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Sample records for mercaptoethylamines

  1. Studies on chemical protectors against radiation, 18

    International Nuclear Information System (INIS)

    Shinoda, Masato; Ohta, Setsuko; Hayase, Yukitoshi

    1978-01-01

    Radiation protective effect of S,2-aminomethylisothiuronium bromide hydrobromide and 2-mercaptoethylamine hydrochloride was tested on mice irradiated with soft x-ray of 70 kVp, using life-prolongation effect as an index. These compounds showed a marked effect on mice irradiated with 11000--13000 R, using a 10 mm acrylate filter. This method seemed to be usable as a potency testing for chemical radioprotectors. (auth.)

  2. Radioprotector modifying influence upon the ion transport ATPase activities

    International Nuclear Information System (INIS)

    Dvoretsky, A.I.; Egorova, E.G.; Ananieva, T.V.; Kulikova, I.A.

    1993-01-01

    The effects of aminothiol and biogenic amine radioprotectors (β-mercaptoethylamine, AET, serotonin, dopamine, histamine) on the basic ion transport enzymes, such as Na, K-ATP ase and Mg, Ca-ATPase activities were investigated in the tissues of numerous organs, with different radiosensitivity in the wistar rats. Experimental results showed that intraperitoneal injection of the used radioprotectors caused preliminary inhibition of the Na, K-ATPase activity in tissues from organs with different radioresistance, but had no influence on the Mg, Ca-ATPase activity in membranes of erythrocytes and rat brain cells. (2 tabs.)

  3. Solvent isotope effects on the rates of alkylation of thiolamine models of papain

    International Nuclear Information System (INIS)

    Wandinger, A.; Creighton, D.J.

    1980-01-01

    As a test of whether it is chemically reasonable to attribute any or all of the observed kinetic solvent deuterium isotope effects reported on papain to the fundamental properties of the tautomerization equilibrium, the magnitudes of the solvent deuterium isotope effects on the rates of alkylation of the tautomeric forms of cysteine and β-mercaptoethylamine were determined for bromo- and chloroacetate, bromo- and chloroacetamide, as well as for methylbromoacetate. These thiolamines are viewed as elementary chemical models of the sulfhydryl group tautomerization equilibrium envisioned in the active site of papain. (Auth.)

  4. Nickel-supported carbon nitride photocatalyst combined with organic dye for visible-light-driven hydrogen evolution from water.

    Science.gov (United States)

    Mori, Kohsuke; Itoh, Taiki; Kakudo, Hiroki; Iwamoto, Tomoyuki; Masui, Yoichi; Onaka, Makoto; Yamashita, Hiromi

    2015-10-07

    A noble-metal-free photocatalytic H2 production system consisting of a Ni-based catalyst, visible-light-responsive organic dye, and graphitic carbon nitride (g-C3N4) as a support has been developed. Characterization by means of XAFS revealed that the deposition of a trinuclear Ni precursor complex, Ni(NiL2)2Cl2 (L = β-mercaptoethylamine), on the g-C3N4 affords a monomeric Ni(ii) species involving β-mercaptoethylamine and aqua ligands in an octahedral coordination geometry. Such a Ni species acts as a hydrogen production site from an aqueous solution without an electron relay reagent by combining with thiazole orange (TO) as a photosensitizer. The emission of the attached TO at around 550 nm decreases with increasing loading amount of Ni catalyst, suggesting electron transfer from TO to the Ni catalyst via the g-C3N4 support. Leaching and agglomeration of the active Ni catalyst and TO are not observed during the photocatalytic reaction. Moreover, the use of highly porous carbon nitride (nanoporous carbon nitride; nanoC3N4) is proven to significantly enhance the photocatalytic activity because of the high surface area due to the unique porous structure as well as high absorption and emission properties of TO associated with nanoC3N4.

  5. Circumvention of the tumor membrane barrier to WR-2721 absorption by reduction of drug hydrophilicity

    International Nuclear Information System (INIS)

    Yuhas, J.M.; Davis, M.E.; Glover, D.; Brown, D.Q.; Ritter, M.

