been designated as formation of biomonomers followed by their polymerization and then to modify in an organized structure leading to the formation of first living cell. Formation of small molecules like amino acids, organic bases, sugar etc. could have occurred in the reducing atmosphere of the primitive Earth. Polymerization of these small molecules could have required some catalyst. In addition to clay, role of metal ions and metal complexes as prebiotic catalyst in the synthesis and polymerization of biomonomers cannot be ruled out. Metal oxides are important constituents of Earth crust and that of other planets. These oxides might have adsorbed organic molecules and catalyzed the condensation processes, which may have led to the formation of first living cell. Different studies were performed in order to investigate the role of metal oxides (especially oxides of iron and manganese) in chemical evolution. Iron oxides (goethite, akaganeite and hematite) as well as manganese oxides (MnO, Mn2O3, Mn3O4 and MnO2) were synthesized and their characterization was done using IR, powder XRD, FE-SEM and TEM. Role of above oxides was studied in the adsorption of ribose nucleotides, formation of nucleobases from formamide and oligomerization of amino acids. Above oxides of iron and manganese were found to have good adsorption affinity towards ribose nucleotides, high catalytic activity in the formation of several nucleobases from formamide and oligomerization of glycine and alanine. Characterization of products was performed using UV, IR, HPLC and ESI-MS techniques. Presence of hematite-water system on Mars has been suggested to be a positive indicator in the chemical evolution on Mars.

Long-range anisotropic effects in a V-shaped Tröger's base diformanilide: Conformational study by NMR assignment and DFT calculations

NASA Astrophysics Data System (ADS)

Trupp, Leandro; Laurella, Sergio L.; Tettamanzi, M. Cristina; Barja, Beatriz C.; Bruttomesso, Andrea C.

2018-04-01

Herein we describe the synthesis and conformational analysis of a Tröger's base diformanilide whose distinctive NMR spectra was fully assigned via DFT calculations. The complexity of the spectra originated by the presence of three conformers in equilibrium shows that the nuclei in each side of the molecule are sensitive to the configuration not only of the closest formamide moiety but also of the farthest one, due to long-range anisotropic effects. The temperature and the solvent polarity influence were analyzed to determine the different conformer populations and the corresponding rotational activation parameters.

Prediction of the glass transition in aqueous solutions of simple amides by molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Kreck, Cara A.; Mandumpal, Jestin B.; Mancera, Ricardo L.

2011-01-01

Some simple amides in aqueous solution are used in the cryopreservation of biological tissues as they are believed to promote the vitrification of water, inhibiting its crystallisation and the ensuing damage from ice formation. Molecular dynamics annealing simulations reveal a broadening in the glass transition of aqueous acetamide and N-methylacetamide solutions, suggesting a thermodynamic stabilisation of the glassy state, which may be responsible for their increased tendency of vitrification and their cryoprotective ability. By contrast, aqueous formamide solutions do not exhibit broadening of the glass transition; instead, it is shifted to lower temperatures, which explains their lack of vitrification properties.

Ionic liquids as advantageous solvents for headspace gas chromatography of compounds with low vapor pressure.

PubMed

Andre, M; Loidl, J; Laus, G; Schottenberger, H; Bentivoglio, G; Wurst, K; Ongania, K-H

2005-01-15

The potential of ionic liquids as solvents for headspace gas chromatography was investigated. Three compounds with boiling points above 200 degrees C were selected to demonstrate the feasibility of the concept described. 2-Ethylhexanoic acid, formamide, and tri-n-butylamine as examples of acidic, neutral, and basic analytes were dissolved in acidic 1-n-butyl-3-methylimidazolium hydrogen sulfate (1), neutral 1-n-butyl-2,3-dimethylimidazolium dicyanamide (2), and 2 containing 1,8-diazabicyclo[5.4.0]undec-7-ene to adjust basic conditions. All analytes could be determined with limits of detection and limits of quantification in the low-ppm concentration range.

Acylation and deacylation mechanism of Helicobacter pylori AmiF formamidase: A computational DFT study

NASA Astrophysics Data System (ADS)

He, Rongxing; Yang, Qinlei; Li, Ming

2014-04-01

The acylation and deacylation mechanisms of Helicobacter pylori AmiF formamidase were investigated using DFT method. In the constructed active site, residues Glu60, Glu141 and His167 were taken into account besides Lys133 and Cys166. Calculations provided insight on the details of mechanism and explained crucial roles played by Glu60, Glu141 and His167. For acetylation, we proposed a new stepwise mechanism in which the thiol group first attacks the carbon atom of formamide and produces tetrahedral intermediate. In deacylation, Glu60 activates a water molecule to perform nucleophilic attack and then forms an intermediate, which is different from the usually suggested mechanism.

Photoinduced molecular chirality probed by ultrafast resonant X-ray spectroscopy

DOE PAGES

Rouxel, Jérémy R.; Kowalewski, Markus; Mukamel, Shaul

2017-07-01

Recently developed circularly polarized X-ray light sources can probe the ultrafast chiral electronic and nuclear dynamics through spatially localized resonant core transitions. Here, we present simulations of time-resolved circular dichroism signals given by the difference of left and right circularly polarized X-ray probe transmission following an excitation by a circularly polarized optical pump with the variable time delay. Application is made to formamide which is achiral in the ground state and assumes two chiral geometries upon optical excitation to the first valence excited state. Probes resonant with various K-edges (C, N, and O) provide different local windows onto the paritymore » breaking geometry change thus revealing the enantiomer asymmetry.« less

1,5-Bis[1-(2,4-dihy­droxy­phen­yl)ethyl­idene]carbonohydrazide dimethyl­formamide disolvate

PubMed Central

He, Qing-Peng; Tan, Bo; Lu, Ze-Hua

2010-01-01

In the title compound, C17H18N4O5·2C3H7NO, two solvent mol­ecules are linked to the main mol­ecule via N—H⋯O and O—H⋯O hydrogen bonds, forming a hydrogen-bonded trimer. Intra­molecular O—H⋯N hydrogen bonds influence the mol­ecular conformation of the main mol­ecule, and the two benzene rings form a dihedral angle of 10.55 (18)°. In the crystal, inter­molecular O—H⋯O hydrogen bonds link hydrogen-bonded trimers into ribbons extending along the b axis. PMID:21589135

Monodispersed ZIF-8 particles with enhanced performance for CO2 adsorption and heterogeneous catalysis

NASA Astrophysics Data System (ADS)

Guan, Yebin; Shi, Juanjuan; Xia, Ming; Zhang, Jun; Pang, Zhenfeng; Marchetti, Alessandro; Wang, Xiaohong; Cai, Jingsong; Kong, Xueqian

2017-11-01

Monodispersed zeolitic imidazolate frameworks (ZIFs) were prepared with a simple method using dimethylsulfoxide (DMSO) as solvent. This method yields ZIF-8 nanoparticles with a narrow particle size distribution of 90-110 nm and the dispersion is highly stable against agglomeration. These particles have larger nanosized porosity and enhanced CO2 adsorption capability compared to ZIF-8 prepared with different solvents such as methanol or N, N-dimethyl formamide. Their uniform size and surface chemistry also lead to superior performance in the Knoevenagel condensation reactions. The ZIF-8 nanoparticles possess high thermal stability up to 550 °C and the preparation steps are easy for scaling up which are favorable for industrial applications.

Photoinduced molecular chirality probed by ultrafast resonant X-ray spectroscopy

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

Rouxel, Jérémy R.; Kowalewski, Markus; Mukamel, Shaul

Recently developed circularly polarized X-ray light sources can probe the ultrafast chiral electronic and nuclear dynamics through spatially localized resonant core transitions. Here, we present simulations of time-resolved circular dichroism signals given by the difference of left and right circularly polarized X-ray probe transmission following an excitation by a circularly polarized optical pump with the variable time delay. Application is made to formamide which is achiral in the ground state and assumes two chiral geometries upon optical excitation to the first valence excited state. Probes resonant with various K-edges (C, N, and O) provide different local windows onto the paritymore » breaking geometry change thus revealing the enantiomer asymmetry.« less

Supercritical CO2 foaming of thermoplastic materials derived from maize: proof-of-concept use in mammalian cell culture applications.

PubMed

Trujillo-de Santiago, Grissel; Portales-Cabrera, Cynthia Guadalupe; Portillo-Lara, Roberto; Araiz-Hernández, Diana; Del Barone, Maria Cristina; García-López, Erika; Rojas-de Gante, Cecilia; de Los Angeles De Santiago-Miramontes, María; Segoviano-Ramírez, Juan Carlos; García-Lara, Silverio; Rodríguez-González, Ciro Ángel; Alvarez, Mario Moisés; Di Maio, Ernesto; Iannace, Salvatore

2015-01-01

Foams are high porosity and low density materials. In nature, they are a common architecture. Some of their relevant technological applications include heat and sound insulation, lightweight materials, and tissue engineering scaffolds. Foams derived from natural polymers are particularly attractive for tissue culture due to their biodegradability and bio-compatibility. Here, the foaming potential of an extensive list of materials was assayed, including slabs elaborated from whole flour, the starch component only, or the protein fraction only of maize seeds. We used supercritical CO2 to produce foams from thermoplasticized maize derived materials. Polyethylene-glycol, sorbitol/glycerol, or urea/formamide were used as plasticizers. We report expansion ratios, porosities, average pore sizes, pore morphologies, and pore size distributions for these materials. High porosity foams were obtained from zein thermoplasticized with polyethylene glycol, and from starch thermoplasticized with urea/formamide. Zein foams had a higher porosity than starch foams (88% and 85%, respectively) and a narrower and more evenly distributed pore size. Starch foams exhibited a wider span of pore sizes and a larger average pore size than zein (208.84 vs. 55.43 μm2, respectively). Proof-of-concept cell culture experiments confirmed that mouse fibroblasts (NIH 3T3) and two different prostate cancer cell lines (22RV1, DU145) attached to and proliferated on zein foams. We conducted screening and proof-of-concept experiments on the fabrication of foams from cereal-based bioplastics. We propose that a key indicator of foamability is the strain at break of the materials to be foamed (as calculated from stress vs. strain rate curves). Zein foams exhibit attractive properties (average pore size, pore size distribution, and porosity) for cell culture applications; we were able to establish and sustain mammalian cell cultures on zein foams for extended time periods.

Two-dimensional vibrational-electronic spectroscopy

NASA Astrophysics Data System (ADS)

Courtney, Trevor L.; Fox, Zachary W.; Slenkamp, Karla M.; Khalil, Munira

2015-10-01

Two-dimensional vibrational-electronic (2D VE) spectroscopy is a femtosecond Fourier transform (FT) third-order nonlinear technique that creates a link between existing 2D FT spectroscopies in the vibrational and electronic regions of the spectrum. 2D VE spectroscopy enables a direct measurement of infrared (IR) and electronic dipole moment cross terms by utilizing mid-IR pump and optical probe fields that are resonant with vibrational and electronic transitions, respectively, in a sample of interest. We detail this newly developed 2D VE spectroscopy experiment and outline the information contained in a 2D VE spectrum. We then use this technique and its single-pump counterpart (1D VE) to probe the vibrational-electronic couplings between high frequency cyanide stretching vibrations (νCN) and either a ligand-to-metal charge transfer transition ([FeIII(CN)6]3- dissolved in formamide) or a metal-to-metal charge transfer (MMCT) transition ([(CN)5FeIICNRuIII(NH3)5]- dissolved in formamide). The 2D VE spectra of both molecules reveal peaks resulting from coupled high- and low-frequency vibrational modes to the charge transfer transition. The time-evolving amplitudes and positions of the peaks in the 2D VE spectra report on coherent and incoherent vibrational energy transfer dynamics among the coupled vibrational modes and the charge transfer transition. The selectivity of 2D VE spectroscopy to vibronic processes is evidenced from the selective coupling of specific νCN modes to the MMCT transition in the mixed valence complex. The lineshapes in 2D VE spectra report on the correlation of the frequency fluctuations between the coupled vibrational and electronic frequencies in the mixed valence complex which has a time scale of 1 ps. The details and results of this study confirm the versatility of 2D VE spectroscopy and its applicability to probe how vibrations modulate charge and energy transfer in a wide range of complex molecular, material, and biological systems.

An air-pressure-free elastomeric valve for integrated nucleic acid analysis by capillary electrophoresis

NASA Astrophysics Data System (ADS)

Jung, Wooseok; Barrett, Matthew; Brooks, Carla; Rivera, Andrew; Birdsell, Dawn N.; Wagner, David M.; Zenhausern, Frederic

2015-12-01

We present a new elastomeric valve for integrated nucleic acid analysis by capillary electrophoresis. The valve functions include metering to capture a designated volume of biological sample into a polymerase chain reaction (PCR) chamber, sealing to preserve the sample during PCR cycling, and transfer of the PCR-products and on-chip formamide post-processing for the analysis of DNA fragments by capillary gel electrophoresis. This new valve differs from prior art polydimethylsiloxane (PDMS) valves in that the valve is not actuated externally by air-pressure or vacuum so that it simplifies a DNA analysis system by eliminating the need for an air-pressure or vacuum source, and off-cartridge solenoid valves, control circuit boards and software. Instead, the new valve is actuated by a thermal cycling peltier assembly integrated within the hardware instrument that tightly comes in contact with a microfluidic cartridge for thermal activation during PCR, so that it spontaneously closes the valve without an additional actuator system. The valve has bumps in the designated locations so that it has a self-alignment that does not require precise alignment of a valve actuator. Moreover, the thickness of the new valve is around 600 μm with an additional bump height of 400 μm so that it is easy to handle and very feasible to fabricate by injection molding compared to other PDMS valves whose thicknesses are around 30-100 μm. The new valve provided over 95% of metering performance in filling the fixed volume of the PCR chamber, preserved over 97% of the sample volume during PCR, and showed very comparable capillary electrophoresis peak heights to the benchtop assay tube controls with very consistent transfer volume of the PCR-product and on-chip formamide. The new valve can perform a core function for integrated nucleic acid analysis by capillary electrophoresis.

Supercritical CO2 Foaming of Thermoplastic Materials Derived from Maize: Proof-of-Concept Use in Mammalian Cell Culture Applications

PubMed Central

Trujillo-de Santiago, Grissel; Portales-Cabrera, Cynthia Guadalupe; Portillo-Lara, Roberto; Araiz-Hernández, Diana; Del Barone, Maria Cristina; García-López, Erika; Rojas-de Gante, Cecilia; de los Angeles De Santiago-Miramontes, María; Segoviano-Ramírez, Juan Carlos; García-Lara, Silverio; Rodríguez-González, Ciro Ángel; Alvarez, Mario Moisés; Di Maio, Ernesto; Iannace, Salvatore

2015-01-01

Background Foams are high porosity and low density materials. In nature, they are a common architecture. Some of their relevant technological applications include heat and sound insulation, lightweight materials, and tissue engineering scaffolds. Foams derived from natural polymers are particularly attractive for tissue culture due to their biodegradability and bio-compatibility. Here, the foaming potential of an extensive list of materials was assayed, including slabs elaborated from whole flour, the starch component only, or the protein fraction only of maize seeds. Methodology/Principal Findings We used supercritical CO2 to produce foams from thermoplasticized maize derived materials. Polyethylene-glycol, sorbitol/glycerol, or urea/formamide were used as plasticizers. We report expansion ratios, porosities, average pore sizes, pore morphologies, and pore size distributions for these materials. High porosity foams were obtained from zein thermoplasticized with polyethylene glycol, and from starch thermoplasticized with urea/formamide. Zein foams had a higher porosity than starch foams (88% and 85%, respectively) and a narrower and more evenly distributed pore size. Starch foams exhibited a wider span of pore sizes and a larger average pore size than zein (208.84 vs. 55.43 μm2, respectively). Proof-of-concept cell culture experiments confirmed that mouse fibroblasts (NIH 3T3) and two different prostate cancer cell lines (22RV1, DU145) attached to and proliferated on zein foams. Conclusions/Significance We conducted screening and proof-of-concept experiments on the fabrication of foams from cereal-based bioplastics. We propose that a key indicator of foamability is the strain at break of the materials to be foamed (as calculated from stress vs. strain rate curves). Zein foams exhibit attractive properties (average pore size, pore size distribution, and porosity) for cell culture applications; we were able to establish and sustain mammalian cell cultures on zein foams for extended time periods. PMID:25859853

Two-dimensional vibrational-electronic spectroscopy.

PubMed

Courtney, Trevor L; Fox, Zachary W; Slenkamp, Karla M; Khalil, Munira

2015-10-21

Two-dimensional vibrational-electronic (2D VE) spectroscopy is a femtosecond Fourier transform (FT) third-order nonlinear technique that creates a link between existing 2D FT spectroscopies in the vibrational and electronic regions of the spectrum. 2D VE spectroscopy enables a direct measurement of infrared (IR) and electronic dipole moment cross terms by utilizing mid-IR pump and optical probe fields that are resonant with vibrational and electronic transitions, respectively, in a sample of interest. We detail this newly developed 2D VE spectroscopy experiment and outline the information contained in a 2D VE spectrum. We then use this technique and its single-pump counterpart (1D VE) to probe the vibrational-electronic couplings between high frequency cyanide stretching vibrations (νCN) and either a ligand-to-metal charge transfer transition ([Fe(III)(CN)6](3-) dissolved in formamide) or a metal-to-metal charge transfer (MMCT) transition ([(CN)5Fe(II)CNRu(III)(NH3)5](-) dissolved in formamide). The 2D VE spectra of both molecules reveal peaks resulting from coupled high- and low-frequency vibrational modes to the charge transfer transition. The time-evolving amplitudes and positions of the peaks in the 2D VE spectra report on coherent and incoherent vibrational energy transfer dynamics among the coupled vibrational modes and the charge transfer transition. The selectivity of 2D VE spectroscopy to vibronic processes is evidenced from the selective coupling of specific νCN modes to the MMCT transition in the mixed valence complex. The lineshapes in 2D VE spectra report on the correlation of the frequency fluctuations between the coupled vibrational and electronic frequencies in the mixed valence complex which has a time scale of 1 ps. The details and results of this study confirm the versatility of 2D VE spectroscopy and its applicability to probe how vibrations modulate charge and energy transfer in a wide range of complex molecular, material, and biological systems.

Investigating vibrational anharmonic couplings in cyanide-bridged transition metal mixed valence complexes using two-dimensional infrared spectroscopy.

PubMed

Slenkamp, Karla M; Lynch, Michael S; Van Kuiken, Benjamin E; Brookes, Jennifer F; Bannan, Caitlin C; Daifuku, Stephanie L; Khalil, Munira

2014-02-28

Using polarization-selective two-dimensional infrared (2D IR) spectroscopy, we measure anharmonic couplings and angles between the transition dipole moments of the four cyanide stretching (νCN) vibrations found in [(NH3)5Ru(III)NCFe(II)(CN)5](-) (FeRu) dissolved in D2O and formamide and [(NC)5Fe(II)CNPt(IV)(NH3)4NCFe(II)(CN)5](4-) (FePtFe) dissolved in D2O. These cyanide-bridged transition metal complexes serve as model systems for studying the role of high frequency vibrational modes in ultrafast photoinduced charge transfer reactions. Here, we focus on the spectroscopy of the νCN modes in the electronic ground state. The FTIR spectra of the νCN modes of the bimetallic and trimetallic systems are strikingly different in terms of frequencies, amplitudes, and lineshapes. The experimental 2D IR spectra of FeRu and FePtFe and their fits reveal a set of weakly coupled anharmonic νCN modes. The vibrational mode anharmonicities of the individual νCN modes range from 14 to 28 cm(-1). The mixed-mode anharmonicities range from 2 to 14 cm(-1). In general, the bridging νCN mode is most weakly coupled to the radial νCN mode, which involves the terminal CN ligands. Measurement of the relative transition dipole moments of the four νCN modes reveal that the FeRu molecule is almost linear in solution when dissolved in formamide, but it assumes a bent geometry when dissolved in D2O. The νCN modes are modelled as bilinearly coupled anharmonic oscillators with an average coupling constant of 6 cm(-1). This study elucidates the role of the solvent in modulating the molecular geometry and the anharmonic vibrational couplings between the νCN modes in cyanide-bridged transition metal mixed valence complexes.

Synthesis and crystalline properties of CdS incorporated polyvinylidene fluoride (PVDF) composite film

NASA Astrophysics Data System (ADS)

Patel, Arunendra Kumar; Sunder, Aishwarya; Mishra, Shweta; Bajpai, Rakesh

2018-05-01

This paper gives an insight on the synthesis and crystalline properties of Polyvinylidene Fluoride (PVDF) (host matrix) composites impregnated with Cadmium Sulphide (CdS) using Dimethyl formamide (DMF) as the base, prepared by the well known solvent casting technique. The effect of doping concentration of CdS in to the PVDF matrix was studied using X-ray diffraction technique. The structural properties like crystallinity Cr, interplanar distance d, average size of the crystalline region (D), and average inter crystalline separation (R) have been estimated for the developed composite. The crystallinity index, crystallite size and inter crystalline separation is increasing with increase in the concentration of CdS in to the PVDF matrix while the interplanar distance d is decreasing.

Magnetic propulsion of robotic sperms at low-Reynolds number

NASA Astrophysics Data System (ADS)

Khalil, Islam S. M.; Fatih Tabak, Ahmet; Klingner, Anke; Sitti, Metin

2016-07-01

We investigate the microswimming behaviour of robotic sperms in viscous fluids. These robotic sperms are fabricated from polystyrene dissolved in dimethyl formamide and iron-oxide nanoparticles. This composition allows the nanoparticles to be concentrated within the bead of the robotic sperm and provide magnetic dipole, whereas the flexibility of the ultra-thin tail enables flagellated locomotion using magnetic fields in millitesla range. We show that these robotic sperms have similar morphology and swimming behaviour to those of sperm cells. Moreover, we show experimentally that our robotic sperms swim controllably at an average speed of approximately one body length per second (around 125 μm s-1), and they are relatively faster than the microswimmers that depend on planar wave propulsion in low-Reynolds number fluids.

Crystal structure of di-methyl-formamidium bis-(tri-fluoro-methane-sulfon-yl)amide: an ionic liquid.

PubMed

Cardenas, Allan Jay P; O'Hagan, Molly

2016-09-01

At 100 K, the title mol-ecular salt, C 3 H 8 NO + ·C 2 F 6 NO 4 S 2 - , has ortho-rhom-bic ( P 2 1 2 1 2 1 ) symmetry; the amino H atom of bis-(tri-fluoro-methane-sulfon-yl)amine (HNTf 2 ) was transferred to the basic O atom of di-methyl-formamide (DMF) when the ionic liquid components were mixed. The structure displays an O-H⋯N hydrogen bond, which links the cation to the anion, which is reinforced by a non-conventional C-H⋯O inter-action, generating an R 2 2 (7) loop. A further very weak C-H⋯O inter-action generates an [001] chain.

Synthesis and characterization of Cd Cr and Zn Cd Cr layered double hydroxides intercalated with dodecyl sulfate

NASA Astrophysics Data System (ADS)

Guo, Ying; Zhang, He; Zhao, Lan; Li, Guo-Dong; Chen, Jie-Sheng; Xu, Lin

2005-06-01

Cd-Cr and Zn-Cd-Cr layered double hydroxides (CdCr-LDH and ZnCdCr-LDH) containing alkyl sulfate as the interlamellar anion have been prepared through a coprecipitation technique. The resulting compounds were characterized using X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Magnetic property measurements indicate that antiferromagnetic interactions occur between the chromium ions in the two compounds at low temperatures. The introduction of zinc influences the ligand field of Cr III and the Cr III-Cr III interactions in the LDH compound. It is found that both CdCr-LDH and ZnCdCr-LDH can be delaminated by dispersion in formamide, leading to translucent and stable colloidal solutions.

Synthesis, spectral features and biological activity of some novel hetarylazo dyes derived from 6-amino-1,3-dimethyluracil

NASA Astrophysics Data System (ADS)

Yousefi, Hessamoddin; Yahyazadeh, Asieh; Yazdanbakhsh, Mohammad Reza; Rassa, Mehdi; Moradi-e-Rufchahi, Enayat O.'llah

2012-05-01

A series of hetarylazoaminouracil dyes were prepared by coupling of 6-amino-1,3-dimethyluracil with eight diazotized heterocyclic amines in nitrosyl sulphuric acid. The prepared azo dyes were characterized by UV-Vis, FT-IR, 13C NMR, 1H NMR spectroscopic techniques and elemental analysis. The solvatochromism of dyes was evaluated with respect to wavelength of maximum absorption (λmax) in seven solvents with different polarities: acetic acid, methanol, water, chloroform, acetonitrile, dimethyl sulfoxide and dimethyl formamide. The effects of acid, base and concentration of the dye on the visible absorption spectra were also reported. In addition, the antimicrobial activity of the synthesized dyes was evaluated on Escherichia coli, Bacillus subtilis, Micrococcus leuteus and Pseudomonas aeruginosa.

Synthesis of 4-substituted pyrido[2,3-d]pyrimidin-4(1H)-one as analgesic and anti-inflammatory agents.

PubMed

El-Gazzar, Abdel-Rahman B A; Hafez, Hend N

2009-07-01

4-Substituted-pyrido[2,3-d]pyrimidin-4(1H)-ones 4a-c were synthesized by oxidation of 4-substituted-dihydropyrido[2,3-d]pyrimidin-4(1H)-ones 3a-c which were in turn prepared from arylidenemalononitriles 1a-c and 6-aminothiouracil 2. The reactivity of compounds 4a-c towards some reagents such as formamide, carbon disulfide, urea, thiourea, formic and acetic acids were studied. All the synthesized compounds were characterized by spectroscopic means and elemental analysis. Compound 4c exhibited 64% and 72% analgesic activity. Also, compound 4b showed 50% and 65% anti-inflammatory activity. Interestingly these compounds showed one-third of ulcer index of the reference aspirin and diclofenac.

4-{2-[2-(4-Formyl-phen-oxy)eth-oxy]eth-oxy}benzaldehyde.

PubMed

Ma, Zhen; Cao, Yiqun

2011-06-01

The title compound, C(18)H(18)O(5), was obtained by the reaction of 4-hy-droxy-benzaldehyde with bis-(2,2-dichloro-eth-yl) ether in dimethyl-formamide. In the crystal, the mol-ecule lies on a twofold rotation axis that passes through the central O atom of the aliphatic chain, thus leading to one half-mol-ecule being present per asymmetric unit. The carbonyl, aryl and O-CH(2)-CH(2) groups are almost coplanar, with an r.m.s. deviation of 0.030 Å. The aromatic rings are approximately perpendicular to each other, forming a dihedral angle of 78.31 sh;H⋯O hydrogen bonds and C-H⋯π inter-actions help to consolidate the three-dimensional network.

Method for producing high surface area chromia materials for catalysis

DOEpatents

Gash, Alexander E [Brentwood, CA; Satcher, Joe [Patterson, CA; Tillotson, Thomas [Tracy, CA; Hrubesh, Lawrence [Pleasanton, CA; Simpson, Randall [Livermore, CA

2007-05-01

Nanostructured chromium(III)-oxide-based materials using sol-gel processing and a synthetic route for producing such materials are disclosed herein. Monolithic aerogels and xerogels having surface areas between 150 m.sup.2/g and 520 m.sup.2/g have been produced. The synthetic method employs the use of stable and inexpensive hydrated-chromium(III) inorganic salts and common solvents such as water, ethanol, methanol, 1-propanol, t-butanol, 2-ethoxy ethanol, and ethylene glycol, DMSO, and dimethyl formamide. The synthesis involves the dissolution of the metal salt in a solvent followed by an addition of a proton scavenger, such as an epoxide, which induces gel formation in a timely manner. Both critical point (supercritical extraction) and atmospheric (low temperature evaporation) drying may be employed to produce monolithic aerogels and xerogels, respectively.

Development of PCR internal controls for DNA profiling with the AmpFℓSTR® SGM Plus® amplification kit.

PubMed

Nathalie, Zahra; Hadi, Sibte; Goodwin, William

2012-09-01

Forensic DNA profiling uses a series of commercial kits that co-amplify several loci in one reaction; the products of the PCR are fluorescently labelled and analysed using CE. Before CE, an aliquot of the PCR is mixed with formamide and an internal lane size standard. Using the SGM Plus amplification kit, we have developed two internal non-amplified controls of 80 bp and 380 bp that are labelled with ROX fluorescent dye and added to the PCR. Combined with two internal amplification controls of 90 bp and 410 bp, they provide additional controls for the PCR, electrokinetic injection, and CE and also function as an internal size standard. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Vibrational spectroscopic studies of an organic non-linear optical crystal 8-hydroxyquinolinium picrate

NASA Astrophysics Data System (ADS)

Krishna Kumar, V.; Nagalakshmi, R.

2007-04-01

8-Hydroxyquinolinium picrate (8-HQP) was synthesized by the addition of equimolar quantities of 8-hydroxyquinoline (8-HQ) and picric acid (PA). Single crystals were grown from N, N dimethyl formamide (DMF) by restricted evaporation method at room temperature. The solubility of 8-HQP was determined in different solvents at various temperatures. The structural characterization of the grown crystals was carried out by X-ray diffraction. Vibrational modes were classified on the basis of group theoretical analysis and the spectral bands were compared with those of parent compounds in order to propose a tentative assignment by recording FT-IR, FT-Raman and polarized Raman spectra in different crystal orientations. The crystal possess lower cut-off at 230 nm and good transparency as confirmed by optical transmittance studies.

"One-pot" preparation of basic amino acid-silica hybrid monolithic column for capillary electrochromatography.

PubMed

Xu, Hongrui; Xu, Zhendong; Yang, Limin; Wang, Qiuquan

2011-08-01

A novel "one-pot" strategy was developed for the preparation of amino acid (AA)-silica hybrid monolithic column. The basic AA (L-Arginine, L-Lysine and L-Histidine) was covalently incorporated into the silica hybrid skeleton via the epoxy ring-opening reaction between the amine group and the glycidyl moiety in γ-glycidoxypropyltrimethoxysilane (GPTMS), which was confirmed by elemental analysis and FT-IR studies, while the basic AA was also found to catalyze the polycondensation of tetramethoxysilane and GPTMS. The average mesopore and macropore sizes of the prepared basic AA-silica hybrid monolithic columns were 3.86 nm and 1.71 μm for the L-Lysine-silica hybrid monolith, 5.38 nm and 4.24 μm for the L-Arginine-silica hybrid monolith, and 6.38 nm and 1.24 μm for the L-Histidine-silica hybrid monolith. The hybrid monolith afforded a zwitterionic stationary phase for CEC, the direction and magnitude of EOF can be controlled by the pH of the mobile phase used. Besides an electrophoretic mechanism, the monoliths behave in a typical hydrophilic interaction with the analytes when ACN percentage in the mobile phase is over 40%. Four polar compounds (toluene, DMF, formamide and thiourea) were tested on the three AA-silica hybrid monolithic columns, and the best separation efficiency was observed in the L-Lysine-silica hybrid monolithic column, its theoretical plate height was down to 5.7 μm for thiourea when 20 mM HCOOH-HCOONH4 containing 20% ACN (pH 4.1) was used as a running buffer. The corresponding theoretical plate number for toluene, DMF, formamide and thiourea were 123,385, 103,620, 121,845 and 105,345 plates/m, respectively. Effective separation of phenols and peptides on the L-Lysine-silica hybrid monolithic column was achieved using CEC. We believe that this strategy paves a way for the easy preparation of various functional silica hybrid monolithic columns, aiming at different separation purposes. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigating vibrational relaxation in cyanide-bridged transition metal mixed-valence complexes using two-dimensional infrared and infrared pump-probe spectroscopies

PubMed Central

Slenkamp, Karla M.; Lynch, Michael S.; Brookes, Jennifer F.; Bannan, Caitlin C.; Daifuku, Stephanie L.; Khalil, Munira

2016-01-01

Using polarization-selective two-dimensional infrared (2D IR) and infrared pump-probe spectroscopies, we study vibrational relaxation of the four cyanide stretching (νCN) vibrations found in [(NH3)5RuIIINCFeII(CN)5]− (FeRu) dissolved in D2O or formamide and [(NC)5FeIICNPtIV(NH3)4NCFeII(CN)5]4− (FePtFe) dissolved in D2O. These cyanide-bridged transition metal complexes serve as models for understanding the role high frequency vibrational modes play in metal-to-metal charge transfers over a bridging ligand. However, there is currently little information about vibrational relaxation and dephasing dynamics of the anharmonically coupled νCN modes in the electronic ground state of these complexes. IR pump-probe experiments reveal that the vibrational lifetimes of the νCN modes are ∼2 times faster when FeRu is dissolved in D2O versus formamide. They also reveal that the vibrational lifetimes of the νCN modes of FePtFe in D2O are almost four times as long as for FeRu in D2O. Combined with mode-specific relaxation dynamics measured from the 2D IR experiments, the IR pump-probe experiments also reveal that intramolecular vibrational relaxation is occurring in all three systems on ∼1 ps timescale. Center line slope dynamics, which have been shown to be a measure of the frequency-frequency correlation function, reveal that the radial, axial, and trans νCN modes exhibit a ∼3 ps timescale for frequency fluctuations. This timescale is attributed to the forming and breaking of hydrogen bonds between each mode and the solvent. The results presented here along with our previous work on FeRu and FePtFe reveal a picture of coupled anharmonic νCN modes where the spectral diffusion and vibrational relaxation dynamics depend on the spatial localization of the mode on the molecular complex and its specific interaction with the solvent. PMID:27158634

Toxicology of dimethyl and monomethyl derivatives of acetamide and formamide: a second update.

PubMed

Kennedy, Gerald L

2012-11-01

Dimethylacetamide (DMAC) and dimethylformamide (DMF) continue to be important, widely used solvents involved in a wide variety of industrial applications. As liquids with relatively low vapor pressures, contact with both the integumentary and respiratory systems is the main source of human exposure. Although airborne control levels for the workplace have been established and industrial hygiene practices to limit dermal contact have been put in place, use of these chemicals has been associated with occupational illness, mainly in Asia where new and expanded uses have led to overexposures. Thus an update of the basic toxicology data including tables indicating the dose/exposure response characteristics of both DMAC and DMF is currently important. Both chemicals are similar from a toxicology perspective. Human experience has generally shown the materials to be without adverse effect except under conditions where airborne and dermal controls were not properly applied. The use of urinary metabolite monitoring has successfully been employed to measure integrated dermal and inhalation worker exposure. The chemicals are not particularly toxic following acute exposure but high doses can produce damage to the liver, the organ which is first affected by these two chemicals. Repeated dose/exposure studies have characterized both the targets of toxicity and the doses required to produce changes by various routes of exposure. Higher doses of these materials can produce changes in developing systems, infrequently in experiments at doses in which the maternal animal is unaffected, thus care needs to be taken when exposures are to women of child-bearing age. The chemicals appear to be low in genetic activity and inhalation exposures have not shown the materials to produce tumors in rodents except with DMF in a situation in which aerosol formation was encountered. This presentation extends the two previous reviews and, like those, includes updated information on acetamide and formamide and their monomethyl derivatives as well as the commercially important DMAC and DMF. Since a large portion of the newer information deals with effects in humans and biomonitoring, these sections are presented at the start of this review.

Tris(1,10-phenanthroline-κ2 N,N′)nickel(II) hexa­oxido-μ-peroxido-disulfate­(VI) N,N-dimethyl­formamide disolvate monohydrate

PubMed Central

Harvey, Miguel Angel; Suarez, Sebastián; Doctorovich, Fabio; Baggio, Ricardo

2013-01-01

The asymmetric unit of the title complex, [Ni(C12H8N2)3]S2O8·2C3H7NO·H2O, consists of a complex [Ni(phen)3]2+ cation and one isolated pds anion, with two DMF mol­ecules and one water mol­ecule as solvates (where phen is 1,10-phenanthroline, pds is the hexa­oxido-μ-peroxoido-di­sulf­ate dianion and DMF is dimethyl­formamide). The [Ni(phen)3]2+ cation is regular, with an almost ideal NiII bond-valence sum of 2.07 v.u. The group, as well as the water solvent mol­ecule, are well behaved in terms of crystallographic order, but the remaining three mol­ecules in the structure display different kinds of disorder, viz. the two DMF mol­ecules mimic a twofold splitting and the pds anion has both S atoms clamped at well-determined positions but with a not-too-well-defined central part. These peculiar behaviours are a consequence of the hydrogen-bonding inter­actions: the outermost SO3 parts of the pds anion are heavily connected to the complex cations via C—H⋯O hydrogen bonding, generating an [Ni(phen)3]pds network and providing for the stability of the terminal pds sites. Also, the water solvent mol­ecule is strongly bound to the structure (being a donor of two strong bonds and an acceptor of one) and is accordingly perfectly ordered. The peroxide O atoms in the pds middle region, instead, appear as much less restrained into their sites, which may explain their tendency to disorder. The cation–anion network leaves large embedded holes, amounting to about 28% of the total crystal volume, which are occupied by the DMF mol­ecules. The latter are weakly inter­acting with the rest of the structure, which renders them much more labile and, accordingly, prone to disorder. PMID:23476355

Reliability of high-strain ionomeric polymer transducers fabricated using the novel direct assembly process

NASA Astrophysics Data System (ADS)

Akle, Barbar; Nawshin, Saila; Leo, Donald

2006-03-01

Ionomeric polymer transducers have received considerable attention in the past several years. These actuators, sometimes referred to as artificial muscles, have the ability to generate large bending strain and moderate stress at low applied voltages. Typically, ionic polymer actuators are composed of Nafion-117 membranes with platinum electrodes and are saturated with water diluents. Recently the authors have developed a novel fabrication technique named the Direct Assembly Process (DAP), which allowed good control on electrode morphology and composition. The DAP consists of spraying two high surface area metal-ionomer electrodes on a Nafion membrane. A single- walled carbon nanotubes (SWNT) and ruthenium dioxide (RuO II) hybrid electrode was sprayed on a Formamide hydrated Nafion-117 membrane using the DAP method. This transducer was shown to generate 9.4% peak-peak strain under the application of +/-2V at a strain rate of 1%/sec. Furthermore using the DAP one is capable of incorporating several types of diluents in ionomeric polymer transducers. Transducers with ionic liquid diluents are demonstrated to operate in air for long periods of time. In this work we will present a reliability study of transducers fabricated using the DAP. Each transducer is tested under a frequency range of 0.2Hz to 1Hz, and a potential of +/-1V to +/-3V. Water hydrated transducers dehydrates and stop moving within 5 minutes while operating in air under +/-2V. Transducers with Formamide diluents operate for 20,000 cycles under +/-1.5V and 0.5Hz (around 11hrs), while they degrade in less than 3000 cycles under +/-2V and 0.5Hz. Ionic liquid based transducers are demonstrated to operate in air for over 400,000 with little loss in performance, and over 1 million cycle with a loss of only 43%. Actuators with several electrode compositions are fabricated and a correlation between the reliability of ionic liquid-ionic polymer transducers and maximum strain will be presented. This correlation will be used to assess the adhesion between the high surface area electrodes and the Nafion membrane. SEM images of tested transducers will be presented.

Investigating vibrational anharmonic couplings in cyanide-bridged transition metal mixed valence complexes using two-dimensional infrared spectroscopy

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

Slenkamp, Karla M.; Lynch, Michael S.; Van Kuiken, Benjamin E.

2014-02-28

Using polarization-selective two-dimensional infrared (2D IR) spectroscopy, we measure anharmonic couplings and angles between the transition dipole moments of the four cyanide stretching (ν{sub CN}) vibrations found in [(NH{sub 3}){sub 5}Ru{sup III}NCFe{sup II}(CN){sub 5}]{sup −} (FeRu) dissolved in D{sub 2}O and formamide and [(NC){sub 5}Fe{sup II}CNPt{sup IV}(NH{sub 3}){sub 4}NCFe{sup II}(CN){sub 5}]{sup 4−} (FePtFe) dissolved in D{sub 2}O. These cyanide-bridged transition metal complexes serve as model systems for studying the role of high frequency vibrational modes in ultrafast photoinduced charge transfer reactions. Here, we focus on the spectroscopy of the ν{sub CN} modes in the electronic ground state. The FTIR spectramore » of the ν{sub CN} modes of the bimetallic and trimetallic systems are strikingly different in terms of frequencies, amplitudes, and lineshapes. The experimental 2D IR spectra of FeRu and FePtFe and their fits reveal a set of weakly coupled anharmonic ν{sub CN} modes. The vibrational mode anharmonicities of the individual ν{sub CN} modes range from 14 to 28 cm{sup −1}. The mixed-mode anharmonicities range from 2 to 14 cm{sup −1}. In general, the bridging ν{sub CN} mode is most weakly coupled to the radial ν{sub CN} mode, which involves the terminal CN ligands. Measurement of the relative transition dipole moments of the four ν{sub CN} modes reveal that the FeRu molecule is almost linear in solution when dissolved in formamide, but it assumes a bent geometry when dissolved in D{sub 2}O. The ν{sub CN} modes are modelled as bilinearly coupled anharmonic oscillators with an average coupling constant of 6 cm{sup −1}. This study elucidates the role of the solvent in modulating the molecular geometry and the anharmonic vibrational couplings between the ν{sub CN} modes in cyanide-bridged transition metal mixed valence complexes.« less

Two-dimensional vibrational-electronic spectroscopy

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

Courtney, Trevor L.; Fox, Zachary W.; Slenkamp, Karla M.

2015-10-21

Two-dimensional vibrational-electronic (2D VE) spectroscopy is a femtosecond Fourier transform (FT) third-order nonlinear technique that creates a link between existing 2D FT spectroscopies in the vibrational and electronic regions of the spectrum. 2D VE spectroscopy enables a direct measurement of infrared (IR) and electronic dipole moment cross terms by utilizing mid-IR pump and optical probe fields that are resonant with vibrational and electronic transitions, respectively, in a sample of interest. We detail this newly developed 2D VE spectroscopy experiment and outline the information contained in a 2D VE spectrum. We then use this technique and its single-pump counterpart (1D VE)more » to probe the vibrational-electronic couplings between high frequency cyanide stretching vibrations (ν{sub CN}) and either a ligand-to-metal charge transfer transition ([Fe{sup III}(CN){sub 6}]{sup 3−} dissolved in formamide) or a metal-to-metal charge transfer (MMCT) transition ([(CN){sub 5}Fe{sup II}CNRu{sup III}(NH{sub 3}){sub 5}]{sup −} dissolved in formamide). The 2D VE spectra of both molecules reveal peaks resulting from coupled high- and low-frequency vibrational modes to the charge transfer transition. The time-evolving amplitudes and positions of the peaks in the 2D VE spectra report on coherent and incoherent vibrational energy transfer dynamics among the coupled vibrational modes and the charge transfer transition. The selectivity of 2D VE spectroscopy to vibronic processes is evidenced from the selective coupling of specific ν{sub CN} modes to the MMCT transition in the mixed valence complex. The lineshapes in 2D VE spectra report on the correlation of the frequency fluctuations between the coupled vibrational and electronic frequencies in the mixed valence complex which has a time scale of 1 ps. The details and results of this study confirm the versatility of 2D VE spectroscopy and its applicability to probe how vibrations modulate charge and energy transfer in a wide range of complex molecular, material, and biological systems.« less

Investigating vibrational relaxation in cyanide-bridged transition metal mixed-valence complexes using two-dimensional infrared and infrared pump-probe spectroscopies.

PubMed

Slenkamp, Karla M; Lynch, Michael S; Brookes, Jennifer F; Bannan, Caitlin C; Daifuku, Stephanie L; Khalil, Munira

2016-03-01

Using polarization-selective two-dimensional infrared (2D IR) and infrared pump-probe spectroscopies, we study vibrational relaxation of the four cyanide stretching (νCN) vibrations found in [(NH3)5Ru(III)NCFe(II)(CN)5](-) (FeRu) dissolved in D2O or formamide and [(NC)5Fe(II)CNPt(IV)(NH3)4NCFe(II)(CN)5](4-) (FePtFe) dissolved in D2O. These cyanide-bridged transition metal complexes serve as models for understanding the role high frequency vibrational modes play in metal-to-metal charge transfers over a bridging ligand. However, there is currently little information about vibrational relaxation and dephasing dynamics of the anharmonically coupled νCN modes in the electronic ground state of these complexes. IR pump-probe experiments reveal that the vibrational lifetimes of the νCN modes are ∼2 times faster when FeRu is dissolved in D2O versus formamide. They also reveal that the vibrational lifetimes of the νCN modes of FePtFe in D2O are almost four times as long as for FeRu in D2O. Combined with mode-specific relaxation dynamics measured from the 2D IR experiments, the IR pump-probe experiments also reveal that intramolecular vibrational relaxation is occurring in all three systems on ∼1 ps timescale. Center line slope dynamics, which have been shown to be a measure of the frequency-frequency correlation function, reveal that the radial, axial, and trans νCN modes exhibit a ∼3 ps timescale for frequency fluctuations. This timescale is attributed to the forming and breaking of hydrogen bonds between each mode and the solvent. The results presented here along with our previous work on FeRu and FePtFe reveal a picture of coupled anharmonic νCN modes where the spectral diffusion and vibrational relaxation dynamics depend on the spatial localization of the mode on the molecular complex and its specific interaction with the solvent.

VizieR Online Data Catalog: Formamide detection with ASAI-IRAM (Lopez-Sepulcre+, 2015)

NASA Astrophysics Data System (ADS)

Lopez-Sepulcre, A.; Jaber, A. A.; Mendoza, E.; Lefloch, B.; Ceccarelli, C.; Vastel, C.; Bachiller, R.; Cernicharo, J.; Codella, C.; Kahane, C.; Kama, M.; Tafalla, M.

2017-11-01

Our source sample consists of 10 well-known pre-stellar and protostellar objects representing different masses and evolutionary states, thus providing a complete view of the various types of objects encountered along the first phases of star formation. The data presented in this work were acquired with the IRAM 30-m telescope near Pico Veleta (Spain) and consist of unbiased spectral surveys at millimetre wavelengths. These are part of the Large Programme ASAI, whose observations and data reduction procedures will be presented in detail in an article by Lefloch & Bachiller (in preparation). Briefly, we gathered the spectral data in several observing runs between 2011 and 2014 using the EMIR receivers at 3 mm (80-116 GHz), 2 mm (129-173 GHz), and 1.3 mm (200-276 GHz). (13 data files).

Multifaceted catalytic hydrogenation of amides via diverse activation of a sterically confined bipyridine-ruthenium framework.

PubMed

Miura, Takashi; Naruto, Masayuki; Toda, Katsuaki; Shimomura, Taiki; Saito, Susumu

2017-05-16

Amides are ubiquitous and abundant in nature and our society, but are very stable and reluctant to salt-free, catalytic chemical transformations. Through the activation of a "sterically confined bipyridine-ruthenium (Ru) framework (molecularly well-designed site to confine adsorbed H 2 in)" of a precatalyst, catalytic hydrogenation of formamides through polyamide is achieved under a wide range of reaction conditions. Both C=O bond and C-N bond cleavage of a lactam became also possible using a single precatalyst. That is, catalyst diversity is induced by activation and stepwise multiple hydrogenation of a single precatalyst when the conditions are varied. The versatile catalysts have different structures and different resting states for multifaceted amide hydrogenation, but the common structure produced upon reaction with H 2 , which catalyzes hydrogenation, seems to be "H-Ru-N-H."

Asymmetric adsorption by quartz - A model for the prebiotic origin of optical activity

NASA Technical Reports Server (NTRS)

Bonner, W. M.; Kavasmaneck, P. R.; Martin, F. S.; Flores, J. J.

1975-01-01

One mechanism previously proposed for the abiotic accumulation of molecules of one chirality in nature is asymmetric adsorption on the chiral surfaces of optically active quartz crystals. Earlier literature in this field is reviewed, with the conclusion that previous investigations of this phenomenon, using optical rotation criteria, have afforded ambiguous results. We now have studied the adsorption of radioactive D- and L-alanine on powdered d- and l-quartz, using change in radioactivity level as a criterion for both gross and differential adsorption, d-Quartz preferentially adsorbed D-alanine from anhydrous dimethyl-formamide solution, and l-quartz L-alanine. The differential adsorption varied between 1.0 and 1.8%. The implications of these observations are discussed from the viewpoint of early chemical evolution and the origin of optically active organic compounds in nature.

Spectroscopic studies, fluorescence quenching by molecular oxygen and amplified spontaneous emission of 1,4-bis [2-(2-pyridyl) vinyl] benzene (P2VB) diolefinic laser dye

NASA Astrophysics Data System (ADS)

El-Daly, Samy A.; Ebeid, E. M.

2014-04-01

The UV-visible electronic absorption spectra, molar absorptivity, fluorescence spectra, fluorescence quantum yield and excited state lifetime of 1,4-bis [2-(2-pyridyl) vinyl] benzene P2VB were measured in different solvents. The fluorescence quenching of P2VB by molecular oxygen was also studied using lifetime measurements. A 2 × 10-4 mol dm-3 solution of P2VB in dimethyl formamide (DMF) gave amplified spontaneous emission (ASE) in blue spectral region with emission maximum at 420 nm upon pumping by 337.1 nitrogen laser pulse. The photochemical quantum yields (ϕc) of trans-cis photoisomerization of P2VB were calculated in different organic solvents. The photoreactivity of P2VB are also studied PMMA matrix.

Delaminating and restacking MgAl-layered double hydroxide monitored and characterized by a range of instrumental methods

NASA Astrophysics Data System (ADS)

Muráth, Szabolcs; Somosi, Zoltán; Tóth, Ildikó Y.; Tombácz, Etelka; Sipos, Pál; Pálinkó, István

2017-07-01

The delamination-restacking properties of MgAl-layered double hydroxide (MgAl-LDH) were studied in various solvents. The LDH samples were successfully delaminated in polar amides (formamide, N-methylformamide, N-methylacetamide). Usually, delamination was finalized by ultrasonic treatment. As rehydrating solutions, numerous Na-salts with single-, double- and triple-charged anions were used. Reconstruction was accomplished with anions of one or two negative charges, but triple-charged ones generally disrupted the rebuilding process, likely, because their salts with the metals of the LDH are very stable, and the thin layers can more readily transform to salts than the ordered materials. Samples and delamination-restacking processes were characterized by X-ray diffractometry (XRD), infrared spectroscopy (IR), dynamic light scattering (DLS), scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX).

Compound-Specific Isotope Analysis of Amino Acids for Stardust-Returned Samples

NASA Technical Reports Server (NTRS)

Cook, Jamie; Elsila, Jamie E.; Stern J. C.; Glavin, D. P.; Dworkin, J. P.

2008-01-01

Significant portions of the early Earth's prebiotic organic inventory , including amino acids, could have been delivered to the Earth's sur face by comets and their fragments. Analysis of comets via spectrosc opic observations has identified many organic molecules, including me thane, ethane, arnmonia, cyanic acid, formaldehyde, formamide, acetal ehyde, acetonitrile, and methanol. Reactions between these identifie d molecules could allow the formation of more complex organics such a s amino acids. Isotopic analysis could reveal whether an extraterrest rial signature is present in the Stardust-exposed amines and amino ac ids. Although bulk isotopic analysis would be dominated by the EACA contaminant's terrestrial signature, compoundspecific isotope analysi s (CSIA) could determine the signature of each of the other individua l amines. Here, we report on progress made towards CSIA of the amino acids glycine and EACA in Stardustreturned samples.

A comparison of certain extracting agents for extraction of adenosine triphosphate (ATP) from microorganisms for use in the firefly luciferase ATP assay

NASA Technical Reports Server (NTRS)

Knust, E. A.; Chappelle, E. W.; Picciolo, G. L.

1975-01-01

Firefly luciferase ATP assay is used in clinical and industrial applications, such as determination of urinary infection levels, microbial susceptibility testing, and monitoring of yeast levels in beverages. Three categories of extractants were investigated for their extracting efficiency. They were ionizing organic solvents, nonionizing organic solvents, and inorganic acids. Dimethylsulfoxide and formamide represented the ionizing organic solvents, while n-butanol, chloroform, ethanol, acetone, and methylene chloride were used for the nonionizing organic solvents. Nitric acid and perchloric acid were chosen for the inorganic acids category. Pathogens were tested with each solvent. They included: Saccharomyces carlsbergensis, E. coli, Staphylococcus aureus, Klebsiella pneumoniae, Enterobacter species, Proteus mirabilis, Proteus vulgaris, Staphylococcus epidermidis, Streptococcus faecalis, Pseudomonas aeruginosa, and Candida albicans. These results are shown in graphic representations.

ANTIGENIC STRUCTURE OF ACTINOMYCETALES VI.

PubMed Central

Kwapinski, J. B.

1963-01-01

Kwapinski, J. B. (University of New England, Armidale, N.S.W., Australia). Antigenic structure of Actinomycetales. VI. Serological relationships between antigenic fractions of Actinomyces and Nocardia. J. Bacteriol. 86:179–186. 1963.—A total of 52 chemical fractions were obtained by a comprehensive technique of preparation from three strains of Actinomyces and three strains of Nocardia. The chemical and serological structures and specificities of disintegrated cells, cell walls, cytoplasms, and individual fractions were thoroughly studied. Cytoplasmic materials were found to be serologically alike or identical. The polysaccharide fractions, extracted from cell walls with alkali, formamide, and phenol, proved to be serologically related. Fractions prepared from the Nocardia by extractions in hot and concentrated solutions of acetic acid and sodium hydroxide, as well as the second protein fraction and the acetate-extracted polysaccharides of both the Nocardia and Actinomyces, proved to be genus-specific. PMID:14058939

Molecular insights into the activity and mechanism of cyanide hydratase enzyme associated with cyanide biodegradation by Serratia marcescens.

PubMed

Kushwaha, Madhulika; Kumar, Virender; Mahajan, Rishi; Bhalla, Tek Chand; Chatterjee, Subhankar; Akhter, Yusuf

2018-05-09

The present study provides molecular insights into the activity and mechanism of cyanide hydratase enzyme associated with degradation of cyanide compounds, using Serratia marcescens RL2b as a model organism. Resting cells harvested after 20 h achieved complete degradation of 12 mmol l - 1 cyanide in approximately 10 h. High-performance liquid chromatography analysis of reaction samples revealed formation of formamide as the only end product, which confirmed the presence of cyanide hydratase activity in S. marcescens RL2b. Comparative structural analysis with the other nitrilase family proteins, which was carried out using a sequence of cyanide hydratase from a phylogenetically related strain S. marcescens WW4, also revealed subtle but significant differences in amino acid residues of the substrate-binding pocket and catalytic triad (Cys-Lys-Glu).

Formation of nucleobases in a Miller-Urey reducing atmosphere.

PubMed

Ferus, Martin; Pietrucci, Fabio; Saitta, Antonino Marco; Knížek, Antonín; Kubelík, Petr; Ivanek, Ondřej; Shestivska, Violetta; Civiš, Svatopluk

2017-04-25

The Miller-Urey experiments pioneered modern research on the molecular origins of life, but their actual relevance in this field was later questioned because the gas mixture used in their research is considered too reducing with respect to the most accepted hypotheses for the conditions on primordial Earth. In particular, the production of only amino acids has been taken as evidence of the limited relevance of the results. Here, we report an experimental work, combined with state-of-the-art computational methods, in which both electric discharge and laser-driven plasma impact simulations were carried out in a reducing atmosphere containing NH 3 + CO. We show that RNA nucleobases are synthesized in these experiments, strongly supporting the possibility of the emergence of biologically relevant molecules in a reducing atmosphere. The reconstructed synthetic pathways indicate that small radicals and formamide play a crucial role, in agreement with a number of recent experimental and theoretical results.

Formation of nucleobases in a Miller–Urey reducing atmosphere

PubMed Central

Ferus, Martin; Pietrucci, Fabio; Saitta, Antonino Marco; Knížek, Antonín; Kubelík, Petr; Ivanek, Ondřej; Shestivska, Violetta; Civiš, Svatopluk

2017-01-01

The Miller–Urey experiments pioneered modern research on the molecular origins of life, but their actual relevance in this field was later questioned because the gas mixture used in their research is considered too reducing with respect to the most accepted hypotheses for the conditions on primordial Earth. In particular, the production of only amino acids has been taken as evidence of the limited relevance of the results. Here, we report an experimental work, combined with state-of-the-art computational methods, in which both electric discharge and laser-driven plasma impact simulations were carried out in a reducing atmosphere containing NH3 + CO. We show that RNA nucleobases are synthesized in these experiments, strongly supporting the possibility of the emergence of biologically relevant molecules in a reducing atmosphere. The reconstructed synthetic pathways indicate that small radicals and formamide play a crucial role, in agreement with a number of recent experimental and theoretical results. PMID:28396441

RNA-primed complementary-sense DNA synthesis of the geminivirus African cassava mosaic virus.

PubMed Central

Saunders, K; Lucy, A; Stanley, J

1992-01-01

The plant DNA virus African cassava mosaic virus (ACMV) is believed to replicate by a rolling circle mechanism. To investigate complementary-sense DNA (lagging strand) synthesis, we have analysed the heterogenous form of complementary-sense DNA (H3 DNA) from infected Nicotiana benthamiana by two-dimensional agarose gel electrophoresis and blot hybridisation. The presence of an RNA moeity is demonstrated by comparison of results for nucleic acids resolved on neutral/alkaline and neutral/formamide gels, suggesting that complementary-sense DNA synthesis on the virus-sense single-stranded DNA template is preceded by the synthesis of an RNA primer. Hybridisation with probes to specific parts of ACMV DNA A genome indicates that synthesis of the putative RNA primer initiates between nucleotides 2581-221, a region that includes intergenic sequences that have been implicated in geminivirus DNA replication and the control of gene expression. Images PMID:1475192

4-{2-[2-(4-Formyl­phen­oxy)eth­oxy]eth­oxy}benzaldehyde

PubMed Central

Ma, Zhen; Cao, Yiqun

2011-01-01

The title compound, C18H18O5, was obtained by the reaction of 4-hy­droxy­benzaldehyde with bis­(2,2-dichloro­eth­yl) ether in dimethyl­formamide. In the crystal, the mol­ecule lies on a twofold rotation axis that passes through the central O atom of the aliphatic chain, thus leading to one half-mol­ecule being present per asymmetric unit. The carbonyl, aryl and O—CH2—CH2 groups are almost coplanar, with an r.m.s. deviation of 0.030 Å. The aromatic rings are approximately perpendicular to each other, forming a dihedral angle of 78.31 sh;H⋯O hydrogen bonds and C—H⋯π inter­actions help to consolidate the three-dimensional network. PMID:21754870

Quantum-chemistry based calibration of the alkali metal cation series (Li(+)-Cs(+)) for large-scale polarizable molecular mechanics/dynamics simulations.

