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Sample records for thiol ester-organostannane cross-coupling

  1. Gas-phase studies of copper catalyzed aerobic cross coupling of thiol esters and arylboronic acids

    Czech Academy of Sciences Publication Activity Database

    Tsybizová, A.; Schröder, Detlef; Roithová, J.; Henke, A.; Šrogl, Jiří

    2014-01-01

    Roč. 27, č. 3 (2014), s. 198-203 ISSN 0894-3230 R&D Projects: GA ČR GAP207/12/0846 Grant - others:GA ČR(CZ) GAP207/11/0338 Institutional support: RVO:61388963 Keywords : boronic acids * catalysis * copper * cross coupling * electrospray ionization * mass spectrometry * kinetic studies Subject RIV: CC - Organic Chemistry Impact factor: 1.380, year: 2014

  2. Copper-mediated C-H activation/C-S cross-coupling of heterocycles with thiols

    KAUST Repository

    Ranjit, Sadananda

    2011-11-04

    We report the synthesis of a series of aryl- or alkyl-substituted 2-mercaptobenzothiazoles by direct thiolation of benzothiazoles with aryl or alkyl thiols via copper-mediated aerobic C-H bond activation in the presence of stoichiometric CuI, 2,2′-bipyridine and Na 2CO 3. We also show that the approach can be extended to thiazole, benzimidazole, and indole substrates. In addition, we present detailed mechanistic investigations on the Cu(I)-mediated direct thiolation reactions. Both computational studies and experimental results reveal that the copper-thiolate complex [(L)Cu(SR)] (L: nitrogen-based bidentate ligand such as 2,2′-bipyridine; R: aryl or alkyl group) is the first reactive intermediate responsible for the observed organic transformation. Furthermore, our computational studies suggest a stepwise reaction mechanism based on a hydrogen atom abstraction pathway, which is more energetically feasible than many other possible pathways including β-hydride elimination, single electron transfer, hydrogen atom transfer, oxidative addition/reductive elimination, and σ-bond metathesis. © 2011 American Chemical Society.

  3. Copper- and Palladium-Catalyzed Cross-Coupling Reactions for the Synthesis of N-Fused Benzo[4,5]imidazo[2,1-b]thiazole Derivatives via Substituted trans-1,2-Diiodoalkenes, 1H-Benzo[d]imidazole-2-thiols, and Halobenzenes.

    Science.gov (United States)

    Shen, Guodong; Yang, Bingchuan; Huang, Xianqiang; Hou, Yaxin; Gao, Huan; Cui, Jichun; Cui, Chuansheng; Zhang, Tongxin

    2017-04-07

    Two transition metal (Cu and Pd)-catalyzed C-S, C-N, and C-C bond cross-coupling reactions for the preparation of N-fused benzo[4,5]imidazo[2,1-b]thiazole derivatives were developed. A variety of 3-substituted and 2,3-disubstituted benzo[4,5]imidazo[2,1-b]thiazoles were efficiently and conveniently synthesized from the coupling reaction via trans-1,2-diiodoalkenes, 1H-benzo[d]imidazole-2-thiols, and halobenzenes in moderate to excellent yields.

  4. Asymptotic behavior for cross coupled parabolic equations

    Directory of Open Access Journals (Sweden)

    Yingzhen XUE

    2017-04-01

    Full Text Available In order to better describe the heat transfer process of three kinds of mixed substances, namely the reaction of the reactants in the three chemical reactions, a class of three variable cross coupling with non parabolic equations of the whole existence of local source and non local boundary flow and the finite time blow up problem with breaking method for the solution of the first commonly used feature value structure are studied. The structure of the equations of the upper and lower solutions by using the method of ordinary differential equation reference is broken, with comparison theorem, the proof shows that obtained by local source power function and exponential function of parabolic equations is broken, with the sufficient conditions for global existence of clegerate purubolic equations solutions cross coupled by local source power function and non local sources exponential function are proved, as soon as the solution of blowing up in finite time degradation of non local sources of cross coupling, providing better support for the theory of heat transfer and chemical reaction problem.

  5. Nanocatalysts for Suzuki cross-coupling reactions

    KAUST Repository

    Fihri, Aziz

    2011-01-01

    This critical review deals with the applications of nanocatalysts in Suzuki coupling reactions, a field that has attracted immense interest in the chemical, materials and industrial communities. We intend to present a broad overview of nanocatalysts for Suzuki coupling reactions with an emphasis on their performance, stability and reusability. We begin the review with a discussion on the importance of Suzuki cross-coupling reactions, and we then discuss fundamental aspects of nanocatalysis, such as the effects of catalyst size and shape. Next, we turn to the core focus of this review: the synthesis, advantages and disadvantages of nanocatalysts for Suzuki coupling reactions. We begin with various nanocatalysts that are based on conventional supports, such as high surface silica, carbon nanotubes, polymers, metal oxides and double hydroxides. Thereafter, we reviewed nanocatalysts based on non-conventional supports, such as dendrimers, cyclodextrin and magnetic nanomaterials. Finally, we discuss nanocatalyst systems that are based on non-conventional media, i.e., fluorous media and ionic liquids, for use in Suzuki reactions. At the end of this review, we summarise the significance of nanocatalysts, their impacts on conventional catalysis and perspectives for further developments of Suzuki cross-coupling reactions (131 references). © 2011 The Royal Society of Chemistry.