    1982-01-01

    In attempting to account for the ability of most solid tumors to restrict the absorption of WR-2721, aminopropyl-aminoethylphosphorothioate, we examined a number of drug characteristics which might allow for this restriction, and observed that drug hypdrophilicity was a major contributing factor. When the highly hydrophilic WR-2721 was dephosphorylated, the drug became less hydrophilic and could readily cross tumor cell membranes. In addition, conventional radioprotectants, such as cysteine and mercaptoethylamine, were shown to be less hydrophilic than WR-2721 and also to cross tumor membranes readily. Therefore, drug hydrophilicity would appear to be the factor underlying the ability of WR-2721 to selectively protect normal tissues while most other protectors alter the radiation resistance of normal and tumor tissue alike. A red blood cell model for studying this problem in greater detail is described

  6. ESR studies on the effects of ionizing radiation in biological media

    International Nuclear Information System (INIS)

    Stockhausen, K.

    1976-01-01

    The various effects of molecular oxygen on the radiosensitivity of bacteria is closely connected with the development of peroxyradicals during radiation exposure and their effects. Irradiated 'molecular mixtures' consisting of sephadex and penicillamine show the phenomenon of energy transfer. This might be a fundamental aspect of the damage to biomolecules on the one hand and of the molecular radiation protection on the other. Very closely connected with this phenomenon is the 'repair' of damaged cell modules by radioprotective substances, such as amino acids containing sulphur. Damaged heads of the spermatozoons of herrings are obviously 'repaired' during storage of several days' duration at room temperature if a few percent of the immunizing substance mercaptoethylamine are added to them during irradiation. ESR-examinations of DNA and its components make the mutagenic effect of ionising radiation plausible. They give information about the points in these macromolecules in which radicals are localized. Quantitative determinations of the yield of radicals in each component of the DNA show that there are significant differences in the radiosensitivity of the different DNA-modules and that energy transfer processes can take place within the macromolecule. Longlived radicals in certain tissues of the living organism, such as bones, fingernails, or teeth, can be very useful to develop methods of dosimetry after radiation accidents and of radiotherapy with the help of the help of the ESR-techniques. (orig.) [de

  7. Emission properties of colloidal quantum dots on polyelectrolyte multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Komarala, Vamsi K [Semiconductor Photonics Group, School of Physics, Trinity College Dublin (Ireland); Rakovich, Yury P [Semiconductor Photonics Group, School of Physics, Trinity College Dublin (Ireland); Bradley, A Louise [Semiconductor Photonics Group, School of Physics, Trinity College Dublin (Ireland); Byrne, Stephen J [School of Chemistry, Trinity College Dublin, Republic of (Ireland); Corr, Serena A [School of Chemistry, Trinity College Dublin, Republic of (Ireland); Gun' ko, Yurii K [School of Chemistry, Trinity College Dublin (Ireland)

    2006-08-28

    We present steady state and time-resolved photoluminescence (PL) characteristics of differently charged CdTe quantum dots (QDs) adsorbed onto a polyelectrolyte (PE) multilayer. The PE multilayer is built up using a layer-by-layer assembly technique. We find that the diffusion of the QDs into the PE multilayer is an important factor in the case of 3-mercapto-1, 2-propanediol stabilized QDs (neutral surface charge), resulting in a {approx}31-fold enhancement in PL intensity accompanied by a blue shift in the PL spectra and an increase in decay lifetime from 3.74 ns to a maximum of 11.65 ns. These modified emission properties are attributed to the enhanced surface related emission resulting from the interaction of the QD's surface with the PE. We find that diffusion does not occur for thioglycolic acid (TGA) stabilized QDs (negative surface charge) or 2-mercaptoethylamine stabilized QDs (positive surface charge), indicating localization of the QDs on top of the PE multilayer. However, the PL lifetime of the TGA stabilized QDs decreases from 9.58 to 5.78 ns with increasing PE multilayer thickness. This provides evidence for increased intrinsic exciton recombination relative to surface related emission, which results in an overall reduction in the average lifetime. Our studies indicate the importance of the QD surface charge in determining the interaction with the PE multilayers and the subsequent modification of the QD emission properties.