PubMed

Dudev, Todor; Devereux, Mike; Meuwly, Markus; Lim, Carmay; Piquemal, Jean-Philip; Gresh, Nohad

2015-02-15

The alkali metal cations in the series Li(+)-Cs(+) act as major partners in a diversity of biological processes and in bioinorganic chemistry. In this article, we present the results of their calibration in the context of the SIBFA polarizable molecular mechanics/dynamics procedure. It relies on quantum-chemistry (QC) energy-decomposition analyses of their monoligated complexes with representative O-, N-, S-, and Se- ligands, performed with the aug-cc-pVTZ(-f) basis set at the Hartree-Fock level. Close agreement with QC is obtained for each individual contribution, even though the calibration involves only a limited set of cation-specific parameters. This agreement is preserved in tests on polyligated complexes with four and six O- ligands, water and formamide, indicating the transferability of the procedure. Preliminary extensions to density functional theory calculations are reported. © 2014 Wiley Periodicals, Inc.

Base-unpaired regions in supercoiled replicative form DNA of coliphage M13

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

Dasgupta, S.; Allison, D.P.; Snyder, C.E.

Superhelical covalently closed circular replicative form DNA (RF I) of coliphage M13 appears as a relaxed molecule that has a base-unpaired region in the form of a bubble (100 to 200 base pairs long) seen in electron micrographs when spread in the presence of formaldehyde and formamide or after pretreatment with glyoxal. S1 endonuclease, specific for single-stranded DNA, converts superhelical M13 RF I DNA, but not nonsuperhelical M13 RF I to a significant extent, into unit-length linear molecules by sequential nicking of two strands. The locations of S1 nuclease-susceptible sites and glyoxal-fixed base-unpaired regions were both related to the fivemore » A-T-rich regions in M13 RF DNA. While S1 nuclease does not show preference for any of these sites, glyoxal-fixed bubbles occur predominantly at the major A-T-rich region in M13 RF DNA.« less

Chemical modification of botryosphaeran: structural characterization and anticoagulant activity of a water-soluble sulfonated (1-->3)(1-->6)-β-D-glucan.

PubMed

Brandi, Jamile; Oliveira, Éder C; Monteiro, Nilson; Vasconcelos, Ana Flora D; Dekker, Robert F H; Barbosa, Aneli M; Silveira, Joana L M; Mourão, Paulo A S; Corradi da Silva, Maria de Lourdes

2011-10-01

The exopolysaccharide botryosphaeran (EPS(GLC); a (1--> 3)(1-->6)-β-D-glucan from Botryosphaeria rhodina MAMB- 05) was sulfonated to produce a water-soluble fraction (EPS(GLC)-S) using pyridine and chlorosulfonic acid in formamid. This procedure was then repeated twice to produce another fraction (EPSGLC-RS) with a higher degree of substitution (DS, 1.64). The purity of each botryosphaeran sample (unsulfonated and sulfonated) was assessed by gel filtration chromatography (Sepharose CL-4B), where each polysaccharide was eluted as a single symmetrical peak. The structures of the sulfonated and re-sulfonated botryosphaerans were investigated using ultraviolet-visible (UV-Vis), Fourier-transform infrared (FT-IR), and (13)C nuclear magnetic resonance ((13)C NMR) spectroscopies. EPS(GLC) and EPS(GLC)-RS were also assayed for anticoagulation activity, and EPS(GLC)-RS was identified as an anticoagulant.

8-Chloro-6-iodo-2-phenyl­chromeno[4,3-c]pyrazol-4(2H)-one N,N-dimethyl­formamide monosolvate

PubMed Central

Lokhande, Pradeep; Hasanzadeh, Kamal; Khaledi, Hamid; Mohd Ali, Hapipah

2011-01-01

In the title compound, C16H8ClIN2O2·C3H7NO, the fused tricyclic pyrazolo­coumarin ring and the N-phenyl ring are almost coplanar, the dihedral angle between them being 1.86 (9)°. In the crystal, these rings stack on top of each other via π–π inter­actions [centroid–centroid distances = 3.489 (2), 3.637 (2), 3.505 (2) and 3.662 (2) Å], forming infinite chains along the a axis. The chains are connected into layers parallel to ac plane through I⋯O inter­actions [3.0011 (18) Å] between pairs of symmetry-related mol­ecules. The DMF solvent mol­ecules are C—H⋯O bonded to this network. PMID:21837089

DNA Sequence Modulates Geometrical Isomerism of the trans-8,9-Dihydro-8-(2,6-diamino-4-oxo-3,4-dihydropyrimid-5-yl-formamido)-9-hydroxy Aflatoxin B1 Adduct

PubMed Central

2016-01-01

Aflatoxin B1 (AFB1), a mycotoxin produced by Aspergillus flavus, is oxidized by cytochrome P450 enzymes to aflatoxin B1-8,9-epoxide, which alkylates DNA at N7-dG. Under basic conditions, this N7-dG adduct rearranges to yield the trans-8,9-dihydro-8-(2,6-diamino-4-oxo-3,4-dihydropyrimid-5-yl-formamido)-9-hydroxy aflatoxin B1 (AFB1–FAPY) adduct. The AFB1–FAPY adduct exhibits geometrical isomerism involving the formamide moiety. NMR analyses of duplex oligodeoxynucleotides containing the 5′-XA-3′, 5′-XC-3′, 5′-XT-3′, and 5′-XY-3′ sequences (X = AFB1–FAPY; Y = 7-deaza-dG) demonstrate that the equilibrium between E and Z isomers is controlled by major groove hydrogen bonding interactions. Structural analysis of the adduct in the 5′-XA-3′ sequence indicates the preference of the E isomer of the formamide group, attributed to formation of a hydrogen bond between the formyl oxygen and the N6 exocyclic amino group of the 3′-neighbor adenine. While the 5′-XA-3′ sequence exhibits the E isomer, the 5′-XC-3′ sequence exhibits a 7:3 E:Z ratio at equilibrium at 283 K. The E isomer is favored by a hydrogen bond between the formyl oxygen and the N4-dC exocyclic amino group of the 3′-neighbor cytosine. The 5′-XT-3′ and 5′-XY-3′ sequences cannot form such a hydrogen bond between the formyl oxygen and the 3′-neighbor T or Y, respectively, and in these sequence contexts the Z isomer is favored. Additional equilibria between α and β anomers and the potential to exhibit atropisomers about the C5–N5 bond do not depend upon sequence. In each of the four DNA sequences, the AFB1–FAPY adduct maintains the β deoxyribose configuration. Each of these four sequences feature the atropisomer of the AFB1 moiety that is intercalated above the 5′-face of the damaged guanine. This enforces the Ra axial conformation for the C5–N5 bond. PMID:25587868

Double proton transfer behavior and one-electron oxidation effect in double H-bonded glycinamide-formic acid complex.

PubMed

Li, Ping; Bu, Yuxiang

2004-11-22

The behavior of double proton transfer occurring in a representative glycinamide-formic acid complex has been investigated at the B3LYP/6-311 + + G( * *) level of theory. Thermodynamic and, especially, kinetic parameters, such as tautomeric energy, equilibrium constant, and barrier heights have been discussed, respectively. The relevant quantities involved in the double proton transfer process, such as geometrical changes, interaction energies, and intrinsic reaction coordinate calculations have also been studied. Computational results show that the participation of a formic acid molecule favors the proceeding of the proton transfer for glycinamide compared with that without mediate-assisted case. The double proton transfer process proceeds with a concerted mechanism rather than a stepwise one since no ion-pair complexes have been located during the proton transfer process. The calculated barrier heights are 11.48 and 0.85 kcal/mol for the forward and reverse directions, respectively. However, both of them have been reduced by 2.95 and 2.61 kcal/mol to 8.53 and -1.76 kcal/mol if further inclusion of zero-point vibrational energy corrections, where the negative barrier height implies that the reverse reaction should proceed with barrierless spontaneously, analogous to that occurring between glycinamide and formamide. Furthermore, solvent effects on the thermodynamic and kinetic processes have also been predicted qualitatively employing the isodensity surface polarized continuum model within the framework of the self-consistent reaction field theory. Additionally, the oxidation process for the double H-bonded glycinamide-formic acid complex has also been investigated. Contrary to that neutral form possessing a pair of two parallel intermolecular H bonds, only a single H bond with a comparable strength has been found in its ionized form. The vertical and adiabatic ionization potentials for the neutral complex have been determined to be about 9.40 and 8.69 eV, respectively, where ionization is mainly localized on the glycinamide fragment. Like that ionized glycinamide-formamide complex, the proton transfer in the ionized complex is characterized by a single-well potential, implying that the proton initially attached to amide N4 in the glycinamide fragment cannot be transferred to carbonyl O13 in the formic acid fragment at the geometry of the optimized complex. Copyright 2004 American Institute of Physics.

DNA Sequence Modulates Geometrical Isomerism of the trans-8,9- Dihydro-8-(2,6-diamino-4-oxo-3,4-dihydropyrimid-5-yl-formamido)- 9-hydroxy Aflatoxin B1 Adduct.

PubMed

Li, Liang; Brown, Kyle L; Ma, Ruidan; Stone, Michael P

2015-02-16

Aflatoxin B(1) (AFB(1)), a mycotoxin produced by Aspergillus flavus, is oxidized by cytochrome P450 enzymes to aflatoxin B(1)-8,9-epoxide, which alkylates DNA at N7-dG. Under basic conditions, this N7-dG adduct rearranges to yield the trans-8,9-dihydro-8-(2,6-diamino-4-oxo-3,4-dihydropyrimid-5-yl-formamido)-9-hydroxy aflatoxin B(1) (AFB(1)−FAPY) adduct. The AFB(1)−FAPY adduct exhibits geometrical isomerism involving the formamide moiety. NMR analyses of duplex oligodeoxynucleotides containing the 5′-XA-3′, 5′-XC-3′, 5′-XT-3′, and 5′-XY-3′ sequences (X = AFB(1)−FAPY; Y = 7-deaza-dG)demonstrate that the equilibrium between E and Z isomers is controlled by major groove hydrogen bonding interactions.Structural analysis of the adduct in the 5′-XA-3′ sequence indicates the preference of the E isomer of the formamide group,attributed to formation of a hydrogen bond between the formyl oxygen and the N(6) exocyclic amino group of the 3′-neighboradenine. While the 5′-XA-3′ sequence exhibits the E isomer, the 5′-XC-3′ sequence exhibits a 7:3 E:Z ratio at equilibrium at 283K. The E isomer is favored by a hydrogen bond between the formyl oxygen and the N(4)-dC exocyclic amino group of the 3′-neighbor cytosine. The 5′-XT-3′ and 5′-XY-3′ sequences cannot form such a hydrogen bond between the formyl oxygen and the 3′-neighbor T or Y, respectively, and in these sequence contexts the Z isomer is favored. Additional equilibria between α and β anomers and the potential to exhibit atropisomers about the C5−N(5) bond do not depend upon sequence. In each of the four DNA sequences, the AFB(1)−FAPY adduct maintains the β deoxyribose configuration. Each of these four sequences feature the atropisomer of the AFB(1) moiety that is intercalated above the 5′-face of the damaged guanine. This enforces the Ra axialc onformation for the C5−N(5) bond.

A Global Scale Scenario for Prebiotic Chemistry: Silica-Based Self-Assembled Mineral Structures and Formamide.

PubMed

Saladino, Raffaele; Botta, Giorgia; Bizzarri, Bruno Mattia; Di Mauro, Ernesto; Garcia Ruiz, Juan Manuel

2016-05-17

The pathway from simple abiotically made organic compounds to the molecular bricks of life, as we know it, is unknown. The most efficient geological abiotic route to organic compounds results from the aqueous dissolution of olivine, a reaction known as serpentinization (Sleep, N.H., et al. (2004) Proc. Natl. Acad. Sci. USA 101, 12818-12822). In addition to molecular hydrogen and a reducing environment, serpentinization reactions lead to high-pH alkaline brines that can become easily enriched in silica. Under these chemical conditions, the formation of self-assembled nanocrystalline mineral composites, namely silica/carbonate biomorphs and metal silicate hydrate (MSH) tubular membranes (silica gardens), is unavoidable (Kellermeier, M., et al. In Methods in Enzymology, Research Methods in Biomineralization Science (De Yoreo, J., Ed.) Vol. 532, pp 225-256, Academic Press, Burlington, MA). The osmotically driven membranous structures have remarkable catalytic properties that could be operating in the reducing organic-rich chemical pot in which they form. Among one-carbon compounds, formamide (NH2CHO) has been shown to trigger the formation of complex prebiotic molecules under mineral-driven catalytic conditions (Saladino, R., et al. (2001) Biorganic & Medicinal Chemistry, 9, 1249-1253), proton irradiation (Saladino, R., et al. (2015) Proc. Natl. Acad. Sci. USA, 112, 2746-2755), and laser-induced dielectric breakdown (Ferus, M., et al. (2015) Proc Natl Acad Sci USA, 112, 657-662). Here, we show that MSH membranes are catalysts for the condensation of NH2CHO, yielding prebiotically relevant compounds, including carboxylic acids, amino acids, and nucleobases. Membranes formed by the reaction of alkaline (pH 12) sodium silicate solutions with MgSO4 and Fe2(SO4)3·9H2O show the highest efficiency, while reactions with CuCl2·2H2O, ZnCl2, FeCl2·4H2O, and MnCl2·4H2O showed lower reactivities. The collections of compounds forming inside and outside the tubular membrane are clearly specific, demonstrating that the mineral self-assembled membranes at the same time create space compartmentalization and selective catalysis of the synthesis of relevant compounds. Rather than requiring odd local conditions, the prebiotic organic chemistry scenario for the origin of life appears to be common at a universal scale and, most probably, earlier than ever thought for our planet.

Effect of P, Na, Mg, and Ag content on the in vitro bioactivity, wettability and mechanical strength of sol-gel glasses

NASA Astrophysics Data System (ADS)

Bouhazma, S.; Chajri, S.; Herradi, S.; Khaldi, M.; El Hachadi, A.; El Bali, B.; Lachkar, M.

2018-03-01

Bioactive glasses of the type SiO2-CaO, SiO 2 -CaO-P2O5, and SiO2-CaO-P2O5-MO (M = Na, Mg, or Ag) were obtained by the sol-gel processing method. The obtained materials was characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS). Contact angle and surface tension variation with time were determined at 25°C, respectively, by the sessile and pendant drop techniques, for distinct testing liquids: water, diiodomethane, formamide, and simulated body fluid (SBF). The in vitro studies showed that all gel-glasses compositions produced were bioactive. In the present work, three effects of elements (Mg, Na, Ag) in the glass were detected: (i) good mechanical strength with satisfactory biodegradability, (ii) formation of hydroxyapatite, which may promote good bone bonding and (iii) the good wettability.

Energy decomposition analysis for exciplexes using absolutely localized molecular orbitals

NASA Astrophysics Data System (ADS)

Ge, Qinghui; Mao, Yuezhi; Head-Gordon, Martin

2018-02-01

An energy decomposition analysis (EDA) scheme is developed for understanding the intermolecular interaction involving molecules in their excited states. The EDA utilizes absolutely localized molecular orbitals to define intermediate states and is compatible with excited state methods based on linear response theory such as configuration interaction singles and time-dependent density functional theory. The shift in excitation energy when an excited molecule interacts with the environment is decomposed into frozen, polarization, and charge transfer contributions, and the frozen term can be further separated into Pauli repulsion and electrostatics. These terms can be added to their counterparts obtained from the ground state EDA to form a decomposition of the total interaction energy. The EDA scheme is applied to study a variety of systems, including some model systems to demonstrate the correct behavior of all the proposed energy components as well as more realistic systems such as hydrogen-bonding complexes (e.g., formamide-water, pyridine/pyrimidine-water) and halide (F-, Cl-)-water clusters that involve charge-transfer-to-solvent excitations.

Novel and economic acid-base indicator based on (p-toluidine) oligomer: Synthesis; characterization and solvatochromism applications

NASA Astrophysics Data System (ADS)

Zoromba, M. Sh.

2017-12-01

A new (p-toluidine) oligomer (PTO) was facile synthesized and economically routed via chemical oxidative polymerization by potassium dichromate as an initiator in an acidic aqueous medium at room temperature. The characterization of (p-toluidine) oligomer (PTO) has been described by various techniques including Fourier transform infra-red (FTIR), UV-Visible measurements, Mass spectra, H NMR, and thermal gravimetric analysis (TGA). Solvatochromism of PTO was studied in different polaritiy solvents such as acetic acid, acetone, dimethyl formamide, ethanol, isopropanol, chloroform, p-xylene, dichloromethane and carbon teterachloride. The absorption bands were bathochromically shifted with increased polarity of the solvent (positive solvatochromism). PTO shows three isosbestic points at 333, 388 and 472 nm in a binary mixture of acetone and chloroform. The deprotonation constants of PTO were found to be 3.1 and 5.8, based on spectrophotometric calculations. PTO was successfully used as an acid-base indicator; the acid solution color sharply turned from pink (acidic medium) to yellow (basic medium) at the end point.

(Trans)esterification of mannose catalyzed by lipase B from Candida antarctica in an improved reaction medium using co-solvents and molecular sieve.

PubMed

Nott, Katherine; Brognaux, Alison; Richard, Gaëtan; Laurent, Pascal; Favrelle, Audrey; Jérôme, Christine; Blecker, Christophe; Wathelet, Jean-Paul; Paquot, Michel; Deleu, Magali

2012-01-01

Four co-solvents (dimethylformamide [DMF], formamide, dimethyl sulfoxide [DMSO], and pyridine) were tested with tert-butanol (tBut) to optimize the initial rate (v₀) and yield of mannosyl myristate synthesis by esterification catalyzed by immobilized lipase B from Candida antarctica. Ten percent by volume of DMSO resulted in the best improvement of v₀ and 48-hr yield (respectively 115% and 13% relative gain compared to pure tBut). Use of molecular sieve (5% w/v) enhances the 48-hr yield (55% in tBut/DMSO [9:1, v/v]). Transesterification in tBut/DMSO (9:1, v/v) with vinyl myristate leads to further improvement of v₀ and 48-hr yield: a relative gain of 85% and 65%, respectively, without sieve and 25% and 10%, respectively, with sieve, compared to esterification. No difference in v₀ and 48-hr yield is observed when transesterification is carried out with or without sieve.

A General Catalytic Method for Highly Cost- and Atom-Efficient Nucleophilic Substitutions.

PubMed

Huy, Peter H; Filbrich, Isabel

2018-05-23

A general formamide-catalyzed protocol for the efficient transformation of alcohols into alkyl chlorides, which is promoted by substoichiometric amounts (down to 34 mol %) of inexpensive trichlorotriazine (TCT), is introduced. This is the first example of a TCT-mediated dihydroxychlorination of an OH-containing substrate (e.g., alcohols and carboxylic acids) in which all three chlorine atoms of TCT are transferred to the starting material. The consequently enhanced atom economy facilitates a significantly improved waste balance (E-factors down to 4), cost efficiency, and scalability (>50 g). Furthermore, the current procedure is distinguished by high levels of functional-group compatibility and stereoselectivity, as only weakly acidic cyanuric acid is released as exclusive byproduct. Finally, a one-pot protocol for the preparation of amines, azides, ethers, and sulfides enabled the synthesis of the drug rivastigmine with twofold S N 2 inversion, which demonstrates the high practical value of the presented method. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aerobic cyanide degradation by bacterial isolates from cassava factory wastewater

PubMed Central

Kandasamy, Sujatha; Dananjeyan, Balachandar; Krishnamurthy, Kumar; Benckiser, Gero

2015-01-01

Ten bacterial strains that utilize cyanide (CN) as a nitrogen source were isolated from cassava factory wastewater after enrichment in a liquid media containing sodium cyanide (1 mM) and glucose (0.2% w/v). The strains could tolerate and grow in cyanide concentrations of up to 5 mM. Increased cyanide levels in the media caused an extension of lag phase in the bacterial growth indicating that they need some period of acclimatisation. The rate of cyanide removal by the strains depends on the initial cyanide and glucose concentrations. When initial cyanide and glucose concentrations were increased up to 5 mM, cyanide removal rate increased up to 63 and 61 per cent by Bacillus pumilus and Pseudomonas putida. Metabolic products such as ammonia and formate were detected in culture supernatants, suggesting a direct hydrolytic pathway without an intermediate formamide. The study clearly demonstrates the potential of aerobic treatment with cyanide degrading bacteria for cyanide removal in cassava factory wastewaters. PMID:26413045

Structure and gas phase stability of complexes L . .. M, where M = Li+, Na+, Mg2+ and L is formaldehyde, formic acid, formate anion, formamide and their sila derivatives

NASA Astrophysics Data System (ADS)

Remko, Milan

Ab initio SCF and DFT methods were used to characterize the gas-phase complexes of selected carbonyl and silacarbonyl bases with Li+ , Na+ and Mg2+ . Geometries were optimized at the Hartree-Fock ab initio and Becke 3LYP DFT levels with the 6-31G* basis set. Frequency computations were performed at the RHF/6-31G* level of theory. Interaction energies of the cation-coordinated systems also were determined with the MP2/6-31G* method. The effect of extension of basis set (to the 6-31+ G* basis) on the computed properties of anion-metal cation complexes was investigated. Calculated energies of formation vary as Mg2+ > Li+ > Na+ . The Becke 3LYP DFT binding energies were comparable with those obtained at the correlated MP2 level and are in good agreement with available experimental data.

Fabrication of TiN nanorods by electrospinning and their electrochemical properties

NASA Astrophysics Data System (ADS)

Sun, Dongfei; Lang, Junwei; Yan, Xingbin; Hu, Litian; Xue, Qunji

2011-05-01

TiN nanorods were synthesized using electrospinning technique followed by thermolysis in different atmospheres. A dimethyl formamide-ethanol solution of poly-(vinyl pyrrolidone) and Ti (IV)-isopropoxide was used as the electrospinning precursor solution and as-spun nanofibers were calcined at 500 °C in air to generate TiO 2 nanofibers. Subsequently, a conversion from TiO 2 nanofibers to TiN nanorods was employed by the nitridation treatment at 600˜1400 °C in ammonia atmosphere. A typical characteristic of the final products was that the pristine nanofibers were cut into nanorods. The conversion from TiO 2 to TiN was realized when the nitridation temperature was above 800 °C. As-prepared nanorods were composed of TiN nano-crystallites and the average crystallite size gradually increased with the increase of the nitridation temperature. Electrochemical properties of TiN nanorods showed strong dependence on the nitridation temperature. The maximum value of the specific capacitance was obtained from the TiN nanorods prepared at 800 °C.

Properties of targeted preamplification in DNA and cDNA quantification.

PubMed

Andersson, Daniel; Akrap, Nina; Svec, David; Godfrey, Tony E; Kubista, Mikael; Landberg, Göran; Ståhlberg, Anders

2015-01-01

Quantification of small molecule numbers often requires preamplification to generate enough copies for accurate downstream enumerations. Here, we studied experimental parameters in targeted preamplification and their effects on downstream quantitative real-time PCR (qPCR). To evaluate different strategies, we monitored the preamplification reaction in real-time using SYBR Green detection chemistry followed by melting curve analysis. Furthermore, individual targets were evaluated by qPCR. The preamplification reaction performed best when a large number of primer pairs was included in the primer pool. In addition, preamplification efficiency, reproducibility and specificity were found to depend on the number of template molecules present, primer concentration, annealing time and annealing temperature. The amount of nonspecific PCR products could also be reduced about 1000-fold using bovine serum albumin, glycerol and formamide in the preamplification. On the basis of our findings, we provide recommendations how to perform robust and highly accurate targeted preamplification in combination with qPCR or next-generation sequencing.

Aerobic cyanide degradation by bacterial isolates from cassava factory wastewater.

PubMed

Kandasamy, Sujatha; Dananjeyan, Balachandar; Krishnamurthy, Kumar; Benckiser, Gero

2015-01-01

Ten bacterial strains that utilize cyanide (CN) as a nitrogen source were isolated from cassava factory wastewater after enrichment in a liquid media containing sodium cyanide (1 mM) and glucose (0.2% w/v). The strains could tolerate and grow in cyanide concentrations of up to 5 mM. Increased cyanide levels in the media caused an extension of lag phase in the bacterial growth indicating that they need some period of acclimatisation. The rate of cyanide removal by the strains depends on the initial cyanide and glucose concentrations. When initial cyanide and glucose concentrations were increased up to 5 mM, cyanide removal rate increased up to 63 and 61 per cent by Bacillus pumilus and Pseudomonas putida. Metabolic products such as ammonia and formate were detected in culture supernatants, suggesting a direct hydrolytic pathway without an intermediate formamide. The study clearly demonstrates the potential of aerobic treatment with cyanide degrading bacteria for cyanide removal in cassava factory wastewaters.

The AB Initio Mia Method: Theoretical Development and Practical Applications

NASA Astrophysics Data System (ADS)

Peeters, Anik

The bottleneck in conventional ab initio Hartree -Fock calculations is the storage of the electron repulsion integrals because their number increases with the fourth power of the number of basis functions. This problem can be solved by a combination of the multiplicative integral approximation (MIA) and the direct SCF method. The MIA approach was successfully applied in the geometry optimisation of some biologically interesting compounds like the neurolepticum Haloperidol and two TIBO derivatives, inactivators of HIV1. In this thesis the potency of the MIA-method is shown by the application of this method in the calculation of the forces on the nuclei. In addition, the MIA method enabled the development of a new model for performing crystal field studies: the supermolecule model. The results for this model are in better agreement with experimental data than the results for the point charge model. This is illustrated by the study of some small molecules in the solid state: 2,3-diketopiperazine, formamide oxime and two polymorphic forms of glycine, alpha-glycine and beta-glycine.

Extraction of extracellular polymeric substances from aerobic granule with compact interior structure.

PubMed

Adav, Sunil S; Lee, Duu-Jong

2008-06-15

Extracellular polymeric substances (EPS) were extracted from aerobic granules of compact interior structure using seven extraction methods. Ultrasound followed by the chemical reagents formamide and NaOH outperformed other methods in extracting EPS from aerobic granules of compact interior. The collected EPS revealed no contamination by intracellular substances and consisted mainly of proteins, polysaccharides, humic substances and lipids. The quantity of extracted proteins exhibited a weak correlation with quantity of extracted carbohydrates but no correlation with quantity of extracted humic substances. The total polysaccharides/total proteins (PN/PS) ratios for sludge flocs were approximately 0.9 regardless of extraction method. Protein content was significantly enriched in the granules, producing a PN/PS ratio of 3.4-6.2. This experimental result correlated with observations using excitation-emission matrix (EEM) and confocal laser scanning microscope technique. However, detailed study disproved the use of EEM results as a quantitative index of extracted EPS from sludge flocs or from granules.

Highly Efficient Red-Emitting Carbon Dots with Gram-Scale Yield for Bioimaging.

PubMed

Ding, Hui; Wei, Ji-Shi; Zhong, Ning; Gao, Qing-Yu; Xiong, Huan-Ming

2017-11-07

Carbon dots (CDs) are a new class of photoluminescent (PL), biocompatible, environment-friendly, and low-cost carbon nanomaterials. Synthesis of highly efficient red-emitting carbon dots (R-CDs) on a gram scale is a great challenge at present, which heavily restricts the wide applications of CDs in the bioimaging field. Herein, R-CDs with a high quantum yield (QY) of 53% are produced on a gram scale by heating a formamide solution of citric acid and ethylenediamine. The as-prepared R-CDs have an average size of 4.1 nm and a nitrogen content of about 30%, with an excitation-independent emission at 627 nm. After detailed characterizations, such strong red fluorescence is ascribed to the contribution from the nitrogen- and oxygen-related surface states and the nitrogen-derived structures in the R-CD cores. Our R-CDs show good photostability and low cytotoxicity, and thus they are excellent red fluorescence probes for bioimaging both in vitro and in vivo.

Structure, mechanical and magnetic properties of Al4C3 reinforced nickel matrix nanocomposites

NASA Astrophysics Data System (ADS)

Chaudhari, Alok Kumar; Singh, Dhananjay Kumar; Singh, V. B.

2018-05-01

A new type of nanocomposite, Ni-Al4C3 was prepared using Al4C3 as reinforcement by cathodic co-deposition at different current densities (1.0 to 5.0 A dm‑2) from a nickel acetate-N-methyl formamide (non-aqueous) bath. Influence of current density and incorporation of Al4C3 particles in nickel matrix on the structure and properties of the composite coatings was investigated. Surface morphology and composition of the deposits were determined by SEM and EDAX. Crystallographic structure and orientation of the electrodeposited Ni-Al4C3 composite were studied by x-ray diffraction. Compared to nickel metal, these nanocomposites exhibited finer grains, higher microhardness, improved corrosion resistance and enhanced soft magnetic properties. Composite deposited at higher current densities (>2 A dm‑2) shows mild texturing along (200) plane. The effect of heat treatment on the microstructure, texture and microhardness of the nanocomposites was also investigated.

Nanosheets of oxides and hydroxides: Ultimate 2D charge-bearing functional crystallites.

PubMed

Ma, Renzhi; Sasaki, Takayoshi

2010-12-01

A wide variety of cation-exchangeable layered transition metal oxides and their relatively rare counterparts, anion-exchangeable layered hydroxides, have been exfoliated into individual host layers, i.e., nanosheets. Exfoliation is generally achieved via a high degree of swelling, typically driven either by intercalation of bulky organic ions (quaternary ammonium cations, propylammonium cations, etc.) for the layered oxides or by solvation with organic solvents (formamide, butanol, etc.) for the hydroxides. Ultimate two-dimensional (2D) anisotropy for the nanosheets, with thickness of around one nanometer versus lateral size ranging from submicrometer to several tens of micrometers, allows them to serve either as an ideal quantum system for fundamental study or as a basic building block for functional assembly. The charge-bearing inorganic macromolecule-like nanosheets can be assembled or organized through various solution-based processing techniques (e.g., flocculation, electrostatic sequential deposition, or the Langmuir-Blodgett method) to produce a range of nanocomposites, multilayer nanofilms, and core-shell nanoarchitectures, which have great potential for electronic, magnetic, optical, photochemical, and catalytic applications.

Synthesis, spectral and structural characterization of isobutyl 4-(2-chlorophenyl)-5-cyano-6-(((dimethylamino)methylene)amino)-2-methyl-4H-pyran-3-carboxylate

NASA Astrophysics Data System (ADS)

Udhaya Kumar, C.; Velayutham Pillai, M.; Gokula Krishnan, K.; Ramalingan, C.

2017-09-01

A fascinating selectivity in the direction of the formation of the formamidine was observed upon the reaction of isobutyl 6-amino-4-(2-chlorophenyl)-5-cyano-2-methyl-4H-pyran-3-carboxylate with N,N-dimethyl formamide. A development in selectivity is explored and a probable mechanism for the reaction is also proposed. The formamidine has been analyzed by FT-IR, FT-Raman, LC-MS and NMR (1D and 2D (1H-1H COSY, 1H-13C COSY and HMBC)) spectra. The experimental findings are compared with the theoretical data calculated by using DFT-B3LYP with 6-311++G(d,p) basis set. A good agreement has been observed between experimental and theoretical data. Single crystal X-ray structural analysis of isobutyl 4-(2-chlorophenyl)-5-cyano-6-(((dimethylamino)methylene)amino)-2-methyl-4H-pyran-3-carboxylate (PDMF), evidences the conformation of pyran ring as "flattened-boat".

Absorption Spectra and Photoreactivity of p-Aminobenzophenone by Time-dependent Density Functional Theory

NASA Astrophysics Data System (ADS)

Cheng, Xue-mei; Huang, Yao; Ma, Jian-yi; Li, Xiang-yuan

2007-06-01

The absorption spectral properties of para-aminobenzophenone (p-ABP) were investigated in gas phase and in solution by time-dependent density functional theory. Calculations suggest that the singlet states vary greatly with the solvent polarities. In various polar solvents, including acetonitrile, methanol, ethanol, dimethyl sulfoxide, and dimethyl formamide, the excited S1 states with charge transfer character result from π → π* transitions. However, in nonpolar solvents, cyclohexane, and benzene, the S1 states are the result of n → π* transitions related to local excitation in the carbonyl group. The excited T1 states were calculated to have ππ* character in various solvents. From the variation of the calculated excited states, the band due to π → π* transition undergoes a redshift with an increase in solvent polarity, while the band due to n → π* transition undergoes a blueshift with an increase in solvent polarity. In addition, the triplet yields and the photoreactivities of p-ABP in various solvents are discussed.

Temperature dependence of the positronium yields in polar and nonpolar pure liquids; an experimental test of a phenomenological model

NASA Astrophysics Data System (ADS)

Lévay, B.

2004-08-01

A phenomenological model describing the temperature dependence of the positronium yields ( IPs, %) was tested in pure liquids of different polarity. The investigated solvents were: m-xylene (m-Xy) and iso-octane (i-C8) as aromatic and aliphatic nonpolar hydrocarbons, methanol (MeOH), water and dimethyl formamide as polar solvents with and without OH group. Arrhenius type linear relationship predicted by the model for the ln Q vs 1/ T function, where Q=(100/ IPs-1), was found to be valid in all cases. The slopes of the lines correspond to the activation energy differences (Δ E*= Erec- EPs) between the two main competing reaction pathways in the positron spur, i.e., solvent recombination (e - + M +) and positronium formation (e - + e +). The slopes were positive, i.e., Δ E*<0 and Erec< EPs. For polar liquids, correlation seems to exists between Δ E* and the electron mobility ( μ) or the activation energy of the viscosity ( Eη).

Enzymatic modification of natural and synthetic polymers using lipases and proteases

NASA Astrophysics Data System (ADS)

Chakraborty, Soma

Enzymatic modification of natural/synthetic polymers [starch nanoparticles, poly (n-alkyl acrylates) and poly(vinyl formamide)] was studied. Enzymes used for catalysis were lipases and proteases. Starch nanoparticles (40nm diameter) were incorporated into AOT-coated reverse micelles. Reactions performed with the acylating agents vinyl stearate, epsilon-caprolactone and maleic anhydride in toluene in presence of Novozyme-435 at 40°C for 36h gave products with degrees of substitution of 0.8, 0.6 and 0.4 respectively. DEPT-135 NMR spectra revealed that the modification occurred regioselectively at the C-6 position of the glucose units. Infrared microspectroscopy showed that the surfactant coated starch nanoparticles diffuse into pores of Novozyme-435 beads, coming in close proximity with CALB to promote modification. The modified products retained nanoscale dimensions. Catalysis of amide bond formation between a low molar mass amine and ester side groups of poly(n-alkyl acrylates)[poly(ethyl acrylate), poly(methyl acrylate) and poly(butyl acrylate)] was also examined. The nucleophiles were mono and diamines. Among the poly(n-alkyl acrylates) and the lipases studied, poly(ethyl acrylate) was the preferred substrate and Novozyme-435 the most active lipase. Poly(ethyl acrylate) in 80% by-volume toluene was reacted with 1 equivalent per repeat unit of hexyl amine at 70°C in presence of Novozyme-435. The product contained 10.6 mol% amide groups. Attempts to increase the amidation beyond 10--11 mol% by increasing the reaction time or use of fresh enzyme were unsuccessful, showing that poly(ethylacrylate-co-10mol%hexylacrylamide) is a poor substrate for further acylation. When chiral amines ([R,S]-alpha-methyl benzylamine, [R,S]-beta-methyl phenyl amine) were used as nucleophiles, Novozyme-435 enantioselectively catalyzed amidation of poly(ethyl acrylate). Poly(vinyl formamide), P(VfAm) by acid or base-catalyzed hydrolysis leads to poly(vinylamine), P(VAm), and corresponding copolymers. As an alternative to chemical hydrolysis a mild and selective enzymatic method was discovered. Fifteen proteases were evaluated for this transformation. Of these, PROT 7 was the most active. Within 24h PROT 7 gave products with 44% hydrolysis. Further hydrolysis was not observed by extending the reaction time because poly(vinylformamide-co-40%vinylamine) is a poor substrate for further hydrolysis. The sequence distribution of copolymers formed by chemical hydrolysis and enzymatic hydrolysis was compared. Chemical hydrolysis gave random copolymer. In contrast, PROT 7 gave block-like arrangement of VAm units.

Characterization of group H streptococcal temperate bacteriophage phi 227.

PubMed

Nugent, K M; Cole, R M

1977-03-01

phi 227, a temperate phage from a group H streptococcus (Streptococcus sanguis), was propagated vegetatively in group H strain Wicky 4-EryR, and its characteristics were determined. A procedure dependent on multiplicity of infection, incubation time, and treatment of crude lysates with diatomaceous earth was found to optimize phage yield, resulting in titers of 1 X 10(10) to 2 X 10(10) PFU/ml. Without prior treatment with diatomaceous earth, subsequent purification procedures (methanol, ammonium sulfate, polyethylene glycol) gave recoveries of less than 1% of crude lysate titers. Adsorption of phi227 to host cells was relatively unaffected by the medium, but calcium (not substituted by magnesium) was required for formation of infectious centers. The phage receptor was present on purified cell walls, resisted trypsin and heat, and was removed ty hydrochloric acid, trichloracetic acid, and hot formamide: however, formamide-extracted material failed to inactivate phage, and the nature of the receptor is unknown. Single-step growth experiments showed a latent period of 39 min and a burst size of 100 PFU/infectious center; results were unaffected by omission of supplemental Ca2+, by supplementation with Mg2, addition of glucose, or changes of pH between 6.35 and 8.0; but increased temperature (40 to 43 degrees C) shortened the latent period and decreased the burst size. The latent period was prolonged in genetically competent host cells and in chemically defined medium; and in the latter, the burst size was smaller. Phage replication was sensitive to those metabolic inhibitors which inhibited the host streptococcus: these included rifampin, fluorodeoxyuridine, hydroxyurea, dihydrostreptomycin, and 6-P-hydroxyphenylazouracil. The data suggest that phi227 does not code for a rifampin-resistant RNA polymerase. However, in a rifampin-resistant host strain, phage replication and lysogen formation were both decreased suggesting that altered host core polymerase had less affinity for (some) promotors on the phi227 template. In transfection, a Ca2+-dependent stabilization step that was inhibited by Mg2+ was demonstrated; transformation was not affected by either Ca2+ or Mg2+, and the site and nature of the stabilization are unknown. More than one molecule of DNA was required for plaque formation. Biophysical characterization showed a type B phage of buoyant density (CsCl) 1.50, containing five proteins and 54.8% DNA. The duplex linear DNA had a molecular weight (calculated from contour length) of 23.2 X 10(6) and a guanine plus cytosine content (calculated from melting point) of 42.3 mol%. Similar characterizations of streptococcal phages, including biophysical data, have not been previously available.

Tests of spool models for DNA packaging in phage lambda.

PubMed

Widom, J; Baldwin, R L

1983-12-25

Experiments are reported which bear on two spool models proposed for packaging the DNA of phage lambda. Both spool models fill an assumed spherical cavity with DNA wrapped in cylindrical or quasi-cylindrical layers composed of adjacent circular turns. In the curved-spool model, a single continuous segment of DNA, about 20% of the DNA length and probably located near the left end of the DNA, is in contact with the coat protein of the phage capsid. In the straight spool model, there are several DNA segments in contact with the capsid; they are concentrated in one half (probably the left half) of lambda DNA. We have identified the loci on the DNA which are in contact with the capsid by chemical crosslinking, induced by ultraviolet-irradiation of phage containing 5-bromodeoxyuridine in place of thymine. In an electron microscope experiment, phage are first lysed with EDTA, and then spread in a cytochrome c film by the formamide method. The disrupted capsid, which has the appearance of a phage ghost, serves as a marker showing where the DNA is crosslinked to the coat. The left end of the DNA is not distinguished from the right end, and so the map of DNA-capsid contacts is folded over on itself. Contacts are found nearly randomly over the entire map. In a second experiment, DNA from lysed, crosslinked phage is cut either with EcoRI or HindIII restriction endonucleases and the cut restriction fragments are labeled at their ends with 32P. Density centrifugation in a CsCl gradient separates free DNA from restriction fragments crosslinked to protein. After digestion with proteinase k, the DNA fragments previously crosslinked to protein are identified by size after agarose gel electrophoresis. DNA fragments from all parts of the genome are found. These two experiments show that, if the DNA of each phage is packaged identically, then the curved-spool model is ruled out and the straight spool model is unlikely. Alternatively, the manner of packaging the DNA may vary from one phage to the next. These results agree with other recent experiments on lambda DNA packaging by Hall & Schellman (1982a,b), and by Haas et al. (1982). A different experiment is also reported. The psoralen derivative aminomethyltrioxalen (AMT) is allowed to intercalate into lambda phage and then the DNA strands are crosslinked by ultraviolet-irradiation after the rapid phase of AMT intercalation is complete. The DNA is subsequently denatured by glyoxal modification and spread for electron microscopy in a cytochrome c film by the formamide method.(ABSTRACT TRUNCATED AT 400 WORDS)

A Global Scale Scenario for Prebiotic Chemistry: Silica-Based Self-Assembled Mineral Structures and Formamide

PubMed Central

2016-01-01

The pathway from simple abiotically made organic compounds to the molecular bricks of life, as we know it, is unknown. The most efficient geological abiotic route to organic compounds results from the aqueous dissolution of olivine, a reaction known as serpentinization (Sleep, N.H., et al. (2004) Proc. Natl. Acad. Sci. USA 101, 12818–12822). In addition to molecular hydrogen and a reducing environment, serpentinization reactions lead to high-pH alkaline brines that can become easily enriched in silica. Under these chemical conditions, the formation of self-assembled nanocrystalline mineral composites, namely silica/carbonate biomorphs and metal silicate hydrate (MSH) tubular membranes (silica gardens), is unavoidable (Kellermeier, M., et al. In Methods in Enzymology, Research Methods in Biomineralization Science (De Yoreo, J., Ed.) Vol. 532, pp 225–256, Academic Press, Burlington, MA). The osmotically driven membranous structures have remarkable catalytic properties that could be operating in the reducing organic-rich chemical pot in which they form. Among one-carbon compounds, formamide (NH2CHO) has been shown to trigger the formation of complex prebiotic molecules under mineral-driven catalytic conditions (Saladino, R., et al. (2001) Biorganic & Medicinal Chemistry, 9, 1249–1253), proton irradiation (Saladino, R., et al. (2015) Proc. Natl. Acad. Sci. USA, 112, 2746–2755), and laser-induced dielectric breakdown (Ferus, M., et al. (2015) Proc Natl Acad Sci USA, 112, 657–662). Here, we show that MSH membranes are catalysts for the condensation of NH2CHO, yielding prebiotically relevant compounds, including carboxylic acids, amino acids, and nucleobases. Membranes formed by the reaction of alkaline (pH 12) sodium silicate solutions with MgSO4 and Fe2(SO4)3·9H2O show the highest efficiency, while reactions with CuCl2·2H2O, ZnCl2, FeCl2·4H2O, and MnCl2·4H2O showed lower reactivities. The collections of compounds forming inside and outside the tubular membrane are clearly specific, demonstrating that the mineral self-assembled membranes at the same time create space compartmentalization and selective catalysis of the synthesis of relevant compounds. Rather than requiring odd local conditions, the prebiotic organic chemistry scenario for the origin of life appears to be common at a universal scale and, most probably, earlier than ever thought for our planet. PMID:27115539

Synthesis of RNA molecules larger than 45 S by isolated rat-liver nucleoli.

PubMed

Grummt, I

1975-09-01

Nucleoli, isolated from rat liver, synthesize in vitro high-molecular-weight RNA, the base composition and sedimentation pattern of which resembles that of ribosomal precursor RNA. In addition, RNA molecules larger than 45 S have been found. In this paper experiments are described which indicate that these large RNA molecules represent geniune transcription products and are not aggregates arising under the experimental conditions employed. This was established by comparing different extraction methods, by sedimentation analysis of the RNA after denaturation with formamide and by pulse-chase experiments. Hybridisation-competition studies showed that 45-S RNA competes with those rapidly molecules to about 80-90%, thus providing evidence for the presence of ribosomal precursor RNA sequences in those long transcription products. Intact nuclei are able to synthesize in the presence of Mg2+ and alpha-amanitin RNA molecules larger than 45 S too, provided that the RNAase activity is suppressed effectively by the addition of cytoplasmic RNAase inhibitor. The significance of these results is discussed with respect to the initial transcript of the rDNA genes in rat liver nucleoli.

Pre-biotic molecules in shocks: the case of L1157

NASA Astrophysics Data System (ADS)

Mendoza, Edgar; Lefloch, Bertrand; López-Sepulcre, Ana; Ceccarelli, Cecilia; Codella, Claudio; Boechat-Roberty, Heloisa M.; Bachiller, Rafael

2015-08-01

Interstellar molecules with a peptide link -NH-C(=O)-, like formamide (NH2CHO) and isocyanic acid (HNCO) are notably interesting for their potential role in pre-biotic chemistry. For first time, we report the detection of both molecules towards the protostellar shock L1157-B1 and L1157-B2, with the IRAM 30m telescope. Analysis of the line profiles shows that the emission arises from the outflow cavities associated with B1 and B2. From a simple rotational diagram analysis, molecular abundance of ≈ (0.4-1.1)×10-8 and (3.3-8.8)×10-8 are derived for NH2CHO and HNCO, respectively. The shock regions B1 and B2 appear to be among the richest Galactic sources of HNCO and NH2CHO molecules. We have observed a narrow linear correlation between their abundances, suggesting that the two species are chemically related. Comparison with astrochemical models favours molecule formation on ice grain mantles, with NH2CHO generated from hydrogenation of HNCO.

Hydrogenation at low temperatures does not always lead to saturation: the case of HNCO

NASA Astrophysics Data System (ADS)

Noble, J. A.; Theule, P.; Congiu, E.; Dulieu, F.; Bonnin, M.; Bassas, A.; Duvernay, F.; Danger, G.; Chiavassa, T.

2015-04-01

Context. It is generally agreed that hydrogenation reactions dominate chemistry on grain surfaces in cold, dense molecular cores, saturating the molecules present in ice mantles. Aims: We present a study of the low temperature reactivity of solid phase isocyanic acid (HNCO) with hydrogen atoms, with the aim of elucidating its reaction network. Methods: Fourier transform infrared spectroscopy and mass spectrometry were employed to follow the evolution of pure HNCO ice during bombardment with H atoms. Both multilayer and monolayer regimes were investigated. Results: The hydrogenation of HNCO does not produce detectable amounts of formamide (NH2CHO) as the major product. Experiments using deuterium reveal that deuteration of solid HNCO occurs rapidly, probably via cyclic reaction paths regenerating HNCO. Chemical desorption during these reaction cycles leads to loss of HNCO from the surface. Conclusions: It is unlikely that significant quantities of NH2CHO form from HNCO. In dense regions, however, deuteration of HNCO will occur. HNCO and DNCO will be introduced into the gas phase, even at low temperatures, as a result of chemical desorption.

A theoretical study of Zn++ interacting with models of ligands present at the thermolysin active site

NASA Astrophysics Data System (ADS)

Giessner-Prettre, Claude; Jacob, Olivier

1989-03-01

The binding energy and the geometrical arrangements of the complexes formed by the zinc dication with OH-, one, four, five or six water molecules, SH-, H2S, formic acid, the formate anion, imidazole, its anion and formamide are calculated using the MNDO method. The comparison of the results obtained with those of ab initio computations on the same complexes induced us to propose for Zn++ a set of parameters different from the one determined by Dewar for the neutral metal atom. Using the two MNDO parametrizations, similar calculations are carried out for Zn++ interacting with two molecules of 2-aminoethanethiol and with models of the four ligands which are present at the thermolysin active site, in order to evaluate the possibilities and limitations of this semiempirical method for theoretical studies concerning zinc metalloenzymes. In the last case, the results obtained suggest that, in the crystal state, the water molecule could be deprotonated. This finding is discussed in relation with the mechanism of action of the enzyme which has been proposed.

Correlated natural transition orbital framework for low-scaling excitation energy calculations (CorNFLEx).

PubMed

Baudin, Pablo; Kristensen, Kasper

2017-06-07

We present a new framework for calculating coupled cluster (CC) excitation energies at a reduced computational cost. It relies on correlated natural transition orbitals (NTOs), denoted CIS(D')-NTOs, which are obtained by diagonalizing generalized hole and particle density matrices determined from configuration interaction singles (CIS) information and additional terms that represent correlation effects. A transition-specific reduced orbital space is determined based on the eigenvalues of the CIS(D')-NTOs, and a standard CC excitation energy calculation is then performed in that reduced orbital space. The new method is denoted CorNFLEx (Correlated Natural transition orbital Framework for Low-scaling Excitation energy calculations). We calculate second-order approximate CC singles and doubles (CC2) excitation energies for a test set of organic molecules and demonstrate that CorNFLEx yields excitation energies of CC2 quality at a significantly reduced computational cost, even for relatively small systems and delocalized electronic transitions. In order to illustrate the potential of the method for large molecules, we also apply CorNFLEx to calculate CC2 excitation energies for a series of solvated formamide clusters (up to 4836 basis functions).

Crystallization-driven one-dimensional self-assembly of polyethylene-b-poly(tert-butylacrylate) diblock copolymers in DMF: effects of crystallization temperature and the corona-forming block.

PubMed

Fan, Bin; Liu, Lei; Li, Jun-Huan; Ke, Xi-Xian; Xu, Jun-Ting; Du, Bin-Yang; Fan, Zhi-Qiang

2016-01-07

Crystallization-driven self-assembly of polyethylene-b-poly(tert-butylacrylate) (PE-b-PtBA) block copolymers (BCPs) in N,N-dimethyl formamide (DMF) was studied. It is found that all three PE-b-PtBA BCPs used in this work can self-assemble into one-dimensional crystalline cylindrical micelles. When the BCP solution is cooled to crystallization temperature (Tc) from 130 °C, the seed micelles may be produced via two competitive processes in the initial period: stepwise micellization/crystallization and simultaneous crystallization/micellization. Subsequently, the seed micelles can undergo growth driven by the epitaxial crystallization of the unimers. The lengths of both the seed micelles and the grown micelles are longer for the BCP with a longer PtBA block at a higher Tc. Quasi-living growth of the PE-b-PtBA crystalline cylindrical micelles is achieved at a higher Tc. A longer PtBA block evidently retards the attachment of unimers to the crystalline micelles, leading to a slower growth rate.

β-Lactam antibiotics. Spectroscopy and molecular orbital (MO) calculations . Part I: IR studies of complexation in penicillin-transition metal ion systems and semi-empirical PM3 calculations on simple model compounds

NASA Astrophysics Data System (ADS)

Kupka, Teobald

1997-12-01

IR studies were preformed to determine possible transition metal ion binding sites of penicillin. the observed changes in spectral position and shape of characteristic IR bands of cloxacillin in the presence of transition metal ions (both in solutions and in the solid state) indicate formation of M-L complexes with engagement of -COO - and/or -CONH- functional groups. The small shift of νCO towards higher frequencies rules out direct M-L interaction via β-lactam carbonyl. PM3 calculations on simple model compounds (substituted formamide, cyclic ketones, lactams and substituted monocyclic β-lactams) have been performed. All structures were fully optimized and the calculated bond lengths, angles, heats of formation and CO stretching frequencies were discussed to determine the β-lactam binding sites and to explain its susceptibility towards nucleophilic attack (hydrolysis in vitro) and biological activity. The relative changes of calculated values were critically compared with available experimental data and same correlation between structural parameters and in vivo activity was shown.

Anisotropic membranes for gas separation

DOEpatents

Gollan, A.Z.

1987-07-21

A gas separation membrane has a dense separating layer about 10,000 Angstroms or less thick and a porous support layer 10 to 400 microns thick that is an integral unit with gradually and continuously decreasing pore size from the base of the support layer to the surface of the thin separating layer and is made from a casting solution comprising ethyl cellulose and ethyl cellulose-based blends, typically greater than 47.5 ethoxyl content ethyl cellulose blended with compatible second polymers, such as nitrocellulose. The polymer content of the casting solution is from about 10% to about 35% by weight of the total solution with up to about 50% of this polymer weight a compatible second polymer to the ethyl cellulose in a volatile solvent such as isopropanol, methylacetate, methanol, ethanol, and acetone. Typical nonsolvents for the casting solutions include water and formamide. The casting solution is cast in air from about zero to 10 seconds to allow the volatile solvent to evaporate and then quenched in a coagulation bath, typically water, at a temperature of 7--25 C and then air dried at ambient temperature, typically 10--30 C. 2 figs.

Solvent induced synthesis, structure and properties of coordination polymers based on 5-hydroxyisophthalic acid as linker and 1,10-phenanthroline as auxiliary ligand

NASA Astrophysics Data System (ADS)

Kariem, Mukaddus; Yawer, Mohd; Sheikh, Haq Nawaz

2015-11-01

Three new coordination polymers [Mn(hip)(phen) (H2O)]n (1), [Co(hip)(phen) (H2O)]n (2), and [Cd(hip) (phen) (H2O)]n (3) (H2hip=5-hydroxyisophthalic acid; phen=1,10-phenanthroline) have been synthesized by solvo-hydrothermal method using diethyl formamide-water (DEF-H2O) as solvent system. Single-crystal X-ray diffraction analysis reveals that all three coordination polymers 1, 2 and 3 crystallize in monoclinic space group P2/n. Metal ions are inter-connected by hydroxyisophthalate anions forming zig-zag 1D chain. 1D chains are further inter-connected by hydrogen bonding and π-π stacking interactions leading to 3D supramolecular architecture. Hydrogen-bonding and π-π stacking provide thermal stability to polymers. Compounds 1 and 2 are paramagnetic at room temperature and variable temperature magnetic moment measurements revealed weak ferromagnetic interactions between metal ions at low temperature. Compound 3 exhibits excellent photoluminescence with large Stokes shift.

Electronic distributions within protein phenylalanine aromatic rings are reflected by the three-dimensional oxygen atom environments.

PubMed Central

Thomas, K A; Smith, G M; Thomas, T B; Feldmann, R J

1982-01-01

The atomic environments of 170 phenylalanine-residue aromatic rings from 28 protein crystal structures are transformed into a common orientation and combined to calculate an average three-dimensional environment. The spatial distribution of atom types in this environment reveals a preferred interaction between oxygen atoms and the edge of the planar aromatic rings. From the difference in frequency of interaction of oxygen atoms with the edge and the top of the ring, an apparent net free energy difference of interaction favoring the edge of the ring is estimated to be about -1 kcal/mol (1 cal = 4.184 J). Ab initio quantum mechanical calculations, performed on a model consisting of benzene and formamide, indicate that the observed geometry is stabilized by a favorable enthalpic interaction. Although benzene rings are considered to be nonpolar, the electron distribution is a complex multipole with no net dipole moment. The observed interaction orientation frequencies demonstrate that these multipolar electron distributions, when occurring at the short distances encountered in densely packed protein molecules, are significant determinants of internal packing geometries. PMID:6956896

Biodegradation of acrylamide by Enterobacter aerogenes isolated from wastewater in Thailand.

PubMed

Buranasilp, Kanokhathai; Charoenpanich, Jittima

2011-01-01

A widespread use of acrylamide, probably a neurotoxicant and carcinogen, in various industrial processes has led to environmental contamination. Fortunately, some microorganisms are able to derive energy from acrylamide. In the present work, we reported the isolation and characterization of a novel acrylamide-degrading bacterium from domestic wastewater in Chonburi, Thailand. The strain grew well in the presence of acrylamide as 0.5% (W/V), at pH 6.0 to 9.0 and 25 degrees C. Identification based on biochemical characteristics and 16S rRNA gene sequence identified the strain as Enterobacter aerogenes. Degradation of acrylamide to acrylic acid started in the late logarithmic growth phase as a biomass-dependent pattern. Specificity of cell-free supernatant towards amides completely degraded butyramide and urea and 86% of lactamide. Moderate degradation took place in other amides with that by formamide > benzamide > acetamide > cyanoacetamide > propionamide. No degradation was detected in the reactions of N,N-methylene bisacrylamide, sodium azide, thioacetamide, and iodoacetamide. These results highlighted the potential of this bacterium in the cleanup of acrylamide/amide in the environment.

Transdermal delivery of lercanidipine hydrochloride: effect of chemical enhancers and ultrasound.