  6. Negishi cross-couplings in the synthesis of amino acids.

    OpenAIRE

    Brittain, W.D.G.; Cobb, S.L.

    2018-01-01

    The Negishi cross-coupling is a powerful C–C bond-forming reaction widely utilised in many areas of organic synthesis. This review details the use of Negishi cross-couplings in the synthesis of unnatural amino acids. The application of this reaction in the preparation of aromatic, heteroaromatic, and, complex amino acid derivatives are reviewed and presented herein.

  7. Regioselective Reductive Cross-Coupling Reactions of Unsymmetrical Alkynes.

    Science.gov (United States)

    Reichard, Holly A; McLaughlin, Martin; Chen, Ming Z; Micalizio, Glenn C

    2010-01-01

    The present microreview summarizes our progress over the last few years in defining regioselective reductive cross-coupling reactions of unsymmetrical alkynes with terminal- and internal alkynes, aldehydes, and imines. We begin with a brief historical perspective of metal-mediated reductive dimerization reactions of aromatic alkynes and discuss the challenges associated with "crossed" versions of this mode of reactivity. Next, a collection of available methods that allow for regioselective reductive cross-coupling of internal alkynes with terminal and internal alkynes, aldehydes, and imines is summarized. After an examination of the requirements for regioselectivity in these cases, the logic behind our design of alkoxide-directed titanium-mediated reductive cross-coupling reactions is presented. A nomenclature is introduced to delineate the presumed mechanistic origin of regioselection associated with each reaction design, and a presentation of alkoxide-directed regioselective reductive cross-coupling reactions of alkynes follows. Throughout, principal issues related to reactivity and selectivity are discussed to assess scope and limitations of available methods and to describe the broad challenges that exist for defining complex fragment union reactions based on reductive cross-coupling chemistry.

  8. Nonlinear Analysis of a Cross-Coupled Quadrature Harmonic Oscillator

    DEFF Research Database (Denmark)

    Djurhuus, Torsten; Krozer, Viktor; Vidkjær, Jens

    2004-01-01

    We derive the dynamic equations governing the cross-coupled quadrature oscillator leading to an expression for the trade-off between signal quadrature and close-in phase noise. The theory shows that nonlinearity in the coupling transconductance results in AM-PM noise close to the carrier, which...... increases with the coupling strength. The results are compared with SPECTRE RF simulations....

  9. Microstrip Cross-coupled Interdigital SIR Based Bandpass Filter

    Directory of Open Access Journals (Sweden)

    R. K. Maharjan

    2012-09-01

    Full Text Available A simple and compact 4.9 GHz bandpass filter for C-band applications is proposed. This paper presents a novel microstrip cross-coupled interdigital half-wavelength stepped impedance resonator (SIR based bandpass filter (BPF.The designed structure is similar to that of a combination of two parallel interdigital capacitors. The scattering parameters of the structure are measured using vector network analyzer (VNA. The self generated capacitive and inductive reactances within the interdigital resonators exhibited in a resonance frequency of 4.9 GHz. The resonant frequency and bandwidth of the capacitive cross-coupled resonator is directly optimized from the physical arrangement of the resonators. The measured insertion loss (S21 and return loss (S11 were 0.3 dB and 28 dB, respectively, at resonance frequency which were almost close to the simulation results.

  10. Enantiospecific and Iterative Suzuki-Miyaura Cross-Couplings.

    Science.gov (United States)

    Rygus, Jason P G; Crudden, Cathleen M

    2017-12-20

    The Suzuki-Miyaura cross-coupling reaction has emerged as one of the most powerful methods for the construction of carbon-carbon bonds. Though most widely utilized for the synthesis of sp 2 -sp 2 linkages, the use of this reaction to form stereochemistry-bearing sp 2 -sp 3 bonds has received widespread attention over the past decade. This Perspective highlights approaches to the synthesis of enantioenriched molecules via the Suzuki-Miyaura reaction. Particular focus is placed on the use of enantiomerically enriched organoboron compounds as coupling partners in stereospecific processes, as well as the development of enantioconvergent and group-selective reactions. In addition, progress in the development of chemoselective, iterative cross-coupling methods will be discussed.

  11. Regioselective Reductive Cross-Coupling Reactions of Unsymmetrical Alkynes

    OpenAIRE

    Reichard, Holly A.; McLaughlin, Martin; Chen, Ming Z.; Micalizio, Glenn C.

    2010-01-01

    The present microreview summarizes our progress over the last few years in defining regioselective reductive cross-coupling reactions of unsymmetrical alkynes with terminal- and internal alkynes, aldehydes, and imines. We begin with a brief historical perspective of metal-mediated reductive dimerization reactions of aromatic alkynes and discuss the challenges associated with “crossed” versions of this mode of reactivity. Next, a collection of available methods that allow for regioselective re...