  8. Designing multilayered nanoplatforms for SERS-based detection of genetically modified organisms

    Science.gov (United States)

    Uluok, Saadet; Guven, Burcu; Eksi, Haslet; Ustundag, Zafer; Tamer, Ugur; Boyaci, Ismail Hakki

    2015-01-01

    In this study, the multilayered surface-enhanced Raman spectroscopy (SERS) platforms were developed for the analysis of genetically modified organisms (GMOs). For this purpose, two molecules [11-mercaptoundecanoic acid (11-MUA) and 2-mercaptoethylamine (2-MEA)] were attached with Aurod and Auspherical nanoparticles to form multilayered constructions on the gold (Au)slide surface. The best multilayered platform structure was chosen depending on SERS enhancement, and this surface was characterised with atomic force microscopy (AFM) and attenuated total reflectance Fourier transform infrared spectroscopy. After the optimum multilayered SERS platform and nanoparticle interaction was identified, the oligonucleotides on the Aurod nanoparticles and Auslide were combined to determine target concentrations from the 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) signals using SERS. The correlation between the SERS intensities for DTNB and target concentrations was found to be linear within a range of 10 pM to 1 µM, and with a detection limit of 34 fM. The selectivity and specificity of the developed sandwich assay were tested using negative and positive controls, and nonsense and real sample studies. The obtained results showed that the multilayered SERS sandwich method allows for sensitive, selective, and specific detection of oligonucleotide sequences.

  9. Enhanced thermal and mechanical properties of PLA/MoS2 nanocomposites synthesized via the in-situ ring-opening polymerization

    Science.gov (United States)

    Chen, Pengpeng; Liang, Xiao; Xu, Ying; Zhou, Yifeng; Nie, Wangyan

    2018-05-01

    In this work, MoS2 nanosheets were employed to reinforce PLA. In order to promote the homogeneous dispersion of MoS2 in PLA and form a strong interface between MoS2 and PLA, the MoS2 nanosheets were firstly modified by mercapto-ethylamine, and then functionalized with PLA chains through ring-opening polymerization of poly(L-lactide). The XRD, XPS, TGA and 1H NMR characterizations confirmed the successful amino and PLA functionalization of MoS2 nanosheets. The obtained MoS2-g-PLA nanosheets were then introduced to reinforce PLA. SEM images displayed that the MoS2-g-PLA nanosheets were dispersed in PLA matrix uniformly. TGA results showed that initial decomposition temperature was improved from 275.6 °C to 334.8 °C with 0.5 wt% of MoS2-g-PLA nanosheets. The storage modulus of PLA/MoS2-g-PLA-0.5 wt% in the glass state and rubber state were both greatly enhanced compared with neat PLA.

  10. Specific behavior of the p-aminothiophenol--silver sol system in their Ultra-Violet-Visible (UV-Visible) and Surface Enhanced Raman (SERS) spectra.

    Science.gov (United States)

    Firkala, Tamás; Tálas, Emília; Mihály, Judith; Imre, Tímea; Kristyán, Sándor

    2013-11-15

    The UV-Visible and Surface Enhanced Raman Spectroscopy (SERS) behavior of silver sol (a typical SERS agent) were studied in the presence of different bifunctional thiols such as p-aminothiophenol, p-mercaptobenzoic acid, p-nitrothiophenol, p-aminothiophenol hydrochloride, and 2-mercaptoethylamine hydrochloride in diluted aqueous solution. Our results confirm that the p-aminothiophenol induced aggregation of citrate stabilized silver colloid originates from its electrostatic nature, as well as the azo-bridge formation cannot be the reason of the observed time dependent UV-Visible spectra. Based on our parallel SERS and electrospray ionization mass spectrometry measurements, we have concluded that certain amount of oxidized form of the probe molecule has to be present for the so-called b2-mode enhancement in the SERS spectrum of p-aminothiophenol. Our findings seem to support the idea that the azo-bridge formation is responsible for the b2-mode enhancement in the SERS spectrum of p-aminothiophenol. Copyright © 2013 Elsevier Inc. All rights reserved.