PubMed

Shetty, Pallavi K; Suthar, Neelam A; Menon, Jyothsna; Deshpande, Praful B; Avadhani, Kiran; Kulkarni, Raghavendra V; Mutalik, Srinivas

2013-08-01

The effects of permeation enhancers and sonophoresis on the transdermal permeation of lercanidipine hydrochloride (LRDP) across mouse skin were investigated. Parameters including drug solubility, partition coefficient, drug degradation and drug permeation in skin were determined. Tween-20, dimethyl formamide, propylene glycol, poly ethylene glycol (5% v/v) and different concentration of ethanol were used for permeation enhancement. Low frequency ultrasound was also applied in the presence and absence of permeation enhancers to assess its effect on augmenting the permeation of drug. All the permeation enhancers, except propylene glycol, increased the transdermal permeation of LRDP. Sonophoresis significantly increased the cumulative amount of LRDP permeating through the skin in comparison to passive diffusion. A synergistic effect was noted when sonophoresis was applied in presence of permeation enhancers. The results suggest that the formulation of LRDP with an appropriate penetration enhancer may be useful in the development of a therapeutic system to deliver LRDP across the skin for a prolonged period (i.e., 24 h). The application of ultrasound in association with permeation enhancers could further serve as non-oral and non-invasive drug delivery modality for the immediate therapeutic effect.

Ultrafast hydrogen bond dynamics and partial electron transfer after photoexcitation of diethyl ester of 7-(diethylamino)-coumarin-3-phosphonic acid and its benzoxaphosphorin analog.

PubMed

Wagner, M S; Ilieva, E D; Petkov, P St; Nikolova, R D; Kienberger, R; Iglev, H

2015-04-21

The solvation dynamics after optical excitation of two phosphono-substituted coumarin derivatives dissolved in various solutions are studied by fluorescence up-conversion spectroscopy and quantum chemical simulations. The Kamlet-Taft analysis of the conventional absorption and emission spectra suggests weakening of the solvent-solute H-bonds upon optical excitation, which is in contrast to the results gained by the quantum simulations and earlier studies reported for coumarin derivatives without phosphono groups. The simulations give evidence that the solvent reorganisation around the excited fluorophore leads to partial electron transfer to the first solvation shell. The process occurs on a timescale between 1 and 10 ps depending on the solvent polarity and leads to a fast decay of the time-resolved emission signal. Using the ultrafast spectral shift of the time-dependent fluorescence we estimated the relaxation time of the H-bonds in the electronically excited state to be about 0.6 ps in water, 1.5 ps in ethanol and 2.8 ps in formamide.

Degradation of the metal-cyano complex tetracyanonickelate (II) by Fusarium oxysporum N-10.

PubMed

Yanase, H; Sakamoto, A; Okamoto, K; Kita, K; Sato, Y

2000-03-01

A fungus with the ability to utilize a metalcyano compound, tetracyanonickelate (II) ¿K2[Ni (CN)4]; TCN¿, as its sole source of nitrogen was isolated from soil and identified as Fusarium oxysporum N-10. Both intact mycelia and cell-free extract of the strain catalyzed hydrolysis of TCN to formate and ammonia and produced formamide as an intermediate, thereby indicating that a hydratase and an amidase sequentially participated in the degradation of TCN. The enzyme catalyzing the hydration of TCN was purified approximately ten-fold from the cell-free extract of strain N-10 with a yield of 29%. The molecular mass of the active enzyme was estimated to be 160 kDa. The enzyme appears to exist as a homotetramer, each subunit having a molecular mass of 40 kDa. The enzyme also catalyzed the hydration of KCN, with a cyanide-hydrating activity 2 x 10(4) times greater than for TCN. The kinetic parameters for TCN and KCN indicated that hydratase isolated from F. oxysporum was a cyanide hydratase able to utilize a broad range of cyano compounds and nitriles as substrates.

[Separation of catechins and caffeine in tea polyphenol by isocratic elution high performance liquid chromatography].

PubMed

Tang, G Y; Wu, H J; Wu, L; Li, Z J; Yao, Y G

2001-05-01

The catechins, particularly in green tea, have been found to possess anti-mutagenic and anti-tumorigenic properties. As each catechin possesses distinct properties, a simple and rapid method that could be used for analysis of individual catechins in a complex mixture would be necessary. A relatively simple and rapid method for simultaneous separation of five catechins and caffeine in tea polyphenol by isocratic elution high performance liquid chromatography has been developed. The analysis could be finished within 30 min. They were measured using Resolve C18 column (at 43 degrees C) and UV detector (at 280 nm), water-85% phosphoric acid aqueous solution-acetonitrile-dimethyl formamide(DMF) (859:1:120:20, V/V) as mobile phase. There was a good linear relationship between the content of component and its peak area for catechins and caffeine, with the correlation coefficients of 0.9992-0.9999. The average recoveries (n = 5) were 83.33%-104.42%, and the relative standard deviations (n = 6) were 0.74%-1.43%. The effect of concentration of DMF in mobile phase was studied.

Correlation of high-temperature stability of alpha-chymotrypsin with 'salting-in' properties of solution.

PubMed

Levitsky VYu; Panova, A A; Mozhaev, V V

1994-01-15

A correlation between the stability of alpha-chymotrypsin against irreversible thermal inactivation at high temperatures (long-term stability) and the coefficient of Setchenov equation as a measure of salting-in/out efficiency of solutes in the Hofmeister series has been found. An increase in the concentration of salting-in solutes (KSCN, urea, guanidinium chloride, formamide) leads to a many-fold decrease of the inactivation rate of the enzyme. In contrast, addition of salting-out solutes has a small effect on the long-term stability of alpha-chymotrypsin at high temperatures. The effects of solutes are additive with respect to their salting-in/out capacities; the stabilizing action of the solutes is determined by the calculated Setchenov coefficient of solution. The correlation is explained by a solute-driven shift of the conformational equilibrium between the 'low-temperature' native and the 'high-temperature' denatured forms of the enzyme within the range of the kinetic scheme put forward in the preceding paper in this journal: irreversible inactivation of the high-temperature form proceeds much more slowly compared with the low-temperature form.

Gallium plasmonic nanoparticles for label-free DNA and single nucleotide polymorphism sensing

NASA Astrophysics Data System (ADS)

Marín, Antonio García; García-Mendiola, Tania; Bernabeu, Cristina Navio; Hernández, María Jesús; Piqueras, Juan; Pau, Jose Luis; Pariente, Félix; Lorenzo, Encarnación

2016-05-01

A label-free DNA and single nucleotide polymorphism (SNP) sensing method is described. It is based on the use of the pseudodielectric function of gallium plasmonic nanoparticles (GaNPs) deposited on Si (100) substrates under reversal of the polarization handedness condition. Under this condition, the pseudodielectric function is extremely sensitive to changes in the surrounding medium of the nanoparticle surface providing an excellent sensing platform competitive to conventional surface plasmon resonance. DNA sensing has been carried out by immobilizing a thiolated capture probe sequence from Helicobacter pylori onto GaNP/Si substrates; complementary target sequences of Helicobacter pylori can be quantified over the range of 10 pM to 3.0 nM with a detection limit of 6.0 pM and a linear correlation coefficient of R2 = 0.990. The selectivity of the device allows the detection of a single nucleotide polymorphism (SNP) in a specific sequence of Helicobacter pylori, without the need for a hybridization suppressor in solution such as formamide. Furthermore, it also allows the detection of this sequence in the presence of other pathogens, such as Escherichia coli in the sample. The broad applicability of the system was demonstrated by the detection of a specific gene mutation directly associated with cystic fibrosis in large genomic DNA isolated from blood cells.A label-free DNA and single nucleotide polymorphism (SNP) sensing method is described. It is based on the use of the pseudodielectric function of gallium plasmonic nanoparticles (GaNPs) deposited on Si (100) substrates under reversal of the polarization handedness condition. Under this condition, the pseudodielectric function is extremely sensitive to changes in the surrounding medium of the nanoparticle surface providing an excellent sensing platform competitive to conventional surface plasmon resonance. DNA sensing has been carried out by immobilizing a thiolated capture probe sequence from Helicobacter pylori onto GaNP/Si substrates; complementary target sequences of Helicobacter pylori can be quantified over the range of 10 pM to 3.0 nM with a detection limit of 6.0 pM and a linear correlation coefficient of R2 = 0.990. The selectivity of the device allows the detection of a single nucleotide polymorphism (SNP) in a specific sequence of Helicobacter pylori, without the need for a hybridization suppressor in solution such as formamide. Furthermore, it also allows the detection of this sequence in the presence of other pathogens, such as Escherichia coli in the sample. The broad applicability of the system was demonstrated by the detection of a specific gene mutation directly associated with cystic fibrosis in large genomic DNA isolated from blood cells. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00926c

Synthesis of substituted 2-(β-D-glucopyranosyl)-benzimidazoles and their evaluation as inhibitors of glycogen phosphorylase.

PubMed

Bokor, Éva; Szilágyi, Enikő; Docsa, Tibor; Gergely, Pál; Somsák, László

2013-11-15

Microwave assisted condensation of O-perbenzoylated C-(β-d-glucopyranosyl)formic acid with 1,2-diaminobenzenes in the presence of triphenylphosphite gave the corresponding O-protected 2-(β-d-glucopyranosyl)-benzimidazoles in moderate yields. O-Perbenzoylated C-(β-d-glucopyranosyl)formamide and -thioformamide were transformed into the corresponding ethyl C-(β-d-glucopyranosyl)formimidate and -thioformimidate, respectively, by Et3O·BF4. Treatment of the formimidate with 1,2-diaminobenzenes afforded O-protected 2-(β-d-glucopyranosyl)-benzimidazoles in good to excellent yields. Similar reaction of the thioformimidate gave these compounds in lower yields. The O-benzoyl protecting groups were removed by the Zemplén protocol. These test compounds were assayed against rabbit muscle glycogen phosphorylase (GP) b, the prototype of liver GP, the rate limiting enzyme of glycogen degradation. The best inhibitors were 2-(β-d-glucopyranosyl)-4-methyl-benzimidazole (Ki=2.8μM) and 2-(β-d-glucopyranosyl)-naphtho[2,3-d]imidazole (Ki=2.1μM) exhibiting a ∼3-4 times stronger binding than the unsubstituted parent compound. Copyright © 2013 Elsevier Ltd. All rights reserved.

Crystal structure of poly[di­aqua­bis­(μ5-benzene-1,3-di­carboxyl­ato)(N,N-di­methyl­formamide)­cadmium(II)disodium(I)

PubMed Central

Sangsawang, Matimon; Chainok, Kittipong; Wannarit, Nanthawat

2017-01-01

The title compound, [CdNa2(C8H4O4)2(C3H7NO)(H2O)2]n or [CdNa2(1,3-bdc)2(DMF)(H2O)2]n, is a new CdII–NaI heterobimetallic coordination polymer. The asymmetric unit consists of one CdII atom, two NaI atoms, two 1,3-bdc ligands, two coordinated water mol­ecules and one coordinated DMF mol­ecule. The CdII atom exhibits a seven-coordinate geometry, while the NaI atoms can be considered to be penta­coordinate. The metal ions and their symmetry-related equivalents are connected via chelating–bridging carboxyl­ate groups of the 1,3-bdc ligands to generate a three-dimensional framework. In the crystal, there are classical O—H⋯O hydrogen bonds involving the coordinated water mol­ecules and the 1,3-bdc carboxyl­ate groups and π–π stacking between the benzene rings of the 1,3-bdc ligands present within the frameworks. PMID:29152332

Marangoni Effect-Driven Motion of Miniature Robots and Generation of Electricity on Water.

PubMed

Zhang, Lidong; Yuan, Yihui; Qiu, Xiaxin; Zhang, Ting; Chen, Qing; Huang, Xinhua

2017-11-07

The well-known Marangoni effect perfectly supports the dynamic mechanism of organic solvent-swollen gels on water. On this basis, we report a series of energy conversion processes of concentrated droplets of polyvinylidene fluoride/dimethyl formamide (PVDF/DMF) that can transfer chemical-free energy to kinetic energy to rapidly rotate itself on water. This droplet (22.2 mg) is capable to offer kinetic energy of 0.099 μJ to propel an artificial paper rocket of 31.8 mg to move over 560 cm on water at an initial velocity of 7.9 cm s -1 . As the droplet increases to 35.0 mg, a paper goldfish of 10.6 mg can be driven to swim longer at a higher initial velocity of 20 cm s -1 . The kinetic energy of the droplet can be further converted to electrical energy through an electromagnetic generator, in which as a 0.5 MΩ resistor is loaded, the peak output reaches 6.5 mV that corresponds to the power density of 0.293 μW kg -1 . We believe that this report would open up a promising avenue to exploit energies for applications in miniature robotics.

Topography and surface free energy of DPPC layers deposited on a glass, mica, or PMMA support.

PubMed

Jurak, Malgorzata; Chibowski, Emil

2006-08-15

An investigation of energetic properties of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) layers deposited on glass, mica, and PMMA (poly(methyl methacrylate)) surfaces was carried out by means of contact angles measurements (advancing and receding) for three probe liquids (diiodomethane, water, and formamide). DPPC was deposited on the surfaces from water (on glass and mica) or methanol (on PMMA) solutions. The topography of the tested surfaces was determined with a help of scanning electron microscopy (SEM) and atomic force microscopy (AFM). Using the measured contact angles, the total apparent surface free energy and its components of the studied layers were determined from van Oss et al.'s (Lifshitz-van der Waals and acid-base components, LWAB) and contact angle hysteresis (CAH) approaches. It allowed us to learn about changes in the surface free energy of the layers (hydrophobicity/hydrophilicity) depending on their number and kind of support. It was found that the changes in the energy greatly depended on the surface properties of the substrate as well as the statistical number of monolayers of DPPC. However, principal changes took place for first three monolayers.

On-chip transduction of nucleic acid hybridization using spatial profiles of immobilized quantum dots and fluorescence resonance energy transfer.

PubMed

Tavares, Anthony J; Noor, M Omair; Vannoy, Charles H; Algar, W Russ; Krull, Ulrich J

2012-01-03

The glass surface of a glass-polydimethylsiloxane (PDMS) microfluidic channel was modified to develop a solid-phase assay for quantitative determination of nucleic acids. Electroosmotic flow (EOF) within channels was used to deliver and immobilize semiconductor quantum dots (QDs), and electrophoresis was used to decorate the QDs with oligonucleotide probe sequences. These processes took only minutes to complete. The QDs served as energy donors in fluorescence resonance energy transfer (FRET) for transduction of nucleic acid hybridization. Electrokinetic injection of fluorescent dye (Cy3) labeled oligonucleotide target into a microfluidic channel and subsequent hybridization (within minutes) provided the proximity for FRET, with emission from Cy3 being the analytical signal. The quantification of target concentration was achieved by measurement of the spatial length of coverage by target along a channel. Detection of femtomole quantities of target was possible with a dynamic range spanning an order of magnitude. The assay provided excellent resistance to nonspecific interactions of DNA. Further selectivity of the assay was achieved using 20% formamide, which allowed discrimination between a fully complementary target and a 3 base pair mismatch target at a contrast ratio of 4:1. © 2011 American Chemical Society

The Effect of Cellulose Acetate Concentration from Coconut Nira on Ultrafiltration Membrane Characters

NASA Astrophysics Data System (ADS)

Vaulina, E.; Widyaningsih, S.; Kartika, D.; Romdoni, M. P.

2018-04-01

Cellulose acetate is one of material in produce ultrafiltration membrane. Many efforts have been done to produce cellulose acetate from natural product to replace commercial one. In this research, ultrafiltration membrane has been produced from coconut flower water (nira). Ultrafiltration membrane is widely used in separation processes. This research aims to determine the characteristics of ultrafiltration membrane at a various concentration of cellulose acetate. The ultrafiltration membrane is conducted by phase inversion method at various concentration of cellulose acetate. The cellulose acetate concentration was 20%, 23% and 25% (w/w) with formamide as additives. The results showed that the greater the concentration of cellulose acetate, the smaller the flux value. The highest flux was a membrane with 20% cellulose acetate concentration with water flux value 55.34 L/(m2. h). But the greater the concentration of cellulose acetate the greater the rejection. The highest rejection value was on a membrane with 25% cellulose acetate concentration of 82.82%. While from the tensile strength test and the pore size analysis, the greater the cellulose acetate concentration the greater the tensile strength and the smaller the pore size

Purification of aflatoxin B1 antibody for the development of aflatoxin biosensor

NASA Astrophysics Data System (ADS)

Prihantoro, E. A. B.; Saepudin, E.; Ivandini, T. A.

2017-07-01

Aflatoxin B1 (AFB1) is produced from agricultural products especially peanuts overgrown with aspergillus flavus during the post-harvest process. Aflatoxin is classified as a highly toxic and carcinogenic substance to humans by the International Agency for Research on Cancer (IARC), WHO. This research was conducted to develop the AFB1 biosensor using antibody that specifically binds to aflatoxin B1. This antibody was produced by injecting an AFB1 hapten-protein (immunogen) to a rabbit. Antibody was obtained from rabbit's blood serum and purified using Protein A affinity chromatography and precipitation at the isoelectric point. The result showed that purification using protein A contains antibody of 4.0 mg/mL, whereas purification using precipitation at isoelectric pH contains antibody of 0.3 mg/mL. The pure antibody was tested for its specificity against AFB1, tetrahydrofuran (THF), dimethyl formamide (DMF), bovine serum albumin (BSA), and ethanol. The result revealed that THF, BSA, and ethanol were bound to antibody, while DMF showed no interaction. It was concluded that the polyclonal antibody which have been successfully purified from rabbit's blood serum using protein A affinity chromatography and precipitation methods showed an unspecific identification.

Biosynthesised ZnO : Dy3+ nanoparticles: Biodiesel properties and reusable catalyst for N-formylation of aromatic amines with formic acid

NASA Astrophysics Data System (ADS)

Reddy Yadav, L. S.; Raghavendra, M.; Sudheer Kumar, K. H.; Dhananjaya, N.; Nagaraju, G.

2018-04-01

ZnO nanoparticles doped with trivalent dysprosium ions (Dy3+) were prepared through the green combustion technique using E. tirucalli plant latex as a fuel. The fundamental and optical properties of the samples are examined via the X-ray diffraction, FTIR, UV-visible analytical methods and morphology by scanning electron microscope and transmission electron microscope. Rietveld refinement results show that the ZnO : Dy3+ were crystallized in the wurtzite hexagonal structure with space group P63mc (No. 186). The average particle size of ZnO : Dy3+ prepared with the different concentration of latex was found to be in the range 30-38nm, which is also confirmed by TEM analysis. A rapid and convenient method for the one-pot preparation of N-formamide derivatives aromatic amines and amino acid esters has been developed using Dy3+ doped ZnO as a catalytic agent. This method provides an efficient and much improved modification over reported protocols regarding yield, clean and work-up procedure milder reaction conditions. In this work, Pongamiapinnata oil was recycled for the preparation of biodiesel via Dy3+ doped ZnO as a catalytic agent.

Solute-solvent interactions in 2,4-dihydroxyacetophenone isonicotinoylhydrazone solutions in N, N-dimethylformamide and dimethyl sulfoxide at 298-313 K on ultrasonic and viscometric data

NASA Astrophysics Data System (ADS)

Dikkar, A. B.; Pethe, G. B.; Aswar, A. S.

2016-02-01

The speed of sound ( u), density (ρ), and viscosity (η) of 2,4-dihydroxyacetophenone isonicotinoylhydrazone (DHAIH) have been measured in N, N-dimethyl formamide and dimethyl sulfoxide at equidistance temperatures 298.15, 303.15, 308.15, and 313.15 K. These data were used to calculate some important ultrasonic and thermodynamic parameters such as apparent molar volume ( V ϕ s st ), apparent molar compressibility ( K ϕ), partial molar volume ( V ϕ 0 ) and partial molar compressibility ( K ϕ 0 ), were estimated by using the values of ( V ϕ 0 ) and ( K ϕ), at infinite dilution. Partial molar expansion at infinite dilution, (ϕ E 0 ) has also been calculated from temperature dependence of partial molar volume V ϕ 0 . The viscosity data have been analyzed using the Jones-Dole equation, and the viscosity, B coefficients are calculated. The activation free energy has been calculated from B coefficients and partial molar volume data. The results have been discussed in the term of solute-solvent interaction occurring in solutions and it was found that DHAIH acts as a structure maker in present systems.

Anisotropic membranes for gas separation

DOEpatents

Gollan, Arye Z.

1987-01-01

A gas separation membrane has a dense separating layer about 10,000 Angstroms or less thick and a porous support layer 10 to 400 microns thick that is an integral unit with gradually and continuously decreasing pore size from the base of the support layer to the surface of the thin separating layer and is made from a casting solution comprising ethyl cellulose and ethyl cellulose-based blends, typically greater than 47.5 ethoxyl content ethyl cellulose blended with compatible second polymers, such as nitrocellulose. The polymer content of the casting solution is from about 10% to about 35% by weight of the total solution with up to about 50% of this polymer weight a compatible second polymer to the ethyl cellulose in a volatile solvent such as isopropanol, methylacetate, methanol, ethanol, and acetone. Typical nonsolvents for the casting solutions include water and formamide. The casting solution is cast in air from about zero to 10 seconds to allow the volatile solvent to evaporate and then quenched in a coagulation bath, typically water, at a temperature of 7.degree.-25.degree. C. and then air dried at ambient temperature, typically 10.degree.-30.degree. C.

Effect of EMA and antioxidants on properties of thermoplastic starch blown films

NASA Astrophysics Data System (ADS)

Threepopnatkul, P.; Kulsetthanchalee, C.; Sittattrakul, A.; Kaewjinda, E.

2015-07-01

The objectives of this study were to investigate the effect of poly(ethylene-co-methyl acrylate) (EMA) at 10, 30 and 50 wt% on the morphological properties, moisture sorption, water vapor permeability and biodegradability of thermoplastic starch (TPS). Urea and formamide were used as a mixed plasticizer. In addition, the effect of antioxidants namely, 3,5-di-tert-butyl-4-hydroxyhydrocinnamate (DTBH), butylated hydroxytoluene (BHT) and bis(octadecyl)hydroxylamine (BOH) at 1 wt% on the properties of TPS/EMA film was investigated. TPS/EMA films were produced by a blown film molding machine and characterized by scanning electron microscropy, moisture sorption, water vapor permeability and biodegradability measurement. Results found that the increment of EMA content in the TPS matrix could improve the water sorption, water vapor permeability and biodegradability properties of TPS/EMA films. For biodegradation, the weight loss of the blended films was directly proportional to TPS content. Regarding the antioxidants effect, the water vapor permeability of TPS/EMA films containing DTBH was higher than the one with BOH and BHT. However, the antioxidants contributed little to the biodegradability of TPS/EMA films and had no effect on the moisture sorption of TPS/EMA films.

Removal of ion-implanted photoresists on GaAs using two organic solvents in sequence

NASA Astrophysics Data System (ADS)

Oh, Eunseok; Na, Jihoon; Lee, Seunghyo; Lim, Sangwoo

2016-07-01

Organic solvents can effectively remove photoresists on III-V channels without damage or etching of the channel material during the process. In this study, a two-step sequential photoresist removal process using two different organic solvents was developed to remove implanted ArF and KrF photoresists at room temperature. The effects of organic solvents with either low molar volumes or high affinities for photoresists were evaluated to find a proper combination that can effectively remove high-dose implanted photoresists without damaging GaAs surfaces. The performance of formamide, acetonitrile, nitromethane, and monoethanolamine for the removal of ion-implanted ArF and KrF photoresists were compared using a two-step sequential photoresist removal process followed by treatment in dimethyl sulfoxide (DMSO). Among the various combinations, the acetonitrile + DMSO two-step sequence exhibited the best removal of photoresists that underwent ion implantation at doses of 5 × 1013-5 × 1015 atoms/cm2 on both flat and trench-structured GaAs surfaces. The ability of the two-step process using organic solvents to remove the photoresists can be explained by considering the affinities of solvents for a polymer and its permeability through the photoresist.

Quantification of Staphylococcus aureus adhesion forces on various dental restorative materials using atomic force microscopy

NASA Astrophysics Data System (ADS)

Merghni, Abderrahmen; Kammoun, Dorra; Hentati, Hajer; Janel, Sébastien; Popoff, Michka; Lafont, Frank; Aouni, Mahjoub; Mastouri, Maha

2016-08-01

In the oral cavity dental restorative biomaterials can act as a reservoir for infection with opportunistic Staphylococcus aureus pathogen, which can lead to the occurrence of secondary caries and treatment failures. Our aim was to evaluate the adhesion forces by S. aureus on four dental restorative biomaterials and to correlate this finding to differences in specific surface characteristics. Additionally, the influence of salivary conditioning films in exerted adhesion forces was investigated. The substrate hydrophobicity was measured by goniometer and the surface free energy was calculated using the equilibrium advancing contact angle values of water, formamide, and diiodomethane on the tested surfaces. The surface roughness was determined using atomic force microscope (AFM). Additionally, cell force spectroscopy was achieved to quantify the forces that drive cell-substrate interactions. S. aureus bacterium exerted a considerable adhesion forces on various dental restorative materials, which decreased in the presence of saliva conditioning film. The influence of the surface roughness and free energy in initial adhesion appears to be more important than the effect of hydrophobicity, either in presence or absence of saliva coating. Hence, control of surface properties of dental restorative biomaterials is of crucial importance in preventing the attachment and subsequent the biofilm formation.

Single-strand breakage of DNA in UV-irradiated uvrA, uvrB, and uvrC mutants of Escherichia coli.

PubMed Central

Tang, M S; Ross, L

1985-01-01

We transduced the uvrA6, uvrB5, uvrC34, and uvrC56 markers from the original mutagenized strains into an HF4714 background. Although in the original mutagenized strains uvrA6 cells are more UV sensitive than uvrB5 and uvrC34 cells, in the new background no significant difference in UV sensitivity is observed among uvrA6, uvrB5, and uvrC34 cells. No DNA single-strand breaks are detected in UV-irradiated uvrA6 or uvrB5 cells, whereas in contrast a significant number of single-strand breaks are detected in both UV-irradiated uvrC34 and uvrC56 cells. The number of single-strand breaks in these cells reaches a plateau at 20-J/m2 irradiation. Since these single-strand breaks can be detected by both alkaline sucrose and neutral formamide-sucrose gradient sedimentation, we concluded that the single-strand breaks observed in UV-irradiated uvrC cells are due to phosphodiester bond interruptions in DNA and are not due to apurinic/apyrimidinic sites. PMID:3882671

Green synthesis of Ag nanoparticles using plant metabolites

NASA Astrophysics Data System (ADS)

Filippi, Antonio; Mattiello, Alessandro; Musetti, Rita; Petrussa, Elisa; Braidot, Enrico; Marchiol, Luca

2017-08-01

Nano-biotechnology is one of the most promising areas in modern nanoscience and technology. In this emerging area of research, nanoparticles (NPs) play an important role since the large-scale production and huge numbers of utilization. Gold and silver nanoparticles are among the most extensively studied nanomaterials, since they show high stability and low chemical reactivity in comparison to other metals. They are commonly synthesized using toxic chemical reducing agents able to reduce metal ions into uncharged NPs and/or high energy supplied procedures. The most commonly used method for the synthesis of NPs requires toxic chemicals like N,N-dimethyl formamide (DMF) or trisodium citrate, but recently a green technique, based on natural reducing agents, has been suggested to substitute the nature-unfriendly chemical methods. Many scientific works put in evidence the efficacy of plant extracts to reduce metal salts into the respective NPs, but this process lacks a clear control of NPs shapes and dimensions, since many different metabolites present into the extracts could participate to the process. This paper aims to clarify the reducing action of single pure natural compounds usually present in plant tissues and to obtain a stable and reproducible protocol for NPs synthesis.

Deflagration of thermite - ammonium nitrate based propellant mixture

NASA Astrophysics Data System (ADS)

Duraes, Luisa; Morgado, Joel; Portugal, Antonio; Campos, Jose

2001-06-01

Reaction between iron oxide (Fe2O3) and aluminum (Al) is the reference of the classic thermite compositions. The efficency of the reaction, for a given initial composition of Fe2O3 and Al, is evaluated by the final temperature and by the mass ratio of Al2O3 /AlO in products of combustion (in condensed phase). In order to increase pressure in products of thermite reaction, the original composition is mixed, with an original twin screw extruder, with a propellant binder composed of ammonium and sodium nitrates, initialy solved in formamide (CH3NO) and mixed with a polyurethane solution. The products of combustion and pyrolysis of this binder, reacting with thermite products, generates high pressure and high temperature conditions. These experimental conditions are also predicted using THOR code. The study presents DSC and TGA results of components and mixtures, and correlates them to the ignition phenomena and reaction properties. The regression rate of combustion and final attained temperature and pressure, in a closed confinement, as a function of composition of thermite components/propellant binder, are presented and discussed. They show the influence of gaseous combustion and pyrolysis products of binder in final reaction.

The extraction and purification of a cysteine transfer ribonucleic acid from baker's yeast.

PubMed Central

Holness, N J; Atfield, G

1976-01-01

1. A modification of the RPC 1 system of A.D. Kelmers, G.D. Novelli & M.P. Stulberg (1965) (J. Biol. Chem. 240, 3979-3983) is described in which the support medium is a Celite of narrow range particle size treated with dichlorodimethylsilane. 2. By using this system an apparently pure preparation of tRNA Cys was isolated from baker's yeast tRNA. 3. This preparation accepted at least 60% of the theoretical quantity of [3-14C]cysteine in a conventional assay and failed to accept isoleucine, phenylalanine, proline, serine or tyrosine. 4. A theoretical countercurrent-distribution curve calculated by assuming a distribution coefficient K of 2.03 was in excellent agreement with the profiles of E260 and cysteine-acceptor ability after 537 transfers in the 1.85 M-phosphate/formamide/propan-2-ol system of C.M. Connelly & B.P. Doctor (1965) (J. Biol. Chem. 241, 715-719). 5. Chromatography of tRNA Cys on Bio-Gel P100 polyacrylamide beads afforded two components one of which was far less efficient than the other in accepting cysteine. The base compositions of the two were similar. PMID:776175

An optimized method for extraction and detection of Coconut cadang-cadang viroid(CCCVd) from oil palm.

PubMed

Mohammadi, M R; Vadamalai, G; Joseph, H

2010-01-01

Coconut cadong-cadong viroid (CCCVd) causes the Lethal cadang-cadang disease of coconut palms in the Philippines and it is recently reported to be associated with the orange spotting disease on oil palm in Malaysia. The low concentration of the viroid RNA in oil palm as well as the high content of polyphenols and polysaccharides in this plant which interfere with the purification steps makes it difficult to extract and detect this viroid from oil palm. A previously described method was modified and optimized for extraction and detection of CCCVd from infected oil palms. Briefly, 7 g of leaf material was homogenized in a mortar or a blender using liquid nitrogen. 10 ml of extraction buffer (100 mM Tris-HCl pH 7.5, 100 mM NaCl, 10 mM EDTA) along with 100 mM 2-mercaptoethanol and 10 ml water saturated phenol was added to the frozen powder. After centrifuging at 4 degrees C, 4000 g for 30 min, the aqueous phase was extracted once more with phenol then once with chloroform-isoamyl alcohol (24:1). After adding sodium acetate, pH 5.6 to 200 mM, the mixture was precipitated with 2.5 vol ethanol overnight in -20 freezer and then the pellet was washed with 70% ethanol and air-dried. One milliliter of 8 M LiCl was added to the dried pellet and after shaking overnight at 4 degrees C and another centrifugation step the supernatant was collected and precipitated again with ethanol and then the resulting pellet was washed and air-dried. To carry out northern blotting, samples equivalent to 40 g of plant tissue were mixed with formamide buffer and loaded onto a 12% polyacrylamide gel containing 7 M urea and after separation by electrophoresis, were electroblotted onto membrane and fixed by UV cross-linking. Pre-hybridization and hybridization using hybridization buffer (50% formamide, 25%SSPE, 0.1% Ficol and PVP, 0.1 % SDS, 0.02 % DNA (5mg/ml)) was carried out at 45 degrees C for 90 min and 16 h, respectively followed by two low stringency washes (0.5 X SSC, 0.1% SDS, at room temperature for 5 min) and one high stringency wash (0.1X SSC, 0.1% SDS at 60 degrees C for 1 hour). In vitro synthesized DIG-labeled full-length CCCVd(-) RNA probe was used in hybridization step. DIG Nucleic Acid Detection Kit (Roche) instructions were followed for detection procedure and as a result the blue bands corresponding to the position of the viroid were appeared on the membrane. The result of this study showed the ability of DIG labeled probe in detection of the viroid and also provided a suitable extraction and hybridization method for the detection of CCCVd from oil palm.

Tubular localization of silent calcium channels in crustacean skeletal muscle fibers.

PubMed

Monterrubio, J; Ortiz, G; Orkand, P M; Zuazaga, C

2002-01-01

Ca2+-induced Ca2+ release (CICR) in the superficial abdominal flexor muscle of the crustacean Atya lanipes appears to be mediated by a local control mechanism similar to that of vertebrate cardiac muscle, but with an unusually high gain. Thus, Ca2+ influx increases sufficiently the local concentration of Ca2+ in the immediate vicinity of the sarcoplasmic reticulum Ca2+ release channels to trigger the highly amplified release of Ca2+ required for contraction, but is too low to generate a macroscopic inward current (i.e., the Ca2+ channels are silent). To determine the localization of the silent Ca2+ Channels, the mechanical, electrophysiological and ultrastructural properties of the muscle were examined before and after formamide treatment, a procedure that produces the disruption of transverse tubules of striated muscle. We found that tubular disruption decreased tension generation by about 90%; reduced inward current (measured as Vmax, the maximum rate of rise of Sr2+ action potentials) by about 80%; and decreased membrane capacitance by about 77%. The results suggest that ca. 80% of the silent Ca2+ channels are located in the tubular system. Thus, these studies provide further evidence to support the local control mechanism of CICR in crustacean skeletal muscle.

Next-Generation in Situ Hybridization Chain Reaction: Higher Gain, Lower Cost, Greater Durability

PubMed Central

2014-01-01

Hybridization chain reaction (HCR) provides multiplexed, isothermal, enzyme-free, molecular signal amplification in diverse settings. Within intact vertebrate embryos, where signal-to-background is at a premium, HCR in situ amplification enables simultaneous mapping of multiple target mRNAs, addressing a longstanding challenge in the biological sciences. With this approach, RNA probes complementary to mRNA targets trigger chain reactions in which metastable fluorophore-labeled RNA hairpins self-assemble into tethered fluorescent amplification polymers. The properties of HCR lead to straightforward multiplexing, deep sample penetration, high signal-to-background, and sharp subcellular signal localization within fixed whole-mount zebrafish embryos, a standard model system for the study of vertebrate development. However, RNA reagents are expensive and vulnerable to enzymatic degradation. Moreover, the stringent hybridization conditions used to destabilize nonspecific hairpin binding also reduce the energetic driving force for HCR polymerization, creating a trade-off between minimization of background and maximization of signal. Here, we eliminate this trade-off by demonstrating that low background levels can be achieved using permissive in situ amplification conditions (0% formamide, room temperature) and engineer next-generation DNA HCR amplifiers that maximize the free energy benefit per polymerization step while preserving the kinetic trapping property that underlies conditional polymerization, dramatically increasing signal gain, reducing reagent cost, and improving reagent durability. PMID:24712299

The Influence of Sizings on the Durability of High-Temperature Polymer Composites

NASA Technical Reports Server (NTRS)

Allred, Ronald E.; Wesson, Sheldon P.; Shin, E. Eugene; Inghram, Linda; McCorkle, Linda; Papadopoulos, Demetrios; Wheeler, Donald; Sutter, James K.

2004-01-01

To increase performance and durability of high-temperature composites for potential rocket engine components, it is necessary to optimize wetting and interfacial bonding between high modulus carbon fibers and high-temperature polyimide resins. Sizings commercially supplied on most carbon fibers are not compatible with polyimides. In this study, the chemistry of sizings on two high-modulus carbon fibers (M40J and M60J, Toray) was characterized as was the chemistry of PMR-II-50 fluorinated polyimide resin. The carbon fibers were characterized using single filament wetting, scanning electron microscopy, fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopic measurements. The polyimide matrix resins were coated onto glass filaments for characterization by wetting measurements. Surface energy components were obtained by wetting with nondispersive (methylene iodide), acidic (ethylene glycol), and basic (formamide) probes. A continuous desizing system that uses an environmentally friendly chemical-mechanical process was developed for tow level fiber. Composites were fabricated with fibers containing the manufacturer's sizing, desized, and further treated with a reactive finish. Results of room-temperature tests after thermal aging show that the reactive finish produces a higher strength and more durable interface compared to the manufacturer's sizing. When exposed to moisture blistering tests, however, the better bonded composite displayed a tendency to delaminate, presumably due to trapping of volatiles.

A facile synthesis of poly(aniline-co-o-bromoaniline) copolymer: Characterization and application as semiconducting material

NASA Astrophysics Data System (ADS)

Mahudeswaran, A.; Vivekanandan, J.; Vijayanand, P. S.; Kojima, T.; Kato, S.

2016-01-01

Poly(aniline-co-o-bromoaniline) (p(an-co-o-BrAn)) copolymer has been synthesized using chemical oxidation method in the hydrochloric acid medium. Copolymerization of aniline with o-bromoaniline of different compositions, such as 1:1, 1:2, 2:1, 1:3 and 3:1 molar ratios were prepared. The synthesized copolymer is soluble in polar solvents like dimethyl sulphoxide (DMSO), dimethyl formamide (DMF), Tetrahydrofuran (THF) and 1-methyl 2-pyrrolidone (NMP). The copolymer is analyzed by various characterization techniques, such as FTIR, UV-Visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), conductivity, Differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). FTIR spectrum confirms the characteristic peaks of the copolymer containing benzenoid and quinoid ring stretching. UV spectrum reveals the formation of π-π∗ transition and n-π∗ transition between the energy levels. XRD peaks reveal that the copolymer possesses amorphous nature. Morphological study reveals that the agglomerated particles form globular structure and size of the each particle is about 100 nm. The electrical conductivity of the copolymers is found in the range of 10-5Scm-1. These organic semiconductor materials can be used to fabricate thinner and cheaper environmental friendly optoelectronic devices that will replace the conventional inorganic semiconductors.

Synthesis of Mono-PEGylated Growth Hormone Releasing Peptide-2 and Investigation of its Biological Activity.

PubMed

Hu, Xiaoyu; Xu, Beihua; Zhou, Ziniu

2015-10-01

The purpose of this study was to investigate an efficient synthetic route to the mono-PEGylated growth hormone releasing peptide-2 (GHRP-2) and its biological activity in vivo. The commercially available key PEGylating reagent, mPEG-NHS ester, was successfully utilized to the synthesis of mono-PEGylated GHRP-2, during which the PEGylation profiles of GHRP-2 were monitored by high-performance liquid chromatography (HPLC). The product was purified by cation exchange chromatography, and its biological activity was conducted in rats. The desired mono-PEGylated GHRP-2 as the major product was readily obtained in anhydrous aprotic solvent, such as dimethyl formamide (DMF) and dimethylsulfoxide (DMSO), when the molar ratio of mPEG-NHS ester to GHRP-2 was fixed to be 0.8:1. The products were characterized by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. The evaluation of the biological activity for the products showed that the mono-PEGylated GHRP-2 gave a more stable activity than GHRP-2, suggesting that PEGylation led to the increase in the half-life of GHRP-2 in plasma without greatly impairing the biological activity. PEGylation of the GHRP-2 is a good choice for the development of the GHRP-2 applications.

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.

Gas Evolution in Activated-Carbon-Based Supercapacitors with Protic Deep Eutectic Solvent as Electrolyte.

PubMed

Phadke, Satyajit; Amara, Samia; Anouti, Mérièm

2017-09-06

One of the primary causes of aging in supercapacitors are the irreversible faradaic reactions occurring near the operating-voltage limit that lead to the production of gases resulting in device swelling, increased resistance, and lowering of the capacitance. In this study, a protic deep eutectic solvent (DES) consisting of mixture of lithium bis(fluorosulfonyl)imide (LiFSI) with formamide (FMD) as H-bond donor (x LiFSI =0.25; C=2.5 m LiFSI) is investigated as electrolyte for activated carbon (AC)-based electrical double layer capacitors (EDLCs). Characterization of the viscosity, conductivity, and the ionicity of the electrolyte in a wide range of temperatures indicates >88 % salt dissociation. In situ pressure measurements are performed to understand the effect of cycling conditions on the rate of gas generation, quantified by the in operando pressure variation dP/dt. These measurements demonstrate that about 25 % of the faradaic reactions leading to gas generation are electrochemically reversible. Cell aging studies demonstrate promising potential of the LiFSI/FMD as a protic electrolyte for AC-based EDLCs and high energy density close to 30 Wh kg -1 at 2.4 V. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of a multiplexed electrospray micro-thruster with post-acceleration and beam containment

NASA Astrophysics Data System (ADS)

Lenguito, G.; Gomez, A.

2013-10-01

We report the development of a compact thruster based on Multiplexed ElectroSprays (MES). It relied on a microfabricated Si array of emitters coupled with an extractor electrode and an accelerator electrode. The accelerator stage was introduced for two purposes: containing beam opening and avoiding electrode erosion due to droplet impingement, as well as boosting specific impulse and thrust. Multiplexing is generally necessary as a thrust multiplier to reach eventually the level required (O(102) μN) by small satellites. To facilitate system optimization and debugging, we focused on a 7-nozzle MES device and compared its performance to that of a single emitter. To ensure uniformity of operation of all nozzles their hydraulic impedance was augmented by packing them with micrometer-size beads. Two propellants were tested: a solution of 21.5% methyl ammonium formate in formamide and the better performing pure ionic liquid ethyl ammonium nitrate (EAN). The 7-MES device spraying EAN at ΔV = 5.93 kV covered a specific impulse range from 620 s to 1900 s and a thrust range from 0.6 μN to 5.4 μN, at 62% efficiency. Remarkably, less than 1% of the beam was demonstrated to impact on the accelerator electrode, which bodes well for long-term applications in space.

Effective Fragment Potential Method for H-Bonding: How To Obtain Parameters for Nonrigid Fragments.

PubMed

Dubinets, Nikita; Slipchenko, Lyudmila V

2017-07-20

Accuracy of the effective fragment potential (EFP) method was explored for describing intermolecular interaction energies in three dimers with strong H-bonded interactions, formic acid, formamide, and formamidine dimers, which are a part of HBC6 database of noncovalent interactions. Monomer geometries in these dimers change significantly as a function of intermonomer separation. Several EFP schemes were considered, in which fragment parameters were prepared for a fragment in its gas-phase geometry or recomputed for each unique fragment geometry. Additionally, a scheme in which gas-phase fragment parameters are shifted according to relaxed fragment geometries is introduced and tested. EFP data are compared against the coupled cluster with single, double, and perturbative triple excitations (CCSD(T)) method in a complete basis set (CBS) and the symmetry adapted perturbation theory (SAPT). All considered EFP schemes provide a good agreement with CCSD(T)/CBS for binding energies at equilibrium separations, with discrepancies not exceeding 2 kcal/mol. However, only the schemes that utilize relaxed fragment geometries remain qualitatively correct at shorter than equilibrium intermolecular distances. The EFP scheme with shifted parameters behaves quantitatively similar to the scheme in which parameters are recomputed for each monomer geometry and thus is recommended as a computationally efficient approach for large-scale EFP simulations of flexible systems.

Determination of transformation products of unsymmetrical dimethylhydrazine in water using vacuum-assisted headspace solid-phase microextraction.

PubMed

Orazbayeva, Dina; Kenessov, Bulat; Psillakis, Elefteria; Nassyrova, Dayana; Bektassov, Marat

2018-06-22

A new, sensitive and simple method based on vacuum-assisted headspace solid-phase microextraction (Vac-HSSPME) followed by gas chromatography-mass-spectrometry (GC-MS), is proposed for the quantification of rocket fuel unsymmetrical dimethylhydrazine (UDMH) transformation products in water samples. The target transformation products were: pyrazine, 1-methyl-1H-pyrazole, N-nitrosodimethylamine, N,N-dimethylformamide, 1-methyl-1Н-1,2,4-triazole, 1-methyl-imidazole and 1H-pyrazole. For these analytes and within shorter sampling times, Vac-HSSPME yielded detection limits (0.5-100 ng L -1 ) 3-10 times lower than those reported for regular HSSPME. Vac-HSSPME sampling for 30 min at 50 °C yielded the best combination of analyte responses and their standard deviations (<15%). 1-Formyl-2,2-dimethylhydrazine and formamide were discarded because of the poor precision and accuracy when using Vac-HSSPME. The recoveries for the rest of the analytes ranged between 80 and 119%. The modified Mininert valve and Thermogreen septum could be used for automated extraction as it ensured stable analyte signals even after long waiting times (>24 h). Finally, multiple Vac-HSSME proved to be an efficient tool for controlling the matrix effect and quantifying UDMH transformation products. Copyright © 2018 Elsevier B.V. All rights reserved.

Self-assembly of a thin highly reduced graphene oxide film and its high electrocatalytic activity

NASA Astrophysics Data System (ADS)

Bai, Yan-Feng; Zhang, Yong-Fang; Zhou, An-Wei; Li, Hai-Wai; Zhang, Yu; Luong, John H. T.; Cui, Hui-Fang

2014-10-01

A thin highly reduced graphene oxide (rGO) film was self-assembled at the dimethyl formamide (DMF)-air interface through evaporation-induced water-assisted thin film formation at the pentane-DMF interface, followed by complete evaporation of pentane. The thin film was transferred onto various solid substrates for film characterization and electrochemical sensing. UV-visible spectrometry, scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrochemistry techniques were used to characterize the film. An rGO film showing 82.8% of the transmittance at 550 nm corresponds to a few layers of rGO nanosheets. The rGO nanosheets cross-stack with each other, lying approximately in the plane of the film. An rGO film collected on a glassy carbon (GC) electrode exhibited improved electrical conductivity compared to GC, with the electrode charge-transfer resistance (Rct) reduced from 31 Ω to 22 Ω. The as-formed rGO/GC electrode was mechanically very stable, exhibiting significantly enhanced electrocatalytic activity to H2O2 and dopamine. Multiple layers of the rGO films on the GC electrode showed even stronger electrocatalytic activity to dopamine than that of the single rGO film layer. The controllable formation of a stable rGO film on various solid substrates has potential applications for nanoelectronics and sensors/biosensors.

Hydrogen Bonding Interaction between Atmospheric Gaseous Amides and Methanol.

PubMed

Zhao, Hailiang; Tang, Shanshan; Xu, Xiang; Du, Lin

2016-12-30

Amides are important atmospheric organic-nitrogen compounds. Hydrogen bonded complexes of methanol (MeOH) with amides (formamide, N -methylformamide, N , N -dimethylformamide, acetamide, N -methylacetamide and N , N -dimethylacetamide) have been investigated. The carbonyl oxygen of the amides behaves as a hydrogen bond acceptor and the NH group of the amides acts as a hydrogen bond donor. The dominant hydrogen bonding interaction occurs between the carbonyl oxygen and the OH group of methanol as well as the interaction between the NH group of amides and the oxygen of methanol. However, the hydrogen bonds between the CH group and the carbonyl oxygen or the oxygen of methanol are also important for the overall stability of the complexes. Comparable red shifts of the C=O, NH- and OH-stretching transitions were found in these MeOH-amide complexes with considerable intensity enhancement. Topological analysis shows that the electron density at the bond critical points of the complexes fall in the range of hydrogen bonding criteria, and the Laplacian of charge density of the O-H∙∙∙O hydrogen bond slightly exceeds the upper value of the Laplacian criteria. The energy decomposition analysis further suggests that the hydrogen bonding interaction energies can be mainly attributed to the electrostatic, exchange and dispersion components.

Hydrogen Bonding Interaction between Atmospheric Gaseous Amides and Methanol

PubMed Central

Zhao, Hailiang; Tang, Shanshan; Xu, Xiang; Du, Lin

2016-01-01

Amides are important atmospheric organic–nitrogen compounds. Hydrogen bonded complexes of methanol (MeOH) with amides (formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide and N,N-dimethylacetamide) have been investigated. The carbonyl oxygen of the amides behaves as a hydrogen bond acceptor and the NH group of the amides acts as a hydrogen bond donor. The dominant hydrogen bonding interaction occurs between the carbonyl oxygen and the OH group of methanol as well as the interaction between the NH group of amides and the oxygen of methanol. However, the hydrogen bonds between the CH group and the carbonyl oxygen or the oxygen of methanol are also important for the overall stability of the complexes. Comparable red shifts of the C=O, NH- and OH-stretching transitions were found in these MeOH–amide complexes with considerable intensity enhancement. Topological analysis shows that the electron density at the bond critical points of the complexes fall in the range of hydrogen bonding criteria, and the Laplacian of charge density of the O–H∙∙∙O hydrogen bond slightly exceeds the upper value of the Laplacian criteria. The energy decomposition analysis further suggests that the hydrogen bonding interaction energies can be mainly attributed to the electrostatic, exchange and dispersion components. PMID:28042825

Thermal wet decomposition of Prussian Blue: implications for prebiotic chemistry.

PubMed

Ruiz-Bermejo, Marta; Rogero, Celia; Menor-Salván, César; Osuna-Esteban, Susana; Martín-Gago, José Angel; Veintemillas-Verdaguer, Sabino

2009-09-01

The complex salt named Prussian Blue, Fe4[Fe(CN)6]3 x 15 H2O, can release cyanide at pH > 10. From the point of view of the origin of life, this fact is of interest, since the oligomers of HCN, formed in the presence of ammonium or amines, leads to a variety of biomolecules. In this work, for the first time, the thermal wet decomposition of Prussian Blue was studied. To establish the influence of temperature and reaction time on the ability of Prussian Blue to release cyanide and to subsequently generate other compounds, suspensions of Prussian Blue were heated at temperatures from room temperature to 150 degrees at pH 12 in NH3 environment for several days. The NH3 wet decomposition of Prussian Blue generated hematite, alpha-Fe2O3, the soluble complex salt (NH4)4[Fe(CN6)] x 1.5 H2O, and several organic compounds, the nature and yield of which depend on the experimental conditions. Urea, lactic acid, 5,5-dimethylhydantoin, and several amino acids and carboxylic acids were identified by their trimethylsilyl (TMS) derivatives. HCN, cyanogen (C2N2), and formamide (HCONH2) were detected in the gas phase by GC/MS analysis.

Effect of lidocaine- and prilocaine-based topical anesthetics on the inflammatory exudates in subcutaneous tissue of rats.

PubMed

Pochapski, Márcia Thaís; Neto, José Laufer; Jassen, Jocélia Lago; Farago, Paulo Vitor; Santos, Fábio André

2012-01-01

The aim of this present study was to evaluate the irritative potential of 2 topical anesthetics used in intrapocket anesthesia for periodontal scaling/root planing when applied in subcutaneous tissue of rats. Sixty animals were divided into 4 groups: group 1, saline solution (control); group 2, poloxamer gel (thermosetting vehicle); group 3, lidocaine and prilocaine poloxamer thermosetting gel; group 4: EMLA, a lidocaine and prilocaine dermatological cream. Injections of 2% Evans blue were administrated intravenously into the lateral caudal vein. In order to analyze vascular permeability, the tested substances were injected intradermally. The rats were sacrificed 3, 6, and 9 hours after injection of the substances. The dorsal skin was dissected and removed. The vascular permeability was evaluated by the measurement of area of dye extravasation and the dye was subsequently extracted after immersion in formamide. Statistical analyses were made by ANOVA with Bonferroni's post hoc test and Pearson correlation. The 2 methods to analyze the exudative phase of the inflammatory process showed statistically significant difference among the groups and periods of evaluation (P < .05). Both methods had a significant correlation (P < .0001). Under the tested conditions, the anesthetic agents showed mild initial inflammatory response when implanted in subcutaneous connective tissue.

Effect of Lidocaine- and Prilocaine-Based Topical Anesthetics on the Inflammatory Exudates in Subcutaneous Tissue of Rats

PubMed Central

Pochapski, Márcia Thaís; Neto, José Laufer; Jassen, Jocélia Lago; Farago, Paulo Vitor; Santos, Fábio André

2012-01-01

The aim of this present study was to evaluate the irritative potential of 2 topical anesthetics used in intrapocket anesthesia for periodontal scaling/root planing when applied in subcutaneous tissue of rats. Sixty animals were divided into 4 groups: group 1, saline solution (control); group 2, poloxamer gel (thermosetting vehicle); group 3, lidocaine and prilocaine poloxamer thermosetting gel; group 4: EMLA, a lidocaine and prilocaine dermatological cream. Injections of 2% Evans blue were administrated intravenously into the lateral caudal vein. In order to analyze vascular permeability, the tested substances were injected intradermally. The rats were sacrificed 3, 6, and 9 hours after injection of the substances. The dorsal skin was dissected and removed. The vascular permeability was evaluated by the measurement of area of dye extravasation and the dye was subsequently extracted after immersion in formamide. Statistical analyses were made by ANOVA with Bonferroni's post hoc test and Pearson correlation. The 2 methods to analyze the exudative phase of the inflammatory process showed statistically significant difference among the groups and periods of evaluation (P < .05). Both methods had a significant correlation (P < .0001). Under the tested conditions, the anesthetic agents showed mild initial inflammatory response when implanted in subcutaneous connective tissue. PMID:22822991

Biodegradation mechanism of 1H-1,2,4-triazole by a newly isolated strain Shinella sp. NJUST26

PubMed Central

Wu, Haobo; Shen, Jinyou; Wu, Ruiqin; Sun, Xiuyun; Li, Jiansheng; Han, Weiqing; Wang, Lianjun

2016-01-01

The highly recalcitrant 1H-1,2,4-triazole (TZ) is widely used in the synthesis of agricultural pesticide and considered to be an environmental pollutant. In this study, a novel strain NJUST26 capable of utilizing TZ as the sole carbon and nitrogen source, was isolated from TZ-contaminated soil, and identified as Shinella sp. The biodegradation assays suggested that optimal temperature and pH for TZ degradation by NJUST26 were 30 °C and 6–7, respectively. With the increase of initial TZ concentration from 100 to 320 mg L−1, the maximum volumetric degradation rate increased from 29.06 to 82.96 mg L−1 d−1, indicating high tolerance of NJUST26 towards TZ. TZ biodegradation could be accelerated through the addition of glucose, sucrose and yeast extract at relatively low dosage. The main metabolites, including 1,2-dihydro-3H-1,2,4-triazol-3-one (DHTO), semicarbazide and urea were identified. Based on these results, biodegradation pathway of TZ by NJUST26 was proposed, i.e., TZ was firstly oxidized to DHTO, and then the cleavage of DHTO ring occurred to generate N-hydrazonomethyl-formamide, which could be further degraded to biodegradable semicarbazide and urea. PMID:27436634

Mixed aqueous solutions as dilution media in the determination of residual solvents by static headspace gas chromatography.

PubMed

D'Autry, Ward; Zheng, Chao; Wolfs, Kris; Yarramraju, Sitaramaraju; Hoogmartens, Jos; Van Schepdael, Ann; Adams, Erwin

2011-06-01

Static headspace (HS) sampling has been commonly used to test for volatile organic chemicals, usually referred to as residual solvents (RS) in pharmaceuticals. If the sample is not soluble in water, organic solvents are used. However, these seriously reduce the sensitivity in the determination of some RS. Here, mixed aqueous dilution media (a mixture of water and an organic solvent like dimethyl formamide, dimethyl sulfoxide or dimethyl acetamide) were studied as alternative media for static HS-gas chromatographic analysis. Although it has been known that mixed aqueous dilution media can often improve sensitivity for many RS, this study used a systematic approach to investigate phase volumes and the organic content in the HS sampling media. Reference solutions using 18 different class 1, 2 and 3 RS were evaluated. The effect of salt addition was also studied in this work. A significant increase in the peak area was observed for all RS using mixed aqueous dilution media, when compared with organic solvents alone. Matrix effects related to the mixed aqueous dilution media were also investigated and reported. Repeatability and linearity obtained with mixed aqueous dilution media were found to be similar to those observed with pure organic solvents. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cyanide hydratases and cyanide dihydratases: emerging tools in the biodegradation and biodetection of cyanide.

PubMed

Martínková, Ludmila; Veselá, Alicja Barbara; Rinágelová, Anna; Chmátal, Martin

2015-11-01

The purpose of this study is to summarize the current knowledge of the enzymes which are involved in the hydrolysis of cyanide, i.e., cyanide hydratases (CHTs; EC 4.2.1.66) and cyanide dihydratases (CynD; EC 3.5.5.1). CHTs are probably exclusively produced by filamentous fungi and widely occur in these organisms; in contrast, CynDs were only found in a few bacterial genera. CHTs differ from CynDs in their reaction products (formamide vs. formic acid and ammonia, respectively). Several CHTs were also found to transform nitriles but with lower relative activities compared to HCN. Mutants of CynDs and CHTs were constructed to study the structure-activity relationships in these enzymes or to improve their catalytic properties. The effect of the C-terminal part of the protein on the enzyme activity was determined by constructing the corresponding deletion mutants. CynDs are less active at alkaline pH than CHTs. To improve its bioremediation potential, CynD from Bacillus pumilus was engineered by directed evolution combined with site-directed mutagenesis, and its operation at pH 10 was thus enabled. Some of the enzymes have been tested for their potential to eliminate cyanide from cyanide-containing wastewaters. CynDs were also used to construct cyanide biosensors.

Analysis of 2D THz-Raman spectroscopy using a non-Markovian Brownian oscillator model with nonlinear system-bath interactions.