  12. Thiol biochemistry of prokaryotes

    Science.gov (United States)

    Fahey, Robert C.

    1986-01-01

    The present studies have shown that GSH metabolism arose in the purple bacteria and cyanobacteria where it functions to protect against oxygen toxicity. Evidence was obtained indicating that GSH metabolism was incorporated into eucaryotes via the endosymbiosis giving rise to mitochrondria and chloroplasts. Aerobic bacteria lacking GSH utilize other thiols for apparently similar functions, the thiol being coenzyme A in Gram positive bacteria and chi-glutamylcysteine in the halobacteria. The thiol biochemistry of prokaryotes is thus seen to be much more highly diversified than that of eucaryotes and much remains to be learned about this subject.

  13. Synthesis of 4-substituted tetrahydropyridines by cross-coupling of enol phosphates

    DEFF Research Database (Denmark)

    Larsen, U.S.; Martiny, L.; Begtrup, M.

    2005-01-01

    Enol phosphates, synthesized from 4-piperidone, react by palladium catalyzed cross-coupling with arylboronic acids and by iron and palladium catalyzed cross-coupling with Grignard reagents to give 4-substituted tetrahydropyridines. (c) 2005 Elsevier Ltd. All rights reserved.......Enol phosphates, synthesized from 4-piperidone, react by palladium catalyzed cross-coupling with arylboronic acids and by iron and palladium catalyzed cross-coupling with Grignard reagents to give 4-substituted tetrahydropyridines. (c) 2005 Elsevier Ltd. All rights reserved....

  14. Nonlinear analysis of a cross-coupled quadrature harmonic oscillator

    DEFF Research Database (Denmark)

    Djurhuus, Torsten; Krozer, Viktor; Vidkjær, Jens

    2005-01-01

    The dynamic equations governing the cross-coupled quadrature harmonic oscillator are derived assuming quasi-sinusoidal operation. This allows for an investigation of the previously reported tradeoff between close-to-carrier phase noise and quadrature precision. The results explain how nonlinearity...... in the coupling transconductances, in conjunction with a finite amplitude relaxation time and de-tuning of the individual oscillators, cause close-to-carrier AM-to-PM noise conversion. A discussion is presented of how the theoretic results translate into design rules for quadrature oscillator ICs. SPECTRE RF...

  15. Cross-coupled control for all-terrain rovers.

    Science.gov (United States)

    Reina, Giulio

    2013-01-08

    Mobile robots are increasingly being used in challenging outdoor environments for applications that include construction, mining, agriculture, military and planetary exploration. In order to accomplish the planned task, it is critical that the motion control system ensure accuracy and robustness. The achievement of high performance on rough terrain is tightly connected with the minimization of vehicle-terrain dynamics effects such as slipping and skidding. This paper presents a cross-coupled controller for a 4-wheel-drive/4-wheel-steer robot, which optimizes the wheel motors' control algorithm to reduce synchronization errors that would otherwise result in wheel slip with conventional controllers. Experimental results, obtained with an all-terrain rover operating on agricultural terrain, are presented to validate the system. It is shown that the proposed approach is effective in reducing slippage and vehicle posture errors.

  16. Cross-Coupled Control for All-Terrain Rovers

    Directory of Open Access Journals (Sweden)

    Giulio Reina

    2013-01-01

    Full Text Available Mobile robots are increasingly being used in challenging outdoor environments for applications that include construction, mining, agriculture, military and planetary exploration. In order to accomplish the planned task, it is critical that the motion control system ensure accuracy and robustness. The achievement of high performance on rough terrain is tightly connected with the minimization of vehicle-terrain dynamics effects such as slipping and skidding. This paper presents a cross-coupled controller for a 4-wheel-drive/4-wheel-steer robot, which optimizes the wheel motors’ control algorithm to reduce synchronization errors that would otherwise result in wheel slip with conventional controllers. Experimental results, obtained with an all-terrain rover operating on agricultural terrain, are presented to validate the system. It is shown that the proposed approach is effective in reducing slippage and vehicle posture errors.

  17. Novel thiols of prokaryotes.

    Science.gov (United States)

    Fahey, R C

    2001-01-01

    Glutathione metabolism is associated with oxygenic cyanobacteria and the oxygen-utilizing purple bacteria, but is absent in many other prokaryotes. This review focuses on novel thiols found in those bacteria lacking glutathione. Included are glutathione amide and its perthiol, produced by phototrophic purple sulfur bacteria and apparently involved in their sulfide metabolism. Among archaebacteria, coenzyme M (2-mercaptoethanesulfonic acid) and coenzyme B (7-mercaptoheptanoylthreonine phosphate) play central roles in the anaerobic production of CH4 and associated energy conversion by methanogens, whereas the major thiol in the aerobic phototrophic halobacteria is gamma-glutamylcysteine. The highly aerobic actinomycetes produce mycothiol, a conjugate of N-acetylcysteine with a pseudodisaccharide of glucosamine and myo-inositol, AcCys-GlcNalpha(1 --> 1)Ins, which appears to play an antioxidant role similar to glutathione. Ergothioneine, also produced by actinomycetes, remains a mystery despite many years of study. Available data on the biosynthesis and metabolism of these and other novel thiols is summarized and key areas for additional study are identified.