  11. Direct Electrochemistry of Methanobactin Functionalized Gold Nanoparticles on Au Electrode.

    Science.gov (United States)

    Xin, Jiaying; Dou, Boxin; Wang, Zhenxing; Wang, Yan; Xia, Chungu; Liu, Zhongfan

    2018-07-01

    Mathanobatins (Mb, Mbtins) were immobilized successfully on nanometer-sized gold colloid particles associated with β-mercaptoethylamine. The structures of Mb functionalized gold nanoparticles were characterized and confirmed by UV-vis spectroscopy (UV-vis), FTIR spectra and electrochemical analyses. Direct electron transfer between Mb or copper-loading Mbtins and the modified electrode was investigated without the aid of any electron mediator. The copper-loading Mbtins act as a better electrocatalyst for the reduction of H2O2 than Mb. The copper-loading Mb, with which gold nanoparticles were functionalized, as a model enzyme, was immobilized on gold electrode to construct a novel H2O2 biosensor. In pH 6.4 phosphate buffer solution, the reduction and oxidation peak potentials of Mb functionalized gold nanoparticles modified Au electrode (copper-loading Mbtins) were 0.115 and 0.222 V. On the surface, capacitance per unite area (Cd) of Mb functionalized gold nanoparticles modified electrode were 38 μF cm-2. The immobilized Mb displayed the features of a peroxidase and gave an excellent electrocatalytic response to the reduction of H2O2. The detection limit of Mb functionalized gold nanoparticles (copper-loading) were 09 × 10-5 mA/M (S/N = 3). The Michaelis-Menten constant (Km) was 0.787 mM. Good stability and sensitivity were assessed for the biosensor.

  12. A comprehensive immunoassay for the detection of microcystins in waters based on polyclonal antibodies

    International Nuclear Information System (INIS)

    Sheng Jianwu; He Miao; Shi Hanchang; Qian Yi

    2006-01-01

    Microcystins (MCs) are a group of closely related toxic cyclic heptapeptides produced by common cyanobacteria (blue-green algae), and microcystin-leucine-arginine (MC-LR) is among the most frequent and most toxic microcystin congeners. In this study, a free amino group was introduced to MC-LR at its seventh amino acid residue with 2-mercaptoethylamine, and the product aminoethyl-MC-LR was coupled to bovine serum albumin (BSA) and horseradish peroxidise (HRP) by glutaraldehyde to be complete antigen (MC-LR-BSA) and labelled hapten (MC-LR-HRP), respectively. Polyclonal antibodies against MC-LR were generated by immunization with MC-LR-BSA. A direct competitive enzyme-linked immunosorbent assay (dc-ELISA) was established to detect the MCs in waters, which showed a good cross-reactivity with MC-LR, MC-RR, MC-YR, MC-LF, MC-LW and nodularin, and have a detection limit for MC-LR 0.12 μg L -1 , the 50% inhibition concentration (IC 50 ) for MC-LR was 0.63 ± 0.06 μg L -1 and the quantitative detection range was from 0.17 to 2.32 μg L -1 , the analysis result of water samples showed good recovery and reliability. So the comprehensive and reliable dc-ELISA will well potentially suit for sensitive analysis for total MCs in drinking as well as resource water samples

  13. Designing multilayered nanoplatforms for SERS-based detection of genetically modified organisms

    Energy Technology Data Exchange (ETDEWEB)

    Uluok, Saadet [Dumlupinar University, Department of Chemistry, Faculty of Arts and Sciences (Turkey); Guven, Burcu [Hacettepe University, Department of Food Engineering, Faculty of Engineering (Turkey); Eksi, Haslet [Hacettepe University, Food Research Center (Turkey); Ustundag, Zafer [Dumlupinar University, Department of Chemistry, Faculty of Arts and Sciences (Turkey); Tamer, Ugur [Gazi University, Department of Analytical Chemistry, Faculty of Pharmacy (Turkey); Boyaci, Ismail Hakki, E-mail: ihb@hacettepe.edu.tr [Hacettepe University, Department of Food Engineering, Faculty of Engineering (Turkey)

    2015-01-15

    In this study, the multilayered surface-enhanced Raman spectroscopy (SERS) platforms were developed for the analysis of genetically modified organisms (GMOs). For this purpose, two molecules [11-mercaptoundecanoic acid (11-MUA) and 2-mercaptoethylamine (2-MEA)] were attached with Au{sub rod} and Au{sub spherical} nanoparticles to form multilayered constructions on the gold (Au){sub slide} surface. The best multilayered platform structure was chosen depending on SERS enhancement, and this surface was characterised with atomic force microscopy (AFM) and attenuated total reflectance Fourier transform infrared spectroscopy. After the optimum multilayered SERS platform and nanoparticle interaction was identified, the oligonucleotides on the Au{sub rod} nanoparticles and Au{sub slide} were combined to determine target concentrations from the 5,5′-dithiobis (2-nitrobenzoic acid) (DTNB) signals using SERS. The correlation between the SERS intensities for DTNB and target concentrations was found to be linear within a range of 10 pM to 1 µM, and with a detection limit of 34 fM. The selectivity and specificity of the developed sandwich assay were tested using negative and positive controls, and nonsense and real sample studies. The obtained results showed that the multilayered SERS sandwich method allows for sensitive, selective, and specific detection of oligonucleotide sequences.