PubMed

Ikeda, Tatsushi; Ito, Hironobu; Tanimura, Yoshitaka

2015-06-07

We explore and describe the roles of inter-molecular vibrations employing a Brownian oscillator (BO) model with linear-linear (LL) and square-linear (SL) system-bath interactions, which we use to analyze two-dimensional (2D) THz-Raman spectra obtained by means of molecular dynamics (MD) simulations. In addition to linear infrared absorption (1D IR), we calculated 2D Raman-THz-THz, THz-Raman-THz, and THz-THz-Raman signals for liquid formamide, water, and methanol using an equilibrium non-equilibrium hybrid MD simulation. The calculated 1D IR and 2D THz-Raman signals are compared with results obtained from the LL+SL BO model applied through use of hierarchal Fokker-Planck equations with non-perturbative and non-Markovian noise. We find that all of the qualitative features of the 2D profiles of the signals obtained from the MD simulations are reproduced with the LL+SL BO model, indicating that this model captures the essential features of the inter-molecular motion. We analyze the fitted 2D profiles in terms of anharmonicity, nonlinear polarizability, and dephasing time. The origins of the echo peaks of the librational motion and the elongated peaks parallel to the probe direction are elucidated using optical Liouville paths.

Calculating two-dimensional THz-Raman-THz and Raman-THz-THz signals for various molecular liquids: the samplers.

PubMed

Ito, Hironobu; Hasegawa, Taisuke; Tanimura, Yoshitaka

2014-09-28

Recently, two-dimensional (2D) THz-Raman spectroscopy has been used to investigate the intermolecular modes of liquid water. We examine such 2D spectroscopy signals by means of full molecular dynamics (MD) simulations. In this way, we carry out a detailed analysis of intermolecular interactions that play an essential role in many important chemical processes. We calculate 2D Raman-THz-THz (RTT), THz-Raman-THz (TRT), and 2D Raman signals for liquid water, methanol, formamide, acetonitrile, formaldehyde, and dimethyl sulfoxide using an equilibrium-non-equilibrium hybrid MD simulation algorithm originally developed for 2D Raman spectroscopy. These signals are briefly analyzed in terms of anharmonicity and nonlinear polarizability of vibrational modes on the basis of the 2D Raman signals calculated from a Brownian oscillator model with a nonlinear system-bath interaction. We find that the anharmonic contribution is dominant in the RTT case, while the nonlinear polarizability contribution is dominant in the TRT case. For water and methanol, we observed vibrational echo peaks of librational motion in the 2D TRT signals. The predicted signal profiles and intensities that we obtained provide valuable information that can be applied to 2D spectroscopy experiments, allowing them to be carried out more efficiently.

Molecularly imprinted polymer cartridges coupled to high performance liquid chromatography (HPLC-UV) for simple and rapid analysis of fenthion in olive oil.

PubMed

Bakas, Idriss; Ben Oujji, Najwa; Istamboulié, Georges; Piletsky, Sergey; Piletska, Elena; Ait-Addi, Elhabib; Ait-Ichou, Ihya; Noguer, Thierry; Rouillon, Régis

2014-07-01

A combination of molecular modelling and a screening of the library of non-imprinted polymers (NIPs) was used to identify acrylamide as a functional monomer with high affinity towards fenthion, organophosphate insecticide, which is frequently used in the treatment of olives. A good correlation was found between the screening tests and modelling of monomer-template interactions performed using a computational approach. Acrylamide-based molecularly imprinted polymer (MIP) and non-imprinted polymer (NIP) were thermally synthesised in dimethyl formamide (porogen) using ethylene glycol dimethacrylate as a cross-linker and 1,1-azo-bis (isobutyronitrile) as an initiator. The chemical and physical properties of the prepared polymers were characterised. The binding of fenthion by the polymers was studied using solvents with different polarities. The developed MIP showed a high selectivity towards fenthion, compared to other organophosphates (dimethoate, methidathion malalthion), and allowed extraction of fenthion from olive oil samples with a recovery rate of about 96%. The extraction of fenthion using MIPs was much more effective than traditional C18 reverse-phase solid phase extraction and allowed to achieve a low detection limit (LOD) (5 µg L(-1)). Copyright © 2014 Elsevier B.V. All rights reserved.

Occurrence of ivermectin in bovine milk from the Brazilian retail market.

PubMed

Lobato, V; Rath, S; Reyes, F G R

2006-07-01

High-performance liquid chromatography (HPLC) with fluorescence detection was used for the quantification of ivermectin residues in bovine milk intended for human consumption. After liquid-liquid extraction of ivermectin and purification of the extract, the compound was derivatized with 1-methylimidazol in N,N-dimethyl formamide to form a fluorescent derivative, which was separated by HPLC, using reversed-phase C18, with methanol : water (96 : 4 v/v) mobile phase at a flow rate 0.7 ml min-1. The excitation and emission wavelengths of the fluorescence detector were adjusted at 360 and 470 nm, respectively. The linearity of the method was in the range 10-100 ng ivermectin ml-1. Based on a sample of 5.0 ml, the limit of detection and the limit of quantification for ivermectin in milk were 0.6 and 2 ng ml-1, respectively. The recovery rate varied from 76.4 to 87.2%, with an average of 77.9 +/- 3.2%, at four fortification levels. The inter-day precision of the method was 13% (n = 5). Of 168 samples analysed, 17.8% contained ivermectin above the limit of quantification. Nevertheless, none of the samples contained ivermectin above the maximum residue limit (10 ng ml-1) established by the Brazilian Ministry of Agriculture.

SINGLE STRAND-CONTAINING REPLICATING MOLECULES OF CIRCULAR MITOCHONDRIAL DNA

PubMed Central

Wolstenholme, David R.; Koike, Katsuro; Cochran-Fouts, Patricia

1973-01-01

Mitochondrial DNAs (mtDNAs) from Chang rat solid hepatomas and Novikoff rat ascites hepatomas were examined in the electron microscope after preparation by the aqueous and by the formamide protein monolayer techniques. MtDNAs from both tumors were found to include double-forked circular molecules with a form and size suggesting they were replicative intermediates. These molecules were of two classes. In molecules of one class, all three segments were apparently totally double stranded. Molecules of the second class were distinguished by the fact that one of the segments spanning the region between the forks in which replication had occurred (the daughter segments) was either totally single stranded, or contained a single-stranded region associated with one of the forks. Daughter segments of both totally double-stranded and single strand-containing replicating molecules varied in length from about 3 to about 80% of the circular contour length of the molecule. Similar classes of replicating molecules were found in mtDNA from regenerating rat liver and chick embryos, indicating them to be normal intermediates in the replication of mtDNA All of the mtDNAs examined included partially single-stranded simple (nonforked) circular molecules. A possible scheme for the replication of mtDNA is presented, based on the different molecular forms observed PMID:4345165

Liquid-Phase Exfoliation into Monolayered BiOBr Nanosheets for Photocatalytic Oxidation and Reduction

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

Yu, Hongjian; Huang, Hongwei; Xu, Kang

2017-09-26

Monolayered photocatalytic materials have attracted huge research interests in terms of their large specific surface area and ample active sites. Sillén-structured layered BiOX (X = Cl, Br, I) casts great prospects owing to their strong photo-oxidation ability and high stability. Fabrication of monolayered BiOX by a facile, low-cost, and scalable approach is highly challenging and anticipated. Herein, we describe the large-scale preparation of monolayered BiOBr nanosheets with a thickness of ~0.85 nm via a readily achievable liquid-phase exfoliation strategy with assistance of formamide at ambient conditions. The as-obtained monolayered BiOBr nanosheets are allowed diverse superiorities, such as enhanced specific surfacemore » area, promoted band structure, and strengthened charge separation. Profiting from these benefits, the advanced BiOBr monolayers not only show excellent adsorption and photodegradation performance for treating contaminants, but also demonstrate a greatly promoted photocatalytic activity for CO2 reduction into CO and CH4. Additionally, monolayered BiOI nanosheets have also been obtained by the same synthetic approach. Our work offers a mild and general approach for preparation of monolayered BiOX, and may have huge potential to be extended to the synthesis of other single-layer two-dimensional materials.« less

Improvement in Electrode Performance of Novel SWCNT Loaded Three-Dimensional Porous RVC Composite Electrodes by Electrochemical Deposition Method

PubMed Central

Almoigli, Mohammed; Meriey, Al Yahya; Alharbi, Khalid N.

2018-01-01

The three-dimensional (3D) composite electrodes were prepared by depositing different amounts of acid-functionalized single-walled carbon nanotubes (a-SWCNTs) on porous reticulated vitreous carbon (RVC) through the electrochemical deposition method. The SWCNT was functionalized by the reflux method in nitric acid and was proven by Raman and visible spectra. The optimum time for sonication to disperse the functionalized SWCNT (a-SWCNT) in dimethyl formamide (DMF) well was determined by UV spectra. The average pore size of RVC electrodes was calculated from scanning electron microscopy (SEM) images. Moreover, the surface morphology of composite electrodes was also examined by SEM study. All 3D electrodes were evaluated for their electrochemical properties by cyclic voltammetry. The result showed that the value of specific capacitance of the electrode increases with the increase in the amount of a-SWCNT in geometric volume. However, the value of specific capacitance per gram decreases with the increase in scan rate as well as the amount of a-SWCNT. The stability of the electrodes was also tested. This revealed that all the electrodes were stable; however, lower a-SWCNT-loaded electrodes had excellent cyclic stability. These results suggest that the a-SWCNT-coated RVC electrodes have promise as an effective technology for desalination. PMID:29301258

Improvement in Electrode Performance of Novel SWCNT Loaded Three-Dimensional Porous RVC Composite Electrodes by Electrochemical Deposition Method.

PubMed

Aldalbahi, Ali; Rahaman, Mostafizur; Almoigli, Mohammed; Meriey, Al Yahya; Alharbi, Khalid N

2018-01-01

The three-dimensional (3D) composite electrodes were prepared by depositing different amounts of acid-functionalized single-walled carbon nanotubes (a-SWCNTs) on porous reticulated vitreous carbon (RVC) through the electrochemical deposition method. The SWCNT was functionalized by the reflux method in nitric acid and was proven by Raman and visible spectra. The optimum time for sonication to disperse the functionalized SWCNT (a-SWCNT) in dimethyl formamide (DMF) well was determined by UV spectra. The average pore size of RVC electrodes was calculated from scanning electron microscopy (SEM) images. Moreover, the surface morphology of composite electrodes was also examined by SEM study. All 3D electrodes were evaluated for their electrochemical properties by cyclic voltammetry. The result showed that the value of specific capacitance of the electrode increases with the increase in the amount of a-SWCNT in geometric volume. However, the value of specific capacitance per gram decreases with the increase in scan rate as well as the amount of a-SWCNT. The stability of the electrodes was also tested. This revealed that all the electrodes were stable; however, lower a-SWCNT-loaded electrodes had excellent cyclic stability. These results suggest that the a-SWCNT-coated RVC electrodes have promise as an effective technology for desalination.

Efficient Active Oxygen Free Radical Generated in Tumor Cell by Loading-(HCONH2)·H2O2 Delivery Nanosystem with Soft-X-ray Radiotherapy

PubMed Central

Xu, Lei; Shao, Yiran; Chang, Chengkang; Zhu, Yingchun

2018-01-01

Tumor hypoxia is known to result in radiotherapy resistance and traditional radiotherapy using super-hard X-ray irradiation can cause considerable damage to normal tissue. Therefore, formamide peroxide (FPO) with high reactive oxygen content was employed to enhance the oxygen concentration in tumor cells and increase the radio-sensitivity of low-energy soft-X-ray. To improve stability of FPO, FPO is encapsulated into polyacrylic acid (PAA)-coated hollow mesoporous silica nanoparticles (FPO@HMSNs-PAA). On account of the pH-responsiveness of PAA, FPO@HMSNs-PAA will release more FPO in simulated acidic tumor microenvironment (pH 6.50) and subcellular endosomes (pH 5.0) than in simulated normal tissue media (pH 7.40). When exposed to soft-X-ray irradiation, the released FPO decomposes into oxygen and the generated oxygen further formed many reactive oxygen species (ROS), leading to significant tumor cell death. The ROS-mediated cytotoxicity of FPO@HMSNs-PAA was confirmed by ROS-induced green fluorescence in tumor cells. The presented FPO delivery system with soft-X-ray irradiation paves a way for developing the next opportunities of radiotherapy toward efficient tumor prognosis. PMID:29649155

Rotational spectroscopy, tentative interstellar detection, and chemical modeling of N-methylformamide

NASA Astrophysics Data System (ADS)

Belloche, A.; Meshcheryakov, A. A.; Garrod, R. T.; Ilyushin, V. V.; Alekseev, E. A.; Motiyenko, R. A.; Margulès, L.; Müller, H. S. P.; Menten, K. M.

2017-05-01

Context. N-methylformamide, CH3NHCHO, may be an important molecule for interstellar pre-biotic chemistry because it contains a peptide bond, which in terrestrial chemistry is responsible for linking amino acids in proteins. The rotational spectrum of the most stable trans conformer of N-methylformamide is complicated by strong torsion-rotation interaction due to the low barrier of the methyl torsion. For this reason, the theoretical description of the rotational spectrum of the trans conformer has, up to now, not been accurate enough to provide a firm basis for its interstellar detection. Aims: In this context, as a prerequisite for a successful interstellar detection, our goal is to improve the characterization of the rotational spectrum of N-methylformamide. Methods: We use two absorption spectrometers in Kharkiv and Lille to measure the rotational spectra over the frequency range 45-630 GHz. The analysis is carried out using the Rho-axis method and the RAM36 code. We search for N-methylformamide toward the hot molecular core Sagittarius (Sgr) B2(N2) using a spectral line survey carried out with the Atacama Large Millimeter/submillimeter Array (ALMA). The astronomical spectra are analyzed under the assumption of local thermodynamic equilibrium. The astronomical results are put into a broader astrochemical context with the help of a gas-grain chemical kinetics model. Results: The new laboratory data set for the trans conformer of N-methylformamide consists of 9469 distinct line frequencies with J ≤ 62, including the first assignment of the rotational spectra of the first and second excited torsional states. All these lines are fitted within experimental accuracy for the first time. Based on the reliable frequency predictions obtained in this study, we report the tentative detection of N-methylformamide toward Sgr B2(N2). We find N-methylformamide to be more than one order of magnitude less abundant than formamide (NH2CHO), a factor of two less abundant than the unsaturated molecule methyl isocyanate (CH3NCO), but only slightly less abundant than acetamide (CH3CONH2). We also report the tentative detection of the 15N isotopolog of formamide (15NH2CHO) toward Sgr B2(N2). The chemical models indicate that the efficient formation of HNCO via NH + CO on grains is a necessary step in the achievement of the observed gas-phase abundance of CH3NCO. Production of CH3NHCHO may plausibly occur on grains either through the direct addition of functional-group radicals or through the hydrogenation of CH3NCO. Conclusions: Provided the detection of N-methylformamide is confirmed, the only slight underabundance of this molecule compared to its more stable structural isomer acetamide and the sensitivity of the model abundances to the chemical kinetics parameters suggest that the formation of these two molecules is controlled by kinetics rather than thermal equilibrium. Full Tables 2 and 3 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/601/A49

Optimization of flavanones extraction by modulating differential solvent densities and centrifuge temperatures.

PubMed

Chebrolu, Kranthi K; Jayaprakasha, G K; Jifon, J; Patil, Bhimanagouda S

2011-07-15

Understanding the factors influencing flavonone extraction is critical for the knowledge in sample preparation. The present study was focused on the extraction parameters such as solvent, heat, centrifugal speed, centrifuge temperature, sample to solvent ratio, extraction cycles, sonication time, microwave time and their interactions on sample preparation. Flavanones were analyzed in a high performance liquid chromatography (HPLC) and later identified by liquid chromatography and mass spectrometry (LC-MS). The five flavanones were eluted by a binary mobile phase with 0.03% phosphoric acid and acetonitrile in 20 min and detected at 280 nm, and later identified by mass spectral analysis. Dimethylsulfoxide (DMSO) and dimethyl formamide (DMF) had optimum extraction levels of narirutin, naringin, neohesperidin, didymin and poncirin compared to methanol (MeOH), ethanol (EtOH) and acetonitrile (ACN). Centrifuge temperature had a significant effect on flavanone distribution in the extracts. The DMSO and DMF extracts had homogeneous distribution of flavanones compared to MeOH, EtOH and ACN after centrifugation. Furthermore, ACN showed clear phase separation due to differential densities in the extracts after centrifugation. The number of extraction cycles significantly increased the flavanone levels during extraction. Modulating the sample to solvent ratio increased naringin quantity in the extracts. Current research provides critical information on the role of centrifuge temperature, extraction solvent and their interactions on flavanone distribution in extracts. Published by Elsevier B.V.

The influence of bias magnetization of nanoparticles on GMR sensor signal and sensitivity for the ultra-low concentration detection

NASA Astrophysics Data System (ADS)

Zhang, Yang; Xu, Jie; Cao, Derang; Li, Qiang; Zhao, Guoxia; Sun, Nian X.; Li, Shandong

2018-05-01

In the broad research of the GMR bio-sensing technology, it is vital to explore appropriate magnetic labels and its influences on the detection signal. In this work, four kinds of ferrite particles of γ-Fe2O3, CoFe2O4, NiFe2O4 and NiZnFe2O4 were prepared through calcining the Dimethyl Formamide (DMF) solution of the transition metal nitrates [Fe(NO3)3 and X(NO3)2, X = Co, Ni, Zn] to study the effect of magnetic properties on detection signals using a DC in-plane measuring method. It was revealed that for four particles, the output voltage differences |ΔV| between with and without magnetic particles exhibit log-linear functions of the particles concentrations x in the range from 0.1 to 10 ng/mL. A very low limitation of detection (LOD) of 0.1 ng/mL for all the samples was obtained, which is two orders smaller than that in the previous work. Moreover, the change of output voltage difference at the LOD (|ΔVlim|) is proportional to the magnetization at bias field (bias magnetization, Mbias), which indicates that larger Mbias leads to a lower LOD. This work provides a useful guidance in selecting or preparing magnetic labels to enhance the sensitivity of GMR biosensors.

Diapause Prevention Effect of Bombyx mori by Dimethyl Sulfoxide

PubMed Central

Yamamoto, Takayuki; Mase, Keisuke; Sawada, Hiroshi

2013-01-01

HCl treatment has been, for about 80 years, the primary method for the prevention of entry into embryonic diapauses of Bombyx mori. This is because no method is as effective as the HCl treatment. In this study, we discovered that dimethyl sulfoxide (DMSO) prevented entry into the diapause of the silkworm, Bombyx mori. The effect of diapause prevention was 78% as a result of treatment with 100% DMSO concentration, and the effect was comparable to that of the HCl treatment. In contrast, in the case of non-diapause eggs, hatchability was decreased by DMSO in a concentration-dependent manner. The effect of DMSO was restricted within 24 hours after oviposition of diapause eggs, and the critical period was slightly shorter than the effective period of the HCl treatment. DMSO analogs, such as dimethyl formamide (DMF) and dimethyl sulfide (DMS), did little preventive effect against the diapause. Furthermore, we also investigated the permeation effects of chemical compounds by DMSO. When treated with an inhibitor of protein kinase CK2 (CK2) dissolved in DMSO, the prevention rate of the diapause was less than 40%. This means that the inhibition effect by the CK2 inhibitor was the inhibition of embryonic development after diapause prevention by DMSO. These data suggest that DMSO has the effects of preventing from entering into the diapause and permeation of chemicals into diapause eggs. PMID:23675522

Preparation and characterization of nanocomposite polymer electrolytes poly(vinylidone fluoride)/nanoclay

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

Rahmawati, Suci A.; Sulistyaningsih,; Putro, Alviansyah Z. A.

2016-02-08

Polymer electrolytes are defined as semi solid electrolytes used as separator in lithium ion battery. Separator used as medium for transfer ions and to prevent electrical short circuits in battery cells. To obtain the optimal battery performance, separator with high porosity and electrolyte uptake is required. This can reduce the resistance in the transfer of ions between cathode and anode. The main objective of this work is to investigate the impact of different solvent (Dimethyl acetamide (DMAc), N-methyl-2-pyrrolidone (NMP) and dimethyl formamide (DMF)), pore forming agent poly(vinylpyrolidone) (PVP) and nanoclay as filler in addition of membrane using phase inversion methodmore » on the morphology, porosity, electrolyte uptake and degree of crystallinity. The membrane was prepared by the phase inversion method by adding PVP and Nanoclay using different solvents. The phase inversion method was prepared by dissolving Nanoclay and PVP in solvent for 1-2 hours, and then add the PVDF with stirring for 4 hours at 60°C. The membranes were characterized by porosity test, electrolyte uptake test, scanning electron microscope (SEM), and X-ray diffraction (XRD). The results showed that DMAc as solvent gives the highest value of porosity and electrolyte uptake. The addition of nanoclay and PVP enlarge the size of the pores and reduce the degree of crystallinity. So, the usage of DMAc as solvent is better than NMP or DMF.« less

Environmentally friendly surface modification of silk fiber: Chitosan grafting and dyeing

NASA Astrophysics Data System (ADS)

Davarpanah, Saideh; Mahmoodi, Niyaz Mohammad; Arami, Mokhtar; Bahrami, Hajir; Mazaheri, Firoozmehr

2009-01-01

In this paper, the surface modification of silk fiber using anhydrides to graft the polysaccharide chitosan and dyeing ability of the grafted silk were studied. Silk fiber was degummed and acylated with two anhydrides, succinic anhydride (SA) and phthalic anhydride (PA), in different solvents (dimethyl sulfoxide (DMSO) and N, N-dimethyl formamide (DMF)). The effects of anhydrides, solvents, anhydride concentration, liquor ratio (L:R) and reaction time on acylation of silk were studied. The polysaccharide chitosan was grafted to the acylated silk fiber and dyed by acid dye (Acid Black NB.B). The effects of pH, chitosan concentration, and reaction time on chitosan grafting of acylated silk were investigated. The physical properties show sensible changes regardless of weight gain. Scanning electron microscopy (SEM) analysis showed the presence of foreign materials firmly attached to the surface of silk. FTIR spectroscopy provided evidence that chitosan was grafted onto the acylated silk through the formation of new covalent bonds. The dyeing of the chitosan grafted-acylated silk fiber indicated the higher dye ability in comparison to the acylated and degummed silk samples. The mechanism of chitosan grafting over degummed silk through anhydride linkage was proposed. The findings of this research support the potential production of new environmentally friendly textile fibers. It is worthwhile to mention that the grafted samples have antibacterial potential due to the antibacterial property of chitosan molecules.

A novel 4-phenyl amino thiourea derivative designed for real-time ratiometric-colorimetric detection of toxic Pb2.

PubMed

Guang, Yi S; Ren, Xia; Zhao, Shuang; Yan, Quan Z; Zhao, Gang; Xu, Yao H

2018-05-12

The objective of this study was to develop a ratiometric and colorimetric organic sensor for Pb 2+ detection in environmental samples. A new probe 4-phenyl amino thiourea (PAT) was designed and synthesized using hydrazine hydrate and phenyl isothiocyanate as raw materials. After its structure was characterized and confirmed, its UV-vis spectral property was investigated in detail. PAT possesses a specifically real-time, ratiometric and colorimetric response to Pb 2+ in dimethyl formamide (DMF)/H 2 O (v/v = 9:1, pH = 7.0) within 18.0 s. There was little interference in the presence of some other common metal ions, such as Fe 3+ , Cd 2+ , Zn 2+ , Mg 2+ , Cr 3+ , Ca 2+ , Ba 2+ , Sn 2+ , Na + , Mn 2+ , Hg 2+ , and Pb 2+ . Under the optimized conditions (DMF/H 2 O with v/v of 9:1, c PAT = 1.0 × 10 -3 mol·L -1 , pH = 7.0), the present sensor PAT was successfully applied for Pb 2+ determination in environmental water samples with satisfied recoveries (83.0%-106.0%) and analytical precision (≤7.2%). The recognition mechanism was confirmed to form a stable 1:1 six-member ring complex between the target dye and Pb 2+ with a coordination constant of 4.96 × 10 4 .

In situ hybridization protocol for enhanced detection of gene expression in the planarian Schmidtea mediterranea

PubMed Central

2013-01-01

Background The freshwater planarian Schmidtea mediterranea has emerged as a powerful model for studies of regenerative, stem cell, and germ cell biology. Whole-mount in situ hybridization (WISH) and whole-mount fluorescent in situ hybridization (FISH) are critical methods for determining gene expression patterns in planarians. While expression patterns for a number of genes have been elucidated using established protocols, determining the expression patterns for particularly low-abundance transcripts remains a challenge. Results We show here that a short bleaching step in formamide dramatically enhances signal intensity of WISH and FISH. To further improve signal sensitivity we optimized blocking conditions for multiple anti-hapten antibodies, developed a copper sulfate quenching step that virtually eliminates autofluorescence, and enhanced signal intensity through iterative rounds of tyramide signal amplification. For FISH on regenerating planarians, we employed a heat-induced antigen retrieval step that provides a better balance between permeabilization of mature tissues and preservation of regenerating tissues. We also show that azide most effectively quenches peroxidase activity between rounds of development for multicolor FISH experiments. Finally, we apply these modifications to elucidate the expression patterns of a few low-abundance transcripts. Conclusion The modifications we present here provide significant improvements in signal intensity and signal sensitivity for WISH and FISH in planarians. Additionally, these modifications might be of widespread utility for whole-mount FISH in other model organisms. PMID:23497040

Density-based Energy Decomposition Analysis for Intermolecular Interactions with Variationally Determined Intermediate State Energies

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

Wu, Q.; Ayers, P.W.; Zhang, Y.

2009-10-28

The first purely density-based energy decomposition analysis (EDA) for intermolecular binding is developed within the density functional theory. The most important feature of this scheme is to variationally determine the frozen density energy, based on a constrained search formalism and implemented with the Wu-Yang algorithm [Q. Wu and W. Yang, J. Chem. Phys. 118, 2498 (2003) ]. This variational process dispenses with the Heitler-London antisymmetrization of wave functions used in most previous methods and calculates the electrostatic and Pauli repulsion energies together without any distortion of the frozen density, an important fact that enables a clean separation of these twomore » terms from the relaxation (i.e., polarization and charge transfer) terms. The new EDA also employs the constrained density functional theory approach [Q. Wu and T. Van Voorhis, Phys. Rev. A 72, 24502 (2005)] to separate out charge transfer effects. Because the charge transfer energy is based on the density flow in real space, it has a small basis set dependence. Applications of this decomposition to hydrogen bonding in the water dimer and the formamide dimer show that the frozen density energy dominates the binding in these systems, consistent with the noncovalent nature of the interactions. A more detailed examination reveals how the interplay of electrostatics and the Pauli repulsion determines the distance and angular dependence of these hydrogen bonds.« less

The effect of poly ethylene glycol additive on the characteristics and performance of cellulose acetate ultrafiltration membrane for removal of Cr(III) from aqueous solution

NASA Astrophysics Data System (ADS)

Mulyati, S.; Aprilia, S.; Safiah; Syawaliah; Armando, M. A.; Mawardi, H.

2018-05-01

The effect of polyethylene glycol (PEG) additive on the characteristics and performance of the cellulose acetate ultrafiltration membrane to chromium metal removal has been studied using some variation of concentration in the casting solution. The concentration of cellulose acetate polymer was 17.5%, whereas the variations of PEG concentration were regulated at 0, 2.5, 5, 7.5 and 10% by weight. Dimethyl formamide (DMF) was used as a solvent. Pure water flux, membrane morphology test, functional group analysis, and molecular weight cut off (MWCO) were investigated to characterize of the prepared membranes. Membrane performance was tested against Cr(III) metal removal. The results confirmed that the pure water flux improved with the increasing of additive concentration. The maximum improvement occurred at membrane with modification using 7.5% PEG. At this PEG concentration, the pure water flux elevated from 49.5 L/m2.h to 62.2 L/m2.h. The addition of PEG successfully improved the membrane flux because the role PEG plays as a pore-forming agent. Membrane with addition of 7.5% PEG showcased rejection result for chromium metal of 31.89%. This value is lower than that of pure CA membrane which rejection value against Cr(III) metal amounted to 35.72%.

Synthesis, Biological Activity, and Docking Study of Novel Isatin Coupled Thiazolidin-4-one Derivatives as Anticonvulsants.

PubMed

Nikalje, Anna P; Ansari, Altamash; Bari, Sanjay; Ugale, Vinod

2015-06-01

A series of 2-(substituted-phenyl)-3-(2-oxoindolin-3-ylidene)amino)-thiazolidin-4-one derivatives were designed and synthesized under microwave irradiation, using an eco-friendly, efficient, microwave-assisted synthetic protocol that involves cyclocondensation of 3-substituted benzylidine-hydrazono-indolin-2-one 3a-j with thioglycolic acid in dimethyl formamide (DMF) as solvent and anhydrous zinc chloride as a catalyst, keeping in view the structural requirement of the pharmacophore. The intermediate compounds 3a-j were obtained by condensation of the hydrazone of indoline-2,3-dione with aromatic aldehydes. The synthesized derivatives were evaluated for CNS depressant activity and anticonvulsant activity in mice using the maximal electroshock seizure (MES) and subcutaneous pentylenetetrazole (sc-PTZ) induced seizure tests. All the derivatives showed good CNS depressant activity and showed protection in the MES test, indicative of their ability to inhibit the seizure spread. A histopathological study was performed to evaluate liver toxicity caused by the synthesized compounds. The compounds were nontoxic. A computational study was performed, in which log P values were calculated experimentally. Virtual screening was performed by molecular docking of the designed compounds into the ATP binding sites of the NMDA and AMPA receptors, to predict if these compounds have analogous binding modes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study of complex formation of 5,5'-(2 E, 2' E)-2,2'-(ethane-1,2-diylidene)bis(hydrazine-1-yl-2-ylidene)bis(4-amino-4H-1,2,4-triazole-3-thiol) (HYT) macrocyclic ligand with Cd2+ cation in non-aqueous solution by spectroscopic and conductometric methods

NASA Astrophysics Data System (ADS)

Mallaekeh, Hassan; Shams, Alireza; Shaker, Mohammad; Bahramzadeh, Ehsan; Arefi, Donya

2014-12-01

In this paper the complexation reaction of the 5,5'-(2 E,2' E)-2,2'-(ethane-1,2-diylidene)bis(hydrazine-1-yl-2-ylidene)bis(4-amino-4H-1,2,4-triazole-3-thiol) ligand (HYT) with Cd2+ education was studied in some binary mixtures of methanol (MeOH), n-propanol (PrOH) and dimethyl-formamide (DMF) at different temperatures using the conductometry and spectrophotometry. The stability constants of the complex was determined using a GENPLOT computer program. The conductance data and absorbance-mole ratio plots show that in all solvent systems, the stoichiometry of the complex formed between (HYT) and Cd2+ cation is 1: 1. The obtained results show that the stability of (HYT)-Cd complex is sensitive to the mixed solvents composition. The values of thermodynamic parameters (Δ G ∘, Δ H ∘, and Δ S ∘) for formation of (HYT)-Cd complex were obtained from temperature dependence of the stability constant using the van't Hoff plots. The results show that in most cases, the complex are enthalpy destabilized but entropy stabilized and the complex formation is affected by pH, time, temperature and the nature of the solvent.

Discovery of novel xylosides in co-culture of basidiomycetes Trametes versicolor and Ganoderma applanatum by integrated metabolomics and bioinformatics

NASA Astrophysics Data System (ADS)

Yao, Lu; Zhu, Li-Ping; Xu, Xiao-Yan; Tan, Ling-Ling; Sadilek, Martin; Fan, Huan; Hu, Bo; Shen, Xiao-Ting; Yang, Jie; Qiao, Bin; Yang, Song

2016-09-01

Transcriptomic analysis of cultured fungi suggests that many genes for secondary metabolite synthesis are presumably silent under standard laboratory condition. In order to investigate the expression of silent genes in symbiotic systems, 136 fungi-fungi symbiotic systems were built up by co-culturing seventeen basidiomycetes, among which the co-culture of Trametes versicolor and Ganoderma applanatum demonstrated the strongest coloration of confrontation zones. Metabolomics study of this co-culture discovered that sixty-two features were either newly synthesized or highly produced in the co-culture compared with individual cultures. Molecular network analysis highlighted a subnetwork including two novel xylosides (compounds 2 and 3). Compound 2 was further identified as N-(4-methoxyphenyl)formamide 2-O-β-D-xyloside and was revealed to have the potential to enhance the cell viability of human immortalized bronchial epithelial cell line of Beas-2B. Moreover, bioinformatics and transcriptional analysis of T. versicolor revealed a potential candidate gene (GI: 636605689) encoding xylosyltransferases for xylosylation. Additionally, 3-phenyllactic acid and orsellinic acid were detected for the first time in G. applanatum, which may be ascribed to response against T.versicolor stress. In general, the described co-culture platform provides a powerful tool to discover novel metabolites and help gain insights into the mechanism of silent gene activation in fungal defense.

The conformational stability, solvation and the assignments of the experimental infrared, Raman, 1H and 13C NMR spectra of the local anesthetic drug lidocaine

NASA Astrophysics Data System (ADS)

Badawi, Hassan M.; Förner, Wolfgang; Ali, Shaikh A.

2015-05-01

The structure, vibrational and 1H and 13C NMR spectra of the local anesthetic drug lidocaine were investigated by the B3LYP/6-311G∗∗ calculations. The molecule was predicted to have the non-planar cis (NCCN ∼ 0°) structures being about 2-6 kcal/mol lower in energy than the corresponding trans (NCCN ∼ 180°) forms. The calculated NCCN (9.6°) and CNCC (-132.2°) torsional angles were in a good qualitative agreement with the reported X-ray angles (3.1 and 13.0°, -102.67 and -77.9°, respectively, for H-bonded dimers). The Gibbs energy of solution of lidocaine in formamide, water, dimethylsulfoxide, acetonitrile, methanol, ethanol and chloroform solutions was estimated at the B3LYP level. The predicted affinity of lidocaine toward the alcohols, acetonitrile and chloroform solutions was in excellent agreement with the reported experimental solubility of the drug in organic solvents. The analysis of the observed vibrational spectra is consistent with the presence of lidocaine in only one conformation at room temperature. The 1H and 13C NMR spectra of lidocaine were interpreted by experimental and DFT calculated chemical shifts of the drug. The RMSD between experimental and theoretical 1H and 13C chemical shifts for lidocaine is 0.47 and 8.26 ppm, respectively.

First detection of cyanamide (NH2CN) towards solar-type protostars

NASA Astrophysics Data System (ADS)

Coutens, A.; Willis, E. R.; Garrod, R. T.; Müller, H. S. P.; Bourke, T. L.; Calcutt, H.; Drozdovskaya, M. N.; Jørgensen, J. K.; Ligterink, N. F. W.; Persson, M. V.; Stéphan, G.; van der Wiel, M. H. D.; van Dishoeck, E. F.; Wampfler, S. F.

2018-05-01

Searches for the prebiotically relevant cyanamide (NH2CN) towards solar-type protostars have not been reported in the literature. We present here the first detection of this species in the warm gas surrounding two solar-type protostars, using data from the Atacama Large Millimeter/Submillimeter Array Protostellar Interferometric Line Survey (PILS) of IRAS 16293-2422 B and observations from the IRAM Plateau de Bure Interferometer of NGC 1333 IRAS2A. We also detected the deuterated and 13C isotopologs of NH2CN towards IRAS 16293-2422 B. This is the first detection of NHDCN in the interstellar medium. Based on a local thermodynamic equilibrium analysis, we find that the deuteration of cyanamide ( 1.7%) is similar to that of formamide (NH2CHO), which may suggest that these two molecules share NH2 as a common precursor. The NH2CN/NH2CHO abundance ratio is about 0.2 for IRAS 16293-2422 B and 0.02 for IRAS2A, which is comparable to the range of values found for Sgr B2. We explored the possible formation of NH2CN on grains through the NH2 + CN reaction using the chemical model MAGICKAL. Grain-surface chemistry appears capable of reproducing the gas-phase abundance of NH2CN with the correct choice of physical parameters.

Discovery of novel xylosides in co-culture of basidiomycetes Trametes versicolor and Ganoderma applanatum by integrated metabolomics and bioinformatics

PubMed Central

Yao, Lu; Zhu, Li-Ping; Xu, Xiao-Yan; Tan, Ling-Ling; Sadilek, Martin; Fan, Huan; Hu, Bo; Shen, Xiao-Ting; Yang, Jie; Qiao, Bin; Yang, Song

2016-01-01

Transcriptomic analysis of cultured fungi suggests that many genes for secondary metabolite synthesis are presumably silent under standard laboratory condition. In order to investigate the expression of silent genes in symbiotic systems, 136 fungi-fungi symbiotic systems were built up by co-culturing seventeen basidiomycetes, among which the co-culture of Trametes versicolor and Ganoderma applanatum demonstrated the strongest coloration of confrontation zones. Metabolomics study of this co-culture discovered that sixty-two features were either newly synthesized or highly produced in the co-culture compared with individual cultures. Molecular network analysis highlighted a subnetwork including two novel xylosides (compounds 2 and 3). Compound 2 was further identified as N-(4-methoxyphenyl)formamide 2-O-β-D-xyloside and was revealed to have the potential to enhance the cell viability of human immortalized bronchial epithelial cell line of Beas-2B. Moreover, bioinformatics and transcriptional analysis of T. versicolor revealed a potential candidate gene (GI: 636605689) encoding xylosyltransferases for xylosylation. Additionally, 3-phenyllactic acid and orsellinic acid were detected for the first time in G. applanatum, which may be ascribed to response against T.versicolor stress. In general, the described co-culture platform provides a powerful tool to discover novel metabolites and help gain insights into the mechanism of silent gene activation in fungal defense. PMID:27616058

Cell adhesion and growth on ultrananocrystalline diamond and diamond-like carbon films after different surface modifications

NASA Astrophysics Data System (ADS)

Miksovsky, J.; Voss, A.; Kozarova, R.; Kocourek, T.; Pisarik, P.; Ceccone, G.; Kulisch, W.; Jelinek, M.; Apostolova, M. D.; Reithmaier, J. P.; Popov, C.

2014-04-01

Diamond and diamond-like carbon (DLC) films possess a set of excellent physical and chemical properties which together with a high biocompatibility make them attractive candidates for a number of medical and biotechnological applications. In the current work thin ultrananocrystalline diamond (UNCD) and DLC films were comparatively investigated with respect to cell attachment and proliferation after different surface modifications. The UNCD films were prepared by microwave plasma enhanced chemical vapor deposition, the DLC films by pulsed laser deposition (PLD). The films were comprehensively characterized with respect to their basic properties, e.g. crystallinity, morphology, chemical bonding nature, etc. Afterwards the UNCD and DLC films were modified applying O2 or NH3/N2 plasmas and UV/O3 treatments to alter their surface termination. The surface composition of as-grown and modified samples was studied by X-ray photoelectron spectroscopy (XPS). Furthermore the films were characterized by contact angle measurements with water, formamide, 1-decanol and diiodomethane; from the results obtained the surface energy with its dispersive and polar components was calculated. The adhesion and proliferation of MG63 osteosarcoma cells on the different UNCD and DLC samples were assessed by measurement of the cell attachment efficiency and MTT assays. The determined cell densities were compared and correlated with the surface properties of as-deposited and modified UNCD and DLC films.

Synthesis, anion exchange, and delamination of Co-Al layered double hydroxide: assembly of the exfoliated nanosheet/polyanion composite films and magneto-optical studies.

PubMed

Liu, Zhaoping; Ma, Renzhi; Osada, Minoru; Iyi, Nobuo; Ebina, Yasuo; Takada, Kazunori; Sasaki, Takayoshi

2006-04-12

This paper describes a systematic study on the synthesis, anion exchange, and delamination of Co-Al layered double hydroxide (LDH), with the aim of achieving fabrication and clarifying the properties of LDH nanosheet/polyanion composite films. Co-Al-CO3 LDH hexagonal platelets of 4 mum in lateral size were synthesized by the urea method under optimized reaction conditions. The as-prepared CO3(2-)-LDH was converted to Cl- -LDH by treating with a NaCl-HCl mixed solution, retaining its high crystallinity and hexagonal platelike morphology. LDHs intercalated with a variety of anions (such as NO3-, ClO4-, acetate, lactate, dodecyl sulfate, and oleate) were further prepared from Cl- -LDH via an anion-exchange process employing corresponding salts. Exchanged products in various anion forms were found to show different delamination behaviors in formamide. Among them, best results were observed for NO3- -LDH in terms of the exfoliating degree and the quality of the exfoliated nanosheets. The delamination gave a pink transparent suspension containing well-defined nanosheets with lateral sizes of up to 2 microm. The resulting nanosheets were assembled layer-by-layer with an anionic polymer, poly(sodium styrene 4-sulfonate) (PSS), onto quartz glass substrates to produce composite films. Magnetic circular dichroism (MCD) measurements revealed that the assembled multilayer films exhibited an interesting magneto-optical response.

Expansion of access tunnels and active-site cavities influence activity of haloalkane dehalogenases in organic cosolvents.

PubMed

Stepankova, Veronika; Khabiri, Morteza; Brezovsky, Jan; Pavelka, Antonin; Sykora, Jan; Amaro, Mariana; Minofar, Babak; Prokop, Zbynek; Hof, Martin; Ettrich, Rudiger; Chaloupkova, Radka; Damborsky, Jiri

2013-05-10

The use of enzymes for biocatalysis can be significantly enhanced by using organic cosolvents in the reaction mixtures. Selection of the cosolvent type and concentration range for an enzymatic reaction is challenging and requires extensive empirical testing. An understanding of protein-solvent interaction could provide a theoretical framework for rationalising the selection process. Here, the behaviour of three model enzymes (haloalkane dehalogenases) was investigated in the presence of three representative organic cosolvents (acetone, formamide, and isopropanol). Steady-state kinetics assays, molecular dynamics simulations, and time-resolved fluorescence spectroscopy were used to elucidate the molecular mechanisms of enzyme-solvent interactions. Cosolvent molecules entered the enzymes' access tunnels and active sites, enlarged their volumes with no change in overall protein structure, but surprisingly did not act as competitive inhibitors. At low concentrations, the cosolvents either enhanced catalysis by lowering K(0.5) and increasing k(cat), or caused enzyme inactivation by promoting substrate inhibition and decreasing k(cat). The induced activation and inhibition of the enzymes correlated with expansion of the active-site pockets and their occupancy by cosolvent molecules. The study demonstrates that quantitative analysis of the proportions of the access tunnels and active-sites occupied by organic solvent molecules provides the valuable information for rational selection of appropriate protein-solvent pair and effective cosolvent concentration. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Arylsulfotransferase from Clostridium innocuum-A new enzyme catalyst for sulfation of phenol-containing compounds.

PubMed

Mozhaev, Vadim V; Khmelnitsky, Yuri L; Sanchez-Riera, Fernando; Maurina-Brunker, Julie; Rosson, Reinhardt A; Grund, Alan D

2002-06-05

Arylsulfotransferase (AST, EC 2.8.2.22), an enzyme capable of sulfating a wide range of phenol-containing compounds was purified from a Clostridium innocuum isolate (strain 554). The enzyme has a molecular weight of 320 kDa and is composed of four subunits. Unlike many mammalian and plant arylsulfotransferases, AST from Clostridium utilizes arylsulfates, including p-nitrophenyl sulfate, as sulfate donors, and is not reactive with 3-phosphoadenosine-5'-phosphosulfate (PAPS). The enzyme possesses broad substrate specificity and is active with a variety of phenols, quinones and flavonoids, but does not utilize primary and secondary alcohols and sugars as substrates. Arylsulfotransferase tolerates the presence of 10 vol% of polar cosolvents (dimethyl formamide, acetonitrile, methanol), but loses significant activity at higher solvent concentrations of 30-40 vol%. The enzyme retains high arylsulfotransferase activity in biphasic systems composed of water and nonpolar solvents, such as cyclohexane, toluene and chloroform, while in biphasic systems with more polar solvents (ethyl acetate, 2-pentanone, methyl tert-butyl ether, and butyl acetate) the enzyme activity is completely lost. High yields of AST-catalyzed sulfation were achieved in reactions with several phenols and tyrosine-containing peptides. Overall, AST studied in this work is a promising biocatalyst in organic synthesis to afford efficient sulfation of phenolic compounds under mild reaction conditions. Copyright 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 567-575, 2002.

Bypass of Aflatoxin B[subscript 1] Adducts by the Sulfolobus solfataricus DNA Polymerase IV

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

Banerjee, Surajit; Brown, Kyle L.; Egli, Martin

Aflatoxin B{sub 1} (AFB{sub 1}) is oxidized to an epoxide in vivo, which forms an N7-dG DNA adduct (AFB{sub 1}-N7-dG). The AFB{sub 1}-N7-dG can rearrange to a formamidopyrimidine (AFB{sub 1}-FAPY) derivative. Both AFB{sub 1}-N7-dG and the {beta}-anomer of the AFB{sub 1}-FAPY adduct yield G {yields} T transversions in Escherichia coli, but the latter is more mutagenic. We show that the Sulfolobus solfataricus P2 DNA polymerase IV (Dpo4) bypasses AFB{sub 1}-N7-dG in an error-free manner but conducts error-prone replication past the AFB{sub 1}-FAPY adduct, including misinsertion of dATP, consistent with the G {yields} T mutations observed in E. coli. Three ternarymore » (Dpo4-DNA-dNTP) structures with AFB{sub 1}-N7-dG adducted template:primers have been solved. These demonstrate insertion of dCTP opposite the AFB{sub 1}-N7-dG adduct, and correct vs incorrect insertion of dATP vs dTTP opposite the 5'-template neighbor dT from a primed AFB{sub 1}-N7-dG:dC pair. The insertion of dTTP reveals hydrogen bonding between the template N3 imino proton and the O{sup 2} oxygen of dTTP, and between the template T O{sup 4} oxygen and the N3 imino proton of dTTP, perhaps explaining why this polymerase does not efficiently catalyze phosphodiester bond formation from this mispair. The AFB{sub 1}-N7-dG maintains the 5'-intercalation of the AFB{sub 1} moiety observed in DNA. The bond between N7-dG and C8 of the AFB{sub 1} moiety remains in plane with the alkylated guanine, creating a 16{sup o} inclination of the AFB{sub 1} moiety with respect to the guanine. A binary (Dpo4-DNA) structure with an AFB{sub 1}-FAPY adducted template:primer also maintains 5'-intercalation of the AFB{sub 1} moiety. The {beta}-deoxyribose anomer is observed. Rotation about the FAPY C5-N{sup 5} bond orients the bond between N{sup 5} and C8 of the AFB{sub 1} moiety out of plane in the 5'-direction, with respect to the FAPY base. The formamide group extends in the 3'-direction. This improves stacking of the AFB{sub 1} moiety above the 5'-face of the FAPY base, as compared to the AFB{sub 1}-N7-dG adduct. Ternary structures with AFB{sub 1}-{beta}-FAPY adducted template:primers show correct vs incorrect insertion of dATP vs dTTP opposite the 5'-template neighbor dT from a primed AFB{sub 1}-{beta}-FAPY:dC pair. For dATP, the oxygen atom of the FAPY formamide group participates in a water-mediated hydrogen bond with Arg332. The insertion of dTTP yields a structure similar to that observed for the AFB{sub 1}-N7-dG adduct. The differential accommodation of these AFB{sub 1} adducts within the active site may, in part, modulate lesion bypass.« less

Hybrid nanomaterial of α-Co(OH)2 nanosheets and few-layer graphene as an enhanced electrode material for supercapacitors.

PubMed

Cheng, J P; Liu, L; Ma, K Y; Wang, X; Li, Q Q; Wu, J S; Liu, F

2017-01-15

Supercapacitor with metal hydroxide nanosheets as electrode can have high capacitance. However, the cycling stability and high rate capacity is low due to the low electrical conductivity. Here, the exfoliated α-Co(OH) 2 nanosheets with high capacitance has been assembled on few-layer graphene with high electric conductivity by a facile yet effective and scalable solution method. Exfoliated hydrotalcite-like α-Co(OH) 2 nanosheets and few-layer graphene suspensions were prepared by a simple ultrasonication in formamide and N-methyl-2-pyrrolidone, respectively. Subsequently, a hybrid was made by self-assembly of α-Co(OH) 2 and few-layer graphene when the two dispersions were mixed at room temperature. The hybrid material provided a high specific capacitance of 567.1F/g at 1A/g, while a better rate capability and better stability were achieved compared to that mad of pristine and single exfoliated α-Co(OH) 2 . When the hybrid nanocomposite was used as a positive electrode and activated carbon was applied as negative electrode to assembly an asymmetric capacitor, an energy density of 21.2Wh/kg at a power density of 0.41kW/kg within a potential of 1.65V was delivered. The high electrochemical performance and facile solution-based synthesis method suggested that the hybrid of exfoliated α-Co(OH) 2 /few-layer graphene could be a potential electrode material for electrochemical capacitor. Copyright © 2016 Elsevier Inc. All rights reserved.

Temperature Dependence of Nonelectrolyte Permeation across Red Cell Membranes

PubMed Central

Galey, W. R.; Owen, J. D.; Solomon, A. K.

1973-01-01

The temperature dependence of permeation across human red cell membranes has been determined for a series of hydrophilic and lipophilic solutes, including urea and two methyl substituted derivatives, all the straight-chain amides from formamide through valeramide and the two isomers, isobutyramide and isovaleramide. The temperature coefficient for permeation by all the hydrophilic solutes is 12 kcal mol-1 or less, whereas that for all the lipophilic solutes is 19 kcal mol-1 or greater. This difference is consonant with the view that hydrophilic molecules cross the membrane by a path different from that taken by the lipophilic ones. The thermodynamic parameters associated with lipophile permeation have been studied in detail. ΔG is negative for adsorption of lipophilic amides onto an oil-water interface, whereas it is positive for transfer of the polar head from the aqueous medium to bulk lipid solvent. Application of absolute reaction rate theory makes it possible to make a clear distinction between diffusion across the water-red cell membrane interface and diffusion within the membrane. Diffusion coefficients and apparent activation enthalpies and entropies have been computed for each process. Transfer of the polar head from the solvent into the interface is characterized by ΔG ‡ = 0 kcal mol-1 and ΔS ‡ negative, whereas both of these parameters have large positive values for diffusion within the membrane. Diffusion within the membrane is similar to what is expected for diffusion through a highly associated viscous fluid. PMID:4708405

Investigation on Tc tuned nano particles of magnetic oxides for hyperthermia applications.

PubMed

Giri, Jyotsnendu; Ray, Amlan; Dasgupta, S; Datta, D; Bahadur, D

2003-01-01

Superparamagnetic as well as fine ferrimagnetic particles such as Fe3O4, have been extensively used in magnetic field induced localized hyperthermia for the treatment of cancer. The magnetic materials with Curie temperature (Tc) between 42 and 50 degrees C, with sufficient biocompatibility are the best candidates for effective treatment such that during therapy it acts as in vivo temperature control switch and thus over heating could be avoided. Ultrafine particles of substituted ferrite Co(1-a)Zn(a)Fe2O4 and substituted yttrium-iron garnet Y3Fe(5-x)Al(x)O12 have been prepared through microwave refluxing and citrate-gel route respectively. Single-phase compounds were obtained with particle size below 100 nm. In order to make these magnetic nano particles biocompatible, we have attempted to coat these above said composition by alumina. The coating of alumina was done by hydrolysis method. The coating of hydrous aluminium oxide has been done over the magnetic particles by aging the preformed solid particles in the solution of aluminium sulfate and formamide at elevated temperatures. In vitro study is carried out to verify the innocuousness of coated materials towards cells. In vitro biocompatibility study has been carried out by cell culture method for a period of three days using human WBC cell lines. Study of cell counts and SEM images indicates the cells viability/growth. The in vitro experiments show that the coated materials are biocompatible.

Genetic relatedness of orbiviruses by RNA-RNA blot hybridization

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

Bodkin, D.K.

1985-01-01

RNA-RNA blot hybridization was developed in order to identify type-specific genes among double-stranded (ds) RNA viruses, to assess the genetic relatedness of dsRNA viruses and to classify new strains. Viral dsRNA segments were electrophoresed through 10% polyacrylamide gels, transferred to membranes, and hybridized to (5'/sup 32/P)-pCp labeled genomic RNA from a related strain. Hybridization was performed at 52/sup 0/C, 50% formamide, 5X SSC. Under these conditions heterologous RNA species must share greater than or equal to 74% sequence homology in order to form stable dsRNA hybrids. Cognate genes of nine members of the Palyam serogroup of orbiviruses were identified andmore » their sequence relatedness to the prototype. Palyam virus, was determined. Reciprocal blot hybridizations were performed using radiolabeled genomic RNA of all members of the Palyam serogroup. Unique and variant genes were identified by lack of cross-homology or by weak homology between segments. Since genes 2 and 6 exhibited the highest degree of sequence variability, response to the vertebrate immune system may be a major cause of sequence divergence among members of a single serogroup. Changuinola serogroup isolates were compared by dot-blot hybridization, while Colorado tick fever (CTF) serogroup isolates were compared by the RNA-RNA blot hybridization procedure described for reovirus and Palyam serogroup isolates. Preliminary blot hybridization data were also obtained on the relatedness of members of different Orbivirus serogroups.« less

Detection of cystic fibrosis transmembrane conductance regulator ΔF508 gene mutation using a paper-based nucleic acid hybridization assay and a smartphone camera.

PubMed

Malhotra, Karan; Noor, M Omair; Krull, Ulrich J

2018-05-29

Diagnostic technology that makes use of paper platforms in conjunction with the ubiquitous availability of digital cameras in cellular telephones and personal assistive devices offers opportunities for development of bioassays that are cost effective and widely distributed. Assays that operate effectively in aqueous solution require further development for implementation in paper substrates, overcoming issues associated with surface interactions on a matrix that offers a large surface-to-volume ratio and constraints on convective mixing. This report presents and compares two related methods for determination of oligonucleotides that serve as indicators of cystic fibrosis, differentiating between the normal wild-type sequence, and a mutant-type sequence that has a 3-base replacement. The transduction strategy operates by selective hybridization of oligonucleotide probes that are conjugated to fluorescent quantum dots, where hybridization of target sequences causes a molecular fluorophore to approach the quantum dot and become emissive through fluorescence resonance energy transfer. Detection can rely on hybridization of a target that is labelled with Cy3 fluorophore, or in the presence of an unlabelled target when a sandwich assay format is implemented with a labelled reporter oligonucleotide. Selectivity to determine the presence of mismatched sequences involves appropriate selection of nucleotide sequences to set melt temperatures, in conjunction with control of stringency conditions using formamide as a chaotrope. It was determined that both direct and sandwich assays on paper substrates are able to distinguish between wild-type and mutant-type samples.

The cannabinoid receptor agonist WIN 55,212-2 inhibits antigen-induced plasma extravasation in guinea pig airways.

PubMed

Fukuda, Hironobu; Abe, Toshio; Yoshihara, Shigemi

2010-01-01

Although neurogenic inflammation of the airways via activation of C-fibers is thought to be important in the pathogenesis of asthma, the mechanisms regulating C-fiber activity remain uncertain. The influence of a cannabinoid receptor agonist, WIN 55,212-2, on C-fiber activation in guinea pig airways was investigated, as was the mechanism by which cannabinoids regulate antigen-induced airway inflammation. The inhibitory effect of WIN 55,212-2 on antigen-induced plasma extravasation was assessed in guinea pig tracheal tissues by photometric measurement of extravasated Evans blue dye after extraction with formamide. Pretreatment with WIN 55,212-2 (0.001, 0.01 or 0.1 mg/kg) significantly and dose-dependently reduced tracheal plasma extravasation induced by inhaling a 5% ovalbumin solution for 2 min after pretreatment with a neutral endopeptidedase inhibitor (phosphoramidon at 2.5 mg/kg i.v.). A cannabinoid CB2 receptor antagonist (SR144528) blunted the inhibitory effect of WIN 55,212-2, while a cannabinoid CB1 antagonist (SR141716A) did not. Pretreatment with a neurokinin-1 receptor antagonist (FK888) significantly reduced ovalbumin-induced extravasation of Evans blue dye. Pretreatment with the combination of WIN 55,212-2 and FK888 reduced antigen-induced plasma extravasation more markedly than FK888 alone. These findings suggest that WIN 55,212-2 inhibits C-fiber activation via the cannabinoid CB2 receptor and thus suppresses antigen-induced inflammation in guinea pig airways. 2010 S. Karger AG, Basel.

Can conventional bases and unsaturated hydrocarbons be converted into gas-phase superacids that are stronger than most of the known oxyacids? The role of beryllium bonds.

PubMed

Yáñez, Manuel; Mó, Otilia; Alkorta, Ibon; Elguero, José

2013-08-26

The association of BeX2 (X: H, F, Cl) derivatives with azoles leads to a dramatic increase of their intrinsic acidity. Hence, whereas 1H-tetrazole can be considered as a typical N base in the gas phase, the complex 1H-tetrazole-BeCl2 is predicted to be, through the use of high-level G4 ab initio calculations, a nitrogen acid stronger than perchloric acid. This acidity enhancement is due to a more favorable stabilization of the deprotonated species after the beryllium bond is formed, because the deprotonated anion is a much better electron donor than the neutral species. Consequently, this is a general phenomenon that should be observed for any Lewis base, including those in which the basic site is a hydroxy group, an amino group, a carbonyl group, an aromatic N atom, a second-row atom, or the π system of unsaturated hydrocarbons. The consequence is that typical bases like aniline or formamide lead to BeX2 complexes that are stronger acids than phosphoric or chloric acids. Similarly, water, methanol, and SH2 become stronger acids than sulfuric acid, pyridine becomes a C acid almost as strong as acetic acid, and unsaturated hydrocarbons such as ethylene and acetylene become acids as strong as nitric and sulfuric acids, respectively. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis, spectroscopic characterization, first order nonlinear optical properties and DFT calculations of novel Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes with 1,3-diphenyl-4-phenylazo-5-pyrazolone ligand

NASA Astrophysics Data System (ADS)

Abdel-Latif, Samir A.; Mohamed, Adel A.