  18. Oxygen Activated, Palladium Nanoparticle Catalyzed, Ultrafast Cross-Coupling of Organolithium Reagents

    NARCIS (Netherlands)

    Heijnen, Dorus; Tosi, Filippo; Vila, Carlos; Stuart, Marc C. A.; Elsinga, Philip H.; Szymanski, Wiktor; Feringa, Ben L.

    2017-01-01

    The discovery of an ultrafast cross-coupling of alkyland aryllithium reagents with a range of aryl bromides is presented. The essential role of molecular oxygen to form the active palladium catalyst was established; palladium nanoparticles that are highly active in cross-coupling reactions with

  19. Catalyst-Controlled Site-Selectivity Switching in Pd-Catalyzed Cross-Coupling of Dihaloarenes

    Directory of Open Access Journals (Sweden)

    Kei Manabe

    2014-08-01

    Full Text Available Pd-catalyzed, site-selective mono-cross-coupling of substrates with two identical halo groups is a useful method for synthesizing substituted monohalogenated arenes. Such arenes constitute an important class of compounds, which are commonly identified as drug components and synthetic intermediates. Traditionally, these site-selective reactions have been realized in a “substrate-controlled” manner, which is based on the steric and electronic differences between the two carbon-halogen bonds of the substrate. Recently, an alternative strategy, “catalyst-controlled” site-selective cross-coupling, has emerged. In this strategy, the preferred reaction site of a dihaloarene can be switched, merely by changing the catalyst used. This type of selective reaction further expands the utility of Pd-catalyzed cross-coupling. In this review, we summarize the reported examples of catalyst-controlled site-selectivity switching in Pd-catalyzed cross-coupling of dihaloarenes.

  20. C (sp2)–C (sp2) cross coupling reaction catalyzed by a palladacycle ...

    Indian Academy of Sciences (India)

    (sp2) cross coupling reaction catalyzed by a palladacycle phosphine complex: A simple and sustainable protocol in aqueous media. Seyyed Javad Sabounchei Marjan Hosseinzadeh. Articles Volume 127 Issue 11 November 2015 pp 1919- ...

  1. Predicting transmission of structure-borne sound power from machines by including terminal cross-coupling

    Science.gov (United States)

    Ohlrich, Mogens

    2011-10-01

    Structure-borne sound generated by audible vibration of machines in vehicles, equipment and house-hold appliances is often a major cause of noise. Such vibration of complex machines is mostly determined and quantified by measurements. It has been found that characterization of the vibratory source strength and the prediction of power transmission to a supporting structure or the machine casing itself can be greatly simplified if all mobility cross-terms and spatial cross-coupling of source velocities can be neglected in the analysis. In many cases this gives an acceptable engineering accuracy, especially at mid- and high-frequencies. For structurally compact machines, however, the influence of cross-coupling cannot always be ignored. The present paper addresses this problem and examines the transmission of structure-borne sound power by including spatial cross-coupling between pairs of translational terminals in a global plane. This paired or bi-coupled power transmission represents the simplest case of cross-coupling. The procedure and quality of the predicted transmission using this improved technique is demonstrated experimentally for an electrical motor unit with an integrated radial fan that was mounted resiliently in a vacuum cleaner casing. It is found that cross-coupling plays a significant role, but only at frequencies below 100 Hz for the examined system.

  2. Predicting transmission of structure-borne sound power from machines by including terminal cross-coupling

    DEFF Research Database (Denmark)

    Ohlrich, Mogens

    2011-01-01

    strength and the prediction of power transmission to a supporting structure or the machine casing itself can be greatly simplified if all mobility cross-terms and spatial cross-coupling of source velocities can be neglected in the analysis. In many cases this gives an acceptable engineering accuracy......, especially at mid- and high-frequencies. For structurally compact machines, however, the influence of cross-coupling cannot always be ignored. The present paper addresses this problem and examines the transmission of structure-borne sound power by including spatial cross-coupling between pairs......Structure-borne sound generated by audible vibration of machines in vehicles, equipment and house-hold appliances is often a major cause of noise. Such vibration of complex machines is mostly determined and quantified by measurements. It has been found that characterization of the vibratory source...

  3. Palladium-Catalyzed Suzuki–Miyaura Cross-Coupling in Continuous Flow

    Directory of Open Access Journals (Sweden)

    Christophe Len

    2017-05-01

    Full Text Available Carbon–carbon cross-coupling reactions are among the most important processes in organic chemistry and Suzuki–Miyaura reactions are the most widely used protocols. For a decade, green chemistry and particularly catalysis and continuous flow, have shown immense potential in achieving the goals of “greener synthesis”. To date, it seems difficult to conceive the chemistry of the 21st century without the industrialization of continuous flow process in the area of pharmaceuticals, drugs, agrochemicals, polymers, etc. A large variety of palladium Suzuki–Miyaura cross-coupling reactions have been developed using a continuous flow sequence for preparing the desired biaryl derivatives. Our objective is to focus this review on the continuous flow Suzuki–Miyaura cross-coupling using homogeneous and heterogeneous catalysts.