  14. Design of a covalently bonded glycosphingolipid microarray

    DEFF Research Database (Denmark)

    Arigi, Emma; Blixt, Klas Ola; Buschard, Karsten

    2012-01-01

    Glycosphingolipids (GSLs) are well known ubiquitous constituents of all eukaryotic cell membranes, yet their normal biological functions are not fully understood. As with other glycoconjugates and saccharides, solid phase display on microarrays potentially provides an effective platform for in vi......Glycosphingolipids (GSLs) are well known ubiquitous constituents of all eukaryotic cell membranes, yet their normal biological functions are not fully understood. As with other glycoconjugates and saccharides, solid phase display on microarrays potentially provides an effective platform......, the major classes of plant and fungal GSLs. In this work, a prototype "universal" GSL-based covalent microarray has been designed, and preliminary evaluation of its potential utility in assaying protein-GSL binding interactions investigated. An essential step in development involved the enzymatic release......-mercaptoethylamine, was also tested. Underivatized or linker-derivatized lyso-GSL were then immobilized on N-hydroxysuccinimide- or epoxide-activated glass microarray slides and probed with carbohydrate binding proteins of known or partially known specificities (i.e., cholera toxin B-chain; peanut agglutinin...

  15. Food allergen analysis for processed food using a novel extraction method to eliminate harmful reagents for both ELISA and lateral-flow tests.

    Science.gov (United States)

    Ito, Kaori; Yamamoto, Takayuki; Oyama, Yuriko; Tsuruma, Rieko; Saito, Eriko; Saito, Yoshikazu; Ozu, Takeshi; Honjoh, Tsutomu; Adachi, Reiko; Sakai, Shinobu; Akiyama, Hiroshi; Shoji, Masahiro

    2016-09-01

    Enzyme-linked immunosorbent assay (ELISA) is commonly used to determine food allergens in food products. However, a significant number of ELISAs give an erroneous result, especially when applied to highly processed food. Accordingly, an improved ELISA, which utilizes an extraction solution comprising the surfactant sodium lauryl sulfate (SDS) and reductant 2-mercaptoethanol (2-ME), has been specially developed to analyze food allergens in highly processed food by enhancing analyte protein extraction. Recently, however, the use of 2-ME has become undesirable. In the present study, a new extraction solution containing a human- and eco-friendly reductant, which is convenient to use at the food manufacturing site, has been established. Among three chemicals with different reducing properties, sodium sulfite, tris(3-hydroxypropyl)phosphine, and mercaptoethylamine sodium sulfite was selected as a 2-ME substitute. The protein extraction ability of SDS/0.1 M sodium sulfite solution was comparable to that of SDS/2-ME solution. Next, the ELISA performance for egg, milk, wheat, peanut, and buckwheat was evaluated by using model-processed foods and commercially available food products. The data showed that the SDS/0.1 M sulfite ELISA significantly correlated with the SDS/2-ME ELISA for all food allergens examined (p food allergens in processed food, showing consistency with the SDS/0.1 M sulfite ELISA results. Accordingly, a harmonized analysis system for processed food comprising a screening LF test and a quantitative ELISA with identical extraction solution has been established. The ELISA based on the SDS/0.1 M sulfite extraction solution has now been authorized as the revised official method for food allergen analysis in Japan.

  16. Binding of the radioprotective agent cysteamine with the phospholipidic membrane headgroup-interface region

    Energy Technology Data Exchange (ETDEWEB)

    Berleur, F.; Roman, V.; Jaskierowicz, D.; Fatome, M.; Leterrier, F.; Ter-Minassian-Saraga, L.; Madelmont, G.