2018-02-01

Novel Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) metal ions with 1,3-diphenyl-4-phenylazo-5-pyrazolone (L) have been prepared and characterized using different analytical and spectroscopic techniques. 1:1 Complexes of Mn(II), Co(II) and Zn(II) are distorted octahedral whereas Ni(II) complex is square planar and Cu(II) is distorted trigonal bipyramid. 1:2 Complexes of Mn(II), Co(II), Cu(II) and Zn(II) are distorted trigonal bipyramid whereas Ni(II) complex is distorted tetrahedral. All complexes behave as non-ionic in dimethyl formamide (DMF). The electronic structure and nonlinear optical parameters (NLO) of the complexes were investigated theoretically at the B3LYP/GEN level of theory. Molecular stability and bond strengths have been investigated by applying natural bond orbital (NBO) analysis. The geometries of the studied complexes are non-planner. DFT calculations have been also carried out to calculate the global properties; hardness (η), global softness (S) and electronegativity (χ). The calculated small energy gap between HOMO and LUMO energies shows that the charge transfer occurs within the complexes. The total static dipole moment (μtot), the mean polarizability (<α>), the anisotropy of the polarizability (Δα) and the mean first-order hyperpolarizability (<β>) were calculated and compared with urea as a reference material. The complexes show implying optical properties.

Preparation of a poly(3'-azido-3'-deoxythymidine-co-propargyl methacrylate-co-pentaerythritol triacrylate) monolithic column by in situ polymerization and a click reaction for capillary liquid chromatography of small molecules and proteins.

PubMed

Lin, Zian; Yu, Ruifang; Hu, Wenli; Zheng, Jiangnan; Tong, Ping; Zhao, Hongzhi; Cai, Zongwei

2015-07-07

Combining free radical polymerization with click chemistry via a copper-mediated azide/alkyne cycloaddition (CuAAC) reaction in a "one-pot" process, a facile approach was developed for the preparation of a poly(3'-azido-3'-deoxythymidine-co-propargyl methacrylate-co-pentaerythritol triacrylate) (AZT-co-PMA-co-PETA) monolithic column. The resulting poly(AZT-co-PMA-co-PETA) monolith showed a relatively homogeneous monolithic structure, good permeability and mechanical stability. Different ratios of monomers and porogens were used for optimizing the properties of a monolithic column. A series of alkylbenzenes, amides, anilines, and benzoic acids were used to evaluate the chromatographic properties of the polymer monolith in terms of hydrophobic, hydrophilic and cation-exchange interactions, and the results showed that the poly(AZT-co-PMA-co-PETA) monolith exhibited more flexible adjustment in chromatographic selectivity than that of the parent poly(PMA-co-PETA) and AZT-modified poly(PMA-co-PETA) monoliths. Column efficiencies for toluene, DMF, and formamide with 35,000-48,000 theoretical plates per m could be obtained at a linear velocity of 0.17 mm s(-1). The run-to-run, column-to-column, and batch-to-batch repeatabilities of the retention factors were less than 4.2%. In addition, the proposed monolith was also applied to efficient separation of sulfonamides, nucleobases and nucleosides, anesthetics and proteins for demonstrating its potential.

Osmotic tolerance limits and membrane permeability characteristics of stallion spermatozoa treated with cholesterol.

PubMed

Glazar, Amanda I; Mullen, Steven F; Liu, Jun; Benson, James D; Critser, John K; Squires, Edward L; Graham, James K

2009-10-01

Stallion spermatozoa exhibit osmotic damage during the cryopreservation process. Recent studies have shown that the addition of cholesterol to spermatozoal membranes increases the cryosurvival of bull, ram and stallion spermatozoa, but the exact mechanism by which added cholesterol improves cryosurvival is not understood. The objectives of this study were to determine if adding cholesterol to stallion sperm membranes alters the osmotic tolerance limits and membrane permeability characteristics of the spermatozoa. In experiment one, stallion spermatozoa were treated with cholesterol-loaded cyclodextrin (CLC), subjected to anisotonic solutions and spermatozoal motility analyzed. The spermatozoa were then returned to isotonic conditions and the percentages of motile spermatozoa again determined. CLC treatment increased the osmotic tolerance limit of stallion spermatozoa in anisotonic solutions and when returned to isotonic conditions. The second and third experiments utilized an electronic particle counter to determine the plasma membrane characteristics of stallion spermatozoa. In experiment two, stallion spermatozoa were determined to behave as linear osmometers. In experiment three, spermatozoa were treated with CLC, incubated with different cryoprotectants (glycerol, ethylene glycol or dimethyl formamide) and their volume excursions measured during cryoprotectant removal at 5 degrees and 22 degrees C. Stallion spermatozoa were less permeable to the cryoprotectants at 5 degrees C than 22 degrees C. Glycerol was the least permeable cryoprotectant in control cells. The addition of CLC's to spermatozoa increased the permeability of stallion spermatozoa to the cryoprotectants. Therefore, adding cholesterol to spermatozoal membranes reduces the amount of osmotic stress endured by stallion spermatozoa during cryopreservation.

Graphitic Nitrogen Triggers Red Fluorescence in Carbon Dots.

PubMed

Holá, Kateřina; Sudolská, Mária; Kalytchuk, Sergii; Nachtigallová, Dana; Rogach, Andrey L; Otyepka, Michal; Zbořil, Radek

2017-12-26

Carbon dots (CDs) are a stable and highly biocompatible fluorescent material offering great application potential in cell labeling, optical imaging, LED diodes, and optoelectronic technologies. Because their emission wavelengths provide the best tissue penetration, red-emitting CDs are of particular interest for applications in biomedical technologies. Current synthetic strategies enabling red-shifted emission include increasing the CD particle size (sp 2 domain) by a proper synthetic strategy and tuning the surface chemistry of CDs with suitable functional groups (e.g., carboxyl). Here we present an elegant route for preparing full-color CDs with well-controllable fluorescence at blue, green, yellow, or red wavelengths. The two-step procedure involves the synthesis of a full-color-emitting mixture of CDs from citric acid and urea in formamide followed by separation of the individual fluorescent fractions by column chromatography based on differences in CD charge. Red-emitting CDs, which had the most negative charge, were separated as the last fraction. The trend in the separation, surface charge, and red-shift of photoluminescence was caused by increasing amount of graphitic nitrogen in the CD structure, as was clearly proved by XPS, FT-IR, Raman spectroscopy, and DFT calculations. Importantly, graphitic nitrogen generates midgap states within the HOMO-LUMO gap of the undoped systems, resulting in significantly red-shifted light absorption that in turn gives rise to fluorescence at the low-energy end of the visible spectrum. The presented findings identify graphitic nitrogen as another crucial factor that can red-shift the CD photoluminescence.

Radiation hardening of low condensation products containing amino group (in Japanese)

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

Okamura, S.; Hayashi, K.; Kaetsu, I.

1967-11-01

An initial condensation product is prepared by condensing a monomer selected from the group of urea, thiourea, melanine, aniline and acidamide with formalin. 0ne or more of the initial condensation product is then mixed with a substance which forms an acid or base by irradiation with an ionizing radiation in the presence or absence of the initial condensation product, except for halogenated hydrocarbon. The mixture is hardened by irradiation of the ionizing radiation to form a resinous substance. Formamide, acetamide, oxalic diamide, succinic diamide, acrylamide, etc. can be used as the acidamide monomer. Phosphonitrile chloride, cyanuric chloride, chloral hydrate, trichloroaceticmore » acid, monochloroacetic acid, ammonium chloride, aluminium chloride, gaseous chlorine, sullurous acid gas, sodium sulfite, aluminium sulfate, potassium hydrogensulfate, sodium pyrophosphate, potassium pyrophosphate, potassium phosphate, ammonia, bromine, bromal, bromal hydrate, dibromoacetic acid, sulfonated benzene, sulfonated toluene, etc. can be used as the acid- or base- forming substance. To the initial condensation product may be added 0.5-20%, in certain cases 20-50%, by weight of the said substances. The ionizing radiation can be electron beams. In an example, 2% chloral hydrate was homogeneously dissolved in the initial urea-formalin condensation product having a degree of condensation of 3--5. The solution was then irradiated by gamma rays at the dose rate of 4 x 10/sup 4/ r/hour from a /sup 60/Co source with a dose 5.0 x 10/sup 6/ roentgens. A white resinous composition was obtained. (JA)« less

Part I: RNA hydrolysis catalyzed by imidazole compounds. Part II. Hydrophobic acceleration of reactions and mimics of thiamin-dependent enzymes

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

Kool, E.T.

1988-01-01

Catalysts modeled after the active site groups of the enzyme Ribonuclease A were synthesized and tested for catalysis of the hydrolysis of poly(rU), using a quantitative assay. The most effective of all the catalysts is N,N{prime}-bis-imidazolylmethane, which gave a four-fold rate enhancement as compared to N-methyl-imidazole. The structure/activity relationships are discussed in light of the ribonuclease mechanism. Also examined were reactions catalyzed by the coenzyme thiamine. In an investigation of the effects of restricting conformational freedom, a thiazolium salt was attached in two positions to {beta}-cyclodextrin. Since the catalyst gave about the same rate for tritium exchange from benzaldehyde asmore » singly-attached catalysts, we surmise that any rate enhancement due to the restriction of bond rotations has been lost by forcing the structure into less productive conformations. The benzoin condensation catalyzed by cyanide was also investigated. The reaction was shown to be faster in water than in most organic solvents. Kinetic salt effects and the effects of added {beta}- and {gamma}-cyclodextrin were measured in water; salting-out ions and {gamma}-cyclodextrin increase the rate, while salting-in ions and {beta}-cyclodextrin decrease it. Negative salt effects were observed in formamide, ethylene glycol, and DMSO. All these media effects are discussed in relation to the compact, hydrophobic transition state for the reaction.« less

Photodissociation pathways and lifetimes of protonated peptides and their dimers

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

Aravind, G.; Klaerke, B.; Rajput, J.

2012-01-07

Photodissociation lifetimes and fragment channels of gas-phase, protonated YA{sub n} (n = 1,2) peptides and their dimers were measured with 266 nm photons. The protonated monomers were found to have a fast dissociation channel with an exponential lifetime of {approx}200 ns while the protonated dimers show an additional slow dissociation component with a lifetime of {approx}2 {mu}s. Laser power dependence measurements enabled us to ascribe the fast channel in the monomer and the slow channel in the dimer to a one-photon process, whereas the fast dimer channel is from a two-photon process. The slow (1 photon) dissociation channel in themore » dimer was found to result in cleavage of the H-bonds after energy transfer through these H-bonds. In general, the dissociation of these protonated peptides is non-prompt and the decay time was found to increase with the size of the peptides. Quantum RRKM calculations of the microcanonical rate constants also confirmed a statistical nature of the photodissociation processes in the dipeptide monomers and dimers. The classical RRKM expression gives a rate constant as an analytical function of the number of active vibrational modes in the system, estimated separately on the basis of the equipartition theorem. It demonstrates encouraging results in predicting fragmentation lifetimes of protonated peptides. Finally, we present the first experimental evidence for a photo-induced conversion of tyrosine-containing peptides into monocyclic aromatic hydrocarbon along with a formamide molecule both found in space.« less

Nonelectrolyte diffusion across lipid bilayer systems

PubMed Central

1976-01-01

The permeability coefficients of a homologous series of amides from formamide through valeramide have been measured in spherical bilayers prepared by the method described by Jung. They do not depend directly on the water:ether partition coefficient which increases regularly with chain length. Instead there is a minimum at acetamide. This has been ascribed to the effect of steric hindrance on diffusion within the bilayer which increases with solute molar volume. This factor is of the same magnitude, though opposite in sign to the effect of lipid solubility, thus accounting for the minimum. The resistance to passage across the interface has been compared to the resistance to diffusion within the membrane. As the solute chain length increases the interface becomes more important, until for valeramide it comprises about 90% of the total resistance. Interface resistance is also important in urea permeation, causing urea to permeate much more slowly than an amide of comparable size, after allowance is made for the difference in the water:ether partition coefficient. Amide permeation coefficients have been compared with relative liposome permeation data measured by the rate of liposome swelling. The ratios of the two measures of permeation vary between 3 and 16 for the homologous amides. The apparent enthalpy of liposome permeation has been measured and found to be in the neighborhood of 12 kcal mol-1 essentially independent of chain length. Comparison of the bilayer permeability coefficients with those of red cells shows that red cell permeation by the lipophilic solutes resembles that of the bilayers, whereas permeation by the hydrophilic solutes differs significantly. PMID:1245835

Common buffers, media, and stock solutions.

PubMed

2001-05-01

This appendix describes the preparation of selected bacterial media and of buffers and reagents used in the manipulation of nucleic acids and proteins. Recipes for cell culture media and reagents are located elsewhere in the manual. RECIPES: Acids, concentrated stock solutions; Ammonium acetate, 10 M; Ammonium hydroxide, concentrated stock solution; ATP, 100 mM; BCIP, 5% (w/v); BSA (bovine serum albumin), 10% (100 mg/ml); Denhardt solution, 100x; dNTPs: dATP, dTTP, dCTP, and dGTP; DTT, 1 M; EDTA, 0.5 M (pH 8.0); Ethidium bromide solution; Formamide loading buffer, 2x; Gel loading buffer, 6x; HBSS (Hanks balanced salt solution); HCl, 1 M; HEPES-buffered saline, 2x; KCl, 1 M; LB medium; LB plates; Loading buffer; 2-ME, (2-mercaptoethanol)50 mM; MgCl(2), 1 M; MgSO(4), 1 M; NaCl, 5 M; NaOH, 10 M; NBT (nitroblue tetrazolium chloride), 5% (w/v); PCR amplification buffer, 10x; Phosphate-buffered saline (PBS), pH approximately 7.3; Potassium acetate buffer, 0.1 M; Potassium phosphate buffer, 0.1 M; RNase a stock solution (DNase-free), 2 mg/ml; SDS, 20%; SOC medium; Sodium acetate, 3 M; Sodium acetate buffer, 0.1 M; Sodium phosphate buffer, 0.1 M; SSC (sodium chloride/sodium citrate), 20x; SSPE (sodium chloride/sodium phosphate/EDTA), 20x; T4 DNA ligase buffer, 10x; TAE buffer, 50x; TBE buffer, 10x; TBS (Tris-buffered saline); TCA (trichloroacetic acid), 100% (w/v); TE buffer; Terrific broth (TB); TrisCl, 1 M; TY medium, 2x; Urea loading buffer, 2x.

Simultaneous hydrogenation and UV-photolysis experiments of NO in CO-rich interstellar ice analogues; linking HNCO, OCN-, NH2CHO, and NH2OH

NASA Astrophysics Data System (ADS)

Fedoseev, G.; Chuang, K.-J.; van Dishoeck, E. F.; Ioppolo, S.; Linnartz, H.

2016-08-01

The laboratory work presented here simulates the chemistry on icy dust grains as typical for the `CO freeze-out stage' in dark molecular clouds. It differs from previous studies in that solid-state hydrogenation and vacuum UV photoprocessing are applied simultaneously to co-depositing molecules. In parallel, the reactions at play are described for fully characterized laboratory conditions. The focus is on the formation of molecules containing both carbon and nitrogen atoms, starting with NO in CO-, H2CO-, and CH3OH-rich ices at 13 K. The experiments yield three important conclusions. (1) Without UV processing hydroxylamine (NH2OH) is formed, as reported previously. (2) With UV processing (energetic) NH2 is formed through photodissociation of NH2OH. This radical is key in the formation of species with an N-C bond. (3) The formation of three N-C bearing species, HNCO, OCN-, and NH2CHO, is observed. The experiments put a clear chemical link between these species; OCN- is found to be a direct derivative of HNCO and the latter is shown to have the same precursor as formamide (NH2CHO). Moreover, the addition of VUV competing channels decreases the amount of NO molecules converted into NH2OH by at least one order of magnitude. Consequently, this decrease in NH2OH formation yield directly influences the amount of NO molecules that can be converted into HNCO, OCN-, and NH2CHO.

Biodegradation of cyanide by acetonitrile-induced cells of Rhodococcus sp. UKMP-5M.

PubMed

Nallapan Maniyam, Maegala; Sjahrir, Fridelina; Ibrahim, Abdul Latif; Cass, Anthony E G

2013-01-01

A Rhodococcus sp. UKMP-5M isolate was shown to detoxify cyanide successfully, suggesting the presence of an intrinsic property in the bacterium which required no prior cyanide exposure for induction of this property. However, in order to promote growth, Rhodococcus sp. UKMP-5M was fully acclimatized to cyanide after 7 successive subcultures in 0.1 mM KCN for 30 days. To further shorten the lag phase and simultaneously increase the tolerance towards higher cyanide concentrations, the bacterium was induced with various nitrile compounds sharing a similar degradatory pathway to cyanide. Acetonitrile emerged as the most favored inducer and the induced cells were able to degrade 0.1 mM KCN almost completely within 18 h. With the addition of subsequent aliquots of 0.1 mM KCN a shorter period for complete removal of cyanide was required, which proved to be advantageous economically. Both resting cells and crude enzyme of Rhodococcus sp. UKMP-5M were able to biodegrade cyanide to ammonia and formate without the formation of formamide, implying the identification of a simple hydrolytic cyanide degradation pathway involving the enzyme cyanidase. Further verification with SDS-PAGE revealed that the molecular weight of the active enzyme was estimated to be 38 kDa, which is consistent with previously reported cyanidases. Since the recent advancement in the application of biological methods in treating cyanide-bearing wastewater has been promising, the discovery of this new bacterium will add value by diversifying the existing microbial populations capable of cyanide detoxification.

Influence of PCR reagents on DNA polymerase extension rates measured on real-time PCR instruments.

PubMed

Montgomery, Jesse L; Wittwer, Carl T

2014-02-01

Radioactive DNA polymerase activity methods are cumbersome and do not provide initial extension rates. A simple extension rate assay would enable study of basic assumptions about PCR and define the limits of rapid PCR. A continuous assay that monitors DNA polymerase extension using noncovalent DNA dyes on common real-time PCR instruments was developed. Extension rates were measured in nucleotides per second per molecule of polymerase. To initiate the reaction, a nucleotide analog was heat activated at 95 °C for 5 min, the temperature decreased to 75 °C, and fluorescence monitored until substrate exhaustion in 30-90 min. The assay was linear with time for over 40% of the reaction and for polymerase concentrations over a 100-fold range (1-100 pmol/L). Extension rates decreased continuously with increasing monovalent cation concentrations (lithium, sodium, potassium, cesium, and ammonium). Melting-temperature depressors had variable effects. DMSO increased rates up to 33%, whereas glycerol had little effect. Betaine, formamide, and 1,2-propanediol decreased rates with increasing concentrations. Four common noncovalent DNA dyes inhibited polymerase extension. Heat-activated nucleotide analogs were 92% activated after 5 min, and hot start DNA polymerases were 73%-90% activated after 20 min. Simple DNA extension rate assays can be performed on real-time PCR instruments. Activity is decreased by monovalent cations, DNA dyes, and most melting temperature depressors. Rational inclusion of PCR components on the basis of their effects on polymerase extension is likely to be useful in PCR, particularly rapid-cycle or fast PCR.

Evolution of interstellar organic compounds under asteroidal hydrothermal conditions

NASA Astrophysics Data System (ADS)

Vinogradoff, V.; Bernard, S.; Le Guillou, C.; Remusat, L.

2018-05-01

Carbonaceous chondrites (CC) contain a diversity of organic compounds. No definitive evidence for a genetic relationship between these complex organic molecules and the simple organic molecules detected in the interstellar medium (ISM) has yet been reported. One of the many difficulties arises from the transformations of organic compounds during accretion and hydrothermal alteration on asteroids. Here, we report results of hydrothermal alteration experiments conducted on a common constituent of interstellar ice analogs, Hexamethylenetetramine (HMT - C6H12N4). We submitted HMT to asteroidal hydrothermal conditions at 150 °C, for various durations (up to 31 days) and under alkaline pH. Organic products were characterized by gas chromatography mass spectrometry, infrared spectroscopy and synchrotron-based X-ray absorption near edge structure spectroscopy. Results show that, within a few days, HMT has evolved into (1) a very diverse suite of soluble compounds dominated by N-bearing aromatic compounds (> 150 species after 31 days), including for instance formamide, pyridine, pyrrole and their polymers (2) an aromatic and N-rich insoluble material that forms after only 7 days of experiment and then remains stable through time. The reaction pathways leading to the soluble compounds likely include HMT dissociation, formose and Maillard-type reactions, e.g. reactions of sugar derivatives with amines. The present study demonstrates that, if interstellar organic compounds such as HMT had been accreted by chondrite parent bodies, they would have undergone chemical transformations during hydrothermal alteration, potentially leading to the formation of high molecular weight insoluble organic molecules. Some of the diversity of soluble and insoluble organic compounds found in CC may thus result from asteroidal hydrothermal alteration.

Evolution of Interstellar Ices

NASA Astrophysics Data System (ADS)

Allamandola, Louis J.; Bernstein, Max P.; Sandford, Scott A.; Walker, Robert L.

1999-10-01

Infrared observations, combined with realistic laboratory simulations, have revolutionized our understanding of interstellar ice and dust, the building blocks of comets. Ices in molecular clouds are dominated by the very simple molecules H2O, CH3OH, NH3, CO, CO2, and probably H2CO and H2. More complex species including nitriles, ketones, and esters are also present, but at lower concentrations. The evidence for these, as well as the abundant, carbon-rich, interstellar, polycyclic aromatic hydrocarbons (PAHs) is reviewed. Other possible contributors to the interstellar/pre-cometary ice composition include accretion of gas-phase molecules and in situ photochemical processing. By virtue of their low abundance, accretion of simple gas-phase species is shown to be the least important of the processes considered in determining ice composition. On the other hand, photochemical processing does play an important role in driving dust evolution and the composition of minor species. Ultraviolet photolysis of realistic laboratory analogs readily produces H2, H2CO, CO2, CO, CH4, HCO, and the moderately complex organic molecules: CH3CH2OH (ethanol), HC(=O)NH2 (formamide), CH3C(=O)NH2 (acetamide), R-CN (nitriles), and hexamethylenetetramine (HMT, C6H12N4), as well as more complex species including amides, ketones, and polyoxymethylenes (POMs). Inclusion of PAHs in the ices produces many species similar to those found in meteorites including aromatic alcohols, quinones and ethers. Photon assisted PAH-ice deuterium exchange also occurs. All of these species are readily formed and are therefore likely cometary constituents.

Seeds Of Life In Space (SOLIS): The Organic Composition Diversity at 300-1000 au Scale in Solar-type Star-forming Regions

NASA Astrophysics Data System (ADS)

Ceccarelli, C.; Caselli, P.; Fontani, F.; Neri, R.; López-Sepulcre, A.; Codella, C.; Feng, S.; Jiménez-Serra, I.; Lefloch, B.; Pineda, J. E.; Vastel, C.; Alves, F.; Bachiller, R.; Balucani, N.; Bianchi, E.; Bizzocchi, L.; Bottinelli, S.; Caux, E.; Chacón-Tanarro, A.; Choudhury, R.; Coutens, A.; Dulieu, F.; Favre, C.; Hily-Blant, P.; Holdship, J.; Kahane, C.; Jaber Al-Edhari, A.; Laas, J.; Ospina, J.; Oya, Y.; Podio, L.; Pon, A.; Punanova, A.; Quenard, D.; Rimola, A.; Sakai, N.; Sims, I. R.; Spezzano, S.; Taquet, V.; Testi, L.; Theulé, P.; Ugliengo, P.; Vasyunin, A. I.; Viti, S.; Wiesenfeld, L.; Yamamoto, S.

2017-12-01

Complex organic molecules have been observed for decades in the interstellar medium. Some of them might be considered as small bricks of the macromolecules at the base of terrestrial life. It is hence particularly important to understand organic chemistry in Solar-like star-forming regions. In this article, we present a new observational project: Seeds Of Life In Space (SOLIS). This is a Large Project using the IRAM-NOEMA interferometer, and its scope is to image the emission of several crucial organic molecules in a sample of Solar-like star-forming regions in different evolutionary stages and environments. Here we report the first SOLIS results, obtained from analyzing the spectra of different regions of the Class 0 source NGC 1333-IRAS4A, the protocluster OMC-2 FIR4, and the shock site L1157-B1. The different regions were identified based on the images of formamide (NH2CHO) and cyanodiacetylene (HC5N) lines. We discuss the observed large diversity in the molecular and organic content, both on large (3000-10,000 au) and relatively small (300-1000 au) scales. Finally, we derive upper limits to the methoxy fractional abundance in the three observed regions of the same order of magnitude of that measured in a few cold prestellar objects, namely ˜ {10}-12-10-11 with respect to H2 molecules. Based on observations carried out under project number L15AA with the IRAM-NOEMA interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

Concurrent Solution and Adsorption of Hydrocarbons in Gas Chromatographic Columns Packed with Different Loadings of 3-Methylsydnone on Chromosorb P

PubMed

Castells; Romero; Nardillo

1997-08-01

Thermodynamic properties of solution in 3-methylsydnone (3MS) and of adsorption at the nitrogen/3MS interface were gas chromatographically measured for a group of fifteen hydrocarbons at infinite dilution conditions. Retention volumes were measured at five temperatures within the range 37-52°C in six columns containing different loadings of 3MS on Chromosorb P AW. Partition and adsorption coefficients were calculated and from their temperature dependence the corresponding enthalpies were obtained, although with considerable error; infinite dilution activity coefficients of the hydrocarbons in the bulk and in the surface phases demonstrated a strong correlation. Bulk activity coefficients in 3MS were very much smaller than those previously measured for the same solutes in formamide (FA) and in ethyleneglycol (EG), and were also smaller than what could be predicted on account of 3MS cohesive energy density as estimated from the quotient sigma/v1/3 (sigma, surface tension; v, molar volume). There was not such a large difference between the surface activity coefficients in the three solvents; furthermore, the quotients (surface activity coefficient/bulk activity coefficient) for a given solute in 3MS were twice as large as in FA and about three times larger than in EG. These results make evident the difficulties inherent in the prediction of surface phase properties from those in the bulk and cast doubts on the pertinency of employing the surface tension to compare cohesive energy densities of polar solvents with important chemical differences.

Nitric oxide-releasing indomethacin enhances susceptibility to Trypanosoma cruzi infection acting in the cell invasion and oxidative stress associated with anemia.

PubMed

Tatakihara, Vera Lucia Hideko; Malvezi, Aparecida Donizette; Panis, Carolina; Cecchini, Rubens; Zanluqui, Nagela Ghabdan; Yamauchi, Lucy Megumi; Martins, Maria Isabel Lovo; da Silva, Rosiane Valeriano; Yamada-Ogatta, Sueli Fumie; Rizzo, Luiz Vicente; Martins-Pinge, Marli Cardoso; Pinge-Filho, Phileno

2015-02-05

Trypanosoma cruzi is the causative agent of Chagas disease. Approximately 8 million people are thought to be affected with this disease worldwide. T. cruzi infection causes an intense inflammatory response, which is critical for the control of parasite proliferation and disease development. Nitric oxide-donating nonsteroidal anti-inflammatory drugs (NO-NSAIDs) are an emergent class of pharmaceutical derivatives with promising utility as chemopreventive agents. In this study, we investigated the effect of NO-indomethacin on parasite burden, cell invasion, and oxidative stress in erythrocytes during the acute phase of infection. NO-indomethacin was dissolved in dimethyl formamide followed by i.p. administration of 50 ppm into mice 30 min after infection with 5×10(3) blood trypomastigote forms (Y strain). The drug was administered every day until the animals died. Control animals received 100 μL of drug vehicle via the same route. Within the NO-indomethacin-treatment group, parasitemia and mortality (100%) were higher and oxidative stress in erythrocytes, anemia, and entry of parasites into macrophages were significantly greater than that seen in controls. Increase in the entry and survival of intracellular T. cruzi was associated with inhibition of nitric oxide production by macrophages treated with NO-indomethacin (2.5 μM). The results of this study provide strong evidence that NO-NSAIDs potently inhibit nitric oxide production, suggesting that NO-NSAID-based therapies against infections would be difficult to design and would require caution. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Use of itaconic acid-based polymers for solid-phase extraction of deoxynivalenol and application to pasta analysis.

PubMed

Pascale, Michelangelo; De Girolamo, Annalisa; Visconti, Angelo; Magan, Naresh; Chianella, Iva; Piletska, Elena V; Piletsky, Sergey A

2008-02-25

Molecular modelling and computational design were used to identify itaconic acid (IA) as a functional monomer with high affinity towards deoxynivalenol (DON), a Fusarium-toxin frequently occurring in cereals. IA-based polymers were photochemically synthesised in dimethyl formamide (porogen) using ethylenglycol dimethacrylate as cross-linker and 1,1'-azo-bis(cyclohexane carbonitrile) as initiator, and the relevant binding interactions with DON in solvents with different polarity were investigated. The performances of the non-imprinted IA-based polymer (blank polymer, BP) and the corresponding molecularly imprinted polymer (MIP) were compared using DON as a template. Both BP and MIP were able to bind about 90% DON either in toluene, water or water containing 5% polyethylene glycol. Non-imprinted polymers with different molar ratios of IA to cross-linker were evaluated as adsorbents for solid-phase extraction (SPE) clean-up and pre-concentration of DON from wheat and pasta samples prior to HPLC analysis. Samples were extracted with PBS/0.1M EDTA solution and cleaned up through a cartridge containing blank IA-based polymer. The column was washed with PBS (pH 9.2) and the toxin was eluted with methanol and quantified by reversed-phase HPLC with UV detector (lambda=220nm), using methanol:water:acetic acid (15:85:0.1, v/v/v) as the mobile phase. Effective removal of matrix interferences was observed only for pasta with DON recoveries higher than 70% (RSD<7%, n=3) at levels close to or higher than EU regulatory limit.

Development of dispersive liquid-liquid microextraction technique using ternary solvents mixture followed by heating for the rapid and sensitive analysis of phthalate esters and di(2-ethylhexyl) adipate.

PubMed

Farajzadeh, Mir Ali; Khoshmaram, Leila

2015-01-30

In this study, for the first time, a dispersive liquid-liquid microextraction technique using a ternary solvent mixture is reported. In order to extract five phthalate esters and di(2-ethylhexyl) adipate with different polarities from aqueous samples, a simplex centroid experimental design method was used to select an optimal mixture of ternary solvents prior to gas chromatographyflame ionization detection. In this work, dimethyl formamide as a disperser solvent containing dichloromethane, chloroform, and carbon tetrachloride as a ternary extraction solvent mixture is injected into sample solution and a cloudy solution is formed. After centrifuging, 250μL of the obtained sedimented phase was transferred into another tube and 5μL DMF was added to it. Then, the tube was heated in a water bath at 75°C for 5min in order to evaporate the main portion of the extraction solvents. Finally, 2μL of the remained phase is injected into the separation system. Under the optimum extraction conditions, the method shows wide linear ranges and low limits of detection and quantification between 0.03-0.15 and 0.09-0.55μgL(-1), respectively. Enrichment factors and extraction recoveries are in the ranges of 980-4500 and 20-90%, respectively. The method is successfully applied in the determination of the target analytes in mineral water, soda, lemon juice, vinegar, dough, and yogurt packed in plastic packages. Copyright © 2014 Elsevier B.V. All rights reserved.

X-ray Constrained Extremely Localized Molecular Orbitals: Theory and Critical Assessment of the New Technique.

PubMed

Genoni, Alessandro

2013-07-09

Following the X-ray constrained wave function approach proposed by Jayatilaka, we have devised a new technique that allows to extract molecular orbitals strictly localized on small molecular fragments from sets of experimental X-ray structure factors amplitudes. Since the novel strategy enables to obtain electron distributions that have quantum mechanical features and that can be easily interpreted in terms of traditional chemical concepts, the method can be also considered as a new useful tool for the determination and the analysis of charge densities from high-resolution X-ray experiments. In this paper, we describe in detail the theory of the new technique, which, in comparison to our preliminary work, has been improved both treating the effects of isotropic secondary extinctions and introducing a new protocol to halt the fitting procedure against the experimental X-ray scattering data. The performances of the novel strategy have been studied both in function of the basis-sets flexibility and in function of the quality of the considered crystallographic data. The tests performed on four different systems (α-glycine, l-cysteine, (aminomethyl)phosphonic acid and N-(trifluoromethyl)formamide) have shown that the achievement of good statistical agreements with the experimental measures mainly depends on the quality of the crystal structures (i.e., geometry positions and thermal parameters) used in the X-ray constrained calculations. Finally, given the reliable transferability of the obtained Extremely Localized Molecular Orbitals (ELMOs), we envisage to exploit the novel approach to construct new ELMOs databases suited to the development of linear-scaling methods for the refinement of macromolecular crystal structures.

Selective complexation of K+ and Na+ in simple polarizable ion-ligating systems.

PubMed

Bostick, David L; Brooks, Charles L

2010-09-29

An influx of experimental and theoretical studies of ion transport protein structure has inspired efforts to understand underlying determinants of ionic selectivity. Design principles for selective ion binding can be effectively isolated and interrogated using simplified models composed of a single ion surrounded by a set of ion-ligating molecular species. While quantum mechanical treatments of such systems naturally incorporate electronic degrees of freedom, their computational overhead typically prohibits thorough dynamic sampling of configurational space and, thus, requires approximations when determining ion-selective free energy. As an alternative, we employ dynamical simulations with a polarizable force field to probe the structure and K(+)/Na(+) selectivity in simple models composed of one central K(+)/Na(+) ion surrounded by 0-8 identical model compounds: N-methylacetamide, formamide, or water. In the absence of external restraints, these models represent gas-phase clusters displaying relaxed coordination structures with low coordination number. Such systems display Na(+) selectivity when composed of more than ∼3 organic carbonyl-containing compounds and always display K(+) selectivity when composed of water molecules. Upon imposing restraints that solely enforce specific coordination numbers, we find all models are K(+)-selective when ∼7-8-fold ion coordination is achieved. However, when models composed of the organic compounds provide ∼4-6-fold coordination, they retain their Na(+) selectivity. From these trends, design principles emerge that are of basic importance in the behavior of K(+) channel selectivity filters and suggest a basis not only for K(+) selectivity but also for modulation of block and closure by smaller ions.

Facile Synthesis and Proposed Mechanism of α,ω-Oxetanyl-Telechelic Poly(3-nitratomethyl-3-methyl oxetane) by an SN2(i) Nitrato Displacement Method in Basic Media

NASA Astrophysics Data System (ADS)

Desai, Hemant J.; Acheampong, Daniel O.; Hudson, Robert; Lacey, Richard; Stanley, Claire; Turner, Helen; Whitmore, Hannah; Torry, Simon; Golding, Peter; Erothu, Harikrishna; Topham, Paul

2017-01-01

The synthesis of a novel heterocyclic-telechelic polymer, α,ω-oxetanyl-telechelic poly(3-nitratomethyl-3-methyl oxetane), is described. Infrared spectroscopy (IR), gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR) spectroscopy have been used to confirm the successful synthesis, demonstrating the presence of the telechelic-oxetanyl moieties. Synthesis of the terminal functionalities has been achieved via displacement of nitrato groups, in a manner similar to that employed with other leaving groups such as azido, bromo, and nitro, initiated by nucleophiles. In the present case, displacement occurs on the ends of a nitrato-functionalized polymer driven by the formation of sodium nitrate, which is supported by the polar aprotic solvent N,N-dimethyl formamide. The formation of an alkoxide at the polymer chain ends is favored and allows internal back-biting to the nearest carbon bearing the nitrato group, intrinsically in an SN2(i) reaction, leading to α,ω-oxetanyl functionalization. The telechelic-oxetanyl moieties have the potential to be cross-linked by chemical (e.g., acidic) or radiative (e.g., ultraviolet) curing methods without the use of high temperatures, usually below 100°C. This type of material was designed for future use as a contraband simulant, whereby it would form the predominant constituent of elastomeric composites comprising rubbery polymer with small quantities of solids, typically crystals of contraband substances, such as explosives or narcotics. This method also provides an alternative approach to ring closure and synthesis of heterocycles.

Overview of VOC emissions and chemistry from PTR-TOF-MS measurements during the SusKat-ABC campaign: high acetaldehyde, isoprene and isocyanic acid in wintertime air of the Kathmandu Valley

NASA Astrophysics Data System (ADS)

Sarkar, C.; Sinha, V.; Kumar, V.; Rupakheti, M.; Panday, A.; Mahata, K. S.; Rupakheti, D.; Kathayat, B.; Lawrence, M. G.

2015-09-01

The Kathmandu Valley in Nepal suffers from severe wintertime air pollution. Volatile organic compounds (VOCs) are key constituents of air pollution, though their specific role in the Valley is poorly understood due to insufficient data. During the SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley-Atmospheric Brown Clouds) field campaign conducted in Nepal in the winter of 2012-2013, a comprehensive study was carried out to characterize the chemical composition of ambient Kathmandu air, including the determination of speciated VOCs by deploying a Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-TOF-MS)-the first such deployment in South Asia. 71 ion peaks (for which measured ambient concentrations exceeded the 2 σ detection limit) were detected in the PTR-TOF-MS mass scan data, highlighting the chemical complexity of ambient air in the Valley. Of the 71 species, 37 were found to have campaign average concentrations greater than 200 ppt and were identified based on their spectral characteristics, ambient diel profiles and correlation with specific emission tracers as a result of the high mass resolution (m/Δm > 4200) and temporal resolution (1 min) of the PTR-TOF-MS. The highest average VOC mixing ratios during the measurement period were (in rank order): acetaldehyde (8.8 ppb), methanol (7.4 ppb), acetone (4.2 ppb), benzene (2.7 ppb), toluene (1.5 ppb), isoprene (1.1 ppb), acetonitrile (1.1 ppb), C8-aromatics (~ 1 ppb), furan (~ 0.5 ppb), and C9-aromatics (0.4 ppb). Distinct diel profiles were observed for the nominal isobaric compounds isoprene (m/z = 69.070) and furan (m/z = 69.033). Comparison with wintertime measurements from several locations elsewhere in the world showed mixing ratios of acetaldehyde (~ 9 ppb), acetonitrile (~ 1 ppb) and isoprene (~ 1 ppb) to be among the highest reported till date. Two "new" ambient compounds namely, formamide (m/z = 46.029) and acetamide (m/z = 60.051), which can photochemically produce isocyanic acid in the atmosphere, are reported in this study along with nitromethane (a tracer for diesel exhaust) which has only recently been detected in ambient studies. Two distinct periods were selected during the campaign for detailed analysis: the first was associated with high wintertime emissions of biogenic isoprene, and the second with elevated levels of ambient acetonitrile, benzene and isocyanic acid from biomass burning activities. Emissions from biomass burning and biomass co-fired brick kilns were found to be the dominant sources for compounds such as propyne, propene, benzene and propanenitrile which correlated strongly with acetonitrile (r2 > 0.7), a chemical tracer for biomass burning. The calculated total VOC OH reactivity was dominated by acetaldehyde (24.0 %), isoprene (20.2 %) and propene (18.7 %), while oxygenated VOCs and isoprene collectively contributed to more than 68 % of the total ozone production potential. Based on known SOA yields and measured ambient concentrations in the Kathmandu Valley, the relative SOA production potential of VOCs were: benzene > naphthalene > toluene > xylenes > monoterpenes > trimethyl-benzenes > styrene > isoprene. The first ambient measurements from any site in South Asia of compounds with significant health effects such as isocyanic acid, formamide, acetamide, naphthalene and nitromethane have been reported in this study. Our results suggest that mitigation of intense wintertime biomass burning activities, in particular point sources such biomass co-fired brick kilns, would be important to reduce the emission and formation of toxic VOCs (such as benzene and isocyanic acid) in the Kathmandu Valley and improve its air quality.

Overview of VOC emissions and chemistry from PTR-TOF-MS measurements during the SusKat-ABC campaign: high acetaldehyde, isoprene and isocyanic acid in wintertime air of the Kathmandu Valley

NASA Astrophysics Data System (ADS)

Sarkar, Chinmoy; Sinha, Vinayak; Kumar, Vinod; Rupakheti, Maheswar; Panday, Arnico; Mahata, Khadak S.; Rupakheti, Dipesh; Kathayat, Bhogendra; Lawrence, Mark G.

2016-03-01

The Kathmandu Valley in Nepal suffers from severe wintertime air pollution. Volatile organic compounds (VOCs) are key constituents of air pollution, though their specific role in the valley is poorly understood due to insufficient data. During the SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley-Atmospheric Brown Clouds) field campaign conducted in Nepal in the winter of 2012-2013, a comprehensive study was carried out to characterise the chemical composition of ambient Kathmandu air, including the determination of speciated VOCs, by deploying a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) - the first such deployment in South Asia. In the study, 71 ion peaks (for which measured ambient concentrations exceeded the 2σ detection limit) were detected in the PTR-TOF-MS mass scan data, highlighting the chemical complexity of ambient air in the valley. Of the 71 species, 37 were found to have campaign average concentrations greater than 200 ppt and were identified based on their spectral characteristics, ambient diel profiles and correlation with specific emission tracers as a result of the high mass resolution (m / Δm > 4200) and temporal resolution (1 min) of the PTR-TOF-MS. The concentration ranking in the average VOC mixing ratios during our wintertime deployment was acetaldehyde (8.8 ppb) > methanol (7.4 ppb) > acetone + propanal (4.2 ppb) > benzene (2.7 ppb) > toluene (1.5 ppb) > isoprene (1.1 ppb) > acetonitrile (1.1 ppb) > C8-aromatics ( ˜ 1 ppb) > furan ( ˜ 0.5 ppb) > C9-aromatics (0.4 ppb). Distinct diel profiles were observed for the nominal isobaric compounds isoprene (m / z = 69.070) and furan (m / z = 69.033). Comparison with wintertime measurements from several locations elsewhere in the world showed mixing ratios of acetaldehyde ( ˜ 9 ppb), acetonitrile ( ˜ 1 ppb) and isoprene ( ˜ 1 ppb) to be among the highest reported to date. Two "new" ambient compounds, namely formamide (m / z = 46.029) and acetamide (m / z = 60.051), which can photochemically produce isocyanic acid in the atmosphere, are reported in this study along with nitromethane (a tracer for diesel exhaust), which has only recently been detected in ambient studies. Two distinct periods were selected during the campaign for detailed analysis: the first was associated with high wintertime emissions of biogenic isoprene and the second with elevated levels of ambient acetonitrile, benzene and isocyanic acid from biomass burning activities. Emissions from biomass burning and biomass co-fired brick kilns were found to be the dominant sources for compounds such as propyne, propene, benzene and propanenitrile, which correlated strongly with acetonitrile (r2 > 0.7), a chemical tracer for biomass burning. The calculated total VOC OH reactivity was dominated by acetaldehyde (24.0 %), isoprene (20.2 %) and propene (18.7 %), while oxygenated VOCs and isoprene collectively contributed to more than 68 % of the total ozone production potential. Based on known secondary organic aerosol (SOA) yields and measured ambient concentrations in the Kathmandu Valley, the relative SOA production potential of VOCs were benzene > naphthalene > toluene > xylenes > monoterpenes > trimethylbenzenes > styrene > isoprene. The first ambient measurements from any site in South Asia of compounds with significant health effects such as isocyanic acid, formamide, acetamide, naphthalene and nitromethane have been reported in this study. Our results suggest that mitigation of intense wintertime biomass burning activities, in particular point sources such biomass co-fired brick kilns, would be important to reduce the emission and formation of toxic VOCs (such as benzene and isocyanic acid) in the Kathmandu Valley.

Electrophoretic extraction of low molecular weight cationic analytes from sodium dodecyl sulfate containing sample matrices for their direct electrospray ionization mass spectrometry.

PubMed

Kinde, Tristan F; Lopez, Thomas D; Dutta, Debashis

2015-03-03

While the use of sodium dodecyl sulfate (SDS) in separation buffers allows efficient analysis of complex mixtures, its presence in the sample matrix is known to severely interfere with the mass-spectrometric characterization of analyte molecules. In this article, we report a microfluidic device that addresses this analytical challenge by enabling inline electrospray ionization mass spectrometry (ESI-MS) of low molecular weight cationic samples prepared in SDS containing matrices. The functionality of this device relies on the continuous extraction of analyte molecules into an SDS-free solvent stream based on the free-flow zone electrophoresis (FFZE) technique prior to their ESI-MS analysis. The reported extraction was accomplished in our current work in a glass channel with microelectrodes fabricated along its sidewalls to realize the desired electric field. Our experiments show that a key challenge to successfully operating such a device is to suppress the electroosmotically driven fluid circulations generated in its extraction channel that otherwise tend to vigorously mix the liquid streams flowing through this duct. A new coating medium, N-(2-triethoxysilylpropyl) formamide, recently demonstrated by our laboratory to nearly eliminate electroosmotic flow in glass microchannels was employed to address this issue. Applying this surface modifier, we were able to efficiently extract two different peptides, human angiotensin I and MRFA, individually from an SDS containing matrix using the FFZE method and detect them at concentrations down to 3.7 and 6.3 μg/mL, respectively, in samples containing as much as 10 mM SDS. Notice that in addition to greatly reducing the amount of SDS entering the MS instrument, the reported approach allows rapid solvent exchange for facilitating efficient analyte ionization desired in ESI-MS analysis.

Solvent induced synthesis, structure and properties of coordination polymers based on 5-hydroxyisophthalic acid as linker and 1,10-phenanthroline as auxiliary ligand

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

Kariem, Mukaddus; Yawer, Mohd; Sheikh, Haq Nawaz, E-mail: hnsheikh@rediffmail.com

2015-11-15

Three new coordination polymers [Mn(hip)(phen) (H{sub 2}O)]{sub n} (1), [Co(hip)(phen) (H{sub 2}O)]{sub n} (2), and [Cd(hip) (phen) (H{sub 2}O)]{sub n} (3) (H{sub 2}hip=5-hydroxyisophthalic acid; phen=1,10-phenanthroline) have been synthesized by solvo-hydrothermal method using diethyl formamide-water (DEF-H{sub 2}O) as solvent system. Single-crystal X-ray diffraction analysis reveals that all three coordination polymers 1, 2 and 3 crystallize in monoclinic space group P2/n. Metal ions are inter-connected by hydroxyisophthalate anions forming zig-zag 1D chain. 1D chains are further inter-connected by hydrogen bonding and π–π stacking interactions leading to 3D supramolecular architecture. Hydrogen-bonding and π–π stacking provide thermal stability to polymers. Compounds 1 and 2more » are paramagnetic at room temperature and variable temperature magnetic moment measurements revealed weak ferromagnetic interactions between metal ions at low temperature. Compound 3 exhibits excellent photoluminescence with large Stokes shift. - Graphical abstract: 1D helical chains of coordination polymers were synthesized by solvo-hydrothermal reaction of 5-hydroxyisopthalic acid and 1,10-phenanthroline with MnCl{sub 2}·4H{sub 2}O / CoCl{sub 2}·6H{sub 2}O / Cd(NO{sub 3}){sub 2}·6H{sub 2}O. - Highlights: • Solvent induced synthesis of three coordination polymers with 1D zig-zag structure. • Crystal structures of coordination polymers are reported and discussed. • 1,10-Phenanthroline influences magnetic and luminescent properties of polymers. • Coordination polymer of Cd is luminescent exhibiting large Stokes shift.« less

Synthesis, Characterization and Conductivity Study of Poly(vinyl 4-HYDROXY-3-METHOXY Benzal) and its Sodio Salt in Solid State

NASA Astrophysics Data System (ADS)

Borah, P.; Hussain, S.; Dutta, A.

Among the various ion-conducting materials, polymer salt complexes are of current interest due to their possible application as solid electrolyte as well as their physical nature in advanced high-energy electrochemical devices such as batteries, fuel cells, electrochromic display devices, photo electro-chemical solar cells52-55 etc. The main advantages of polymeric electrolytes are their mechanical properties, ease of fabrication of thin films of desired sizes and their ability to form proper electrode-electrolyte contact. Polymer electrolyte usually consists of a polymer and a salt and is considered to be solid solutions in which the polymer functions as solvent. In the present paper the synthesis, characterization and the conductivity study of the polymer poly (vinyl 4-hydroxy-3-methoxy benzal) (PV-HMB) and its sodio salt (PV-HMB-Na) have been reported. The polymer was prepared by carrying out homogenous acetalization between the prepolymer poly vinylalcohol (PVA) and 4-hydroxy-3-methoxy benzaldehyde (vanilline). PVA was dissolved in dimethyl formamide (DMF) and lithium chloride (LiCl) system i.e., in non-aqueous medium. The sodio salt was prepared by alkalization. The polymer and its salt were characterized by IR, 1H NMR and DSC. Frequency and temperature dependence of ac conductivity has been studied to learn about the electrical conduction behaviour in this material. The electrical conductivity of the new polymeric salt was found to be in the range 10-4 to 10-6 Scm-1. There is about 103 to 104 fold increase in the conductivity of the new polymer salt. Apparent activation energy of the polymer and its salt were found to be 0.139 and 0.08998 ev respectively.

Specificity Re-evaluation of Oligonucleotide Probes for the Detection of Marine Picoplankton by Tyramide Signal Amplification-Fluorescent In Situ Hybridization.

PubMed

Riou, Virginie; Périot, Marine; Biegala, Isabelle C

2017-01-01

Oligonucleotide probes are increasingly being used to characterize natural microbial assemblages by Tyramide Signal Amplification-Fluorescent in situ Hybridization (TSA-FISH, or CAtalysed Reporter Deposition CARD-FISH). In view of the fast-growing rRNA databases, we re-evaluated the in silico specificity of eleven bacterial and eukaryotic probes and competitor frequently used for the quantification of marine picoplankton. We performed tests on cell cultures to decrease the risk for non-specific hybridization, before they are used on environmental samples. The probes were confronted to recent databases and hybridization conditions were tested against target strains matching perfectly with the probes, and against the closest non-target strains presenting one to four mismatches. We increased the hybridization stringency from 55 to 65% formamide for the Eub338+EubII+EubIII probe mix to be specific to the Eubacteria domain. In addition, we found that recent changes in the Gammaproteobacteria classification decreased the specificity of Gam42a probe, and that the Roseo536R and Ros537 probes were not specific to, and missed part of the Roseobacter clade. Changes in stringency conditions were important for bacterial probes; these induced, respectively, a significant increase, in Eubacteria and Roseobacter and no significant changes in Gammaproteobacteria concentrations from the investigated natural environment. We confirmed the eukaryotic probes original conditions, and propose the Euk1209+NChlo01+Chlo02 probe mix to target the largest picoeukaryotic diversity. Experiences acquired through these investigations leads us to propose the use of seven steps protocol for complete FISH probe specificity check-up to improve data quality in environmental studies.

Autonomous parvovirus LuIII encapsidates equal amounts of plus and minus DNA strands

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

Bates, R.C.; Snyder, C.E.; Banerjee, P.T.

1984-02-01

Autonomous parvoviruses are thought to uniquely encapsidate single-stranded DNA of minus polarity. In contrast, the defective adeno-associated viruses separately encapsidate equal amounts of plus and minus DNA strands. The uniqueness of minus strand encapsidation is reexamined for the autonomous parvoviruses. Although it was found that Kilham rat virus and H-1 virus encapsidate varying but small amounts of complementary-strand DNA, it was unexpected to find that LuIII virus encapsidated equal amounts of plus and minus DNA. The extracted LuIII DNA possessed properties of double-stranded replicative-form DNA, including insensitivity to S1 endonuclease, cleavage by restriction enzymes, and conversion to unit-length, single-stranded DNAmore » when electrophoresed under denaturing conditions. However, the inability of this DNA to form single-stranded DNA circles when denatured and then renatured in the presence of formamide and the lack of double-stranded DNA circle formation after treatment with exonuclease III and reannealing shows a lack of sequence homology of the 3' and 5' termini of LuIII DNA, in contrast to adeno-associated virus DNA. Digestion of LuIII double-stranded DNA with EcoRI and HincII and separation of plus and minus DNA strands on composite agarose-acrylamide gels identified a heterogeneity present only in the plus DNA strand. These results suggest that strand specificity of viral DNA encapsidation is not a useful property for differentiation between the autonomous and defective parvoviruses. Furthermore, encapsidation by LuIII of equal amounts of complementary DNA strands in contrast to encapsidation of minus strands by H-1 virus, when propagated in the same host cell type, suggests that selection of strands for encapsidation is a virus-coded rather than host-controlled event.« less

Pharmacophore modeling using Site-Identification by Ligand Competitive Saturation (SILCS) with multiple probe molecules

PubMed Central

Yu, Wenbo; Lakkaraju, Sirish Kaushik; Raman, E. Prabhu; Fang, Lei; MacKerell, Alexander D.

2015-01-01

Receptor-based pharmacophore modeling is an efficient computer-aided drug design technique that uses the structure of the target protein to identify novel leads. However, most methods consider protein flexibility and desolvation effects in a very approximate way, which may limit their use in practice. The Site-Identification by Ligand Competitive Saturation (SILCS) assisted pharmacophore modeling protocol (SILCS-Pharm) was introduced recently to address these issues as SILCS naturally takes both protein flexibility and desolvation effects into account by using full MD simulations to determine 3D maps of the functional group-affinity patterns on a target receptor. In the present work, the SILCS-Pharm protocol is extended to use a wider range of probe molecules including benzene, propane, methanol, formamide, acetaldehyde, methylammonium, acetate and water. This approach removes the previous ambiguity brought by using water as both the hydrogen-bond donor and acceptor probe molecule. The new SILCS-Pharm protocol is shown to yield improved screening results as compared to the previous approach based on three target proteins. Further validation of the new protocol using five additional protein targets showed improved screening compared to those using common docking methods, further indicating improvements brought by the explicit inclusion of additional feature types associated with the wider collection of probe molecules in the SILCS simulations. The advantage of using complementary features and volume constraints, based on exclusion maps of the protein defined from the SILCS simulations, is presented. In addition, re-ranking using SILCS-based ligand grid free energies is shown to enhance the diversity of identified ligands for the majority of targets. These results suggest that the SILCS-Pharm protocol will be of utility in rational drug design. PMID:25622696

Sarcolemmal localisation of Na+/H+ exchange and Na+–HCO3− co-transport influences the spatial regulation of intracellular pH in rat ventricular myocytes

PubMed Central

Garciarena, Carolina D; Ma, Yu-ling; Swietach, Pawel; Huc, Laurence; Vaughan-Jones, Richard D

2013-01-01

Membrane acid extrusion by Na+/H+ exchange (NHE1) and Na+–HCO3− co-transport (NBC) is essential for maintaining a low cytoplasmic [H+] (∼60 nm, equivalent to an intracellular pH (pHi) of 7.2). This protects myocardial function from the high chemical reactivity of H+ ions, universal end-products of metabolism. We show here that, in rat ventricular myocytes, fluorescent antibodies map the NBC isoforms NBCe1 and NBCn1 to lateral sarcolemma, intercalated discs and transverse tubules (t-tubules), while NHE1 is absent from t-tubules. This unexpected difference matches functional measurements of pHi regulation (using AM-loaded SNARF-1, a pH fluorophore). Thus, myocyte detubulation (by transient exposure to 1.5 m formamide) reduces global acid extrusion on NBC by 40%, without affecting NHE1. Similarly, confocal pHi imaging reveals that NBC stimulation induces spatially uniform pHi recovery from acidosis, whereas NHE1 stimulation induces pHi non-uniformity during recovery (of ∼0.1 units, for 2–3 min), particularly at the ends of the cell where intercalated discs are commonly located, and where NHE1 immunostaining is prominent. Mathematical modelling shows that this induction of local pHi microdomains is favoured by low cytoplasmic H+ mobility and long H+ diffusion distances, particularly to surface NHE1 transporters mediating high membrane flux. Our results provide the first evidence for a spatial localisation of [H+]i regulation in ventricular myocytes, suggesting that, by guarding pHi, NHE1 preferentially protects gap junctional communication at intercalated discs, while NBC locally protects t-tubular excitation–contraction coupling. PMID:23420656

Functional subcellular distribution of β1- and β2-adrenergic receptors in rat ventricular cardiac myocytes

PubMed Central

Cros, Caroline; Brette, Fabien

2013-01-01

β-adrenergic stimulation is a key regulator of cardiac function. The localization of major cardiac adrenergic receptors (β1 and β2) has been investigated using biochemical and biophysical approaches and has led to contradictory results. This study investigates the functional subcellular localization of β1- and β2-adrenergic receptors in rat ventricular myocytes using a physiological approach. Ventricular myocytes were isolated from the hearts of rat and detubulated using formamide. Physiological cardiac function was measured as Ca2+ transient using Fura-2-AM and cell shortening. Selective activation of β1- and β2-adrenergic receptors was induced with isoproterenol (0.1 μmol/L) and ICI-118,551 (0.1 μmol/L); and with salbutamol (10 μmol/L) and atenolol (1 μmol/L), respectively. β1- and β2-adrenergic stimulations induced a significant increase in Ca2+ transient amplitude and cell shortening in intact rat ventricular myocytes (i.e., surface sarcolemma and t-tubules) and in detubulated cells (depleted from t-tubules, surface sarcolemma only). Both β1- and β2-adrenergic receptors stimulation caused a greater effect on Ca2+ transient and cell shortening in detubulated myocytes than in control myocytes. Quantitative analysis indicates that β1-adrenergic stimulation is ∼3 times more effective at surface sarcolemma compared to t-tubules, whereas β2- adrenergic stimulation occurs almost exclusively at surface sarcolemma (∼100 times more effective). These physiological data demonstrate that in rat ventricular myocytes, β1-adrenergic receptors are functionally present at surface sarcolemma and t-tubules, while β2-adrenergic receptors stimulation occurs only at surface sarcolemma of cardiac cells. PMID:24303124

Covalent functionalization of MoS2 nanosheets synthesized by liquid phase exfoliation to construct electrochemical sensors for Cd (II) detection.