  4. Cross-Coupled Eye Movement Supports Neural Origin of Pattern Strabismus

    Science.gov (United States)

    Ghasia, Fatema F.; Shaikh, Aasef G.; Jacobs, Jonathan; Walker, Mark F.

    2015-01-01

    Purpose. Pattern strabismus describes vertically incomitant horizontal strabismus. Conventional theories emphasized the role of orbital etiologies, such as abnormal fundus torsion and misaligned orbital pulleys as a cause of the pattern strabismus. Experiments in animal models, however, suggested the role of abnormal cross-connections between the neural circuits. We quantitatively assessed eye movements in patients with pattern strabismus with a goal to delineate the role of neural circuits versus orbital etiologies. Methods. We measured saccadic eye movements with high-precision video-oculography in 14 subjects with pattern strabismus, 5 with comitant strabismus, and 15 healthy controls. We assessed change in eye position in the direction orthogonal to that of the desired eye movement (cross-coupled responses). We used fundus photography to quantify the fundus torsion. Results. We found cross-coupling of saccades in all patients with pattern strabismus. The cross-coupled responses were in the same direction in both eyes, but larger in the nonviewing eye. All patients had clinically apparent inferior oblique overaction with abnormal excylotorsion. There was no correlation between the amount of the fundus torsion or the grade of oblique overaction and the severity of cross-coupling. The disconjugacy in the saccade direction and amplitude in pattern strabismics did not have characteristics predicted by clinically apparent inferior oblique overaction. Conclusions. Our results validated primate models of pattern strabismus in human patients. We found no correlation between ocular torsion or oblique overaction and cross-coupling. Therefore, we could not ascribe cross-coupling exclusively to the orbital etiology. Patients with pattern strabismus could have abnormalities in the saccade generators. PMID:26024072

  5. Aqueous microwaves assisted cross-coupling reactions applied to unprotected nucleosides.

    Directory of Open Access Journals (Sweden)

    CHRISTOPHE eLEN

    2015-02-01

    Full Text Available Nucleoside analogues have attracted much attention due to their potential biological activities. Amongst all synthetic nucleosides, C5-modified pyrimidines and C7- or C8-modified purines have mostly been prepared using palladium cross-coupling reactions and then studied as antitumoral and antiviral agents. Our objective is to focus this review on the Suzuki-Miyaura and on the Heck cross-couplings of nucleosides using microwave irradiations which are an alternative technology compatible with green chemistry and sustainable development.

  6. Ruthenium(ii)-catalyzed olefination via carbonyl reductive cross-coupling.

    Science.gov (United States)

    Wei, Wei; Dai, Xi-Jie; Wang, Haining; Li, Chenchen; Yang, Xiaobo; Li, Chao-Jun

    2017-12-01

    Natural availability of carbonyl groups offers reductive carbonyl coupling tremendous synthetic potential for efficient olefin synthesis, yet the catalytic carbonyl cross-coupling remains largely elusive. We report herein such a reaction, mediated by hydrazine under ruthenium(ii) catalysis. This method enables facile and selective cross-couplings of two unsymmetrical carbonyl compounds in either an intermolecular or intramolecular fashion. Moreover, this chemistry accommodates a variety of substrates, proceeds under mild reaction conditions with good functional group tolerance, and generates stoichiometric benign byproducts. Importantly, the coexistence of KO t Bu and bidentate phosphine dmpe is vital to this transformation.

  7. pincer complex in Suzuki–Miyaura cross-coupling reaction under

    Indian Academy of Sciences (India)

    in microwave-assisted Suzuki–Miyaura cross-coupling. ∗. For correspondence reactions of aryl and heteroaryl halides (figure 1). To the best of our knowledge, this is the first report of a pin- cer complex employed in microwave-assisted catalytic reactions. 2. Experimental. All bromo compounds and boronic acid derivatives.

  8. Synthesis, cross-coupling, and anionic cyclization of ortho-substituted naphthaleneboronic esters

    DEFF Research Database (Denmark)

    Lysén, M.; Madden, M.; Kristensen, Jesper Langgaard

    2006-01-01

    1-Fluoro-, 1-chloro- and 1-cyanonaphthalene were lithiated and then borylated at the 2-position. The 1-substituted naphthaleneboronic esters were cross-coupled with aryl halides to give 2-aryl-1-fluoro-, 2-aryl-1-chloro- and 2-aryl-1-cyanonaphthalenes. The 2-aryl-1-cyano- and 2-aryl-1-fluoronapht...