    1985-09-01

    The interaction of the aminothiol radioprotector cysteamine (..beta..-mercaptoethylamine)(CYST) with dipalmitoylphosphatidylcholine (DPPC) artificial membranes has been studied by differential scanning calorimetry (DSC), turbidimetry and spin labeling. This hydrophilic molecule displays a biphasic, concentration-dependent binding to the phospholipidic head groups at neutral pH. In the CYST/DPPC molar ratio 1:160-1:2 (mole/mole) an increasing ordering effect is observed. At high concentrations (over 3:1 ratio), this ordering effect decreases. With the symmetric disulfide dimer cystamine, the biphasic effect is not shown and the membrane rigidity decrease is obtained only at concentration ratio higher than 1:1. The charge repartition of the cysteamine molecule has been shown to be disymmetric, +0.52 e on the NH/sub 3/ group and +0.19 e on the SH extremity, whereas the cystamine molecule is electrostatically symmetrical. These properties could be related to their membrane effects. With cysteamine, at a low concentration, an electrostatic bridging between the negatively charged phosphate groups of the polar heads induces the increase in membrane stability: the molecules behave like a divalent cation. At high concentration a displacement of the slightly charged SH extremity by the amine disrupts the bridges and induces the decrease in rigidity: the drug behaves like a monovalent cation. Due to its symmetric charge and its double length, such an effect is not observed with cystamine. This study could bring further information about the interactions between cysteamine and polyelectrolytic structures (ADN for example) and about the radioprotective properties of this drug.

  17. The effects of cysteamine on the radiation-induced apoptosis

    International Nuclear Information System (INIS)

    Choi, Young Min; Cho, Heung Lae; Park, Chang Gyo; Lee, Hyung Sik; Hur, Won Joo

    2000-01-01

    To investigate the pathways of radiation induced apoptosis and the effect of cysteamine (β-mercaptoethylamine), as a radioprotector, on it. HL-60 cells were assigned to control, irradiated, and cysteamine (1 mM, 10 mM) pretreated groups. Irradiation was given in a single fraction of 10 Gy (6 MV x-ray) and cysteamine was administered 1 hour before irradiation. The activities of caspase-8 were measured in control and irradiated group to evaiuate its relation to the radiation induced apoptosis. To evaluate the role of cysteamine in radiation induced apoptosis, the number of viable cells, the expression and activity or caspase-3, and the expression of poly (ADP-ribose) polymerase (PARP) were measured and compared after irradiating the HL cells with cysteamine pretreatment or not. The intracellular caspase-8 activity, known to be related to the death receptor induced apoptosis, was not affected by irradiation( p>0.05). The number of viable cells began to decrease from 6 hours after irradiation (p>0.05), but the number of viable cells in 1 mM cysteamine pretreated group was not decreased after irradiation and was similar to those in the control group. In caspase-3 analyses, known as apoptosis executioner, its expression was not different but its activity was increased by irradialion(p>0.05). However, this increase of activity was suppressed by the pretreatment of 1 mM cysteamine. The cleavage of PARP, thought to be resulted from caspase-3 activation, occurred, after irradiation, which was attenuated by the pretreatment of 1 mM cysteamine. These results show that radiation induced apoptotic process is somewhat different from death receptor induced one and the pretreatment of 1 mM cysteamine has a tendency to decrease the radiation-induced apoptosis in HL-60 cells

  18. Kinetics and mechanism of the conversion of a coordinated thiol to a coordinated disulfide by the one-equivalent oxidants neptunium(VI) and cobalt(III) in aqueous perchloric acid

    International Nuclear Information System (INIS)

    Woods, M.; Karbwang, J.; Sullivan, J.C.; Deutsch, E.