PubMed

Gan, Xiaorong; Zhao, Huimin; Wong, Kwok-Yin; Lei, Dang Yuan; Zhang, Yaobin; Quan, Xie

2018-05-15

Surface functionalization is an effective strategy in the precise control of electronic surface states of two-dimensional materials for promoting their applications. In this study, based on the strong coordination interaction between the transition-metal centers and N atoms, the surface functionalization of few-layer MoS 2 nanosheets was successfully prepared by liquid phase exfoliation method in N, N-dimethylformamide (DMF), 1-methyl-2-pyrrolidinone, and formamide. The cytotoxicity of surface-functionalized MoS 2 nanosheets was for the first time evaluated by the methylthiazolyldiphenyl-tetrazoliumbromide assays. An electrochemical sensor was constructed based on glass carbon electrode (GCE) modified by MoS 2 nanosheets obtained in DMF, which exhibits relatively higher sensitivity to Cd 2+ detection and lower cytotoxicity against MCF-7 cells. The mechanisms of surface functionalization and selectively detecting Cd 2+ were investigated by density functional theory calculations together with various spectroscopic measurements. It was found that surface-functionalized MoS 2 nanosheets could be generated through Mo-N covalent bonds due to the orbital hybridization between the 5 s orbitals of Mo atoms and the 2p orbitals of N atoms of the solvent molecules. The high selectivity of the sensor is attributed to the coordination reaction between Cd 2+ and O donor atoms of DMF adsorbed on MoS 2 nanosheets. The robust anti-interference is ascribed to the strong binding energy of Cd 2+ and O atoms of DMF. Under the optimum conditions, the electrochemical sensor exhibits highly sensitive and selective assaying of Cd 2+ with a measured detection limit of 0.2 nM and a linear range from 2 nM to 20 μM. Copyright © 2018 Elsevier B.V. All rights reserved.

Electron dynamics in complex environments with real-time time dependent density functional theory in a QM-MM framework

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

Morzan, Uriel N.; Ramírez, Francisco F.; Scherlis, Damián A., E-mail: damian@qi.fcen.uba.ar, E-mail: mcgl@qb.ffyb.uba.ar

2014-04-28

This article presents a time dependent density functional theory (TDDFT) implementation to propagate the Kohn-Sham equations in real time, including the effects of a molecular environment through a Quantum-Mechanics Molecular-Mechanics (QM-MM) hamiltonian. The code delivers an all-electron description employing Gaussian basis functions, and incorporates the Amber force-field in the QM-MM treatment. The most expensive parts of the computation, comprising the commutators between the hamiltonian and the density matrix—required to propagate the electron dynamics—, and the evaluation of the exchange-correlation energy, were migrated to the CUDA platform to run on graphics processing units, which remarkably accelerates the performance of the code.more » The method was validated by reproducing linear-response TDDFT results for the absorption spectra of several molecular species. Two different schemes were tested to propagate the quantum dynamics: (i) a leap-frog Verlet algorithm, and (ii) the Magnus expansion to first-order. These two approaches were confronted, to find that the Magnus scheme is more efficient by a factor of six in small molecules. Interestingly, the presence of iron was found to seriously limitate the length of the integration time step, due to the high frequencies associated with the core-electrons. This highlights the importance of pseudopotentials to alleviate the cost of the propagation of the inner states when heavy nuclei are present. Finally, the methodology was applied to investigate the shifts induced by the chemical environment on the most intense UV absorption bands of two model systems of general relevance: the formamide molecule in water solution, and the carboxy-heme group in Flavohemoglobin. In both cases, shifts of several nanometers are observed, consistently with the available experimental data.« less

Electron dynamics in complex environments with real-time time dependent density functional theory in a QM-MM framework

NASA Astrophysics Data System (ADS)

Morzan, Uriel N.; Ramírez, Francisco F.; Oviedo, M. Belén; Sánchez, Cristián G.; Scherlis, Damián A.; Lebrero, Mariano C. González

2014-04-01

This article presents a time dependent density functional theory (TDDFT) implementation to propagate the Kohn-Sham equations in real time, including the effects of a molecular environment through a Quantum-Mechanics Molecular-Mechanics (QM-MM) hamiltonian. The code delivers an all-electron description employing Gaussian basis functions, and incorporates the Amber force-field in the QM-MM treatment. The most expensive parts of the computation, comprising the commutators between the hamiltonian and the density matrix—required to propagate the electron dynamics—, and the evaluation of the exchange-correlation energy, were migrated to the CUDA platform to run on graphics processing units, which remarkably accelerates the performance of the code. The method was validated by reproducing linear-response TDDFT results for the absorption spectra of several molecular species. Two different schemes were tested to propagate the quantum dynamics: (i) a leap-frog Verlet algorithm, and (ii) the Magnus expansion to first-order. These two approaches were confronted, to find that the Magnus scheme is more efficient by a factor of six in small molecules. Interestingly, the presence of iron was found to seriously limitate the length of the integration time step, due to the high frequencies associated with the core-electrons. This highlights the importance of pseudopotentials to alleviate the cost of the propagation of the inner states when heavy nuclei are present. Finally, the methodology was applied to investigate the shifts induced by the chemical environment on the most intense UV absorption bands of two model systems of general relevance: the formamide molecule in water solution, and the carboxy-heme group in Flavohemoglobin. In both cases, shifts of several nanometers are observed, consistently with the available experimental data.

Glutathione Transferase U13 Functions in Pathogen-Triggered Glucosinolate Metabolism.

PubMed

Piślewska-Bednarek, Mariola; Nakano, Ryohei Thomas; Hiruma, Kei; Pastorczyk, Marta; Sanchez-Vallet, Andrea; Singkaravanit-Ogawa, Suthitar; Ciesiołka, Danuta; Takano, Yoshitaka; Molina, Antonio; Schulze-Lefert, Paul; Bednarek, Paweł

2018-01-01

Glutathione (GSH) and indole glucosinolates (IGs) exert key functions in the immune system of the model plant Arabidopsis ( Arabidopsis thaliana ). Appropriate GSH levels are important for execution of both pre- and postinvasive disease resistance mechanisms to invasive pathogens, whereas an intact PENETRATION2 (PEN2)-pathway for IG metabolism is essential for preinvasive resistance in this species. Earlier indirect evidence suggested that the latter pathway involves conjugation of GSH with unstable products of IG metabolism and further processing of the resulting adducts to biologically active molecules. Here we describe the identification of Glutathione- S -Transferase class-tau member 13 (GSTU13) as an indispensable component of the PEN2 immune pathway for IG metabolism. gstu13 mutant plants are defective in the pathogen-triggered biosynthesis of end products of the PEN2 pathway, including 4-O-β-d-glucosyl-indol-3-yl formamide, indole-3-ylmethyl amine, and raphanusamic acid. In line with this metabolic defect, lack of functional GSTU13 results in enhanced disease susceptibility toward several fungal pathogens including Erysiphe pisi , Colletotrichum gloeosporioides , and Plectosphaerella cucumerina Seedlings of gstu13 plants fail also to deposit the (1,3)-β-glucan cell wall polymer, callose, after recognition of the bacterial flg22 epitope. We show that GSTU13 mediates specifically the role of GSH in IG metabolism without noticeable impact on other immune functions of this tripeptide. We postulate that GSTU13 connects GSH with the pathogen-triggered PEN2 pathway for IG metabolism to deliver metabolites that may have numerous functions in the innate immune system of Arabidopsis. © 2018 American Society of Plant Biologists. All Rights Reserved.

Direct Detection of Complex Organic Products in Ultraviolet (Lyα) and Electron-irradiated Astrophysical and Cometary Ice Analogs Using Two-step Laser Ablation and Ionization Mass Spectrometry

NASA Astrophysics Data System (ADS)

Henderson, Bryana L.; Gudipati, Murthy S.

2015-02-01

As discovery of complex molecules and ions in our solar system and the interstellar medium has proliferated, several groups have turned to laboratory experiments in an effort to simulate and understand these chemical processes. So far only infrared (IR) and ultraviolet (UV) spectroscopy has been able to directly probe these reactions in ices in their native, low-temperature states. Here we report for the first time results using a complementary technique that harnesses two-step two-color laser ablation and ionization to measure mass spectra of energetically processed astrophysical and cometary ice analogs directly without warming the ices—a method for hands-off in situ ice analysis. Electron bombardment and UV irradiation of H2O, CH3OH, and NH3 ices at 5 K and 70 K led to complex irradiation products, including HCO, CH3CO, formamide, acetamide, methyl formate, and HCN. Many of these species, whose assignment was also strengthened by isotope labeling studies and correlate with IR-based spectroscopic studies of similar irradiated ices, are important ingredients for the building blocks of life. Some of them have been detected previously via astronomical observations in the interstellar medium and in cometary comae. Other species such as CH3CO (acetyl) are yet to be detected in astrophysical ices or interstellar medium. Our studies suggest that electron and UV photon processing of astrophysical ice analogs leads to extensive chemistry even in the coldest reaches of space, and lend support to the theory of comet-impact-induced delivery of complex organics to the inner solar system.

Electron dynamics in complex environments with real-time time dependent density functional theory in a QM-MM framework.

PubMed

Morzan, Uriel N; Ramírez, Francisco F; Oviedo, M Belén; Sánchez, Cristián G; Scherlis, Damián A; Lebrero, Mariano C González

2014-04-28

This article presents a time dependent density functional theory (TDDFT) implementation to propagate the Kohn-Sham equations in real time, including the effects of a molecular environment through a Quantum-Mechanics Molecular-Mechanics (QM-MM) hamiltonian. The code delivers an all-electron description employing Gaussian basis functions, and incorporates the Amber force-field in the QM-MM treatment. The most expensive parts of the computation, comprising the commutators between the hamiltonian and the density matrix-required to propagate the electron dynamics-, and the evaluation of the exchange-correlation energy, were migrated to the CUDA platform to run on graphics processing units, which remarkably accelerates the performance of the code. The method was validated by reproducing linear-response TDDFT results for the absorption spectra of several molecular species. Two different schemes were tested to propagate the quantum dynamics: (i) a leap-frog Verlet algorithm, and (ii) the Magnus expansion to first-order. These two approaches were confronted, to find that the Magnus scheme is more efficient by a factor of six in small molecules. Interestingly, the presence of iron was found to seriously limitate the length of the integration time step, due to the high frequencies associated with the core-electrons. This highlights the importance of pseudopotentials to alleviate the cost of the propagation of the inner states when heavy nuclei are present. Finally, the methodology was applied to investigate the shifts induced by the chemical environment on the most intense UV absorption bands of two model systems of general relevance: the formamide molecule in water solution, and the carboxy-heme group in Flavohemoglobin. In both cases, shifts of several nanometers are observed, consistently with the available experimental data.

Tobacco smoke aging in the presence of ozone: A room-sized chamber study

NASA Astrophysics Data System (ADS)

Petrick, Lauren M.; Sleiman, Mohamad; Dubowski, Yael; Gundel, Lara A.; Destaillats, Hugo

2011-09-01

Exposure to tobacco pollutants that linger indoors after smoking has taken place ( thirdhand smoke, THS) can occur over extended periods and is modulated by chemical processes involving atmospheric reactive species. This study investigates the role of ozone and indoor surfaces in chemical transformations of tobacco smoke residues. Gas and particle constituents of secondhand smoke (SHS) as well as sorbed SHS on chamber internal walls and model materials (cotton, paper, and gypsum wallboard) were characterized during aging. After smoldering 10 cigarettes in a 24-m 3 room size chamber, gas-phase nicotine was rapidly removed by sorption to chamber surfaces, and subsequently re-emitted during ventilation with clean air to a level of ˜10% that during the smoking phase. During chamber ventilation in the presence of ozone (180 ppb), ozone decayed at a rate of 5.6 h -1 and coincided with a factor of 5 less nicotine sorbed to wallboard. In the presence of ozone, no gas phase nicotine was detected as a result of re-emission, and higher concentrations of nicotine oxidation products were observed than when ventilation was performed with ozone-free air. Analysis of the model surfaces showed that heterogeneous nicotine-ozone reaction was faster on paper than cotton, and both were faster than on wallboard. However, wallboard played a dominant role in ozone-initiated reaction in the chamber due to its large total geometric surface area and sink potential compared to the other substrates. This study is the first to show in a room-sized environmental chamber that the heterogeneous ozone chemistry of sorbed nicotine generates THS constituents of concern, as observed previously in bench-top studies. In addition to the main oxidation products (cotinine, myosmine and N-methyl formamide), nicotine-1-oxide was detected for the first time.

Optimization on electrochemical synthesis of HKUST-1 as candidate catalytic material for Green diesel production

NASA Astrophysics Data System (ADS)

Lestari, W. W.; Nugraha, R. E.; Winarni, I. D.; Adreane, M.; Rahmawati, F.

2016-04-01

In the effort to support the discovery of new renewable energy sources in Indonesia, biofuel is one of promising options. The conversion of vegetable oil into ready-biofuel, especially green diesel, needs several steps, one of which is a hydrogenation or hydro-deoxygenation reaction. In this case, the catalyst plays a very important role regarding to its activity and selectivity, and Metal-Organic Frameworks (MOFs) becoming a new generation of heterogeneous catalyst in this area. In this research, a preliminary study to optimize electrochemical synthesis of the catalytic material based on MOFs, namely HKUST-1 [Cu3(BTC)2], has been conducted. Some electrochemical reaction parameters were tested, for example by modifying the electrochemical synthetic conditions, i.e. by performing variation of voltages (12, 13, 14, and 15 Volt), temperatures (RT, 40, 60, and 80 °C) and solvents (ethanol, water, methanol and dimethyl-formamide (DMF)). Material characterization was carried out by XRD, SEM, FTIR, DTA/TG and SAA. The results showed that the optimum synthetic conditions of HKUST-1 are performed at room temperature in a solvent combination of water: ethanol (1: 1) and a voltage of 15 Volt for 2 hours. The XRD-analysis revealed that the resulted peaks are identical to the simulated powder pattern generated from single crystal data and comparable to the peaks of solvothermal method. However, the porosity of the resulting material through electrochemical method is still in the range of micro-pore according to IUPAC and 50% smaller than the porosity resulted from solvothermal synthesis. The corresponding compounds are thermally stable until 300 °C according to TG/DTA.

Role of renal metabolism and excretion in 5-nitrofuran-induced uroepithelial cancer in the rat.

PubMed Central

Spry, L A; Zenser, T V; Cohen, S M; Davis, B B

1985-01-01

5-Nitrofurans have been used in the study of chemical carcinogenesis. There is substantial evidence that N-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide (FANFT) is deformylated to 2-amino-4-(5-nitro-2-furyl)thiazole (ANFT) in the process of FANFT-induced bladder cancer. Paradoxically, ANFT is less potent as a uroepithelial carcinogen than FANFT when fed to rats. Feeding aspirin with FANFT to rats decreases the incidence of bladder cancer. Isolated kidneys were perfused with 5-nitrofurans to determine renal clearances and whether aspirin acts to decrease urinary excretion of the carcinogen. In FANFT-perfused kidneys, FANFT was deformylated to ANFT and excreted (1.06 +/- 0.22 nmol/min) at a rate eightfold higher than excretion of FANFT. In kidneys perfused with equimolar ANFT, excretion of ANFT was 0.25 +/- 0.05 nmol/min, which suggests a coupling of renal deformylation of FANFT to excretion of ANFT in FANFT-perfused kidneys. Neither aspirin nor probenecid altered the urinary excretion or half-life of FANFT or ANFT. In rats fed 0.2% FANFT as part of their diet, coadministration of aspirin (0.5%) increased urinary excretion of ANFT during a 12-wk feeding study, which suggests decreased tissue binding or metabolism of ANFT. Kidney perfusion with acetylated ANFT (NFTA), a much less potent uroepithelial carcinogen, resulted in no ANFT excretion or accumulation, which indicates the specificity of renal deformylase. Renal deformylase activity was found in broken cell preparations of rat and human kidney. These data describe a unique renal metabolic/excretory coupling for these compounds that appears to explain the differential carcinogenic potential of the 5-nitrofurans tested. These results are consistent with the hypothesis that aspirin decreases activation of ANFT by inhibiting prostaglandin H synthase. PMID:4044826

Preparation, Characterization and Application of a Molecularly Imprinted Polymer for Selective Recognition of Sulpiride

PubMed Central

Zhang, Wei; She, Xuhui; Wang, Liping; Fan, Huajun; Zhou, Qing; Huang, Xiaowen; Tang, James Z.

2017-01-01

A novel molecular imprinting polymer (MIP) was prepared by bulk polymerization using sulpiride as the template molecule, itaconic acid (ITA) as the functional monomer and ethylene glycol dimethacrylate (EGDMA) as the crosslinker. The formation of the MIP was determined as the molar ratio of sulpiride-ITA-EGDMA of 1:4:15 by single-factor experiments. The MIP showed good adsorption property with imprinting factor α of 5.36 and maximum adsorption capacity of 61.13 μmol/g, and was characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR) and surface area analysis. With the structural analogs (amisulpride, tiapride, lidocaine and cisapride) and small molecules containing a mono-functional group (p-toluenesulfonamide, formamide and 1-methylpyrrolidine) as substrates, static adsorption, kinetic adsorption, and rebinding experiments were also performed to investigate the selective adsorption ability, kinetic characteristic, and recognition mechanism of the MIP. A serial study suggested that the highly selective recognition ability of the MIP mainly depended on binding sites provided by N-functional groups of amide and amine. Moreover, the MIP as solid-phase extractant was successfully applied to extraction of sulpiride from the mixed solution (consisted of p-toluenesulfonamide, sulfamethoxazole, sulfanilamide, p-nitroaniline, acetanilide and trimethoprim) and serum sample, and extraction recoveries ranged from 81.57% to 86.63%. The tentative tests of drug release in stimulated intestinal fluid (pH 6.8) demonstrated that the tablet with the MIP–sulpiride could obviously inhibit sulpiride release rate. Thus, ITA-based MIP is an efficient and promising alternative to solid-phase adsorbent for extraction of sulpiride and removal of interferences in biosample analysis, and could be used as a potential carrier for controlled drug release. PMID:28772831

Multipole-Based Force Fields from ab Initio Interaction Energies and the Need for Jointly Refitting All Intermolecular Parameters.

PubMed

Kramer, Christian; Gedeck, Peter; Meuwly, Markus

2013-03-12

Distributed atomic multipole (MTP) moments promise significant improvements over point charges (PCs) in molecular force fields, as they (a) more realistically reproduce the ab initio electrostatic potential (ESP) and (b) allow to capture anisotropic atomic properties such as lone pairs, conjugated systems, and σ holes. The present work focuses on the question of whether multipolar electrostatics instead of PCs in standard force fields leads to quantitative improvements over point charges in reproducing intermolecular interactions. To this end, the interaction energies of two model systems, benzonitrile (BZN) and formamide (FAM) homodimers, are characterized over a wide range of dimer conformations. It is found that although with MTPs the monomer ab initio ESP can be captured better by about an order of magnitude compared to point charges (PCs), this does not directly translate into better describing ab initio interaction energies compared to PCs. Neither ESP-fitted MTPs nor refitted Lennard-Jones (LJ) parameters alone demonstrate a clear superiority of atomic MTPs. We show that only if both electrostatic and LJ parameters are jointly optimized in standard, nonpolarizable force fields, atomic are MTPs clearly beneficial for reproducing ab initio dimerization energies. After an exhaustive exponent scan, we find that for both BZN and FAM, atomic MTPs and a 9-6 LJ potential can reproduce ab initio interaction energies with ∼30% (RMSD 0.13 vs 0.18 kcal/mol) less error than point charges (PCs) and a 12-6 LJ potential. We also find that the improvement due to using MTPs with a 9-6 LJ potential is considerably more pronounced than with a 12-6 LJ potential (≈ 10%; RMSD 0.19 versus 0.21 kcal/mol).

Organic Compounds Produced by Photolysis of Realistic Interstellar and Cometary Ice Analogs Containing Methanol

NASA Astrophysics Data System (ADS)

Bernstein, Max P.; Sandford, Scott A.; Allamandola, Louis J.; Chang, Sherwood; Scharberg, Maureen A.

1995-11-01

The infrared (IR) spectra of ultraviolet (UV) and thermally processed, methanol-containing interstellar/ cometary ice analogs at temperatures from 12 to 300 K are presented. Infrared spectroscopy, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, and gas chromatography-mass spectrometry indicate that CO (carbon monoxide), CO2 (carbon dioxide), CH4 (methane), HCO (the formyl radical), H2CO (formaldehyde), CH3CH2OH (ethanol), HC(=O)NH2 (formamide), CH3C(=O)NH2 (acetamide), and R-C=-N (nitriles) are formed. In addition, the organic materials remaining after photolyzed ice analogs have been warmed to room temperature contain (in rough order of decreasing abundance), (1) hexamethylenetetramine (HMT, C6H12N4), (2) ethers, alcohols, and compounds related to polyoxymethylene {POM, ( CH2O )n}, and (3) ketones {R-C(=O)-R'} and amides {H2NC(=O)-R}. Most of the carbon in these residues is thought to come from the methanol in the original ice. Deuterium and 13C isotopic labeling demonstrates that methanol is definitely the source of carbon in HMT. High concentrations of HMT in interstellar and cometary ices could have important astrophysical consequences. The ultraviolet photolysis of HMT frozen in H2O ice readily produces the "XCN" band observed in the spectra of protostellar objects and laboratory ices, as well as other nitriles. Thus, HMT may be a precursor of XCN and a source of CN in comets and the interstellar medium. Also, HMT is known to hydrolyze under acidic conditions to yield ammonia, formaldehyde, and amino acids. Thus, HMT may be a significant source of prebiogenic compounds on asteroidal parent bodies. A potential mechanism for the radiative formation of HMT in cosmic ices is outlined.

The proximal straight tubule (PST) basolateral cell membrane water channel: selectivity characteristics.

PubMed

Gutiérrez, A M; González, E; Echevarría, M; Hernández, C S; Whittembury, G

1995-02-01

Proximal straight tubules (PST) were dissected from rabbit kidneys, held by crimping pipettes in a chamber and bathed in a buffered isosmotic (295 mOsm/kg) solution containing 200 mM mannitol (MBS). Changes in tubule diameter were monitored on line with an inverted microscope, TV camera and image processor. The PST were then challenged for 20 sec with MBS made 35 mOsm/kg hyperosmotic by addition of either NaCl, KCl, mannitol (M), glycerol (G), ethylene glycol (E), glycine (g), urea (U), acetamide (A) or formamide (F). With NaCl, KCl, M, G, E, g, U, and A, tubules shrunk osmometrically within 0.5 sec and remained shrunk for as long as 20 sec without recovering their original volume (sometimes A showed some recovery). PST barely shrunk with F and quickly recovered their original volume. The permeability coefficients were 0 microns/sec (NaCl, M, g, E and U), 1 micron/sec (A), 84 microns/sec (F) and 0.02 micron/sec (G). The reflection coefficients sigma = 1.0 (NaCl, KCl, M, G, E, g and U), 0.95 (A) and 0.62 (F). Similar sigma values were obtained by substituting 200 mOsm/kg M in MBS by either NaCl, KCl, G, E, g, U, a or F. The olive oil/water partition coefficients are 5 (M), 15 (U), 85 (A) and 75 (F) (all x 10(-5)). Thus, part of F permeates the cell membrane through the lipid bilayer. The probing molecules van der Waals diameters are 7.4 x 8.2 x 12.0 (M), 3.6 x 5.2 x 5.4 (U), 3.8 x 5.2 x 5.4 (A) and (3.4 x 4.5 x 5.4 (F) A.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of vibrational spectra of 3-halo-1-propanols CH(2)XCH(2)CH(2)OH (X is Cl and Br).

PubMed

Badawi, Hassan M; Förner, Wolfgang

2008-12-01

The conformational stability and the three rotor internal rotations in 3-chloro- and 3-bromo-1-propanols were investigated by DFT-B3LYP/6-311+G and ab initio MP2/6-311+G, MP3/6-311+G and MP4(SDTQ)//MP3/6-311+G levels of theory. On the calculated potential energy surface twelve distinct minima were located all of which were not predicted to have imaginary frequencies at the B3LYP level of theory. The calculated lowest energy minimum in the potential curves of both molecules was predicted to correspond to the Gauche-gauche-trans (Ggt) conformer in excellent agreement with earlier microwave and electron diffraction results. The equilibrium constants for the conformational interconversion of the two 3-halo-1-propanols were calculated at the B3LYP/6-311+G level of calculation and found to correspond to an equilibrium mixture of about 32% Ggt, 18% Ggg1, 13% Tgt, 8% Tgg and 8% Gtt conformations for 3-chloro-1-propanol and 34% Ggt, 15% Tgt, 13% Ggg1, 9% Tgg and 7% Gtt conformations for 3-bromo-1-propanol at 298.15K. The nature of the high energy conformations was verified by carrying out solvent experiments using formamide ( epsilon=109.5) and MP3 and MP4//MP3 calculations. The vibrational frequencies of each molecule in its three most stable forms were computed at the B3LYP level and complete vibrational assignments were made based on normal coordinate calculations and comparison with experimental data of the molecules.

Pharmacological characterization of ecstasy synthesis byproducts with recombinant human monoamine transporters.

PubMed

Pifl, Christian; Nagy, Gabor; Berényi, Sándor; Kattinger, Alexandra; Reither, Harald; Antus, Sándor

2005-07-01

Ecstasy samples often contain byproducts of the illegal, uncontrolled synthesis of N-methyl-3,4-methylenedioxy-amphetamine or 3,4-methylenedioxymethamphetamine (MDMA). MDMA and eight chemically defined byproducts of MDMA synthesis were investigated for their interaction with the primary sites of action of MDMA, namely the human plasmalemmal monamine transporters for norepinephrine, serotonin, and dopamine [(norepinephrine transporter (NET), serotonin transporter (SERT), and dopamine transporter (DAT)]. SK-N-MC neuroblastoma and human embryonic kidney cells stably transfected with the transporter cDNA were used for uptake and release experiments. Two of the eight compounds, 1,3-bis (3,4-methylenedioxyphenyl)-2-propanamine (12) and N-formyl-1,3-bis (3,4-methylenedioxyphenyl)-prop-2-yl-amine (13) had uptake inhibitory potencies with IC50 values in the low micromolar range similar to MDMA. Compounds with nitro instead of amino groups and a phenylethenyl instead of a phenylethyl structure or a formamide or acetamide modification had IC50 values beyond 100 microM. MDMA, 12, and 13 were examined for induction of carrier-mediated release by superfusion of transporter expressing cells preloaded with the metabolically inert transporter substrate [3H]1-methyl-4-phenylpyridinium. MDMA induced release mediated by NET, SERT, or DAT with EC50 values of 0.64, 1.12, and 3.24 microM, respectively. 12 weakly released from NET- and SERT-expressing cells with maximum effects less than one-tenth of that of MDMA and did not release from DAT cells. 13 had no releasing activity. 12 and 13 inhibited release induced by MDMA, and the concentration dependence of this effect correlated with their uptake inhibitory potency at the various transporters. These results do not support a neurotoxic potential of the examined ecstasy synthesis byproducts and provide interesting structure-activity relationships on the transporters.

Formation and Atmosphere of Complex Organic Molecules of the HH 212 Protostellar Disk

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

Lee, Chin-Fei; Ho, Paul T. P.; Hirano, Naomi

HH 212 is a nearby (400 pc) Class 0 protostellar system recently found to host a “hamburger”-shaped dusty disk with a radius of ∼60 au, deeply embedded in an infalling-rotating flattened envelope. We have spatially resolved this envelope-disk system with the Atacama Large Millimeter/submillimeter Array at up to ∼16 au (0.″04) resolution. The envelope is detected in HCO{sup +} J = 4–3 down to the dusty disk. Complex organic molecules (COMs) and doubly deuterated formaldehyde (D{sub 2}CO) are detected above and below the dusty disk within ∼40 au of the central protostar. The COMs are methanol (CH{sub 3}OH), deuterated methanolmore » (CH{sub 2}DOH), methyl mercaptan (CH{sub 3}SH), and formamide (NH{sub 2}CHO, a prebiotic precursor). We have modeled the gas kinematics in HCO{sup +} and COMs and found a centrifugal barrier (CB) at a radius of ∼44 au, within which a Keplerian rotating disk is formed. This indicates that HCO{sup +} traces the infalling-rotating envelope down to the CB and COMs trace the atmosphere of a Keplerian rotating disk within the CB. The COMs are spatially resolved for the first time, both radially and vertically, in the atmosphere of a disk in the earliest, Class 0 phase of star formation. Our spatially resolved observations of COMs favor their formation in the disk rather than a rapidly infalling (warm) inner envelope. The abundances and spatial distributions of the COMs provide strong constraints on models of their formation and transport in low-mass star formation.« less

Solution phase synthesis of aluminum-doped silicon nanoparticles via room-temperature, solvent based chemical reduction of silicon tetrachloride

NASA Astrophysics Data System (ADS)

Mowbray, Andrew James

We present a method of wet chemical synthesis of aluminum-doped silicon nanoparticles (Al-doped Si NPs), encompassing the solution-phase co-reduction of silicon tetrachloride (SiCl4) and aluminum chloride (AlCl 3) by sodium naphthalide (Na[NAP]) in 1,2-dimethoxyethane (DME). The development of this method was inspired by the work of Baldwin et al. at the University of California, Davis, and was adapted for our research through some noteworthy procedural modifications. Centrifugation and solvent-based extraction techniques were used throughout various stages of the synthesis procedure to achieve efficient and well-controlled separation of the Si NP product from the reaction media. In addition, the development of a non-aqueous, formamide-based wash solution facilitated simultaneous removal of the NaCl byproduct and Si NP surface passivation via attachment of 1-octanol to the particle surface. As synthesized, the Si NPs were typically 3-15 nm in diameter, and were mainly amorphous, as opposed to crystalline, as concluded from SAED and XRD diffraction pattern analysis. Aluminum doping at various concentrations was accomplished via the inclusion of aluminum chloride (AlCl3); which was in small quantities dissolved into the synthesis solution to be reduced alongside the SiCl4 precursor. The introduction of Al into the chemically-reduced Si NP precipitate was not found to adversely affect the formation of the Si NPs, but was found to influence aspects such as particle stability and dispersibility throughout various stages of the procedure. Analytical techniques including transmission electron microscopy (TEM), FTIR spectroscopy, and ICP-optical emission spectroscopy were used to comprehensively characterize the product NPs. These methods confirm both the presence of Al and surface-bound 1-octanol in the newly formed Si NPs.

Enhanced plasmid DNA utilization in transiently transfected CHO-DG44 cells in the presence of polar solvents.

PubMed

Rajendra, Yashas; Balasubramanian, Sowmya; Kiseljak, Divor; Baldi, Lucia; Wurm, Florian M; Hacker, David L

2015-01-01

Although the protein yields from transient gene expression (TGE) with Chinese hamster ovary (CHO) cells have recently improved, the amount of plasmid DNA (pDNA) needed for transfection remains relatively high. We describe a strategy to reduce the pDNA amount by transfecting CHO-DG44 cells with 0.06 μg pDNA/10(6) cells (10% of the optimal amount) in the presence of nonspecific (filler) DNA and various polar solvents including dimethylsufoxide, dimethyl formamide, acetonitrile, dimethyl acetamide (DMA), and hexamethyl phosphoramide (HMP). All of the polar solvents with the exception of HMP increased the production of a recombinant antibody in comparison to the untreated control transfection. In the presence of 0.25% DMA, the antibody yield in a 7-day batch culture was 500 mg/L. This was fourfold higher than the yield from the untreated control transfection. Mechanistic studies revealed that the polar solvents did not affect polyethylenimine-mediated pDNA delivery into cells or nuclei. The steady-state transgene mRNA level was elevated in the presence of each of the polar solvents tested, while the transgene mRNA half-life remained the same. These results indicated that the polar solvents enhanced transgene transcription. When screening a panel of recombinant antibodies and Fc-fusion proteins for production in the presence of the polar solvents, the highest increase in yield was observed following DMA addition for 11 of the 12 proteins. These results are expected to enhance the applicability of high-yielding TGE processes with CHO-DG44 cells by decreasing the amount of pDNA required for transfection. © 2015 American Institute of Chemical Engineers.

Surface properties of Ti-6Al-4V alloy part I: Surface roughness and apparent surface free energy.

PubMed

Yan, Yingdi; Chibowski, Emil; Szcześ, Aleksandra

2017-01-01

Titanium (Ti) and its alloys are the most often used implants material in dental treatment and orthopedics. Topography and wettability of its surface play important role in film formation, protein adhesion, following osseointegration and even duration of inserted implant. In this paper, we prepared Ti-6Al-4V alloy samples using different smoothing and polishing materials as well the air plasma treatment, on which contact angles of water, formamide and diiodomethane were measured. Then the apparent surface free energy was calculated using four different approaches (CAH, LWAB, O-W and Neumann's Equation of State). From LWAB approach the components of surface free energy were obtained, which shed more light on the wetting properties of samples surface. The surface roughness of the prepared samples was investigated with the help of optical profilometer and AFM. It was interesting whether the surface roughness affects the apparent surface free energy. It was found that both polar interactions the electron donor parameter of the energy and the work of water adhesion increased with decreasing roughness of the surfaces. Moreover, short time plasma treatment (1min) caused decrease in the surface hydrophilic character, while longer time (10min) treatment caused significant increase in the polar interactions and the work of water adhesion. Although Ti-6Al-4V alloy has been investigated many times, to our knowledge, so far no paper has been published in which surface roughness and changes in the surface free energy of the alloy were compared in the quantitative way in such large extent. This novel approach deliver better knowledge about the surface properties of differently smoothed and polished samples which may be helpful to facilitate cell adhesion, proliferation and mineralization. Therefore the results obtained present also potentially practical meaning. Copyright © 2016 Elsevier B.V. All rights reserved.

Preparation, characterization and in vitro anticoagulant activity of corn stover xylan sulfates.

PubMed

Cheng, He-Li; Liu, Hao; Feng, Qing-Hua; Xie, Yi-Min; Zhan, Huai-Yu

2017-02-01

A new anticoagulant agent was prepared by introducing sulfate groups into corn stover xylan through homogeneous reactions. Three organic solvents, N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and formamide (FA), were adopted as reaction media, with the assistance of LiCl. Structural characterization by FT-IR and 13 CNMR showed that xylan sulfate (XS) could be successfully synthesized with SO 3 ∙Pyridine (SO 3 ∙Py) complexes sulfation reagent in the three media. The effect of sulfation temperature, sulfation time, media type and molar ratio of -SO 3 /-OH on the degree of substitution (DS) and degree of the polymerization (DP) were studied. DMF/LiCl were more effective than DMSO/LiCl and FA/LiCl in preparation of xylan sulfate with high DS. The optimal conditions for sulfation were obtained when SO 3 ∙Py complex was added to DMF/LiCl with -SO 3 /-OH ratio of 1.5:1 and maintained at 50 °C for 3 h. Degree of polymerization of xylan was decreased during the sulfation process and DMF/LiCl offered the least xylan degradation as compared with DMSO/LiCl or FA/LiCl. Anticoagulant activities of the resultant xylan sulfates with different DS were evaluated by using activated partial thromboplastin time (APTT), thrombin time (TT), and prothrombin time (PT). Results indicated that the introducing of sulfate groups into xylan did endow the polysaccharides with anticoagulant activity. The APTT and TT of XS with DS of 1.20 reached 141 and 45.3 s at a dosage of 20 μg/mL, while the APTT and TT values for the blank sample were only 35.5 and 15.6 s. Furthermore, coagulation time was prolonged with the increase of DS and the concentration of XS. Our findings provide new insights into the value-added utilization of agricultural biomass.

1H NMR spectra. Part 30(+): 1H chemical shifts in amides and the magnetic anisotropy, electric field and steric effects of the amide group.

PubMed

Abraham, Raymond J; Griffiths, Lee; Perez, Manuel

2013-03-01

The (1)H spectra of 37 amides in CDCl(3) solvent were analysed and the chemical shifts obtained. The molecular geometries and conformational analysis of these amides were considered in detail. The NMR spectral assignments are of interest, e.g. the assignments of the formamide NH(2) protons reverse in going from CDCl(3) to more polar solvents. The substituent chemical shifts of the amide group in both aliphatic and aromatic amides were analysed using an approach based on neural network data for near (≤3 bonds removed) protons and the electric field, magnetic anisotropy, steric and for aromatic systems π effects of the amide group for more distant protons. The electric field is calculated from the partial atomic charges on the N.C═O atoms of the amide group. The magnetic anisotropy of the carbonyl group was reproduced with the asymmetric magnetic anisotropy acting at the midpoint of the carbonyl bond. The values of the anisotropies Δχ(parl) and Δχ(perp) were for the aliphatic amides 10.53 and -23.67 (×10(-6) Å(3)/molecule) and for the aromatic amides 2.12 and -10.43 (×10(-6) Å(3)/molecule). The nitrogen anisotropy was 7.62 (×10(-6) Å(3)/molecule). These values are compared with previous literature values. The (1)H chemical shifts were calculated from the semi-empirical approach and also by gauge-independent atomic orbital calculations with the density functional theory method and B3LYP/6-31G(++) (d,p) basis set. The semi-empirical approach gave good agreement with root mean square error of 0.081 ppm for the data set of 280 entries. The gauge-independent atomic orbital approach was generally acceptable, but significant errors (ca. 1 ppm) were found for the NH and CHO protons and also for some other protons. Copyright © 2013 John Wiley & Sons, Ltd.

The formation of urea in space. I. Ion-molecule, neutral-neutral, and radical gas-phase reactions

NASA Astrophysics Data System (ADS)

Brigiano, Flavio Siro; Jeanvoine, Yannick; Largo, Antonio; Spezia, Riccardo

2018-02-01

Context. Many organic molecules have been observed in the interstellar medium thanks to advances in radioastronomy, and very recently the presence of urea was also suggested. While those molecules were observed, it is not clear what the mechanisms responsible to their formation are. In fact, if gas-phase reactions are responsible, they should occur through barrierless mechanisms (or with very low barriers). In the past, mechanisms for the formation of different organic molecules were studied, providing only in a few cases energetic conditions favorable to a synthesis at very low temperature. A particularly intriguing class of such molecules are those containing one N-C-O peptide bond, which could be a building block for the formation of biological molecules. Urea is a particular case because two nitrogen atoms are linked to the C-O moiety. Thus, motivated also by the recent tentative observation of urea, we have considered the synthetic pathways responsible to its formation. Aims: We have studied the possibility of forming urea in the gas phase via different kinds of bi-molecular reactions: ion-molecule, neutral, and radical. In particular we have focused on the activation energy of these reactions in order to find possible reactants that could be responsible for to barrierless (or very low energy) pathways. Methods: We have used very accurate, highly correlated quantum chemistry calculations to locate and characterize the reaction pathways in terms of minima and transition states connecting reactants to products. Results: Most of the reactions considered have an activation energy that is too high; but the ion-molecule reaction between NH2OHNH2OH2+ and formamide is not too high. These reactants could be responsible not only for the formation of urea but also of isocyanic acid, which is an organic molecule also observed in the interstellar medium.

Tens of micron-sized unilamellar nanosheets of Y/Eu layered rare-earth hydroxide: efficient exfoliation via fast anion exchange and their self-assembly into oriented oxide film with enhanced photoluminescence

NASA Astrophysics Data System (ADS)

Zhu, Qi; Li, Ji-Guang; Li, Xiaodong; Sun, Xudong; Qi, Yang; Zhu, Miaoyong; Sakka, Yoshio

2014-02-01

Layered rare-earth hydroxide (LRH) crystals of (Y0.95Eu0.05)2(OH)5NO3·nH2O with a lateral size of ˜ 300 μm and a thickness of ˜ 9 μm have been synthesized via a hydrothermal reaction of mixed nitrate solutions in the presence of mineralizer NH4NO3 at 200 °C for 24 h. LRH exhibits the ability to undergo intercalation and anion exchange with DS- (C12H25OSO3-) via hydrothermal treatment. Compared with traditional anion exchange at room temperature, hydrothermal processing not only shortens the anion exchange time from 720 to 24 h but also increases the basal spacing. The arrangements of DS- in the interlayer of LRH are significantly affected by the DS- concentration and reaction temperature, and the basal spacing of the LRH-DS sample in the crystal edge is assumed to be larger than that in the crystal center. A higher DS- concentration and reaction temperature both induce more intercalation of DS- anions into the interlayer gallery, thus yielding a larger basal spacing. Unilamellar nanosheets with a lateral size of ⩾60 μm and a thickness of ˜ 1.6 nm can be obtained by delaminating LRH-DS in formamide. The resultant unilamellar nanosheets are single crystalline. Transparent (Y0.95Eu0.05)2O3 phosphor films with a uniform [111] orientation and a layer thickness of ˜ 90 nm were constructed with the nanosheets as building blocks via spin-coating, followed by proper annealing. The oriented oxide film exhibits a strong red emission at 614 nm (the 5D0-7F2 transition of Eu3+), whose intensity is ˜ 2 times that of the powder form owing to the significant exposure of the (222) facets.

A critical overview of non-aqueous capillary electrophoresis. Part I: mobility and separation selectivity.

PubMed

Kenndler, Ernst

2014-03-28

This two-part review critically gives an overview on the theoretical and practical advances in non-aqueous capillary electrophoresis (NACE) achieved over the recent five years. Part I starts out by reviewing the aspects relevant to electromigration in organic solvents and evaluates potential advantages of the latter in comparison to aqueous solvent systems. The crucial role of solubility for the species involved in CE - analytes and back ground electrolyte constituents - is discussed both for ionic and neutral compounds. The impact of organic solvents on the electrophoretic and electroosmotic mobility and on the ionization (pKa values) of weak acids and bases is highlighted. Special emphasis is placed on methanol, acetonitrile and mixtures of these solvents, being the most frequent employed media for NACE applications. In addition, also solvents less commonly used in NACE will be covered, including other alcohols, amides (formamide, N-methylformamide, N,N-dimethylformamide, N,N-dimethylacetamide), propylene carbonate, dimethylsulphoxide, and nitromethane. The discussions address the consequences of dramatic pKa shifts frequently seen for weak acids and bases, and the important contributions of medium-specific electroosmotic flow (EOF) to electromigration in nonaqueous media. Important for NACE, the role of the water content on pKa and mobility is analyzed. Finally, association phenomena rather specific to nonaqueous solvents (ion pairing, homo- and heteroconjugation) will be addressed, along with their potential advantages for the development of NACE separation protocols. It is pointed out that this review is not intended as a listing of all papers that have been published on NACE in the period mentioned above. It rather deals with general aspects of migration and selectivity in organic solvent systems, and discusses - critically - examples from the literature with particular interest to the topic. An analog discussion about the role of the solvent on efficiency will be presented in Part II. Copyright © 2014 Elsevier B.V. All rights reserved.

Cellular distribution of calcium current is unaltered during compensated hypertrophy in the spontaneously hypertensive rat.

PubMed

Fowler, Mark R; Orchard, Clive H; Harrison, Simon M

2007-01-01

Changes in cellular calcium (Ca(2+)) handling are thought to underlie the altered contraction that occurs during cardiac hypertrophy and failure. Recent work has highlighted the importance of t-tubules in the control of intracellular Ca(2+). The present study was performed to investigate whether changes in the distribution of I (Ca) between the surface and t-tubule membranes might contribute to the altered Ca(2+) handling observed during compensated hypertrophy in the spontaneously hypertensive rat (SHR). Experiments were performed on ventricular myocytes isolated from 5-month-old SHR and normotensive Wistar-Kyoto (WKY) control rats. Osmotic shock using formamide was used to disrupt the t-tubular system and the whole-cell patch clamp technique used to monitor I (Ca) in the presence and absence of t-tubules. Membrane capacitance and I (Ca) were greater in control SHR than WKY myocytes; following detubulation, cell capacitance and I (Ca) both decreased and were no longer significantly different in the two cell types. The density of I (Ca) was not significantly different in control SHR and WKY cells or in detubulated myocytes from the two species. These data suggest that the distribution of I (Ca) is unchanged in SHR myocytes compared to WKY controls; I (Ca) density in the t-tubules was 1.2-fold greater than in the sarcolemma in both strains. These data also imply that the increase in surface area in SHR myocytes is due principally to an increase in t-tubular area, which is accompanied by an approximately equivalent increase in I (Ca), so that the density of I (Ca) at the cell surface and in the t-tubules remains the same. These changes would be expected to retain cell function and synchronicity of Ca(2+) release in the SHR at this stage of compensated hypertrophy.

Evaluation of 14 Organic Solvents and Carriers for Screening Applications in Zebrafish Embryos and Larvae

PubMed Central

Maes, Jan; Verlooy, Lien; Buenafe, Olivia E.; de Witte, Peter A. M.; Esguerra, Camila V.; Crawford, Alexander D.

2012-01-01

Zebrafish are rapidly growing in popularity as an in vivo model system for chemical genetics, drug discovery, and toxicology, and more recently also for natural product discovery. Experiments involving the pharmacological evaluation of small molecules or natural product extracts in zebrafish bioassays require the effective delivery of these compounds to embryos and larvae. While most samples to be screened are first solubilized in dimethyl sulfoxide (DMSO), which is then diluted in the embryo medium, often this method is not sufficient to prevent the immediate or eventual precipitation of the sample. Certain compounds and extracts are also not highly soluble in DMSO. In such instances the use of carriers and/or other solvents might offer an alternative means to achieve the required sample concentration. Towards this end, we determined the maximum tolerated concentration (MTC) of several commonly used solvents and carriers in zebrafish embryos and larvae at various developmental stages. Solvents evaluated for this study included acetone, acetonitrile, butanone, dimethyl formamide, DMSO, ethanol, glycerol, isopropanol, methanol, polyethylene glycol (PEG-400), propylene glycol, and solketal, and carriers included albumin (BSA) and cyclodextrin (2-hydroxypropyl-beta-cyclodextrin, or HPBCD). This study resulted in the identification of polyethylene glycol (PEG400), propylene glycol, and methanol as solvents that were relatively well-tolerated over a range of developmental stages. In addition, our results showed that acetone was well-tolerated by embryos but not by larvae, and 1% cyclodextrin (HPBCD) was well-tolerated by both embryos and larvae, indicating the utility of this carrier for compound screening in zebrafish. However, given the relatively small differences (2–3 fold) between concentrations that are apparently safe and those that are clearly toxic, further studies – e.g. omics analyses –should be carried out to determine which cellular processes and signalling pathways are affected by any solvents and carriers that are used for small-molecule screens in zebrafish. PMID:23082109

Hierarchical hollow microsphere and flower-like indium oxide: Controllable synthesis and application as H{sub 2}S cataluminescence sensing materials

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

Cai, Pingyang, E-mail: cpyxx@163.com; Bai, Wei, E-mail: weibaiscu@gmail.com; Zhang, Lichun, E-mail: lichun0203@yahoo.cn

Graphical abstract: Hierarchical hollow microsphere and flower-like In{sub 2}O{sub 3} were controllable fabricated through a novel and simple hydrothermal process, and the former showed superior cataluminescence sensing performance to H{sub 2}S. Highlights: ► In{sub 2}O{sub 3} hierarchical hollow sphere were prepared via a hydrothermal route. ► The growth process of In{sub 2}O{sub 3} hierarchical hollow sphere has been investigated. ► The sensor based on prepared In{sub 2}O{sub 3} shows good sensing performance to H{sub 2}S. -- Abstract: In the present work, In{sub 2}O{sub 3} hierarchical hollow microsphere and flower-like microstructure were achieved controllably by a hydrothermal process in the sodiummore » dodecyl sulfate (SDS)-N,N-dimethyl-formamide (DMF) system. XRD, SEM, HRTEM and N{sub 2} adsorption measurements were used to characterize the as-prepared indium oxide materials and the possible mechanism for the microstructures formation was briefly discussed. The cataluminescence gas sensor based on the as-prepared In{sub 2}O{sub 3} was utilized to detect H{sub 2}S concentrations in flowing air. Comparative gas sensing results revealed that the sensor based on hierarchical hollow microsphere exhibited much higher sensing sensitivity in detecting H{sub 2}S gas than the sensor based on flower-like microstructure. The present gas sensor had a fast response time of 5 s and a recovery time of less than 25 s, furthermore, the cataluminescence intensity vs. H{sub 2}S concentration was linear in range of 2–20 μg mL{sup −1} with a detection limit of 0.5 μg mL{sup −1}. The present highly sensitive, fast-responding, and low-cost In{sub 2}O{sub 3}-based gas sensor for H{sub 2}S would have many practical applications.« less

Search for liquids electrospraying the smallest possible nanodrops in vacuo

NASA Astrophysics Data System (ADS)

Alonso-Matilla, R.; Fernández-García, J.; Congdon, H.; Fernández de la Mora, J.

2014-12-01

Prior work with electrosprays in vacuum of mixtures of ionic liquids (ILs) and the moderately high boiling point (Tb) solvents formamide (FM) and propylene carbonate (PC) (Tb of 210 and 241 °C) has shown that the charged drops produced have reasonably narrow charge/mass distributions, controllable over a wide mass/charge range. This enables their use as propellants in electrical propulsion with specific impulse Isp varying from a few hundred to a few thousand seconds (10 kV beam energy) and with excellent propulsion efficiency. However, some limitations are imposed by the finite room temperature volatility of FM and PC. Here, we seek improved performance from propellants based on the polar but viscous solvent Sulfolane (SF; ɛ = 43.2, μ = 10.3 cP) and the low viscosity but less polar solvent tributyl phosphate (TBP; ɛ = 8.9, μ = 3.4 cP), both with Tb > 280 °C. Neither TBP nor its low viscosity mixtures with SF achieve the electrical conductivities needed to yield high Isp. Most ILs used in SF/IL mixtures tested were based on the 1-ethyl-3-methylimidazolium (EMI) or 1,3-dimethylimidazolium (DMI) cations, including EMI-BF4, EMI-N(CN)2, and DMI-N(CN)2. These combinations reach high conductivities, some approaching 3 S/m, but have limited propulsive performance because evaporation of ions directly from the electrified meniscus produces undesirable mixed beams of drops and ions. Exceptional characteristics are found in mixtures of SF with ethylammonium nitrate (EAN), where the small EA+ cation is strongly bound to the solvent, greatly delaying ion evaporation from the meniscus. Evidence on the formation of nano-jets with diameters as small as 1 nm is seen. Although unprecedented, this finding agrees with what would be expected if ion evaporation were suppressed. SF/EAN mixtures thus provide the best available sources to produce the smallest possible nanodrops, minimally polluted by ions.

Mechanical continuity and reversible chromosome disassembly within intact genomes removed from living cells

NASA Technical Reports Server (NTRS)

Maniotis, A. J.; Bojanowski, K.; Ingber, D. E.

1997-01-01

Chromatin is thought to be structurally discontinuous because it is packaged into morphologically distinct chromosomes that appear physically isolated from one another in metaphase preparations used for cytogenetic studies. However, analysis of chromosome positioning and movement suggest that different chromosomes often behave as if they were physically connected in interphase as well as mitosis. To address this paradox directly, we used a microsurgical technique to physically remove nucleoplasm or chromosomes from living cells under isotonic conditions. Using this approach, we found that pulling a single nucleolus or chromosome out from interphase or mitotic cells resulted in sequential removal of the remaining nucleoli and chromosomes, interconnected by a continuous elastic thread. Enzymatic treatments of interphase nucleoplasm and chromosome chains held under tension revealed that mechanical continuity within the chromatin was mediated by elements sensitive to DNase or micrococcal nuclease, but not RNases, formamide at high temperature, or proteases. In contrast, mechanical coupling between mitotic chromosomes and the surrounding cytoplasm appeared to be mediated by gelsolin-sensitive microfilaments. Furthermore, when ion concentrations were raised and lowered, both the chromosomes and the interconnecting strands underwent multiple rounds of decondensation and recondensation. As a result of these dynamic structural alterations, the mitotic chains also became sensitive to disruption by restriction enzymes. Ion-induced chromosome decondensation could be blocked by treatment with DNA binding dyes, agents that reduce protein disulfide linkages within nuclear matrix, or an antibody directed against histones. Fully decondensed chromatin strands also could be induced to recondense into chromosomes with pre-existing size, shape, number, and position by adding anti-histone antibodies. Conversely, removal of histones by proteolysis or heparin treatment produced chromosome decondensation which could be reversed by addition of histone H1, but not histones H2b or H3. These data suggest that DNA, its associated protein scaffolds, and surrounding cytoskeletal networks function as a structurally-unified system. Mechanical coupling within the nucleoplasm may coordinate dynamic alterations in chromatin structure, guide chromosome movement, and ensure fidelity of mitosis.

Laboratory Analysis Of Water, Hydrocarbon And Ammonia Ice Mixtures Exposed To High-energy Electron Irradiation

NASA Astrophysics Data System (ADS)

Hand, Kevin P.; Carlson, R. W.; Tsapin, A. I.

2006-09-01

Irradiation of low temperature ices in the laboratory provides insight into processes that may be occurring on icy bodies in the solar system. Here we report on results from high-energy (10keV) electron irradiation of thin ice films at 1e-8 torr and 70-120K. Mixtures include water with CO2, C3H8, C3H6, C4H10 (butane and isobutane), C4H8,(1-butene and cis/trans-2-butene), and NH3. During irradiation of H2O + alkane films at 80K, CO2 and CH4 production is observed and both species are retained in the ice, possibly trapped in clathrates. The -CH3 infrared bands initially present are seen to decrease with increasing dose. Bands associated with -CH2- persist, indicating polymerization of the initial short-chain hydrocarbons. In alkenes a similar evolution toward polymerization is observed, however the first step appears to be the destruction of the C=C bond. Upon warming of the film, mass spectra data compliment the mid-infrared data and indicate the production of H2CO, however glycolic acid is not explicitly seen in the mass spectra. When warmed to 300K, residues remained for all irradiated films except that of the H2O + CO2 mixtures. Residues were analyzed with Matrix Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI). Results show the production of large aliphatic, very refractory, hydrocarbons (with m/z up to 2500). Mid-infrared spectra of the residues indicate carbonyls and alcohols, likely due to polymerized aldehydes and carboxylic acids. Films of H2O + C3H8 + NH3 at 70K show the production of OCN- (cyanate ion), formamide, along with other possible amides and hydrocarbons. HPLC results indicate the production of racemic alanine. Finally, results of abiotic experiments are compared to results from the irradiation of bacterial spores in ice. The application to Europa and Enceladus is discussed.

Evaluation of fresh and frozen-thawed semen of individual ganders by assessment of spermatozoa motility and morphology.

PubMed

Łukaszewicz, Ewa; Kruszyński, Wojciech

2003-04-01

Individual differences in gander Anser anser L. reaction to semen collection procedure, quality and quantity of fresh semen and its susceptibility to the freezing process are discussed. Semen was collected individually by dorso-abdominal massage, from 1-year old White Koluda ganders (n = 12) every 2-3 days. Ganders' reactions to massage were observed during the entire reproductive cycle (from 11 February to 13 June, from every male 40 semen collections were performed). For individual evaluation and freezing purpose semen was collected 13 times from every male. In the fresh semen, the following parameters were evaluated: ejaculate volume, color, density, blood or fecal contamination, motility, concentration and morphology of spermatozoa. Motility and spermatozoa morphology were evaluated in the frozen-thawed semen. Semen diluted in 2:1 ratio with EK diluent was frozen with 6% of dimethyl-formamide (DMF) to -140 degrees C at a rate 60 degrees C/min. Semen was thawed by placing the straws in a 60 degrees C water-bath for 4-5 s. Ten out of 12 ganders had from 67.5 to 100.0% positive reactions resulting in semen ejaculation. Significant (P < or = 0.01) differences in fresh semen quality of particular ganders were observed for all evaluated traits. In 1-year-old gander semen morphologically intact spermatozoa constitute only 27.8-45.2% of all cells. Therefore, the sperm quality factor (SQF), proposed by the authors, which includes ejaculate volume, sperm concentration and the percentage of live normal spermatozoa, seems to be a good predictor of gander semen fertilizing ability. The SQF of individual ganders varied from 7.7 to 11.5. The percentage of live normal spermatozoa in the frozen-thawed semen depended mainly on fresh semen quality. In relation to the fresh semen average from 57.2 to 63.2% of spermatozoa survived freezing process and from 23.9 to 38.5% remained morphologically intact.

Mutant Allele-Specific Uncoupling of PENETRATION3 Functions Reveals Engagement of the ATP-Binding Cassette Transporter in Distinct Tryptophan Metabolic Pathways1[OPEN

PubMed Central

Lu, Xunli; Dittgen, Jan; Piślewska-Bednarek, Mariola; Molina, Antonio; Schneider, Bernd; Doubský, Jan; Schneeberger, Korbinian; Schulze-Lefert, Paul

2015-01-01

Arabidopsis (Arabidopsis thaliana) PENETRATION (PEN) genes quantitatively contribute to the execution of different forms of plant immunity upon challenge with diverse leaf pathogens. PEN3 encodes a plasma membrane-resident pleiotropic drug resistance-type ATP-binding cassette transporter and is thought to act in a pathogen-inducible and PEN2 myrosinase-dependent metabolic pathway in extracellular defense. This metabolic pathway directs the intracellular biosynthesis and activation of tryptophan-derived indole glucosinolates for subsequent PEN3-mediated efflux across the plasma membrane at pathogen contact sites. However, PEN3 also functions in abiotic stress responses to cadmium and indole-3-butyric acid (IBA)-mediated auxin homeostasis in roots, raising the possibility that PEN3 exports multiple functionally unrelated substrates. Here, we describe the isolation of a pen3 allele, designated pen3-5, that encodes a dysfunctional protein that accumulates in planta like wild-type PEN3. The specific mutation in pen3-5 uncouples PEN3 functions in IBA-stimulated root growth modulation, callose deposition induced with a conserved peptide epitope of bacterial flagellin (flg22), and pathogen-inducible salicylic acid accumulation from PEN3 activity in extracellular defense, indicating the engagement of multiple PEN3 substrates in different PEN3-dependent biological processes. We identified 4-O-β-d-glucosyl-indol-3-yl formamide (4OGlcI3F) as a pathogen-inducible, tryptophan-derived compound that overaccumulates in pen3 leaf tissue and has biosynthesis that is dependent on an intact PEN2 metabolic pathway. We propose that a precursor of 4OGlcI3F is the PEN3 substrate in extracellular pathogen defense. These precursors, the shared indole core present in IBA and 4OGlcI3F, and allele-specific uncoupling of a subset of PEN3 functions suggest that PEN3 transports distinct indole-type metabolites in distinct biological processes. PMID:26023163

Empirical parameters for solvent acidity, basicity, dipolarity, and polarizability of the ionic liquids [BMIM][BF4] and [BMIM][PF6].