  9. The Manganese-Catalyzed Cross-Coupling Reaction and the Influence of Trace Metals

    DEFF Research Database (Denmark)

    Santilli, Carola; Beigbaghlou, Somayyeh Sarvi; Ahlburg, Andreas

    2017-01-01

    The substrate scope of the MnCl2-catalyzed cross-coupling between aryl halides and Grignard reagents has been extended to several methyl-substituted aryl iodides by performing the reaction at elevated temperature in a microwave oven. A radical clock experiment revealed the presence of an aryl...

  10. Catalytic Intermolecular Cross-Couplings of Azides and LUMO-Activated Unsaturated Acyl Azoliums

    KAUST Repository

    Li, Wenjun

    2017-02-15

    An example for the catalytic synthesis of densely functionalized 1,2,3-triazoles through a LUMO activation mode has been developed. The protocol is enabled by intermolecular cross coupling reactions of azides with in situ-generated alpha,beta-unsaturated acyl azoliums. High yields and broad scope as well as the investigation of reaction mechanism are reported.

  11. pincer complex in Suzuki–Miyaura cross-coupling reaction under ...

    Indian Academy of Sciences (India)

    high catalytic activity in Suzuki–Miyaura cross coupling reaction under microwave irradiation for a variety of aryl bromides and aryl boronic acids. The complex showed the same efficiency for gram scale reactions. Keywords. Pincer complex; bisphosphomide; Suzuki–Miyaura coupling; microwave irradiation; palladium(II). 1.

  12. MICROWAVE-ACCELERATED SUZUKI CROSS-COUPLING REACTION IN POLYETHYLENE GLYCOL (PEG)

    Science.gov (United States)

    Polyethylene glycol (PEG) is found to be an inexpensive and nontoxic reaction medium for the microwave-assisted Suzuki cross-coupling of arylboronic acids with aryl halides. This environmentally friendly microwave protocol offers the ease of operation and enables the recyclabilit...

  13. Covalent bond formation between amino acids and lignin: cross-coupling between proteins and lignin.

    Science.gov (United States)

    Cong, Fang; Diehl, Brett G; Hill, Joseph Lee; Brown, Nicole R; Tien, Ming

    2013-12-01

    The present study characterized the products formed from the reaction of amino acids and in turn, proteins, with lignin resulting in cross-coupling. When added to reaction mixtures containing coniferyl alcohol, horseradish peroxidase and H2O2, three amino acids (Cys, Tyr, and Thr) are able to form adducts. The low molecular weight products were analyzed by HPLC and from each reaction mixture, one product was isolated and analyzed by LC/MS. LC/MS results are consistent with bond formation between the polar side-chain of these amino acids with Cα. These results are consistent with the cross-coupling of Cys, Tyr and Thr through a quinone methide intermediate. In addition to the free amino acids, it was found that the cross-coupling of proteins with protolignin through Cys or Tyr residues. The findings provide a mechanism by which proteins and lignin can cross-couple in the plant cell wall. Copyright © 2013 Elsevier Ltd. All rights reserved.

  14. AM to PM noise conversion in a cross-coupled quadrature harmonic oscillator

    DEFF Research Database (Denmark)

    Djurhuus, Torsten; Krozer, Viktor; Vidkjær, Jens

    2006-01-01

    We derive the dynamic equations governing the cross-coupled quadrature oscillator, perturbed by noise, leading to an expression for the close-in phase noise. The theory shows that a nonlinear coupling transconductance results in AM-PM noise conversion close to the carrier, which increases...... with the coupling strength. A simple linear time-domain model is employed to illustrate the results...

  15. A new paradigm for carbon-carbon bond formation: Aerobic, copper-templated cross-coupling

    Czech Academy of Sciences Publication Activity Database

    Villalobos, J. M.; Šrogl, Jiří; Liebeskind, L. S.

    2007-01-01

    Roč. 129, č. 51 (2007), s. 15734-15735 ISSN 0002-7863 Institutional research plan: CEZ:AV0Z40550506 Keywords : cross-coupling * copper * palladium Subject RIV: CC - Organic Chemistry Impact factor: 7.885, year: 2007

  16. Introducing Undergraduates to Research Using a Suzuki-Miyaura Cross-Coupling Organic Chemistry Miniproject

    Science.gov (United States)

    Oliveira, Deyvid G. M.; Rosa, Clarissa H.; Vargas, Bruna P.; Rosa, Diego S.; Silveira, Ma´rcia V.; de Moura, Neusa F.; Rosa, Gilber R.

    2015-01-01

    A five-week miniproject is described for an upper-division experimental organic chemistry course. The activities include synthesis of a phenylboronic acid via a Grignard reaction and its use in a Suzuki-Miyaura cross-coupling reaction. Technical skills and concepts normally presented in practical organic chemistry courses are covered, including…

  17. Higher dimensional models of cross-coupled oscillators and application to design

    KAUST Repository

    Elwakil, Ahmed S.

    2010-06-01

    We present four-dimensional and five-dimensional models for classical cross-coupled LC oscillators. Using these models, sinusoidal oscillation condition, frequency and amplitude can be found. Further, undesired behaviors such as relaxation-mode oscillations and latchup can be explained and detected. A simple graphical design procedure is also described. © 2010 World Scientific Publishing Company.