    1976-01-01

    Reaction of excess (2-mercaptoethylamine-N,S)bis(ethylenediamine)cobalt(III), I, with the 1-equiv oxidant Np(VI) (or Co 3+ (aq)) in aqueous perchloric acid media is shown to lead to (2-aminoethyl-N 2-ammonioethyl disulfide-S 1 ) bis(ethylenediamine)cobalt(III), II, according to the stoichiometry 5H + + 2I + Np(VI) → II + Co 2+ (aq) + Np(V) + 2enH 2 2+ . This reaction follows the rate law -d[I]/dt = k'' [I] [oxidant]. For Np(VI) as oxidant k'' is independent of [H + ]; at 25 0 C, μ = 1.00 M (LiClO 4 ), k'' = k 0 = 2842 +- 15 M -1 s -1 , ΔH 0 * = 7.57 +- 0.08 kcal/mol, and ΔS 0 * = -17.4 +- 0.3 eu. For Co 3+ (aq) as oxidant, k'' = k 0 + k/sub -1/[H + ] -1 where the inverse acid path is taken to reflect oxidation by CoOH 2+ (aq); at 25 0 C, μ = 1.00 M (LiClO 4 ), k 0 = 933 +- 32 M -1 s -1 , k/sub -1/ = 1152 +- 22 s -1 , ΔH 0 * = 12.5 +- 0.7 kcal/mol, ΔH*/sub -1/ = 18.0 +- 0.4 kcal/mol, ΔS 0 *= -3.1 +- 2.4 eu, and ΔS*/sub -1/ = 15.8 +- 1.2 eu. It is proposed that the conversion of I to II proceeds by initial 1-equiv oxidation of the coordinated thiol, reaction of the resultant coordinated thiol radical (RS.) with additional I to form a relatively stable radical ion dimer (RSSR. - ), and then internal electron transfer within the dimer to yield Co 2+ (aq) and II which contains a coordinated disulfide. The possible generality of this mechanism and its relevance to biological metal-thiol-disulfide interactions are noted

  19. Synthesis, structure, and H2O2-dependent catalytic functions of disulfide-bridged dicopper(I) and related thioether-copper(I) and thioether-copper(II) complexes.

    Science.gov (United States)

    Ohta, T; Tachiyama, T; Yoshizawa, K; Yamabe, T; Uchida, T; Kitagawa, T

    2000-09-18

    A disulfide-bridged dicopper(I) complex, [Cu2(Py2SSPy2)](ClO4)2 (1) (Py2SSPy2 = bis(2-[N,N-bis(2-pyridylethyl)-amino]-1,1- dimethylethyl)disulfide), a thioether-copper(I) complex, [Cu(iPrSPy2)](ClO4) (2) (iPrSPy2 = N-(2-isopropylthio-2-methyl)propyl-N,N-bis-2-(2-pyridyl)ethylamine, and a thioether-copper(II) complex, [Cu-(PheSPy2)(H2O)](ClO4)2 (3) (PheSPy2 = N-(2-methyl-2-phenethylthio)propyl-N,N-bis-2-(2- pyridyl)ethylamine), were newly synthesized by the reactions of Cu(ClO4)2.6H2O with a thiol ligand of Py2SH (N,N-bis[2-(2-pyridyl)-ethyl]-1,1-dimethyl-2- mercaptoethylamine) and thioether ligands of iPrSPy2 and PheSPy2, respectively. For complexes 1 and 2, X-ray analyses were performed. Complex 1 crystallizes in the triclinic space group P1, and complex 2 crystallizes in the orthorhombic space group Pbca with the following unit cell parameters: for 1, a = 15.165 (3) A, b = 22.185 (4) A, c = 14.989 (3) A, alpha = 105.76 (1) degrees, beta = 90.82 (2) degrees, gamma = 75.23 (1) degrees, and Z = 2; for 2, a = 17.78 (2) A, b = 17.70 (1) A, c = 15.75 (1) A, and Z = 8. Complex 1 is the first structurally characterized example obtained by the redox reaction Cu(II) + RSH-->Cu(I) + RSSR and has two independent structures (1a, 1b) which mainly differ in S-S bond distances, Cu(I)...Cu(I) separations, and C-S-S-C dihedral angles of the disulfide units. The S-S bond distances of 2.088(7) A in 1a and 2.070(7) A in 1b are indicative of significant activation of the S-S bonds by the dicopper centers. Fragment molecular orbital (FMO) analyses and molecular orbital overlap population (MOOP) analyses based on the extended Hückel method clarify the preferable formation of the disulfide S-S bond in 1 rather than the formation of a thiolate-copper(II) complex within the Py2S- ligand framework. Catalytic functions of complexes 1-3 were investigated with peroxides (H2O2 and tBuOOH) as oxidants. Complex 1 catalyzed the selective oxidation of cyclohexane to cyclohexanol and mediated the