PubMed

del Valle, J C; García Blanco, F; Catalán, J

2015-04-02

The empirical solvent scales for polarizability (SP), dipolarity (SdP), acidity (SA), and basicity (SB) have been successfully used to interpret the solvatochromism of compounds dissolved in organic solvents and their solvent mixtures. Providing that the published solvatochromic parameters for the ionic liquids 1-(1-butyl)-3-methylimidazolium tetrafluoroborate, [BMIM][BF4] and 1-(1-butyl)-3-methylimidazolium hexafluorophosphate, [BMIM][PF6], are excessively widespread, their SP, SdP, SA, and SB values are measured herein at temperatures from 293 to 353 K. Four key points are emphasized herein: (i) the origin of the solvatochromic solvent scales--the gas phase, that is the absence of any medium perturbation--; (ii) the separation of the polarizability and dipolarity effects; (iii) the simplification of the probing process in order to obtain the solvatochromic parameters; and (iv) the SP, SdP, SA, and SB solvent scales can probe the polarizability, dipolarity, acidity, and basicity of ionic liquids as well as of organic solvents and water-organic solvent mixtures. From the multiparameter approach using the four pure solvent scales one can draw the conclusion that (a) the solvent influence of [BMIM][BF4] parallels that of formamide at 293 K, both of them miscible with water; (b) [BMIM][PF6] shows a set of solvatochromic parameters similar to that of chloroacetonitrile, both of them water insoluble; and (c) that the corresponding solvent acidity and basicity of the ionic liquids can be explained to a great extent from the cation species by comparing the empirical parameters of [BMIM](+) with those of the solvent 1-methylimidazole. The insolubility of [BMIM][PF6] in water as compared to [BMIM][BF4] is tentatively connected to some extent to the larger molar volume of the anion [PF6](-), and to the difference in basicity of [PF6](-) and [BF4](-).

Influence of cryoprotectants glycerol and amides, combined with antioxidants on quality of frozen-thawed boar sperm.

PubMed

Buranaamnuay, K; Grossfeld, R; Struckmann, C; Rath, D

2011-08-01

The present study was undertaken to examine whether the cooling and freezing extenders containing a mixture of antioxidants (AOs) catalase, Na-pyruvate and mercaptoethanol and one of three types of cryoprotectants (CPs) would be able to improve the quality of frozen-thawed boar sperm. The collected semen, only the sperm-rich fraction, was diluted 1:1 with Androhep plus™ extender, stored at 15°C for 2 h and centrifuged. The centrifuged sperm pellet was re-suspended in lactose-egg yolk extender and divided into four groups for mixing with freezing extenders containing different kinds of CPs at 5°C: (I) glycerol (GLY) as control; (II) GLY with AOs; (III) dimethyl formamide (DMF) with AOs and (IV) dimethyl acetamide (DMA) with AOs. Processed sperm were packaged in 0.25-mL straws and frozen using a controlled rate freezer. After thawing, the diluted thawed sperm were incubated at 38°C for 10 min and was assessed for motility by CASA, membrane/acrosome integrity by FITC-PNA/PI and DNA integrity (DFI) by SCSA. All sperm parameters evaluated, except DFI, were negatively affected (P<0.001) when using DMF (III) or DMA (IV) as CPs instead of GLY (I and II). Total sperm motility was lower (P<0.001) in the samples supplemented with AOs (32.4 ± 1.2, 23.9 ± 1.5, 6.9 ± 0.7, and 10.3 ± 0.9%, for treatments I, II, III and IV, respectively). The quality of sperm frozen in DMF was not different from DMA (P>0.05). There was no difference in DFI among the studied groups (P>0.05). In conclusion, based on the present results, addition of AOs to cooling and freezing extenders and/or replacement of GLY with DMF or DMA could not improve quality of frozen-thawed boar sperm. Copyright © 2011 Elsevier B.V. All rights reserved.

Cryopreservation of stallion spermatozoa using different cryoprotectants and combinations of cryoprotectants.

PubMed

Wu, Zhuangyuan; Zheng, Xinbiao; Luo, Yongming; Huo, Fei; Dong, Hong; Zhang, Guoting; Yu, Weihao; Tian, Fang; He, Liangjun; Chen, Jingbo

2015-12-01

The present study investigates the effects of five cryoprotectants (CPAs) and cryoprotectant combinations on the post-thaw total motility, progressive motility, viability, mitochondrial membrane potential and acrosome integrity in stallion spermatozoa. In Experiment 1, the objective was to compare the impact of different concentrations (2.5%, 3.5% and 5%) of a single CPA, including glycerol (Gly), ethylene glycol (EG), dimethyl sulphoxide (DMSO), methyl formamide (MF), and dimethylformamide (DMF) for stallion spermatozoa cryopreservation. In Experiment 2, two or more CPAs were used to assess whether this improved post-thaw spermatozoa quality. Gly, MF and DMF, were used to prepare seven combinations of freezing extender with different mixtures of cryoprotectant, and the 3.5% Gly, MF and DMF were used as a control group. The results show that post-thaw total motility, progressive motility, viability, and mitochondrial membrane potential for all concentrations of EG and DMSO were less than the 3.5% and 5% Gly and MF and 2.5% and 3.5% DMF (P<0.05). Use of the 3.5% concentration resulted in the greater post-thaw total motility and progressive motility than the 2.5% and 5% concentrations for all CPAs. The results for the use of different combinations of cryoprotectant indicate there are differences in progressive motility and viability. The viability with the use of Gly(2/3)+MF(1/3) was 44.65% and was greater than the Gly(1/3)+MF(1/3)+DMF(1/3) (30.96%), MF(2/3)+DMF(1/3) (35.05%), Gly (32.21%) and MF(33.76%) (P<0.05). The progressive motility with the use of the MF(2/3)+Gly(1/3) combination was 36.0% and was greater than in the DMF (25.0%) and MF(2/3)+DMF(1/3) (22.7%) (P<0.05). These results suggest that using the appropriate cryoprotectant combination instead of a single cryoprotectant can improve horse spermatozoa cryopreservation. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of solvent polarity on the vibrational dephasing dynamics of the nitrosyl stretch in an Fe(II) complex revealed by 2D IR spectroscopy.

PubMed

Brookes, Jennifer F; Slenkamp, Karla M; Lynch, Michael S; Khalil, Munira

2013-07-25

The vibrational dephasing dynamics of the nitrosyl stretching vibration (ν(NO)) in sodium nitroprusside (SNP, Na2[Fe(CN)5NO]·2H2O) are investigated using two-dimensional infrared (2D IR) spectroscopy. The ν(NO) in SNP acts as a model system for the nitrosyl ligand found in metalloproteins which play an important role in the transportation and detection of nitric oxide (NO) in biological systems. We perform a 2D IR line shape study of the ν(NO) in the following solvents: water, deuterium oxide, methanol, ethanol, ethylene glycol, formamide, and dimethyl sulfoxide. The frequency of the ν(NO) exhibits a large vibrational solvatochromic shift of 52 cm(-1), ranging from 1884 cm(-1) in dimethyl sulfoxide to 1936 cm(-1) in water. The vibrational anharmonicity of the ν(NO) varies from 21 to 28 cm(-1) in the solvents used in this study. The frequency-frequency correlation functions (FFCFs) of the ν(NO) in SNP in each of the seven solvents are obtained by fitting the experimentally obtained 2D IR spectra using nonlinear response theory. The fits to the 2D IR line shape reveal that the spectral diffusion time scale of the ν(NO) in SNP varies from 0.8 to 4 ps and is negatively correlated with the empirical solvent polarity scales. We compare our results with the experimentally determined FFCFs of other charged vibrational probes in polar solvents and in the active sites of heme proteins. Our results suggest that the vibrational dephasing dynamics of the ν(NO) in SNP reflect the fluctuations of the nonhomogeneous electric field created by the polar solvents around the nitrosyl and cyanide ligands. The solute solvent interactions occurring at the trans-CN ligand are sensed through the π-back-bonding network along the Fe-NO bond in SNP.

Quantification of transformation products of rocket fuel unsymmetrical dimethylhydrazine in soils using SPME and GC-MS.

PubMed

Bakaikina, Nadezhda V; Kenessov, Bulat; Ul'yanovskii, Nikolay V; Kosyakov, Dmitry S

2018-07-01

Determination of transformation products (TPs) of rocket fuel unsymmetrical dimethylhydrazine (UDMH) in soil is highly important for environmental impact assessment of the launches of heavy space rockets from Kazakhstan, Russia, China and India. The method based on headspace solid-phase microextraction (HS SPME) and gas chromatography-mass spectrometry is advantageous over other known methods due to greater simplicity and cost efficiency. However, accurate quantification of these analytes using HS SPME is limited by the matrix effect. In this research, we proposed using internal standard and standard addition calibrations to achieve proper combination of accuracies of the quantification of key TPs of UDMH and cost efficiency. 1-Trideuteromethyl-1H-1,2,4-triazole (MTA-d3) was used as the internal standard. Internal standard calibration allowed controlling matrix effects during quantification of 1-methyl-1H-1,2,4-triazole (MTA), N,N-dimethylformamide (DMF), and N-nitrosodimethylamine (NDMA) in soils with humus content < 1%. Using SPME at 60 °C for 15 min by 65 µm Carboxen/polydimethylsiloxane fiber, recoveries of MTA, DMF and NDMA for sandy and loamy soil samples were 91-117, 85-123 and 64-132%, respectively. For improving the method accuracy and widening the range of analytes, standard addition and its combination with internal standard calibration were tested and compared on real soil samples. The combined calibration approach provided greatest accuracies for NDMA, DMF, N-methylformamide, formamide, 1H-pyrazole, 3-methyl-1H-pyrazole and 1H-pyrazole. For determination of 1-formyl-2,2-dimethylhydrazine, 3,5-dimethylpyrazole, 2-ethyl-1H-imidazole, 1H-imidazole, 1H-1,2,4-triazole, pyrazines and pyridines, standard addition calibration is more suitable. However, the proposed approach and collected data allow using both approaches simultaneously. Copyright © 2018 Elsevier B.V. All rights reserved.

Stabilization of antioxidant gallate in layered double hydroxide by exfoliation and reassembling reaction

NASA Astrophysics Data System (ADS)

Ansy, Kanakappan Mickel; Lee, Ji-Hee; Piao, Huiyan; Choi, Goeun; Choy, Jin-Ho

2018-06-01

As for the stabilization of chemically sensitive bioactive molecule in this study, gallic acid (GA) with antioxidant property was intercalated into interlayer space of layered double hydroxide (LDH), which was realized by exfoliation and reassembling reaction. At first, the pristine nitrate-type Zn2Al-LDH in solid state was synthesized via co-precipitation followed by the hydrothermal treatment at 80 °C for 6 h, and then exfoliated in formamide to form a colloidal solution of exfoliated LDH nanosheets, and finally reassembled in the presence of GA to prepare GA intercalated LDH (GA-LDH) desired, where the pH was adjusted to 8.0 in order to deprotonate GA to form gallate anion. According to the XRD analysis, GA-LDH showed well-developed (00l) diffraction peaks with a basal spacing of 1.15 nm, which was estimated to be larger than that of the pristine LDH (0.88 nm), indicating that gallate molecules were incorporated into LDH layers with perpendicular orientation. From the FT-IR spectra it was found that gallic acid was completely deprotonated into gallate, and stabilized in between LDH lattices via electrostatic interaction. The content of GA in GA-LDH was determined to be around 23 wt% by UV-vis spectroscopic study, which was also confirmed by HPLC analysis. According to the in-vitro release of GA out of GA-LDH in PBS solution (pH 7.4) at 4 °C, GA was sustainably released from GA-LDH nanohybrid up to 86% within 72 h. The antioxidant property of GA-LDH was almost the same with that of intact GA which was examined by DPPH. The photostability of GA-LDH under UV light irradiation was immensely enhanced compared to intact GA. It is, therefore, concluded that the present GA-LDH nanohybrid can be considered as an excellent antioxidant material with high chemical- and photo-stabilities, and controlled release property.

Processing of analogues of plume fallout in cold regions of Enceladus by energetic electrons

NASA Astrophysics Data System (ADS)

Bergantini, A.; Pilling, S.; Nair, B. G.; Mason, N. J.; Fraser, H. J.

2014-10-01

Context. Enceladus, a small icy moon of Saturn, is one of the most remarkable bodies in the solar system. This moon is a geologically active object, and despite the lower temperatures on most of its surface, the geothermally heated south polar region presents geysers that spouts a plume made of water (~90%), carbon dioxide, methane, ammonia, and methanol, among other molecules. Most of the upward-moving particles do not have the velocity to escape from the gravitational influence of the moon and fall back to the surface. The molecules in the ice are continuously exposed to ionizing radiation, such as UV and X-rays photons, cosmic rays, and electrons. Over time, the ionizing radiation promotes molecular bond rupture, destroying and also forming molecules, radicals, and fragments. Aims: We analyse the processing of an ice mixture analogue to the Enceladus fallout ice in cold resurfaced areas (north pole) by 1 keV electrons. The main goal is to search for complex species that have not yet been detected in this moon, and to determine relevant physico-chemical parameters, such as destruction and formation cross-sections and the half-life of the studied molecules in the ice. Methods: The experiment consisted of the electron irradiation of an Enceladus-like ice mixture (H2O:CO2:CH4:NH3:CH3OH) in an ultra-high vacuum chamber at 20 K. The analysis was made by infrared spectrometry in the mid-infrared region (4000-800 cm-1 or 2.5-12.5 μm). Results: The absolute dissociation cross-sections of the parent molecules, the formation cross-section of daughter species, and the half-life of the parental species in a simulated Enceladus irradiation scenario were determined. Among the produced species, CO (carbon monoxide), OCN- (cyanate anion), HCONH2 (formamide), and H2CO (formaldehyde) were tentatively detected.

Organic Compounds Produced by Photolysis of Realistic Interstellar and Cometary Ice Analogs Containing Methanol

NASA Technical Reports Server (NTRS)

Bernstein, Max P.; Sandford, Scott A.; Allamandola, Louis J.; Chang, Sherwood; Scharberg, Maureen A.

1995-01-01

The InfraRed (IR) spectra of UltraViolet (UV) and thermally processed, methanol-containing interstellar / cometary ice analogs at temperatures from 12 to 300 K are presented. Infrared spectroscopy, H-1 and C-13 Nuclear Magnetic Resonance (NMR) spectroscopy, and gas chromatography-mass spectrometry indicate that CO (carbon monoxide), CO2 (carbon dioxide), CH4 (methane), HCO (the formyl radical), H2CO (formaldehyde), CH3CH2OH (ethanol), HC([double bond]O)NH2 (formamide), CH3C([double bond]O)NH2 (acetamide), and R[single bond]C[triple bond]N (nitriles) are formed. In addition, the organic materials remaining after photolyzed ice analogs have been warmed to room temperature contain (in rough order of decreasing abundance), (1) hexamethylenetetramine (HMT, C6H12N4), (2) ethers, alcohols, and compounds related to PolyOxyMethylene (POM, ([single bond]CH2O[single bond](sub n)), and (3) ketones (R[single bond]C([double bond]O)[single bond]R') and amides (H2NC([double bond]O)[single bond]R). Most of the carbon in these residues is thought to come from the methanol in the original ice. Deuterium and C-13 isotopic labeling demonstrates that methanol is definitely the source of carbon in HMT. High concentrations of HMT in interstellar and cometary ices could have important astrophysical consequences. The ultraviolet photolysis of HMT frozen in H2O ice readily produces the 'XCN' band observed in the spectra of protostellar objects and laboratory ices, as well as other nitriles. Thus, HMT may be a precursor of XCN and a source of CN in comets and the interstellar medium. Also, HMT is known to hydrolyze under acidic conditions to yield ammonia, formaldehyde, and amino acids. Thus, HMT may be a significant source of prebiogenic compounds on asteroidal parent bodies. A potential mechanism for the radiative formation of HMT in cosmic ices is outlined.

Metabolomics Investigation of an Association of Induced Features and Corresponding Fungus during the Co-culture of Trametes versicolor and Ganoderma applanatum

PubMed Central

Xu, Xiao-Yan; Shen, Xiao-Ting; Yuan, Xiao-Jie; Zhou, Yuan-Ming; Fan, Huan; Zhu, Li-Ping; Du, Feng-Yu; Sadilek, Martin; Yang, Jie; Qiao, Bin; Yang, Song

2018-01-01

The co-culture of Trametes versicolor and Ganoderma applanatum is a model of intense basidiomycete interaction, which induces many newly synthesized or highly produced features. Currently, one of the major challenges is an identification of the origin of induced features during the co-culture. Herein, we report a 13C-dynamic labeling analysis used to determine an association of induced features and corresponding fungus even if the identities of metabolites were not available or almost nothing was known of biochemical aspects. After the co-culture of T. versicolor and G. applanatum for 10 days, the mycelium pellets of T. versicolor and G. applanatum were sterilely harvested and then mono-cultured in the liquid medium containing half fresh medium with 13C-labeled glucose as carbon source and half co-cultured supernatants collected on day 10. 13C-labeled metabolome analyzed by LC-MS revealed that 31 induced features including 3-phenyllactic acid and orsellinic acid were isotopically labeled in the mono-culture after the co-culture stimulation. Twenty features were derived from T. versicolor, 6 from G. applanatum, and 5 features were synthesized by both T. versicolor and G. applanatum. 13C-labeling further suggested that 12 features such as previously identified novel xyloside [N-(4-methoxyphenyl)formamide 2-O-beta-D-xyloside] were likely induced through the direct physical interaction of mycelia. Use of molecular network analysis combined with 13C-labeling provided an insight into the link between the generation of structural analogs and producing fungus. Compound 1 with m/z 309.0757, increased 15.4-fold in the co-culture and observed 13C incorporation in the mono-culture of both T. versicolor and G. applanatum, was purified and identified as a phenyl polyketide, 2,5,6-trihydroxy-4, 6-diphenylcyclohex-4-ene-1,3-dione. The biological activity study indicated that this compound has a potential to inhibit cell viability of leukemic cell line U937. The current work sets an important basis for further investigations including novel metabolites discovery and biosynthetic capacity improvement. PMID:29375514

The Influence of Selective Laser Melting (SLM) Process Parameters on In-Vitro Cell Response.

PubMed

Wysocki, Bartłomiej; Idaszek, Joanna; Zdunek, Joanna; Rożniatowski, Krzysztof; Pisarek, Marcin; Yamamoto, Akiko; Święszkowski, Wojciech

2018-05-30

The use of laser 3D printers is very perspective in the fabrication of solid and porous implants made of various polymers, metals, and its alloys. The Selective Laser Melting (SLM) process, in which consolidated powders are fully melted on each layer, gives the possibility of fabrication personalized implants based on the Computer Aid Design (CAD) model. During SLM fabrication on a 3D printer, depending on the system applied, there is a possibility for setting the amount of energy density (J/mm³) transferred to the consolidated powders, thus controlling its porosity, contact angle and roughness. In this study, we have controlled energy density in a range 8⁻45 J/mm³ delivered to titanium powder by setting various levels of laser power (25⁻45 W), exposure time (20⁻80 µs) and distance between exposure points (20⁻60 µm). The growing energy density within studied range increased from 63 to 90% and decreased from 31 to 13 µm samples density and Ra parameter, respectively. The surface energy 55⁻466 mN/m was achieved with contact angles in range 72⁻128° and 53⁻105° for water and formamide, respectively. The human mesenchymal stem cells (hMSCs) adhesion after 4 h decreased with increasing energy density delivered during processing within each parameter group. The differences in cells proliferation were clearly seen after a 7-day incubation. We have observed that proliferation was decreasing with increasing density of energy delivered to the samples. This phenomenon was explained by chemical composition of oxide layers affecting surface energy and internal stresses. We have noticed that TiO₂, which is the main oxide of raw titanium powder, disintegrated during selective laser melting process and oxygen was transferred into metallic titanium. The typical for 3D printed parts post-processing methods such as chemical polishing in hydrofluoric (HF) or hydrofluoric/nitric (HF/HNO₃) acid solutions and thermal treatments were used to restore surface chemistry of raw powders and improve surface.

Evolution of Interstellar Grains

NASA Technical Reports Server (NTRS)

Allamandola, Lou J.; DeVincenzi, Donald L. (Technical Monitor)

1998-01-01

During the past two decades observations combined with laboratory simulations, have revolutionized our understanding of interstellar ice and dust, the raw materials from which planets, comets and stars form. Most interstellar material is concentrated in large molecular clouds where simple molecules are formed by dust-grain and gas-phase reactions. Gaseous species striking the cold (10K) dust stick, forming an icy grain mantle. This accretion, coupled with UV photolysis, produces a complex chemical mixture containing volatile, non-volatile, and isotopically fractionated species. Ices in molecular clouds contain the very simple molecules H2O, CH3OH, CO, CO2, H2, and perhaps some NH3 and H2CO, as well as more complex species. The evidence for these compounds, as well as carbon-rich materials, will be reviewed and the possible connections with comets and meteorites will be presented in the first part of the talk . The second part of the presentation will focus on interstellar/precometary ice photochemical evolution and the species likely to be found in comets. The chemical composition and photochemical evolution of realistic interstellar/pre-cometary ice analogs will be discussed. Ultraviolet photolysis of these ices produces H2, H2CO, CO2, CO, CH4, HCO, and more complex molecules. When ices representative of interstellar grains and comets are exposed to UV radiation at low temperature a series of moderately complex organic molecules are formed in the ice including: CH3CH2OH (ethanol), HC(=O)NH2 (formamide), CH3C(=O)NH2 (acetamide), and R-C=N (nitriles). Several of these are already known to be in the interstellar medium, and their presence indicates the importance of grain processing. After warming to room temperature an organic residue remains. This is composed primarily of hexamethylenetetramine (HMT, C6H12N4), with lesser amounts of polyoxymethylene-related species (POMs), amides, and ketones. This is in sharp contrast to the organic residues produced by irradiating unrealistic interstellar ice analogs or thermally promoted polymerization-type reactions in unirradiated realistic ice mixtures.

Search for liquids electrospraying the smallest possible nanodrops in vacuo

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

Alonso-Matilla, R.; Fernández-García, J.; Congdon, H.

2014-12-14

Prior work with electrosprays in vacuum of mixtures of ionic liquids (ILs) and the moderately high boiling point (T{sub b}) solvents formamide (FM) and propylene carbonate (PC) (T{sub b} of 210 and 241 °C) has shown that the charged drops produced have reasonably narrow charge/mass distributions, controllable over a wide mass/charge range. This enables their use as propellants in electrical propulsion with specific impulse I{sub sp} varying from a few hundred to a few thousand seconds (10 kV beam energy) and with excellent propulsion efficiency. However, some limitations are imposed by the finite room temperature volatility of FM and PC. Here, wemore » seek improved performance from propellants based on the polar but viscous solvent Sulfolane (SF; ε = 43.2, μ = 10.3 cP) and the low viscosity but less polar solvent tributyl phosphate (TBP; ε = 8.9, μ = 3.4 cP), both with T{sub b} > 280 °C. Neither TBP nor its low viscosity mixtures with SF achieve the electrical conductivities needed to yield high I{sub sp}. Most ILs used in SF/IL mixtures tested were based on the 1-ethyl-3-methylimidazolium (EMI) or 1,3-dimethylimidazolium (DMI) cations, including EMI-BF{sub 4}, EMI-N(CN){sub 2}, and DMI-N(CN){sub 2}. These combinations reach high conductivities, some approaching 3 S/m, but have limited propulsive performance because evaporation of ions directly from the electrified meniscus produces undesirable mixed beams of drops and ions. Exceptional characteristics are found in mixtures of SF with ethylammonium nitrate (EAN), where the small EA{sup +} cation is strongly bound to the solvent, greatly delaying ion evaporation from the meniscus. Evidence on the formation of nano-jets with diameters as small as 1 nm is seen. Although unprecedented, this finding agrees with what would be expected if ion evaporation were suppressed. SF/EAN mixtures thus provide the best available sources to produce the smallest possible nanodrops, minimally polluted by ions.« less

Characterizing and locating air pollution sources in a complex industrial district using optical remote sensing technology and multivariate statistical modeling.

PubMed

Chang, Pao-Erh Paul; Yang, Jen-Chih Rena; Den, Walter; Wu, Chang-Fu

2014-09-01

Emissions of volatile organic compounds (VOCs) are most frequent environmental nuisance complaints in urban areas, especially where industrial districts are nearby. Unfortunately, identifying the responsible emission sources of VOCs is essentially a difficult task. In this study, we proposed a dynamic approach to gradually confine the location of potential VOC emission sources in an industrial complex, by combining multi-path open-path Fourier transform infrared spectrometry (OP-FTIR) measurement and the statistical method of principal component analysis (PCA). Close-cell FTIR was further used to verify the VOC emission source by measuring emitted VOCs from selected exhaust stacks at factories in the confined areas. Multiple open-path monitoring lines were deployed during a 3-month monitoring campaign in a complex industrial district. The emission patterns were identified and locations of emissions were confined by the wind data collected simultaneously. N,N-Dimethyl formamide (DMF), 2-butanone, toluene, and ethyl acetate with mean concentrations of 80.0 ± 1.8, 34.5 ± 0.8, 103.7 ± 2.8, and 26.6 ± 0.7 ppbv, respectively, were identified as the major VOC mixture at all times of the day around the receptor site. As the toxic air pollutant, the concentrations of DMF in air samples were found exceeding the ambient standard despite the path-average effect of OP-FTIR upon concentration levels. The PCA data identified three major emission sources, including PU coating, chemical packaging, and lithographic printing industries. Applying instrumental measurement and statistical modeling, this study has established a systematic approach for locating emission sources. Statistical modeling (PCA) plays an important role in reducing dimensionality of a large measured dataset and identifying underlying emission sources. Instrumental measurement, however, helps verify the outcomes of the statistical modeling. The field study has demonstrated the feasibility of using multi-path OP-FTIR measurement. The wind data incorporating with the statistical modeling (PCA) may successfully identify the major emission source in a complex industrial district.

An alternative origin for extraterrestrial biomolecules from the hot and ionized photosphere of the protosolar nebula.

NASA Astrophysics Data System (ADS)

Bekaert, D. V.; Derenne, S.; Tissandier, L.; Marrocchi, Y.; Anquetil, C.; Marty, B.

2017-12-01

Organic matter (OM) synthesized from plasma experiments (so-called Nebulotron) can provide an insight into the processes of organosynthesis within the ionized gas phase of the protosolar nebula (PSN). Organic materials recovered from Nebulotron experiments have a record of success in reproducing key features of chondritic insoluble organic matter (IOM), including the aromatic/aliphatic and soluble/insoluble ratios [1], the occurrence of D/H hot and cold spots [2], spectral features as well as elementary and isotopic patterns observed in trapped noble gases [3]. However, up until now little attention has been paid to the soluble fraction of the recovered OM (SOM). In this study, a high-vacuum plasma setting was designed to produce organic condensates from a CO-N2-H2 gas mixture reminiscent of the PSN. The chemical diversity of the synthetized SOM has been investigated by gas chromatography - mass spectrometry. Our results show that a large range of biomolecules detected in meteorites and comets could have been directly synthetized from the gas phase of the PSN under high ionization rates and temperatures > 800 K. Among other molecules, urea, formamide, glycerol, hydantoin, carboxylic acids, as well as amino acid and nucleobase derivatives are reported. While photochemical processing of interstellar icy grains or asteroidal aqueous alteration are often advocated for the origin of biomolecules in extraterrestrial samples, our results suggest that biomolecule production was also effective in the hot and ionized photosphere of the PSN. Interestingly, solid-state 13C Nuclear Magnetic Resonance spectra of the Nebulotron IOM, indicates that they are very low in aromatics relative to extraterrestrial samples. Given that aromatic units in meteoritic IOM likely result from the cyclization/aromatization of aliphatic chains in the gas [1], Nebulotron-like aliphatic materials could represent the initial precursors of meteoritic OM [4]. These materials would be widespread in the protoplanetary disk through turbulent diffusion, thus representing potential precursors of meteoritic organics before their subsequent modification by secondary parent body processes. [1] Biron et al. (2015) MAPS 50(8); [2] Robert et al. (2017) PNAS 114(5); [3] Kuga et al. (2015) PNAS 112(23); [4] Derenne and Robert (2010) MAPS 45(9).

HYBRIDIZATION PROPERTIES OF DNA SEQUENCES DIRECTING THE SYNTHESIS OF MESSENGER RNA AND HETEROGENEOUS NUCLEAR RNA

PubMed Central

Greenberg, Jay R.; Perry, Robert P.

1971-01-01

The relationship of the DNA sequences from which polyribosomal messenger RNA (mRNA) and heterogeneous nuclear RNA (NRNA) of mouse L cells are transcribed was investigated by means of hybridization kinetics and thermal denaturation of the hybrids. Hybridization was performed in formamide solutions at DNA excess. Under these conditions most of the hybridizing mRNA and NRNA react at values of Dot (DNA concentration multiplied by time) expected for RNA transcribed from the nonrepeated or rarely repeated fraction of the genome. However, a fraction of both mRNA and NRNA hybridize at values of Dot about 10,000 times lower, and therefore must be transcribed from highly redundant DNA sequences. The fraction of NRNA hybridizing to highly repeated sequences is about 1.7 times greater than the corresponding fraction of mRNA. The hybrids formed by the rapidly reacting fractions of both NRNA and mRNA melt over a narrow temperature range with a midpoint about 11°C below that of native L cell DNA. This indicates that these hybrids consist of partially complementary sequences with approximately 11% mismatching of bases. Hybrids formed by the slowly reacting fraction of NRNA melt within 4°–6°C of native DNA, indicating very little, if any, mismatching of bases. Hybrids of the slowly reacting components of mRNA, formed under conditions of sufficiently low RNA input, have a high thermal stability, similar to that observed for hybrids of the slowly reacting NRNA component. However, when higher inputs of mRNA are used, hybrids are formed which have a strikingly lower thermal stability. This observation can be explained by assuming that there is sufficient similarity among the relatively rare DNA sequences coding for mRNA so that under hybridization conditions, in which these DNA sequences are not truly in excess, reversible hybrids exhibiting a considerable amount of mispairing are formed. The fact that a comparable phenomenon has not been observed for NRNA may mean that there is less similarity among the relatively rare DNA sequences coding for NRNA than there is among the rare sequences coding for mRNA. PMID:4999767

Mineral Grains, Dimples, and Hot Volcanic Organic Streams: Dynamic Geological Backstage of Macromolecular Evolution.

PubMed

Skoblikow, Nikolai E; Zimin, Andrei A

2018-04-01

The hypothesis of hot volcanic organic stream as the most probable and geologically plausible environment for abiogenic polycondensation is proposed. The primary synthesis of organic compounds is considered as result of an explosive volcanic (perhaps, meteorite-induced) eruption. The eruption was accompanied by a shock wave propagating in the primeval atmosphere and resulting in the formation of hot cloud of simple organic compounds-aldehydes, alcohols, amines, amino alcohols, nitriles, and amino acids-products, which are usually obtained under the artificial conditions in the spark-discharge experiments. The subsequent cooling of the organic cloud resulted in a gradual condensation and a serial precipitation of organic compounds (in order of decreasing boiling point values) into the liquid phase forming a hot, viscous and muddy organic stream (named "lithorheos"). That stream-even if the time of its existence was short-is considered here as a geologically plausible environment for abiogenic polycondensation. The substances successively prevailing in such a stream were cyanamide, acetamide, formamide, glycolonitrile, acetonitrile. An important role was played by mineral (especially, phosphate-containing) grains (named "lithosomes"), whose surface was modified with heterocyclic nitrogen compounds synthesized in the course of eruption. When such grains got into hot organic streams, their surface catalytic centers (named "lithozymes") played a decisive role in the emergence, facilitation and maintenance of prebiotic reactions and key processes characteristic of living systems. Owing to its cascade structure, the stream was a factor underlying the formation of mineral-polymeric aggregates (named "lithocytes") in the small natural streambed cavities (dimples)-as well as a factor of their further spread within larger geological locations which played a role of chemo-ecological niches. All three main stages of prebiotic evolution (primary organic synthesis, polycondensation, and formation of proto-cellular structures) are combined within a common dynamic geological process. We suppose macromolecular evolution had an extremely fast, "flash" start: the period from volcanic eruption to formation of lithocyte "populations" took not million years but just several tens of minutes. The scenario proposed can be verified experimentally with a three-module setup working with principles of dynamic (flow) chemistry in its core element.

The Na conductance in the sarcolemma and the transverse tubular system membranes of mammalian skeletal muscle fibers

PubMed Central

DiFranco, Marino

2011-01-01

Na (and Li) currents and fluorescence transients were recorded simultaneously under voltage-clamp conditions from mouse flexor digitorum brevis fibers stained with the potentiometric dye di-8-ANEPPS to investigate the distribution of Na channels between the surface and transverse tubular system (TTS) membranes. In fibers rendered electrically passive, voltage pulses resulted in step-like fluorescence changes that were used to calibrate the dye response. The effects of Na channel activation on the TTS voltage were investigated using Li, instead of Na, because di-8-ANEPPS transients show anomalies in the presence of the latter. Na and Li inward currents (INa, ILi; using half of the physiological ion concentration) showed very steep voltage dependences, with no reversal for depolarizations beyond the calculated equilibrium potential, suggesting that most of the current originates from a noncontrolled membrane compartment. Maximum peak ILi was ∼30% smaller than for INa, suggesting a Li-blocking effect. ILi activation resulted in the appearance of overshoots in otherwise step-like di-8-ANEPPS transients. Overshoots had comparable durations and voltage dependence as those of ILi. Simultaneously measured maximal overshoot and peak ILi were 54 ± 5% and 773 ± 53 µA/cm2, respectively. Radial cable model simulations predicted the properties of ILi and di-8-ANEPPS transients when TTS access resistances of 10–20 Ωcm2, and TTS-to-surface Na permeability density ratios in the range of 40:60 to 70:30, were used. Formamide-based osmotic shock resulted in incomplete detubulation. However, results from a subpopulation of treated fibers (low capacitance) provide confirmatory evidence that a significant proportion of ILi, and the overshoot in the optical signals, arises from the TTS in normal fibers. The quantitative evaluation of the distribution of Na channels between the sarcolemma and the TTS membranes, as provided here, is crucial for the understanding of the radial and longitudinal propagation of the action potential, which ultimately govern the mechanical activation of muscle in normal and diseased conditions. PMID:21948948

Measuring molecular abundances in comet C/2014 Q2 (Lovejoy) using the APEX telescope

NASA Astrophysics Data System (ADS)

de Val-Borro, M.; Milam, S. N.; Cordiner, M. A.; Charnley, S. B.; Coulson, I. M.; Remijan, A. J.; Villanueva, G. L.

2018-02-01

Comet composition provides critical information on the chemical and physical processes that took place during the formation of the Solar system. We report here on millimetre spectroscopic observations of the long-period bright comet C/2014 Q2 (Lovejoy) using the Atacama Pathfinder Experiment (APEX) band 1 receiver between 2015 January UT 16.948 and 18.120, when the comet was at heliocentric distance of 1.30 au and geocentric distance of 0.53 au. Bright comets allow for sensitive observations of gaseous volatiles that sublimate in their coma. These observations allowed us to detect HCN, CH3OH (multiple transitions), H2CO and CO, and to measure precise molecular production rates. Additionally, sensitive upper limits were derived on the complex molecules acetaldehyde (CH3CHO) and formamide (NH2CHO) based on the average of the strongest lines in the targeted spectral range to improve the signal-to-noise ratio. Gas production rates are derived using a non-LTE molecular excitation calculation involving collisions with H2O and radiative pumping that becomes important in the outer coma due to solar radiation. We find a depletion of CO in C/2014 Q2 (Lovejoy) with a production rate relative to water of 2.0 per cent, and relatively low abundances of Q(HCN)/Q(H2O), 0.1 per cent, and Q(H2CO)/Q(H2O), 0.2 per cent. In contrast, the CH3OH relative abundance Q(CH3OH)/Q(H2O), 2.2 per cent, is close to the mean value observed in other comets. The measured production rates are consistent with values derived for this object from other facilities at similar wavelengths taking into account the difference in the fields of view. Based on the observed mixing ratios of organic molecules in four bright comets including C/2014 Q2, we find some support for atom addition reactions on cold dust being the origin of some of the molecules.

Metabolomics Investigation of an Association of Induced Features and Corresponding Fungus during the Co-culture of Trametes versicolor and Ganoderma applanatum.

PubMed

Xu, Xiao-Yan; Shen, Xiao-Ting; Yuan, Xiao-Jie; Zhou, Yuan-Ming; Fan, Huan; Zhu, Li-Ping; Du, Feng-Yu; Sadilek, Martin; Yang, Jie; Qiao, Bin; Yang, Song

2017-01-01

The co-culture of Trametes versicolor and Ganoderma applanatum is a model of intense basidiomycete interaction, which induces many newly synthesized or highly produced features. Currently, one of the major challenges is an identification of the origin of induced features during the co-culture. Herein, we report a 13 C-dynamic labeling analysis used to determine an association of induced features and corresponding fungus even if the identities of metabolites were not available or almost nothing was known of biochemical aspects. After the co-culture of T. versicolor and G. applanatum for 10 days, the mycelium pellets of T. versicolor and G. applanatum were sterilely harvested and then mono-cultured in the liquid medium containing half fresh medium with 13 C-labeled glucose as carbon source and half co-cultured supernatants collected on day 10. 13 C-labeled metabolome analyzed by LC-MS revealed that 31 induced features including 3-phenyllactic acid and orsellinic acid were isotopically labeled in the mono-culture after the co-culture stimulation. Twenty features were derived from T. versicolor , 6 from G. applanatum , and 5 features were synthesized by both T. versicolor and G. applanatum . 13 C-labeling further suggested that 12 features such as previously identified novel xyloside [N-(4-methoxyphenyl)formamide 2-O-beta-D-xyloside] were likely induced through the direct physical interaction of mycelia. Use of molecular network analysis combined with 13 C-labeling provided an insight into the link between the generation of structural analogs and producing fungus. Compound 1 with m/z 309.0757, increased 15.4-fold in the co-culture and observed 13 C incorporation in the mono-culture of both T. versicolor and G. applanatum , was purified and identified as a phenyl polyketide, 2,5,6-trihydroxy-4, 6-diphenylcyclohex-4-ene-1,3-dione. The biological activity study indicated that this compound has a potential to inhibit cell viability of leukemic cell line U937. The current work sets an important basis for further investigations including novel metabolites discovery and biosynthetic capacity improvement.

Application of Reverse Transcriptase-PCR-DGGE as a rapid method for routine determination of Vibrio spp. in foods.

PubMed

Chahorm, Kanchana; Prakitchaiwattana, Cheunjit

2018-01-02

The aim of this research was to evaluate the feasibility of PCR-DGGE and Reverse Transcriptase-PCR-DGGE techniques for rapid detection of Vibrio species in foods. Primers GC567F and 680R were initially evaluated for amplifying DNA and cDNA of ten references Vibrio species by PCR method. The GC-clamp PCR amplicons were separated according to their sequences by the DGGE using 10% (w/v) polyacrylamide gel containing 45-70% urea and formamide denaturants. Two pair of Vibrio species, which could not be differentiated on the gel, was Vibrio fluvialis - Vibrio furnissii and Vibrio parahaemolyticus - Vibrio harveyi. To determine the detection limit, in the community of 10 reference strains containing the same viable population, distinct DNA bands of 3 species; Vibrio cholerae, Vibrio mimicus and Vibrio alginolyticus were consistently observed by PCR-DGGE technique. In fact, 5 species; Vibrio cholerae, Vibrio mimicus, Vibrio alginolyticus, Vibrio parahaemolyticus and Vibrio fluvialis consistently observed by Reverse Transcriptase-PCR-DGGE. In the community containing different viable population increasing from 10 2 to 10 5 CFU/mL, PCR-DGGE analysis only detected the two most prevalent species, while RT-PCR-DGGE detected the five most prevalent species. Therefore, Reverse Transcriptase-PCR-DGGE was also selected for detection of various Vibrio cell conditions, including viable cell (VC), injured cells from frozen cultures (IVC) and injured cells from frozen cultures with pre-enrichment (PIVC). It was found that cDNA band of all cell conditions gave the same migratory patterns, except that multiple cDNA bands of Plesiomonas shigelloides under IVC and PIVC conditions were found. When Reverse Transcriptase-PCR-DGGE was used for detecting Vibrio parahaemolyticus in the pathogen-spiked food samples, Vibrio parahaemolyticus could be detected in the spiked samples containing at least 10 2 CFU/g of this pathogen. The results obtained also corresponded to standard method (USFDA, 2004). In comparison with the detection of the Vibrio profiles in fourteen food samples using standard method, Reverse Transcriptase-PCR-DGGE resulted in 100%, 75% and 50% similarity in 3, 1 and 6 food samples, respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

Nanofibrous poly(lactide-co-glycolide) membranes loaded with diamond nanoparticles as promising substrates for bone tissue engineering

PubMed Central

Parizek, Martin; Douglas, Timothy EL; Novotna, Katarina; Kromka, Alexander; Brady, Mariea A; Renzing, Andrea; Voss, Eske; Jarosova, Marketa; Palatinus, Lukas; Tesarek, Pavel; Ryparova, Pavla; Lisa, Věra; dos Santos, Ana M; Bacakova, Lucie

2012-01-01

Background Nanofibrous scaffolds loaded with bioactive nanoparticles are promising materials for bone tissue engineering. Methods In this study, composite nanofibrous membranes containing a copolymer of L-lactide and glycolide (PLGA) and diamond nanoparticles were fabricated by an electrospinning technique. PLGA was dissolved in a mixture of methylene chloride and dimethyl formamide (2:3) at a concentration of 2.3 wt%, and nanodiamond (ND) powder was added at a concentration of 0.7 wt% (about 23 wt% in dry PLGA). Results In the composite scaffolds, the ND particles were either arranged like beads in the central part of the fibers or formed clusters protruding from the fibers. In the PLGA-ND membranes, the fibers were thicker (diameter 270 ± 9 nm) than in pure PLGA meshes (diameter 218 ± 4 nm), but the areas of pores among these fibers were smaller than in pure PLGA samples (0.46 ± 0.02 μm2 versus 1.28 ± 0.09 μm2 in pure PLGA samples). The PLGA-ND membranes showed higher mechanical resistance, as demonstrated by rupture tests of load and deflection of rupture probe at failure. Both types of membranes enabled the attachment, spreading, and subsequent proliferation of human osteoblast-like MG-63 cells to a similar extent, although these values were usually lower than on polystyrene dishes. Nevertheless, the cells on both types of membranes were polygonal or spindle-like in shape, and were distributed homogeneously on the samples. From days 1–7 after seeding, their number rose continuously, and at the end of the experiment, these cells were able to create a confluent layer. At the same time, the cell viability, evaluated by a LIVE/DEAD viability/cytotoxicity kit, ranged from 92% to 97% on both types of membranes. In addition, on PLGA-ND membranes, the cells formed well developed talin-containing focal adhesion plaques. As estimated by the determination of tumor necrosis factor-alpha levels in the culture medium and concentration of intercellular adhesion molecule-1, MG-63 cells, and RAW 264.7 macrophages on these membranes did not show considerable inflammatory activity. Conclusion This study shows that nanofibrous PLGA membranes loaded with diamond nanoparticles have interesting potential for use in bone tissue engineering. PMID:22619532

Generalization of the Gaussian electrostatic model: Extension to arbitrary angular momentum, distributed multipoles, and speedup with reciprocal space methods

NASA Astrophysics Data System (ADS)

Cisneros, G. Andrés; Piquemal, Jean-Philip; Darden, Thomas A.

2006-11-01

The simulation of biological systems by means of current empirical force fields presents shortcomings due to their lack of accuracy, especially in the description of the nonbonded terms. We have previously introduced a force field based on density fitting termed the Gaussian electrostatic model-0 (GEM-0) J.-P. Piquemal et al. [J. Chem. Phys. 124, 104101 (2006)] that improves the description of the nonbonded interactions. GEM-0 relies on density fitting methodology to reproduce each contribution of the constrained space orbital variation (CSOV) energy decomposition scheme, by expanding the electronic density of the molecule in s-type Gaussian functions centered at specific sites. In the present contribution we extend the Coulomb and exchange components of the force field to auxiliary basis sets of arbitrary angular momentum. Since the basis functions with higher angular momentum have directionality, a reference molecular frame (local frame) formalism is employed for the rotation of the fitted expansion coefficients. In all cases the intermolecular interaction energies are calculated by means of Hermite Gaussian functions using the McMurchie-Davidson [J. Comput. Phys. 26, 218 (1978)] recursion to calculate all the required integrals. Furthermore, the use of Hermite Gaussian functions allows a point multipole decomposition determination at each expansion site. Additionally, the issue of computational speed is investigated by reciprocal space based formalisms which include the particle mesh Ewald (PME) and fast Fourier-Poisson (FFP) methods. Frozen-core (Coulomb and exchange-repulsion) intermolecular interaction results for ten stationary points on the water dimer potential-energy surface, as well as a one-dimensional surface scan for the canonical water dimer, formamide, stacked benzene, and benzene water dimers, are presented. All results show reasonable agreement with the corresponding CSOV calculated reference contributions, around 0.1 and 0.15kcal/mol error for Coulomb and exchange, respectively. Timing results for single Coulomb energy-force calculations for (H2O)n, n =64, 128, 256, 512, and 1024, in periodic boundary conditions with PME and FFP at two different rms force tolerances are also presented. For the small and intermediate auxiliaries, PME shows faster times than FFP at both accuracies and the advantage of PME widens at higher accuracy, while for the largest auxiliary, the opposite occurs.

Nanofibrous poly(lactide-co-glycolide) membranes loaded with diamond nanoparticles as promising substrates for bone tissue engineering.

PubMed

Parizek, Martin; Douglas, Timothy E L; Novotna, Katarina; Kromka, Alexander; Brady, Mariea A; Renzing, Andrea; Voss, Eske; Jarosova, Marketa; Palatinus, Lukas; Tesarek, Pavel; Ryparova, Pavla; Lisa, Věra; dos Santos, Ana M; Warnke, Patrick H; Bacakova, Lucie

2012-01-01

Nanofibrous scaffolds loaded with bioactive nanoparticles are promising materials for bone tissue engineering. In this study, composite nanofibrous membranes containing a copolymer of L-lactide and glycolide (PLGA) and diamond nanoparticles were fabricated by an electrospinning technique. PLGA was dissolved in a mixture of methylene chloride and dimethyl formamide (2:3) at a concentration of 2.3 wt%, and nanodiamond (ND) powder was added at a concentration of 0.7 wt% (about 23 wt% in dry PLGA). In the composite scaffolds, the ND particles were either arranged like beads in the central part of the fibers or formed clusters protruding from the fibers. In the PLGA-ND membranes, the fibers were thicker (diameter 270 ± 9 nm) than in pure PLGA meshes (diameter 218 ± 4 nm), but the areas of pores among these fibers were smaller than in pure PLGA samples (0.46 ± 0.02 μm(2) versus 1.28 ± 0.09 μm(2) in pure PLGA samples). The PLGA-ND membranes showed higher mechanical resistance, as demonstrated by rupture tests of load and deflection of rupture probe at failure. Both types of membranes enabled the attachment, spreading, and subsequent proliferation of human osteoblast-like MG-63 cells to a similar extent, although these values were usually lower than on polystyrene dishes. Nevertheless, the cells on both types of membranes were polygonal or spindle-like in shape, and were distributed homogeneously on the samples. From days 1-7 after seeding, their number rose continuously, and at the end of the experiment, these cells were able to create a confluent layer. At the same time, the cell viability, evaluated by a LIVE/DEAD viability/cytotoxicity kit, ranged from 92% to 97% on both types of membranes. In addition, on PLGA-ND membranes, the cells formed well developed talin-containing focal adhesion plaques. As estimated by the determination of tumor necrosis factor-alpha levels in the culture medium and concentration of intercellular adhesion molecule-1, MG-63 cells, and RAW 264.7 macrophages on these membranes did not show considerable inflammatory activity. This study shows that nanofibrous PLGA membranes loaded with diamond nanoparticles have interesting potential for use in bone tissue engineering.

Overview of VOC emissions and chemistry from PTR-TOF-MS measurements during the SusKat-ABC campaign: high acetaldehyde, ketene, isoprene and isocyanic acid in wintertime air of the Kathmandu Valley

NASA Astrophysics Data System (ADS)

Sarkar, C.; Sinha, V.; Kumar, V.; Rupakheti, M.; Panday, A. K.; Mahata, K.; Rupakheti, D.; Kathayat, B.; Lawrence, M. G.

2015-12-01

During SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley-Atmospheric Brown Clouds) field campaign conducted in the winter of 2012-2013, a comprehensive study was carried out to characterize the chemical composition of ambient Kathmandu air for speciated VOCs by deploying a Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-TOF-MS), the first time to be deployed in South Asia. Due to its high mass resolution (m/Δm > 4200) and temporal resolution (1 minute), 71 ion peaks were detected in the PTR-TOF-MS mass scan data, highlighting the chemical complexity of ambient air in the Valley. Of the 71, 38 species were found to have campaign average concentrations > 200 ppt and were identified based on their spectral characteristics, ambient diel profiles and correlation with specific emission tracers. Distinct diel profiles were observed for the nominal isobaric compounds isoprene (m/z=69.070) and furan (m/z=69.033). Comparison with several sites elsewhere in the world showed mixing ratios of acetaldehyde (~ 9 ppb), acetonitrile (~1 ppb) and isoprene (~ 1 ppb) to be among the highest measured anywhere in the world. Two "new" ambient compounds namely, methanamide (m/z = 46.029) and acetamide (m/z=60.051) which can photochemically produce isocyanic acid in the atmosphere, are reported in this study alongwith nitromethane (a tracer for diesel exhaust) and ketene (a very reactive compound). Two distinct periods were identified during the campaign based on high daytime biogenic emissions of isoprene even in winter and biomass fired brick kiln emissions of acetonitrile, benzene and isocyanic acid. Biomass burning and biomass fired brick kiln emissions were found to be the dominant source for compounds such as propyne, propene, benzene and propanenitrile which correlated strongly with biomass burning tracer acetonitrile (r2 > 0.7). The calculated total VOC OH reactivity was dominated by acetaldehyde (20.1%), ketene (ethenone) (17.1%), isoprene (16.8 %) and propene (15.6%), while oxygenated VOCs and isoprene collectively contributed to more than 70% of the total ozone production potential. The first ambient measurements from any site in South Asia of compounds with significant health effects such as isocyanic acid, formamide, acetamide, naphthalene and nitromethane are reported in this study.

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

Kanatzidis, Mercouri; Riley, Brian; Chun, Jaehun

This report documents the work done under NEUP grant to examine the capability of novel chalcogels and some binary metal chalcogenides as a host matrix for the capture of gaseous iodine and the feasibility of their iodine-laden materials to be converted into a permanent waste form. The presented work was conducted over last two years. A number of novel chalcogels Zn 2Sn 2S 6, Sb 4Sn 4S 12, NiMoS 4, CoMoS 4, antimony sulfide (SbS x) chalcogels, silver functionalized chalcogels and binary metal sulfides (Sb 2S 3) were developed and studies for their iodine absorption efficacies. A new and simplemore » route was devised for the large scale preparation of antimony sulfide chalcogel. The chalcogel was obtained by treating Sb 2S 3 with Na 2S in the presence of water followed by addition of formamide. The obtained gels have a low-density sponge like network of meso porous nature having BET surface area of 125 m 2/g. The chalcogels, silver functionalized chalcogel and the binary metal sulfides were exposed to iodine vapors in a closed container. Silver-functionalized chalcogels and Sb 2S 3 powders showed iodine uptake up to 100 wt%, the highest iodine uptake of 200 wt% was observed for the SbS-III chalcogel. The PXRD patterns of iodine-laden specimens revealed that iodine shows spontaneous chemisorption to the matrix used. The iodine loaded chalcogels and the binary chalcogenides were sealed under vacuum in fused silica ampoules and heated in a temperature controlled furnace. The consolidated products were analyzed by PXRD, energy dispersive spectroscopy (EDS), UV-Vis and Raman spectroscopy. The final products were found to be amorphous in most of the cases with high amount (~4-35 wt%) of iodine and aapproximately ~60- 90 % of the absorbed iodine could be consolidated into the final waste form. Alginate reinforced composite scaffolds with SbS/SnS chalcogels and Sb 2S 3 bulk powder were also fabricated aiming to study their efficacy as host matrices in capturing the gaseous molecular iodine in dynamic mode from nuclear spent fuel. The obtained composites looks robust in comparison to their respective pristine chalcogels and Sb 2S 3 bulk powder.« less

Differential speciation of ferriprotoporphyrin IX in the presence of free base and diprotic 4-aminoquinoline antimalarial drugs

NASA Astrophysics Data System (ADS)

Gildenhuys, Johandie; Müller, Ronel; le Roex, Tanya; de Villiers, Katherine A.

2017-03-01

The crystal structures of the μ-propionato dimer and π-π dimer of ferriprotoporphyrin IX (Fe(III)PPIX) have been determined by single crystal X-ray diffraction (SCD). Both species were obtained in the presence of the synthetic 4-aminoquinoline antimalarial drug, amodiaquine (AQ). The solution that afforded the μ-propionato dimer contained AQ as a free base (i.e. with both quinoline and terminal amine nitrogen atoms neutral). On the other hand, when the diprotic salt of AQ was included in the crystallization medium, the Fe(III)PPIX π-π dimer was obtained. The structure of the μ-propionato dimer, which is the discrete structural unit that constitutes haemozoin (malaria pigment), is identical to that obtained previously in presence of chloroquine free base. We suspect that the drug, via its two available basic sites, facilitates dissociation of one of the two Fe(III)PPIX propionic acid groups to yield a propionate group that is required for reciprocal coordination of the metal centre to form the centrosymmetric dimer. On the other hand, this proton transfer is not possible when the drug is present as a diprotic salt. In this case, the π-π dimer of Fe(III)PPIX is obtained. In the current study, the π-π dimer of haemin (chloro-Fe(III)PPIX) was obtained as a DMF solvate from non-aqueous aprotic solution (dimethyl formamide and chloroform), however the π-π dimer is also known to exist in aqueous solution (as aqua- or hydroxo-Fe(III)PPIX), where it is purportedly involved in the nucleation of haemozoin. We have been able to unambiguously determine the positions of all non-hydrogen atoms, as well as locate or assign all hydrogen atoms in the structure of the π-π dimer, which was not possible in the SCD structure of haemin reported by Koenig in 1965 owing to disorder in the vinyl and methyl substituents. Interestingly, no disorder in the methyl and vinyl groups is observed in the current structure. Both the π-π and μ-propionato dimers of Fe(III)PPIX are important species in the haem detoxification pathway in the malaria parasite and other blood-feeding organisms, and the structural insight gained in this study may assist target-driven design of new chemotherapeutic agents.

Generalization of the Gaussian electrostatic model: Extension to arbitrary angular momentum, distributed multipoles, and speedup with reciprocal space methods

PubMed Central

Cisneros, G. Andrés; Piquemal, Jean-Philip; Darden, Thomas A.

2007-01-01

The simulation of biological systems by means of current empirical force fields presents shortcomings due to their lack of accuracy, especially in the description of the nonbonded terms. We have previously introduced a force field based on density fitting termed the Gaussian electrostatic model-0 (GEM-0) J.-P. Piquemal et al. [J. Chem. Phys. 124, 104101 (2006)] that improves the description of the nonbonded interactions. GEM-0 relies on density fitting methodology to reproduce each contribution of the constrained space orbital variation (CSOV) energy decomposition scheme, by expanding the electronic density of the molecule in s-type Gaussian functions centered at specific sites. In the present contribution we extend the Coulomb and exchange components of the force field to auxiliary basis sets of arbitrary angular momentum. Since the basis functions with higher angular momentum have directionality, a reference molecular frame (local frame) formalism is employed for the rotation of the fitted expansion coefficients. In all cases the intermolecular interaction energies are calculated by means of Hermite Gaussian functions using the McMurchie-Davidson [J. Comput. Phys. 26, 218 (1978)] recursion to calculate all the required integrals. Furthermore, the use of Hermite Gaussian functions allows a point multipole decomposition determination at each expansion site. Additionally, the issue of computational speed is investigated by reciprocal space based formalisms which include the particle mesh Ewald (PME) and fast Fourier-Poisson (FFP) methods. Frozen-core (Coulomb and exchange-repulsion) intermolecular interaction results for ten stationary points on the water dimer potential-energy surface, as well as a one-dimensional surface scan for the canonical water dimer, formamide, stacked benzene, and benzene water dimers, are presented. All results show reasonable agreement with the corresponding CSOV calculated reference contributions, around 0.1 and 0.15 kcal/mol error for Coulomb and exchange, respectively. Timing results for single Coulomb energy-force calculations for (H2O)n, n=64, 128, 256, 512, and 1024, in periodic boundary conditions with PME and FFP at two different rms force tolerances are also presented. For the small and intermediate auxiliaries, PME shows faster times than FFP at both accuracies and the advantage of PME widens at higher accuracy, while for the largest auxiliary, the opposite occurs. PMID:17115732

Development and study of the displaced foam dispersion methodology for the manufacture of multiscale/hybrid composites

NASA Astrophysics Data System (ADS)

McCrary-Dennis, Micah C. L.