  18. Palladium-catalysed direct cross-coupling of secondary alkyllithium reagents

    NARCIS (Netherlands)

    Vila, Carlos; Giannerini, Massimo; Hornillos, Valentin; Fananas-Mastral, Martin; Feringa, Ben L.

    2014-01-01

    Palladium-catalysed cross-coupling of secondary C(sp(3)) organometallic reagents has been a long-standing challenge in organic synthesis, due to the problems associated with undesired isomerisation or the formation of reduction products. Based on our recently developed catalytic C-C bond formation

  19. Frequency Splitting Elimination and Cross-Coupling Rejection of Wireless Power Transfer to Multiple Dynamic Receivers

    Directory of Open Access Journals (Sweden)

    Narayanamoorthi R.

    2018-01-01

    Full Text Available Simultaneous power transfer to multiple receiver (Rx system is one of the key advantages of wireless power transfer (WPT system using magnetic resonance. However, determining the optimal condition to uniformly transfer the power to a selected Rx at high efficiency is the challenging task under the dynamic environment. The cross-coupling and frequency splitting are the dominant issues present in the multiple Rx dynamic WPT system. The existing analysis is performed by considering any one issue present in the system; on the other hand, the cross coupling and frequency splitting issues are interrelated in dynamic Rx’s, which requires a comprehensive design strategy by considering both the problems. This paper proposes an optimal design of multiple Rx WPT system, which can eliminate cross coupling, frequency splitting issues and increase the power transfer efficiency (PTE of selected Rx. The cross-coupling rejection, uniform power transfer is performed by adding an additional relay coil and independent resonance frequency tuning with capacitive compensation to each Rx unit. The frequency splitting phenomena are eliminated using non-identical transmitter (Tx and Rx coil structure which can maintain the coupling between the coil under the critical coupling limit. The mathematical analysis of the compensation capacitance calculation and optimal Tx coil size identification is performed for the four Rx WPT system. Finite element analysis and experimental investigation are carried out for the proposed design in static and dynamic conditions.

  20. Aqueous-phase Suzuki-Miyaura cross-coupling reactions of free halopurine bases

    Czech Academy of Sciences Publication Activity Database

    Čapek, Petr; Vrábel, Milan; Hasník, Zbyněk; Pohl, Radek; Hocek, Michal

    -, č. 20 (2006), s. 3515-3526 ISSN 0039-7881 R&D Projects: GA ČR(CZ) GA203/05/0043 Institutional research plan: CEZ:AV0Z40550506 Keywords : purines * cross-coupling * reactions Subject RIV: CC - Organic Chemistry Impact factor: 2.333, year: 2006

  1. Palladium-Catalyzed Cross-Coupling Reactions of Perfluoro Organic Compounds

    Directory of Open Access Journals (Sweden)

    Masato Ohashi

    2014-09-01

    Full Text Available In this review, we summarize our recent development of palladium(0-catalyzed cross-coupling reactions of perfluoro organic compounds with organometallic reagents. The oxidative addition of a C–F bond of tetrafluoroethylene (TFE to palladium(0 was promoted by the addition of lithium iodide, affording a trifluorovinyl palladium(II iodide. Based on this finding, the first palladium-catalyzed cross-coupling reaction of TFE with diarylzinc was developed in the presence of lithium iodide, affording α,β,β-trifluorostyrene derivatives in excellent yield. This coupling reaction was expanded to the novel Pd(0/PR3-catalyzed cross-coupling reaction of TFE with arylboronates. In this reaction, the trifluorovinyl palladium(II fluoride was a key reaction intermediate that required neither an extraneous base to enhance the reactivity of organoboronates nor a Lewis acid additive to promote the oxidative addition of a C–F bond. In addition, our strategy utilizing the synergetic effect of Pd(0 and lithium iodide could be applied to the C–F bond cleavage of unreactive hexafluorobenzene (C6F6, leading to the first Pd(0-catalyzed cross-coupling reaction of C6F6 with diarylzinc compounds.

  2. Mechanistic Implications for the Ni(I-Catalyzed Kumada Cross-Coupling Reaction

    Directory of Open Access Journals (Sweden)

    Linda Iffland

    2017-11-01

    Full Text Available Herein we report on the cross-coupling reaction of phenylmagnesium bromide with aryl halides using the well-defined tetrahedral Ni(I complex, [(TriphosNiICl] (Triphos = 1,1,1-tris(diphenylphosphinomethylethane. In the presence of 0.5 mol % [(TriphosNiICl], good to excellent yields (75–97% of the respective coupling products within a reaction time of only 2.5 h at room temperature were achieved. Likewise, the tripodal Ni(IIcomplexes [(κ2-TriphosNiIICl2] and [(κ3-TriphosNiIICl](X (X = ClO4, BF4 were tested as potential pre-catalysts for the Kumada cross-coupling reaction. While the Ni(II complexes also afford the coupling products in comparable yields, mechanistic investigations by UV/Vis and electron paramagnetic resonance (EPR spectroscopy indicate a Ni(I intermediate as the catalytically active species in the Kumada cross-coupling reaction. Based on experimental findings and density functional theory (DFT calculations, a plausible Ni(I-catalyzed reaction mechanism for the Kumada cross-coupling reaction is presented.