Incorporating nanostructured functional constituents within polymers has become extensive in processes and products for manufacturing composites. The conception of carbon nanotubes (CNTs) and their heralded attributes yielding property enhancements to the carrier system is leading many industries and research endeavors. Displaced Foam Dispersion (DFD) methodology is a novel and effective approach to facilitating the incorporation of CNTs within fiber reinforced polymer composites (FRPC). The methodology consists of six separate solubility phases that lead to the manufacture of CNT-FRPCs (also termed hybrid/multiscale composites). This study was primarily initiated to characterize the interaction parameters of nanomaterials (multiwall carbon nanotubes), polymers (polystyrene), and solvents (dimethyl formamide (DMF) and acetone) in the current paradigm of the DFD materials manufacture. Secondly, we sought to illustrate the theoretical potential for the methodology to be used in conjunction with other nanomaterial-polymer-solvent systems. Herein, the theory of Hansen's solubility parameters (HSP) is employed to explain the DFD constituents manufacturing combination parameters and aid in the explanation of the experimental results. The results illustrate quantitative values for the relative energy differences between each polymer-solvent system. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were used to characterize the multiwalled carbon nanotubes (MWCNTs) in each of the solubility stages and culminates with an indication of good dispersion potential in the final multiscale composite. Additionally, acetone absorption, evaporation mass loss and retention are reported for the sorbed plasticized PS-CNT (CNTaffy) nanocomposites that has successfully achieved up through approximately 60 weight percent loading. The findings indicate that as CNT loading percentage increases the acetone absorbency also increases, but the materials retention of acetone over time decreases. This directly influences the manufacturability of the porous polymer nanocomposite (P-PNC) in the DFD methodology. Localized interlaminar CNT enrichment was achieved through 60 wt. % loading within the P-PNC and verified under two-electrode electrical conductivity testing of the final multiscale composite. The electrical properties of low weight percent (approximately 0.15 - 2.5 wt. %) nanomaterials show a decreasing trend in the materials' resistivity that indicates the ability to become increasingly conductive with increasing CNT loadings. Finally, the mechanical properties will show evidence of toughness, increased strain to failure, and the potential for greater energy absorption.

Syntheses and characterizations of secondary Pb-O bonding supported Pb(II)-sulfonate complexes

NASA Astrophysics Data System (ADS)

Huang, Guo-Zhen; Zou, Xin; Zhu, Zhi-Biao; Deng, Zhao-Peng; Huo, Li-Hua; Gao, Shan

2018-06-01

The reaction of Pb(II) salts and mono- or disulfonates leads to the formation of eight new Pb(II)-mono/disulfonate complexes, [Pb(L1)(H2O)]2 (1), [Pb4(L2)2(AcO)2]n·5nH2O (2), [Pb(L3)(H2O)]2 (3), [Pb(HL4)(H2O)2]n·nH2O (4), [Pb(HL5)(H2O)2]n·2nH2O (5), [Pb(H2L6)(H2O)]n·nDMF·2nH2O (6), [Pb2(H3L7)4(H2O)6]·2H2O (7) and [Pb(H2L7)(H2O)]n·nH2O (8) (H2L1= 2-hydroxy-5-methyl-benzenesulfonic acid, H3L2= 2-hydroxyl-5-methyl- 1,3-benzenedisulfonic acid, H2L3= 2-hydroxy-5-nitro-benzenesulfonic acid, H3L4= 2-hydroxyl-5-bromo-1,3- benzenedisulfonic acid, H3L5= 2-hydroxyl-5-carboxyl-benzenesulfonic acid, H4L6= 2,5-dihydroxyl-3-carboxyl- benzenesulfonic acid, H4L7= 2,4-dihydroxyl-5-carboxyl-benzenesulfonic acid, DMF = N,N'-dimethyl-formamide, AcO- = acetate), which have been characterized by elemental analysis, IR, TG, PL, powder and single-crystal X-ray diffraction. In view of the primary Pb-O bonds, these eight complexes exhibit diverse dinuclear (1, 3 and 7), helical chain (4), wave-like chain (5), linear chain (6), zigzag chain (8) and layer structure (2), in which the Pb(II) cations present different hemi-directed geometries. Taking the secondary Pb-O bonds into account, chain structure for complex 7, layer motifs for complexes 1 and 3-6, as well as 3-D framework for complex 8 are observed with Pb(II) cations showing more intricate holo-directed geometries. The various coordination modes of these seven different mono/disulfonate anions are responsible for the formation of these multiple structures. Furthermore, the introduction of hydroxyl and carboxyl groups increases the coordination ability of sulfonate to the p-block metal cation. Luminescent analyses indicate that complex 7 presents purple emission at 395 nm at room temperature.

Interpreting contact angle results under air, water and oil for the same surfaces

NASA Astrophysics Data System (ADS)

Ozkan, Orkun; Yildirim Erbil, H.

2017-06-01

Under-water and under-oil superhydropobicity and superhydrophilicity have gained significant attention over the last few years. In this study, contact angles on five flat surfaces (polypropylene, poly(methyl methacrylate), polycarbonate, TEFLON-FEP and glass slide) were measured in water drop-in-air, air bubble-under-water, oil drop-in-air, air bubble-under-oil, oil drop-under-water and water drop-under-oil conditions. Heptane, octane, nonane, decane, dodecane, and hexadecane hydrocarbons were used as oils. Immiscible water/oil pairs were previously mutually saturated to provide thermodynamical equilibrium conditions and their surface and interfacial tensions were determined experimentally. These pairs were used in the two-liquid contact angle measurements. Surface free energies of the solid surfaces in air were determined independently by using the van Oss-Good method, using the contact angle results of pure water, ethylene glycol, formamide, methylene iodide and α-bromonaphalene. In addition, Zisman’s ‘critical surface tension’ values were also determined for comparison. In theory, the summation of contact angle results in a complementary case would give a total of 180° for ideal surfaces. However, it was determined that there are large deviations from this rule in practical cases and these deviations depend on surface free energies of solids. Three complementary cases of (water-in-air with air bubble-under-water); (oil-in-air with air bubble-under-oil); and (oil-under-water with water-under-oil) were investigated in particular to determine the deviations from ideality. A novel approach, named ‘complementary hysteresis’ [γ WA(cosθ 1  -  cosθ 2) and γ OW(cosθ 6  -  cosθ 5)] was developed where γ WA and γ OW represent the interfacial tensions of water/air and oil/water, and θ 1, θ 2, θ 5, and θ 6 were the contact angles of water/air, air bubble/water, oil/water and water/oil respectively. It was experimentally determined that complementary hysteresis varies almost linearly with the surface free energy of the flat solid samples. This is the first report showing the relation of the surface free energy of a solid which is determined under-air with the contact angles obtained on the same solid in different three-phase systems.

Analysis of the Photomagnetic Properties of Cyano-Bridged Heterobimetallic Complexes by X-Ray Diffraction

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

Svendsen, Helle; Jørgensen, Mads Ry Vogel; Overgaard, Jacob

2012-10-11

Single crystal synchrotron X-ray diffraction measurements have been carried out on [Nd(DMF){sub 4}(H{sub 2}O){sub 3}({mu}-CN)Fe(CN){sub 5}] {center_dot} H{sub 2}O (DMF = dimethyl-formamide), 1; [Y(DMF){sub 4}(H{sub 2}O){sub 3}({mu}-CN)Fe(CN){sub 5}] {center_dot} H{sub 2}O, 2; [Ce(DMF){sub 4}(H{sub 2}O){sub 3}({mu}-CN)Fe(CN){sub 5}] {center_dot} H{sub 2}O, 3; [Sm(DMF){sub 4}(H{sub 2}O){sub 3}({mu}-CN)Fe(CN){sub 5}] {center_dot} H{sub 2}O, 4; [Tb(DMF){sub 4}(H{sub 2}O)3({mu}-CN)Fe(CN){sub 5}] {center_dot} H{sub 2}O, 5; [Yb(DMF){sub 4}(H{sub 2}O){sub 3}({mu}-CN)Fe(CN){sub 5}] {center_dot} H{sub 2}O, 6; and [Nd(DMF){sub 4}(H{sub 2}O){sub 3}({mu}-CN)Co(CN){sub 5}] {center_dot} H{sub 2}O, 7, at 15(2) K with and without UV illumination of the crystals. Significant changes in unit cell parameters are observed for all of themore » iron-containing complexes, while compound 7 shows no response to UV illumination. These results are consistent with previous results and are furthermore reproduced by powder synchrotron X-ray diffraction for compounds 1 and 7. Photoexcited crystal structures have been determined for 1-6 from refinements of two-conformer models, and excited state occupancies in the range 80-94% are found. Significant bond length changes are observed for the Fe-ligand bonds (up to 0.06 {angstrom}), the cyano bonds (up to 0.02 {angstrom}), and the lanthanide-ligand bonds (up to 0.1 {angstrom}). On the contrary, powder X-ray diffraction on the simple compound K{sub 3}Fe(CN)6, 8, upon UV illumination does not show any structural changes, suggesting that the photomagnetic effect requires the presence of both the transition metal and the lanthanide ion. Photomagnetic measurements show an increase in magnetization of the excited state of 1 of up to 3%, which is much diminished compared with previously published values of 45%. Furthermore, they show that the isostructural complex [La(DMF){sub 4}(H{sub 2}O){sub 3}({mu}-CN)Fe(CN){sub 5}] {center_dot} H{sub 2}O, 9, exhibits identical magnetic responses in the UV-induced excited crystal structure.« less

Layered rare-earth hydroxide (LRH, R = Tb, Y) composites with fluorescein: delamination, tunable luminescence and application in chemosensoring for detecting Fe(iii) ions.

PubMed

Su, Feifei; Guo, Rong; Yu, Zihuan; Li, Jian; Liang, Zupei; Shi, Keren; Ma, Shulan; Sun, Genban; Li, Huifeng

2018-04-17

We demonstrate a novel example of tunable luminescence and the application of the delaminated FLN/OS-LRH composites (LRHs are layered rare-earth hydroxides, R = Tb, Y; FLN is the fluorescein named 2-(6-hydroxy-3-oxo-(3H)-xanthen-9-yl)benzoic acid; OS is the anionic surfactant 1-octane sulfonic acid sodium) in detecting Fe(iii) ions. The FLNxOS1-x species (x = 0.02, 0.05, 0.10, and 0.20) are intercalated into the LTbyY1-yH layers (y = 1, 0.9, 0.7, 0.5, 0.3, 0.1 and 0) by ion exchange reactions to yield the composites FLNxOS1-x-LTbyY1-yH. In the solid state, the LYH composites display green emission (564 nm) arising from the organic FLN, while in LTbH composites, the luminescence of the Tb3+ in the layers (545 nm) and the FLN in the interlayers is co-quenched. In the delaminated state in formamide (FM), FLNxOS1-x-LTbH composites display green to yellowish-green luminescence (540-574 nm) following the increasing FLN/OS ratio; while the FLN0.02OS0.98-LTbyY1-yH composites show green emission at ∼540 nm. The fluorescence lifetimes of the composites (4.22-4.63 ns) are comparable to the free FLN-Na, and the quantum yields (31.62-78.70%) of the composites especially that (78.70%) of the FLN0.02OS0.98-LYH are much higher than that (28.40%) of free FLN-Na. The recognition ability of the FLN0.02OS0.98-LYH composite for metal cations is researched. The delaminated FLN0.02OS0.98-LYH colloidal suspension exhibits high selectivity for Fe3+ over other ions (Mg2+, Al3+, Ni2+, Co2+, Cu2+, Zn2+, Mn2+, Pb2+, and Cd2+) with fluorescence quenching, which can work as a kind of turn-off fluorescence sensor for the detection of Fe3+. The detection limit of Fe3+ is determined to be 2.58 × 10-8 M and the quenching constant (Ksv) is 1.70 × 103 M-1. This is the first work on LRH materials working as a chemosensor for recognising metal cations. It provides a new approach for the design of LRH materials to be applied in fluorescence chemosensing.

Chemical segregation in hot cores with disk candidates. An investigation with ALMA

NASA Astrophysics Data System (ADS)

Allen, V.; van der Tak, F. F. S.; Sánchez-Monge, Á.; Cesaroni, R.; Beltrán, M. T.

2017-07-01

Context. In the study of high-mass star formation, hot cores are empirically defined stages where chemically rich emission is detected toward a massive YSO. It is unknown whether the physical origin of this emission is a disk, inner envelope, or outflow cavity wall and whether the hot core stage is common to all massive stars. Aims: We investigate the chemical makeup of several hot molecular cores to determine physical and chemical structure. We use high spectral and spatial resolution submillimeter observations to determine how this stage fits into the formation sequence of a high-mass star. Methods: The submillimeter interferometer ALMA (Atacama Large Millimeter Array) was used to observe the G35.20-0.74N and G35.03+0.35 hot cores at 350 GHz in Cycle 0. We analyzed spectra and maps from four continuum peaks (A, B1, B2 and B3) in G35.20-0.74N, separated by 1000-2000 AU, and one continuum peak in G35.03+0.35. We made all possible line identifications across 8 GHz of spectral windows of molecular emission lines down to a 3σ line flux of 0.5 K and determined column densities and temperatures for as many as 35 species assuming local thermodynamic equilibrium (LTE). Results: In comparing the spectra of the four continuum peaks, we find each has a distinct chemical composition expressed in over 400 different transitions. In G35.20, B1 and B2 contain oxygen- and sulfur-bearing organic and inorganic species but few nitrogen-bearing species whereas A and B3 are strong sources of O-, S-, and N-bearing organic and inorganic species (especially those with the CN bond). Column densities of vibrationally excited states are observed to be equal to or greater than the ground state for a number of species. Deuterated methyl cyanide is clearly detected in A and B3 with D/H ratios of 8 and 13%, respectively, but is much weaker at B1 and undetected at B2. No deuterated species are detected in G35.03, but similar molecular abundances to G35.20 were found in other species. We also find co-spatial emission of isocyanic acid (HNCO) and formamide (NH2CHO) in both sources indicating a strong chemical link between the two species. Conclusions: The chemical segregation between N-bearing organic species and others in G35.20 suggests the presence of multiple protostars surrounded by a disk or torus.

Synthesis, characterization, DFT calculations and biological studies of Mn(II), Fe(II), Co(II) and Cd(II) complexes based on a tetradentate ONNO donor Schiff base ligand

NASA Astrophysics Data System (ADS)

Abdel-Rahman, Laila H.; Ismail, Nabawia M.; Ismael, Mohamed; Abu-Dief, Ahmed M.; Ahmed, Ebtehal Abdel-Hameed

2017-04-01

This study highlights synthesis and characterization of a tetradentate ONNO Schiff base ligand namely (1, 1‧- (pyridine-2, 3-dimethyliminomethyl) naphthalene-2, 2‧-diol) and hereafter denotes as "HNDAP″ and selected metal complexes including Mn(II), Fe(II), Co(II) and Cd(II) as a central metal. HNDAP was synthesized from 1:2 M ratio condensation of 2, 3-diaminopyridine and 2- hydroxy-1-naphthaldhyde, respectively. The stoichiometric ratios of the prepared complexes were estimated using complementary techniques such as; elemental analyses (-C, H, N), FT-IR, magnetic measurements and molar conductivity. Furthermore, their physicochemical studies were carried out using thermal TGA, DTA and kinetic-thermodynamic studies along with DFT calculations. The results of elemental analyses showed that these complexes are present in a 1:1 metal-to- ligand molar ratio. Moreover, the magnetic susceptibilities values at room temperature revealed that Mn(II), Fe(II) and Co(II) complexes are paramagnetic in nature and have an octahedral (Oh) geometry. In contrast, Cd(II) is diamagnetic and stabilizes in square planar sites. The molar conductivity measurements indicated that all complexes are nonelectrolytes in dimethyl formamide. Spectral data suggested that the ligand is as tetradentate and coordinated with Co(II) ion through two phenolic OH and two azomethine nitrogen. However, for Mn(II), Fe(II) and Cd(II) complexes, the coordination occurred through two phenolic oxygen and two azomethine nitrogen with deprotonation of OH groups. The proposed chemical structures have been validated by quantum mechanics calculations. Antimicrobial activities of both the HNDAP Schiff base ligand and its metal complexes were tested against strains of Gram (-ve) E. coli and Gram (+ve) B. subtilis and S. aureus bacteria and C. albicans, A. flavus and T. rubrum fungi. All the prepared compounds showed good results of inhibition against the selected pathogenic microorganisms. The investigated HNDAP Schiff base complexes showed higher activity and stability than their corresponding HNDAP Schiff base ligand and the highest activity observed for Cd(II) complex. Moreover, the prepared Schiff base ligand and its Mn(II) and Co(II) complexes have been evaluated for their anticancer activities against two cancer cell lines namely; colon carcinoma cells (HCT-116 cell line) and hepatocellular carcinoma (Hep-G2) cell lines The interaction of Mn(II) and Co(II) complexes with calf thymus DNA (CT-DNA) was studied by absorption spectroscopic technique and viscosity measurements. Both complexes showed a successful interaction with CT-DNA via intercalation mode.

Evaluation of Cryoprotectant and Cooling Rate for Sperm Cryopreservation in the Euryhaline Fish Medaka Oryzias latipes

PubMed Central

Yang, Huiping; Norris, Michelle; Winn, Richard; Tiersch, Terrence R.

2017-01-01

Medaka Oryzias latipes is a well-recognized biomedical fish model because of advantageous features such as small body size, transparency of embryos, and established techniques for gene knockout and modification. The goal of this study was to evaluate two critical factors, cryoprotectant and cooling rate, for sperm cryopreservation in 0.25-ml French straws. The objectives were to: 1) evaluate the acute toxicity of methanol, 2-methoxyethanol (ME), dimethyl sulfoxide (Me2SO), N, N- dimethylacetamide (DMA), N, N,-dimethyl formamide (DMF), and glycerol with concentrations of 5, 10, and 15% for 60 min of incubation at 4 °C; 2) evaluate cooling rates from 5 to 25 °C/min for freezing and their interaction with cryoprotectants, and 3) test fertility of thawed sperm cryopreserved with selected cryoprotectants and associated cooling rates. Evaluation of cryoprotectant toxicity showed that methanol and ME (5 and 10%) did not change the sperm motility after 30 min; Me2SO, DMA, and DMF (10 and 15%) and glycerol (5, 10 and 15%) significantly decreased the motility of sperm within 1 min after mixing. Based on these results, methanol and ME were selected as cryoprotectants (10%) to evaluate with different cooling rates (from 5 °C/min to 25 °C/min) and were compared to Me2SO and DMF (10%) (based on their use as cryoprotectants in previous publications). Post-thaw motility was affected by cryoprotectant, cooling rate, and their interaction (P ≤ 0.000). The highest post-thaw motility (50 ± 10%) was observed at a cooling rate of 10 °C/min with methanol as cryoprotectant. Comparable post-thaw motility (37 ± 12%) was obtained at a cooling rate of 15 °C/min with ME as cryoprotectant. With DMF, post-thaw motility at all cooling rates was ≤ 10% which was significantly lower than that of methanol and ME. With Me2SO, post-thaw motilities were less than 1% at all cooling rates, and significantly lower compared to the other three cryoprotectants (P ≤ 0.000). When sperm from individual males were cryopreserved with 10% methanol at a cooling rate of 10 °C/min and 10% ME with a rate of 15 °C/min, no difference was found in post-thaw motility. Fertility testing of thawed sperm cryopreserved with 10% methanol at a rate of 10 °C/min showed average hatching of 70 ± 30% which was comparable to that of fresh sperm (86 ± 15%). Overall, this study established a baseline for high-throughput sperm cryopreservation of medaka provides an outline for protocol standardization and use of automated processing equipment in the future. PMID:20654608

Comparative bladder tumor promoting activity of sodium saccharin, sodium ascorbate, related acids, and calcium salts in rats.

PubMed

Cohen, S M; Ellwein, L B; Okamura, T; Masui, T; Johansson, S L; Smith, R A; Wehner, J M; Khachab, M; Chappel, C I; Schoenig, G P

1991-04-01

Sodium saccharin and sodium ascorbate are known to promote urinary bladder carcinogenesis in rats following initiation with N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT) or N-butyl-N-(4-hydroxybutyl) nitrosamine. Sodium salts of other organic acids have also been shown to be bladder tumor promoters. In addition, these substances increase urothelial proliferation in short term assays in rats when fed at high doses. When they have been tested, the acid forms of these salts are without either promoting or cell proliferative inducing activity. The following experiment was designed to compare the tumor promoting activity of various forms of saccharin and to evaluate the role in promotion of urinary sodium, calcium, and pH as well as other factors. Twenty groups of 40 male F344 rats, 5 weeks of age, were fed either FANFT or control diet during a 6-week initiation phase followed by feeding of a test compound for 72 weeks in the second phase. The chemicals were administered to the first 18 groups in Agway Prolab 3200 diet and the last 2 groups were fed NIH-07 diet. The treatments were as follows: (a) FANFT----5% sodium saccharin (NaS); (b) FANFT----3% NaS; (c) FANFT----5.2% calcium saccharin (CaS); (d) FANFT----3.12% CaS; (e) FANFT----4.21% acid saccharin (S); (f) FANFT----2.53% S; (g) FANFT----5% sodium ascorbate; (h) FANFT----4.44% ascorbic acid; (i) FANFT----5% NaS plus 1.15% CaCO3; (j) FANFT----5.2% CaS plus 1.34% NaCl; (k) FANFT----5% NaS plus 1.23% NH4Cl; (l) FANFT----1.15% CaCO3; (m) FANFT----1.34% NaCl; (n) FANFT----control; (o) control----5% NaS; (p) control----5.2% CaS; (q) control----4.21% S; (r) Control----control; (s) FANFT----5% NaS (NIH-07 diet); (t) FANFT----control (NIH-07 diet). NaS, CaS and S without prior FANFT administration were without tumorigenic activity. NaS was found to have tumor promoting activity, showing a positive response at the 5 and 3% dose levels, with significantly greater activity at the higher dose. CaS had slight tumor promoting activity but without a dose response, and S showed no tumor promoting activity. In addition, NaCl showed weak tumor promoting activity, but CaCO3 was without activity. NH4Cl completely inhibited the tumor promoting activity of NaS when concurrently administered with it. NaCl administered with CaS or CaCO3 administered with NaS showed activity similar to that of NaS. Sodium ascorbate was also shown to have tumor promoting activity, with slightly less activity than NaS. Ascorbic acid showed no tumor promoting activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Antiedematogenic effects of the polar fractions of Persea cordata Mez. (Lauraceae) on microvascular extravasation in rat skin.

PubMed

Schlemper, Valfredo; Schlemper, Susana Regina de Mello; Zampirolo, Júlio Araújo

2013-10-28

Persea cordata Mez. (Lauraceae) is a medicinal plant used in veterinary ethnopharmacology, which is a popular medicine used as an anti-inflammatory and healing agent, mainly on animal skin diseases, characterized by cutaneous open wounds, in South Brazil. The purpose of this study was to investigate a possible antiedematogenic effect of ethyl acetate (EtAc) and butanol (BuOH) polar fractions of Persea cordata on Evans blue dye leakage induced by pro-inflammatory agents in rat skin. Male Wistar rats (180-200 g, n=5-6) were pretreated with a single intraperitoneal administration of EtAc or BuOH (1 to 600 mg kg(-1)) fractions followed by intravenous Evans blue dye injection (1%, 30 mg kg(-1), i.v.), 60 min before the injection of phlogistic agents. Animals received intradermal injections (0.05 ml) of carrageenan (CAR, 300 µg/site), 48/80 compound (C4880, 10 µg/site), histamine (HIS, 0.3 µg/site), serotonin (5-HT, 0.01 µg/site), dextran (DEX, 200 µg/site), bradykinin (BK, 0.003 µg/site), capsaicin (CPS, 400 µg/site), substance P (SP, 0.003 µg/site) or prostaglandin E2 (PGE2 10 nmol/site) and they were submitted to euthanasia after 60 min. Skin samples were obtained in the extravasation sites of Evans blue dye. Skin fragments were soaked in formamide at 37°C (during 24h) for Evans blue extraction. The amount of dye leakage in the tissue fragment was determined by a spectrophotometer (620 nm). In a very similar manner in terms of potency and efficacy, systemic administration of EtAc and BuOH fractions caused dose-dependent inhibition of vascular Evans blue dye leakage induced by phlogistic agents in the rat skin. The results obtained (ID50 values in mgkg(-1) and maximal inhibition in %) with EtAc fraction, as follows were: CAR (34.42 and 63.0), 4880 (8.52 and 59.1), HIS (21.22 and 66.8), 5-HT (32.99 and 73.4), DEX (41.74 and 67.0), BK (34.03 and 68.0), CPS (100.7 and 77), SP (2.1 and 78.9) and PGE2 (133 and 71.0). BuOH fraction significantly inhibited CAR (25.9 and 70)-, 4880 (36.8 and 66)-, HIS (17.6 and 77)-, 5-HT (32.8 and 56)-, DEX (89.6 and 75)-, BK (28.0 and 66)-, CPS (136.37 and 71)-, SP (5.6 and 78)- and PGE2 (109.64 and 56)-induced VE, respectively. Systemic administration of Persea cordata polar fractions exerts a non-specific inhibitory effect on microvascular leakage induced by pro-inflammatory agents in rat skin, probably to interfering with different biological systems involved in the development of the inflammatory process, reinforcing the popular use of Persea cordata as an anti-inflammatory and healing agent for skin. © 2013 Elsevier Ireland Ltd. All rights reserved.

Is Water a Universal Solvent for Life?

NASA Technical Reports Server (NTRS)

Pohorill, Andrew

2012-01-01

There are strong reasons to believe that the laws, principles and constraints of physics and chemistry are universal. It is much less clear how this universality translates into our understanding of the origins of life. Conventionally, discussions of this topic focus on chemistry that must be sufficiently rich to seed life. Although this is clearly a prerequisite for the emergence of living systems, I propose to focus instead on self-organization of matter into functional structures capable of reproduction, evolution and responding to environmental changes. In biology, most essential functions are largely mediated by noncovalent interactions (interactions that do not involve making or breaking chemical bonds). Forming chemical bonds is only a small part of what living systems do. There are specific implications of this point of view for universality. I will concentrate on one of these implications. Strength of non-covalent interactions must be properly tuned. If they were too weak, the system would exhibit undesired, uncontrolled response to natural fluctuations of physical and chemical parameters. If they were too strong kinetics of biological processes would be slow and energetics costly. This balance, however, is not a natural property of complex chemical systems. Instead, it has to be achieved with the aid of an appropriate solvent for life. In particular, potential solvents for life must be characterized by a high dielectric constant to ensure solubility of polar species and sufficient flexibility of biological structures stabilized by electrostatic interactions. Among these solvents, water exhibits a remarkable trait that it also promotes solvophobic (hydrophobic) interactions between non-polar species, typically manifested by a tendency of these species to aggregate and minimize their contacts with the aqueous solvent. Hydrophobic interactions are responsible, at least in part, for many self-organization phenomena in biological systems, such as the formation of cellular boundary structures or protein folding. Strengths of electrostatic and hydrophobic interactions are similar and can be balanced over a wide range of temperatures, which considerably increases the repertoire of interactions that can be used to modulate biological functions. Some properties of water, e.g. its chemical activity against polymerization reactions, are considered as unfavorable to life. In actuality, this might be a favorable trait because life requires a balance between constructive and destructive processes. For example, molecules synthesized in response to specific conditions must be degraded once these conditions change. Otherwise regulation of biological processes would be virtually impossible. Water might not be the only liquid with favorable properties for supporting life. It has been proposed that formamide, which might be present elsewhere in the universe in sufficient quantities to warrant interest, could be a potential alternative to water for the origin of life. However, this will remain highly hypothetical until it is demonstrated in further studies on its physical, chemical and biological properties it is capable of mediating self-organization of matter and providing proper balance between different types of non-covalent interactions.

Development and Use of Integrated Microarray-Based Genomic Technologies for Assessing Microbial Community Composition and Dynamics

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

Zhou, J.; Wu, L.; Gentry, T.

2006-04-05

To effectively monitor microbial populations involved in various important processes, a 50-mer-based oligonucleotide microarray was developed based on known genes and pathways involved in: biodegradation, metal resistance and reduction, denitrification, nitrification, nitrogen fixation, methane oxidation, methanogenesis, carbon polymer decomposition, and sulfate reduction. This array contains approximately 2000 unique and group-specific probes with <85% similarity to their non-target sequences. Based on artificial probes, our results showed that at hybridization conditions of 50 C and 50% formamide, the 50-mer microarray hybridization can differentiate sequences having <88% similarity. Specificity tests with representative pure cultures indicated that the designed probes on the arrays appearedmore » to be specific to their corresponding target genes. Detection limits were about 5-10ng genomic DNA in the absence of background DNA, and 50-100ng ({approx}1.3{sup o} 10{sup 7} cells) in the presence background DNA. Strong linear relationships between signal intensity and target DNA and RNA concentration were observed (r{sup 2} = 0.95-0.99). Application of this microarray to naphthalene-amended enrichments and soil microcosms demonstrated that composition of the microflora varied depending on incubation conditions. While the naphthalene-degrading genes from Rhodococcus-type microorganisms were dominant in enrichments, the genes involved in naphthalene degradation from Gram-negative microorganisms such as Ralstonia, Comamonas, and Burkholderia were most abundant in the soil microcosms (as well as those for polyaromatic hydrocarbon and nitrotoluene degradation). Although naphthalene degradation is widely known and studied in Pseudomonas, Pseudomonas genes were not detected in either system. Real-time PCR analysis of 4 representative genes was consistent with microarray-based quantification (r{sup 2} = 0.95). Currently, we are also applying this microarray to the study of several different microbial communities and processes at the NABIR-FRC in Oak Ridge, TN. One project involves the monitoring of the development and dynamics of the microbial community of a fluidized bed reactor (FBR) used for reducing nitrate and the other project monitors microbial community responses to stimulation of uranium reducing populations via ethanol donor additions in situ and in a model system. Additionally, we are developing novel strategies for increasing microarray hybridization sensitivity. Finally, great improvements to our methods of probe design were made by the development of a new computer program, CommOligo. CommOligo designs unique and group-specific oligo probes for whole-genomes, metagenomes, and groups of environmental sequences and uses a new global alignment algorithm to design single or multiple probes for each gene or group. We are now using this program to design a more comprehensive functional gene array for environmental studies. Overall, our results indicate that the 50mer-based microarray technology has potential as a specific and quantitative tool to reveal the composition of microbial communities and their dynamics important to processes within contaminated environments.« less

Low Energy Electrons as Probing Tool for Astrochemical Reaction Mechanisms

NASA Astrophysics Data System (ADS)

Hendrik Bredehöft, Jan; Swiderek, Petra; Hamann, Thorben

The complexity of molecules found in space varies widely. On one end of the scale of molecular complexity is the hydrogen molecule H2 . Its formation from H atoms is if not understood than at least thoroughly investigated[1]. On the other side of said spectrum the precursors to biopolymers can be found, such as amino acids[2,3], sugars[4], lipids, cofactors[5], etc, and the kerogen-like organic polymer material in carbonaceous meteorites called "black stuff" [6]. These have also received broad attention in the last decades. Sitting in the middle between these two extremes are simple molecules that are observed by radio astronomy throughout the Universe. These are molecules like methane (CH4 ), methanol (CH3 OH), formaldehyde (CH2 O), hydrogen cyanide (HCN), and many many others. So far more than 40 such species have been identified.[7] They are often used in laboratory experiments to create larger complex molecules on the surface of simulated interstellar dust grains.[2,8] The mechanisms of formation of these observed starting materials for prebiotic chemistry is however not always clear. Also the exact mechanisms of formation of larger molecules in photochemical experiments are largely unclear. This is mostly due to the very complex chemistry going on which involves many different radicals and ions. The creation of radicals and ions can be studied in detail in laboratory simulations. They can be created in a setup mimicking interstellar grain chemistry using slow electrons. There is no free electron radiation in space. What can be found though is a lot of radiation of different sorts. There is electromagnetic radiation (UV light, X-Rays, rays, etc.) and there is particulate radiation as well in the form of high energy ions. This radiation can provide energy that drives chemical reactions in the ice mantles of interstellar dust grains. And while the multitude of different kinds of radiation might be a little confusing, they all have one thing in common: Upon hitting anything solid, they will create secondary electrons. These electrons are in fact the energy source needed to run interstellar chemistry. Slow electrons can in principle trigger three different primary processes in a molecule. The first is ionisation by electron impact (EI), which is used to create ions in mass spectrometry. In this process an electron hits a molecule M and knocks an outer shell electron to create a cation. This occurs whenever the electron energy is above the ionisation threshold of the target molecule. Another possibility is the attachment of a slow electron to a molecule to create an anion. This can occur at sharply defined resonance energies specific to the molecule M. A third possibility is to excite the molecule M to a neutral state M∗ .[9] M + e- -> M+ + 2 e- (Electron impact ionisation) M + e- -> M- (Electron attachment) M + e- -> M∗ + e- (Neutral excitation) The created states M+ , M- and M∗ are usually not stable states so they very often dissociate into ions and radicals, which can then further react with neighbouring molecules to form new chemical species. In these chemical reactions some products can be formed even at very low temperatures that would otherwise require a lot of thermal energy and/or special catalysts. The formation of ethylamine from ethylene and ammonia by hydroamination is one such example. The reaction is characterized by a high activation barrier caused by the electronic repulsion between the electron density rich C=C double bound and the lone pair electrons of ammo-nia. The reaction also has a highly negative entropy, so it becomes less favourable at higher temperatures, ruling out heat as a means to facilitate the reaction. In classical chemistry this problem is overcome by the use of catalysts. Unfortunately there still is no general catalyst for this kind of reaction. Recently it was shown that the reaction can efficiently be induced by low energy electron radiation.[10] One of the reaction partners is ionized and the reaction barrier is drastically lowered so that instant reaction between ethylene and ammonia occurs. This hydroamination reaction by means of low energy electrons or an analogous reaction mechanism could also help in clarifying the formation of the intermediate molecules observed in interstellar dust clouds. The formation for example of formamide from CO and NH3 could be facilitated by a very similar process. Formamide is a very interesting molecule in Astrochemistry as well as Astrobiology, since it is the smallest molecule with a peptide bond, the kind of bond that forms proteins from amino acids. Such ionisation-driven reactions leading to the formation of larger molecules appear to be more generally relevant than previously thought as will be discussed in this contribution. [1] Cazaux S., Caselli P., Tielens A.G.G.M., Le Bourlot J., Walmsley M: Molecular Hydrogen formation on grain surfaces. J of Phys. Conf. Series 6 (2005), 155-160 [2] Muñoz Caro G.M., Meierhenrich U.J., Schutte U.W., Barbier B., Arcones Segovia A., Rosen-n bauer H., Thiemann W.H.-P., Brack A. and Greenberg J.M.: Amino acids from ultraviolet irradiation of interstellar ice analogues. Nature 416 (2002), 403-406 [3] Bredehüft, J.H., Meierhenrich U.: Amino acid structures from UV irradiation of simulated interstellar ices. in Takenaka N. (ed): Recent Developments of Chemistry and Photochemistry in Ice. Transworld Research Network, Kerala, India (2008) [4] Cooper G., Kimmich N., Belisle W., Sarinana J., Brabham K. and Garrel L.: Carbonaceous meteorites as a source of sugar-related organic compounds for the early Earth. Nature 414 (2001), 879-883 [5] Meierhenrich U.J., Muñoz Caro G.M., Schutte W.A., Thiemann W.H.-P. Barbier B., Brack n A.: Precursors of biological cofactors from ultraviolet irradiation of circumstellar/interstellar ice analogs. Chemistry -A European Journal 11 (2005), 4895-4900 [6] Matthews C.N. and Minard R.D.: Hydrogen cyanide polymers, comets and the origin of life. Faraday Discuss., 133 (2006), 393-401 [7] Snow T.P. and Bierbaum V.M.: Ion chemistry in the interstellar medium. Ann. Rev. Analyt. Chem. 1 (2008), 229-259. [8] Nuevo M., Meierhenrich U.J., Muñoz Caro G.M., Dartois E., d'Hendecourt L., Deboffle D., n Auger G., Blanot D., Bredehüft J.H. and Nahon L.: The effects of circularly polarized light on amino acid enantiomers produced by the UV irradiation of interstellar ice analogs. AA 457 (2006), 741-751 [9] Shimamura I and Takayanagi K. (eds): Electron-Molecule Collisions. Plenum Press, New York, USA (1984) [10] Hamann T., Bühler E., Swiderek P.: Low-energy-electron-induced hydroamination of an alkene. Angew Chem Int Ed Engl. 48(25) (2009), 4643-4645.

Interstellar/Precometary Organic Material and the Photochemical Evolution of Complex Organics

NASA Technical Reports Server (NTRS)

Allamandola, Lou J.; Bernstein, Max; Sandford, Scott; Witteborn, Fred (Technical Monitor)

1996-01-01

During the past two decades ground-, air-, and space-based infrared spectroscopic observations, combined with realistic laboratory simulations, have revolutionized our understanding of interstellar ice and dust, the raw materials from which planets, comets and stars form. Most interstellar material is concentrated in Large molecular clouds where simple molecules are formed by dust grain and gas phase reactions. Gaseous species striking the cold (10 K) dust will stick, forming an icy grain mantle. This accretion, coupled with energetic particle bombardment and UV photolysis, will produce a complex chemical mixture containing volatile, non-volatile, and isotopically fractionated species. Ices in molecular clouds contain the very simple molecules H2O, CH3OH, CO, CO2, H2, and perhaps some NH3 and H2CO, as well as more complex species including nitriles and ketones or esters. The evidence for these compounds as well as carbon rich materials such as polycyclic aromatic hydrocarbons (PAHs), microdiamonds, and amorphous carbon will be reviewed and the possible connections with comets and meteorites will be presented in the first part of the talk. The second part of the presentation will focus on interstellar/precometary ice photochemical evolution. The chemical composition and photochemical evolution of realistic interstellar/pre-cometary ice analogs containing methanol will be discussed. ultraviolet photolysis of these ices produces H2, H2CO, CO2, CO, CH4, HCO, and more complex molecules. Infrared spectroscopy, H-1 and C-13 nuclear magnetic resonance (NMR) spectroscopy, and gas chromatography-mass spectrometry demonstrate that when ices representative of interstellar grains and comets are exposed to UV radiation at low temperature a series of moderately complex organic molecules are formed in the ice including: CH3CH2OH (ethanol), HC(=O)NH2 (formamide), CH3C(=O)NH2 (acetamide), and R-C(integral)N (nitriles). Several of these are already known to be in the interstellar medium, and their presence indicates the importance of grain processing. After warming to room temperature what remains is an organic residue composed primarily of Hexamethylenetetramine (HMT, C6H12N4), with lesser amounts of polyoxymethylene related species (POMs), amides, and ketones. This is in sharp contrast to the organic residues produced by irradiating ices which do not contain methanol (unrealistic interstellar ice analogs) or thermally promoted polymerization-type reactions in unirradiated realistic ice mixtures. Here HMT is only a minor product in a residue dominated by a mixture of polyoxymethylene related species. The implications, for infrared astronomy and astrochemistry, of high concentrations of HMT in interstellar and cometary ices may be profound. The ultraviolet photolysis of HMT frozen in H20 ice produces the "XCN" band observed in the spectra of protostellar objects and laboratory ices, as well as carbon oxides and other nitriles. Thus, HMT may be a precursor of XCN in protostellar objects and a source of CN and CO in the tail of comets. Also, HMT is known to hydrolyze under acidic conditions to yield ammonia and formaldehyde as well as amino acids. Thus, HMT may have been a source of organic material delivered to the early earth by comets.

Trypanosoma Cruzi Cyp51 Inhibitor Derived from a Mycobacterium Tuberculosis Screen Hit

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

Chen, Chiung-Kuang; Doyle, Patricia S.; Yermalitskaya, Liudmila V.

2009-02-18

The two front-line drugs for chronic Trypanosoma cruzi infections are limited by adverse side-effects and declining efficacy. One potential new target for Chagas disease chemotherapy is sterol 14{alpha}-demethylase (CYP51), a cytochrome P450 enzyme involved in biosynthesis of membrane sterols. In a screening effort targeting Mycobacterium tuberculosis CYP51 (CYP51{sub Mt}), we previously identified the N-[4-pyridyl]-formamide moiety as a building block capable of delivering a variety of chemotypes into the CYP51 active site. In that work, the binding modes of several second generation compounds carrying this scaffold were determined by high-resolution co-crystal structures with CYP51{sub Mt}. Subsequent assays against the CYP51 orthologuemore » in T. cruzi, CYP51{sub Tc}, demonstrated that two of the compounds tested in the earlier effort bound tightly to this enzyme. Both were tested in vitro for inhibitory effects against T. cruzi and the related protozoan parasite Trypanosoma brucei, the causative agent of African sleeping sickness. One of the compounds had potent, selective anti-T. cruzi activity in infected mouse macrophages. Cure of treated host cells was confirmed by prolonged incubation in the absence of the inhibiting compound. Discrimination between T. cruzi and T. brucei CYP51 by the inhibitor was largely based on the variability (phenylalanine versus isoleucine) of a single residue at a critical position in the active site. CYP51{sub Mt}-based crystal structure analysis revealed that the functional groups of the two tightly bound compounds are likely to occupy different spaces in the CYP51 active site, suggesting the possibility of combining the beneficial features of both inhibitors in a third generation of compounds to achieve more potent and selective inhibition of CYP51{sub Tc}. Enzyme sterol 14{alpha}-demethylase (CYP51) is a well-established target for anti-fungal therapy and is a prospective target for Chagas disease therapy. We previously identified a chemical scaffold capable of delivering a variety of chemical structures into the CYP51 active site. In this work the binding modes of several second generation compounds carrying this scaffold were determined in high-resolution co-crystal structures with CYP51 of Mycobacterium tuberculosis. Subsequent assays against CYP51 in Trypanosoma cruzi, the agent of Chagas disease, demonstrated that two of the compounds bound tightly to the enzyme. Both were tested for inhibitory effects against T. cruzi and the related protozoan parasite Trypanosoma brucei. One of the compounds had potent, selective anti-T. cruzi activity in infected mouse macrophages. This compound is currently being evaluated in animal models of Chagas disease. Discrimination between T. cruzi and T. brucei CYP51 by the inhibitor was largely based on the variability of a single amino acid residue at a critical position in the active site. Our work is aimed at rational design of potent and highly selective CYP51 inhibitors with potential to become therapeutic drugs. Drug selectivity to prevent host-pathogen cross-reactivity is pharmacologically important, because CYP51 is present in human host.« less

Focal cerebral ischemic tolerance and change in blood-brain barrier permeability after repetitive pure oxygen exposure preconditioning in a rodent model.

PubMed

Wang, Xi; Kang, Kai; Wang, Shiquan; Yao, Jianhua; Zhang, Xijing

2016-10-01

OBJECTIVE The goal of this study was to demonstrate that repetitive pure oxygen exposure preconditioning (O 2 PC) for 8 hours per day for 3 or 7 days, a practicable preconditioning for clinical use, is able to induce cerebral ischemic tolerance (IT) and further clarify the accompanying changes in the blood-brain barrier (BBB) that may be involved. METHODS A total of 68 adult male Sprague-Dawley rats and eight 1-day-old rat pups were used in this study. The adult rats were exposed to pure O 2 (38 rats) 8 hours a day for 3 or 7 days or to room air (in an identical setup) for 8 hours a day for 7 days as controls (30 rats). Arterial O 2 tension (PaO 2 ) was measured in 6 rats exposed to O 2 and 3 controls. Focal cerebral ischemia was elicited by middle cerebral artery occlusion (MCAO) in 37 rats, of which 21 had been exposed to pure O 2 for 3 or 7 days and 16 to room air for 7 days as controls. Neurological behavior was scored with the Garcia score in 15 MCAO rats, of which 10 had been exposed to pure O 2 for 3 or 7 days and 5 to room air for 7 days as controls, and cerebral infarct volumes were assessed with TTC (2,3,5-triphenyltetrazolium chloride) staining in 10 rats (5 from each group) after 7 days of exposure. Formamide-extraction method was used to detect leakage of Evans blue (EB) dye in 7 rats exposed to pure O 2 for 7 days and 7 exposed to room air for 7 days. Fluorescence microscopy was used to analyze the leaked EB in the nonischemic areas of 4 rats exposed to pure O 2 for 7 days and 4 exposed to room air for 7 days before MCAO and the brain of the rats that had not been subjected to MCAO. Astrocyte changes associated with O 2 PC were evaluated by means of fluorescence microscopy and electron microscopy in 14 rats that were exposed to the same O 2 or control conditions as the MCAO rats but without MCAO. Astrocytes were also obtained from 8 rat pups and cultured; levels of AQP4 and VEGF were detected by Western blot and ELISA in cells with and without O 2 treatment. RESULTS A significant increase in PaO 2 was seen after O 2 PC. The neurological score was significantly increased in the O 2 PC groups (10.6 ± 0.6 in the 3-day O 2 PC group, p < 0.05; 12 ± 0.84 in the 7-day O 2 PC group, p < 0.05) compared with the control group (7 ± 0.55). The ratio of cerebral infarct volume to contralateral cerebral hemisphere volume was significantly lower in the O 2 PC group than in the control group (0.204 ± 0.03 vs 0.48 ± 0.05, p < 0.05). The amount of leaked EB in the ischemic cerebral hemisphere was also lower in the O 2 -treated rats than in controls (7.53 ± 1.4 vs 11.79 ± 3.3 μg EB/g brain weight, p < 0.05). However, fluorescence microscopy showed significantly greater BBB permeability in the nonischemic areas in the O 2 PC group than in controls (p < 0.05). More red fluorescence could be observed in the nonischemic areas in both the ipsilateral and contralateral sides of the ischemic brain in the O 2 PC animals than in the nonischemic areas in the corresponding sides of the controls. Further investigation of the effect of the O 2 PC itself on the BBB of rats that were not subjected to MCAO showed that there was no EB leakage in the brain parenchyma in the rats exposed to room air, but some red fluorescence patches were noticed in the normal brain from the rats in the O 2 PC group. Astrocytes, including those from areas around the BBB, were activated in the O 2 PC group. Levels of both aquaporin 4 (AQP4) and vascular endothelial growth factor (VEGF) were significantly increased in cultured astrocytes after O 2 PC. CONCLUSIONS These findings suggest that O 2 PC is able to induce IT, which makes it a strong candidate for clinical use. Moreover, O 2 PC can also promote BBB opening, which may contribute to the induction of IT as well as representing a possible strategy for promoting drug transportation into the CNS. Activated astrocytes are likely to be involved in these processes through astrocyte-derived factors, such as AQP4 and VEGF.

Handbook of acute toxicity of chemicals to fish and aquatic invertebrates : summaries of toxicity tests conducted at Columbia National Fisheries Research Laboratory, 1965-78

USGS Publications Warehouse

Johnson, W. Waynon; Finley, Mack T.

1980-01-01

Acute toxicity is a major subject of research at Columbia National Fisheries Research Laboratory for evaluating the impact of toxic chemicals on fishery resources. The Laboratory has played a leading role in developing research technology for toxicity testing and data interpretation. In 1965-78, more than 400 chemicals were tested against a variety of invertebrates and fish species representative of both cold- and warm-water climates.The use of acute toxicity tests for assessing the potential hazard of chemical contaminants to aquatic organisms is well documented (Boyd 1957; Henderson et al. 1960; Sanders and Cope 1966; Macek and McAllister 1970). Static acute toxicity tests provide rapid and (within limits) reproducible concentration-response curves for estimating toxic effects of chemicals on aquatic organisms. These tests provide a database for determining relative toxicity of a large number of chemicals to a variety of species and for estimating acute effects of chemical spills on natural aquatic systems; they also assist in determining priority and design of additional toxicity studies.Acute toxicity tests usually provide estimates of the exposure concentration causing 50% mortality (LC50) to test organisms during a specified period of time. For certain invertebrates, the effective concentration is based on immobilization, or some other identifiable endpoint, rather than on lethality. The application of the LC50 has gained acceptance among toxicologists and is generally the most highly rated test for assessing potential adverse effects of chemical contaminants to aquatic life (Brungs and Mount 1978; American Institute for Biological Sciences 1978a).The literature contains numerous papers dealing with the acute toxicity of chemicals to freshwater organisms. However, there is a tremendous need for a concise compendium of toxicity data covering a large variety of chemicals and test species. This Handbook is a compilation of a large volume of acute toxicity data from the Columbia Laboratory and its field laboratories. It presents definitive acute toxicity data on 271 chemicals tested against a variety of freshwater invertebrates and fishes. The chemicals represent all major groups of pesticides, as well as numerous industrial chemicals. This compilation should serve as a useful database for the many agencies and organizations dealing with research and management programs concerned with the impact of chemicals on aquatic resources.The Columbia Laboratory has played a major role in developing currently used standard methodology for static acute toxicity testing. The use of standardized methodology greatly reduces variation in results. The data presented here have been carefully scrutinized to eliminate tests that failed to follow acceptable procedures. Handling of test organisms and procedures for static toxicity tests followed those described by Lennon and Walker (1964) and Macek and McAllister (1970), and conform well with those recommended by Brauhn and Schoettger (1975) and the Committee on Methods for Toxicity Tests with Aquatic Organisms (1975).The species of fish and invertebrates that were tested are listed in phylogenetic order in Tables 1 and 2. Fish were obtained from Federal and State hatcheries as either eggs or fry. Original stocks of invertebrates were collected and cultured from wild populations with no known source of contamination; these populations were replenished regularly. The invertebrates were cultured in the Laboratory by methods similar to those described by Sanders and Cope (1966).Test chemicals usually consisted of technical or analytical grade samples of known purity. Formulations of the chemicals were also tested when available. When purity of test chemicals was known, all calculated concentrations were based on percent active ingredients. Stock solutions were prepared immediately before each test, with commercial grade acetone as the carrier solvent. Occasionally, ethanol or dimethyl-formamide was substituted. Solvent concentrations did not exceed 0.5 mL/L in final dilution water.Test water (dilution water) was reconstituted from deionized water of at least 106 ohms resistivity by the addition of appropriate reagent grade chemicals (Marking 1969). Water was buffered to maintain a pH of 7.2 to 7.5, an alkalinity of 30 to 35 mg/L, and a hardness of 40 to 50 mg/L as CaCO3. Test water was mixed thoroughly and aerated before transfer into test chambers. Fish were acclimated to dilution water by gradually changing the water in acclimated tanks from 100% well water to 100% reconstituted water over a 1- to 3-day period at the desired testing temperature. Invertebrates were acclimated from well water to dilution water over a 4- to 6-h period. Toxicity tests were conducted under static conditions without aeration, and the organisms were not fed during acclimation or testing. Temperature of test solutions was maintained within ± 1°C of that required for a given test.Toxicity tests with fish were conducted in 18.9-liter (5-gal) wide-mouthed jars containing 15 liters of test solution. Fingerling fish weighing 0.2 to 1.5 g were tested at each concentration. Caution was taken not to exceed 0.8 g of test organisms per liter of solution. Duplicate test chambers were used to accommodate larger fish. Test chambers varied in size for invertebrates, depending on the species used; volume of test solution ranged from 0.25 to 4 liters. At least 10 organisms were exposed to each concentration for all definitive tests. At least six concentrations were used per toxicity test.The tests began upon initial exposure to the toxicant and continued for 96 h. Immobilization tests with invertebrates were conducted for only 48 h. The number of dead or affected organisms in each test chamber were recorded and the dead organisms were removed every 24 h; general observations on the condition of test organisms were also recorded at these times.Toxicity data were analyzed by a statistical method described by Litchfield and Wilcoxon (1949) to determine LC50 (theoretical estimate of the concentration lethal to 50% of the test animals) and 95% confidence intervals. This method is recommended by the American Public Health Association (1971) and by Sprague (1969) for determining median lethal concentrations. The procedure is easily modified for computing a single LC50 when replicate tests are performed.

Researchers Use NRAO Telescope to Study Formation Of Chemical Precursors to Life

NASA Astrophysics Data System (ADS)

2006-08-01

In just two years of work, an international research team has discovered eight new complex, biologically-significant molecules in interstellar space using the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) in West Virginia. "This is a feat unprecedented in the 35-year history of searching for complex molecules in space and suggests that a universal prebiotic chemistry is at work," said Jan M. Hollis of the NASA Goddard Space Flight Center, leader of the research team. Chemistry Cycle The Cosmic Chemistry Cycle CREDIT: Bill Saxton, NRAO/AUI/NSF Full Size Image Files Interactive Graphic With "Mouseover" Text Blocks Chemical Cycle Graphic (above image, JPEG, 129K) Graphic With Text Blocks (JPEG, 165K) High-Res TIFF (44.2M) High-Res TIFF With Text Blocks (44.2M) Green Bank Telescope and Molecule Diagrams (JPEG, 58K) Green Bank Telescope and Molecule Diagrams (TIFF, 21M) New Molecules: Chemical Diagrams (PDF, 64K) The new discoveries are helping scientists unlock the secrets of how the molecular precursors to life can form in the giant clouds of gas and dust in which stars and planets are born. "The first of the many chemical processes that ultimately led to life on Earth probably took place even before our planet was formed. The GBT has taken the leading role in exploring the origin of biomolecules in interstellar clouds," said Phil Jewell of the National Radio Astronomy Observatory (NRAO). The eight new molecules discovered with the GBT bring the total to 141 different molecular species found in interstellar space. About 90 percent of those interstellar molecules contain carbon, which is required for a molecule to be classified as organic. The newly-discovered molecules all contain carbon and are composed of 6 to 11 atoms each. These results suggest, the scientists say, that chemical evolution occurs routinely in the gas and dust from which stars and planets eventually are born. The mass of an interstellar cloud is 99 percent gas and one percent dust. The GBT discoveries have been made in just two prototypical interstellar clouds. The molecules acetamide (CH3CONH2), cyclopropenone (H2C3O), propenal (CH2CHCHO), propanal (CH3CH2CHO), and ketenimine (CH2CNH) were found in a cloud called Sagittarius B2(N), which is near the center of our Milky Way Galaxy some 26,000 light years from Earth. This star-forming region is the largest repository of complex interstellar molecules known. The molecules methyl-cyano-diacetylene (CH3C5N), methyl-triacetylene (CH3C6H), and cyanoallene (CH2CCHCN) were found in the Taurus Molecular Cloud (TMC-1), which is relatively nearby at a distance of 450 light years. The starless TMC-1 cloud is dark and cold with a temperature of only 10 degrees above absolute zero and may eventually evolve into a star-forming region. "The discovery of these large organic molecules in the coldest regions of the interstellar medium has certainly changed the belief that large organic molecules would only have their origins in hot molecular cores. It has forced us to rethink the paradigms of interstellar chemistry," said Anthony Remijan of the NRAO. These large molecules found with the GBT are built up from smaller ones, the scientists say, by two principal mechanisms. In the first, simple chemical reactions add an atom to a molecular structure residing on the surface of a dust grain. As an example of this process, the researchers cite a molecule called cyclopropenylidene (c-C3H2, where "c-" means cyclic), which contains three carbon atoms in a ring. Cyclopropenylidene was discovered in interstellar space in 1987, and is known to be highly reactive. In 2005, using the GBT, scientists discovered another molecule, cyclopropenone (c-H2C3O), which can be produced by adding an oxygen atom to cyclopropenylidene. The second method for constructing larger molecules from smaller ones involves neutral-radical reactions that can occur within the gas in an interstellar cloud. For example, in 2006, the scientists discovered acetamide (CH3CONH2), which can be formed when a previously-discovered neutral molecule called formamide (HCONH2) combines with radicals such as CH2 and CH3, also previously discovered. Acetamide is particularly interesting because it contains a peptide bond which is the means for linking amino acids together to form proteins. Once interstellar molecules are ejected from dust grains into the gas phase, presumably by shock waves, they are free to rotate end-over-end. As gas molecules change their rotational modes, they can emit or absorb radiation at precise radio frequencies, called transitions, that are unique to each type of molecule. By detecting several rotational transitions, astronomers can unambiguously identify a specific interstellar molecule. "It is important to note that likely interstellar molecule candidates are first studied in gas-phase laboratory experiments so that transition frequencies are known in advance of an interstellar experiment," said Frank Lovas of the National Institute of Standards and Technology. Along the line of sight from the interstellar cloud to the telescope, thousands of billions of molecules undergo the exact same transition, producing a signal strong enough to be detected by sensitive equipment. For this type of work, the GBT is the world's most sensitive tool that can be accurately pointed and track astronomical objects. In addition to Hollis, Jewell, Remijan, and Lovas, the research team included Lewis Snyder of the University of Illinois; Harald Mollendal of the University of Oslo, Norway; Vadim Ilyushin of the Institute of Radio Astronomy of the National Academy of Sciences of the Ukraine; and Isabell Kleiner of the Universite Paris, France. The astronomers' reports on their results appeared in 8 separate editions of the Astrophysical Journal. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.