  3. Manganese-Catalyzed Cross-Coupling of Aryl Halides and Grignard Reagents by a Radical Mechanism

    DEFF Research Database (Denmark)

    Antonacci, Giuseppe; Ahlburg, Andreas; Fristrup, Peter

    2017-01-01

    The substrate scope and the mechanism have been investigated for the MnCl2-catalyzed cross-coupling reaction between aryl halides and Grignard reagents. The transformation proceeds rapidly and in good yield when the aryl halide component is an aryl chloride containing a cyano or an ester group...... in the para position or a cyano group in the ortho position. A range of other substituents gave no conversion of the aryl halide or led to the formation of side products. A broader scope was observed for the Grignard reagents, where a variety of alkyl- and arylmagnesium chlorides participated in the coupling....... Two radical-clock experiments were carried out, and in both cases an intermediate aryl radical was successfully trapped. The cross-coupling reaction is therefore believed to proceed by an SRN1 mechanism, with a triorganomanganate complex serving as the most likely nucleophile and single-electron donor...

  4. A stepwise dechlorination/cross-coupling strategy to diversify the vancomycin 'in-chloride'.

    Science.gov (United States)

    Wadzinski, Tyler J; Gea, Katherine D; Miller, Scott J

    2016-02-01

    In an effort to rapidly access vancomycin analogues bearing diverse functionality at the 6c-Cl (the 'in-chloride') position, a two-step dechlorination/cross-coupling protocol was developed. Conditions for efficient cross-coupling of the relatively unreactive 6c-Cl group were found that ensure high conversion with minimal product decomposition. A set of 2c-dechloro-6c-functionalized vancomycin derivatives was prepared, and antibiotic activities of the compounds were evaluated against a panel of vancomycin-resistant and vancomycin-susceptible strains. Results from biological testing further underscore the steric sensitivity of vancomycin's binding pocket. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Applications of Palladium-Catalyzed C–N Cross-Coupling Reactions

    Science.gov (United States)

    2016-01-01

    Pd-catalyzed cross-coupling reactions that form C–N bonds have become useful methods to synthesize anilines and aniline derivatives, an important class of compounds throughout chemical research. A key factor in the widespread adoption of these methods has been the continued development of reliable and versatile catalysts that function under operationally simple, user-friendly conditions. This review provides an overview of Pd-catalyzed N-arylation reactions found in both basic and applied chemical research from 2008 to the present. Selected examples of C–N cross-coupling reactions between nine classes of nitrogen-based coupling partners and (pseudo)aryl halides are described for the synthesis of heterocycles, medicinally relevant compounds, natural products, organic materials, and catalysts. PMID:27689804

  6. Organocatalysis in cross-coupling: DMEDA-catalyzed direct C-H arylation of unactivated benzene.

    Science.gov (United States)

    Liu, Wei; Cao, Hao; Zhang, Hua; Zhang, Heng; Chung, Kin Ho; He, Chuan; Wang, Haibo; Kwong, Fuk Yee; Lei, Aiwen

    2010-12-01

    A striking breakthrough to the frame of traditional cross-couplings/C-H functionalizations using an organocatalyst remains unprecedented. We uncovered a conceptually different approach toward the biaryl syntheses by using DMEDA as the catalyst to promote the direct C-H arylation of unactivated benzene in the presence of potassium tert-butoxide. The arylation of unactivated benzene with aryl iodides, or aryl bromides and even chlorides under the assistance of an iodo-group, could simply take place at 80 °C. The new methodology presumably involves an aryl radical anion as an intermediate. This finding offers an option toward establishing a new horizon for direct C-H/cross-coupling reactions.

  7. Nonlinear Analysis of Ring Oscillator and Cross-Coupled Oscillator Circuits

    KAUST Repository

    Ge, Xiaoqing

    2010-12-01

    Hassan Khalil’s research results and beautifully written textbook on nonlinear systems have influenced generations of researchers, including the authors of this paper. Using nonlinear systems techniques, this paper analyzes ring oscillator and cross-coupled oscillator circuits, which are essential building blocks in digital systems. The paper first investigates local and global stability properties of an n-stage ring oscillator by making use of its cyclic structure. It next studies global stability properties of a class of cross-coupled oscillators which admit the representation of a dynamic system in feedback with a static nonlinearity, and presents su cient conditions for almost global convergence of the solutions to a limit cycle when the feedback gain is in the vicinity of a bifurcation point. The result are also extended to the synchronization of interconnected identical oscillator circuits.

  8. Preferential cross-coupling of naphthol derivatives mediated by copper(II)

    Czech Academy of Sciences Publication Activity Database

    Koščová, Simona; Roithová, J.; Hodačová, J.

    2013-01-01

    Roč. 26, č. 9 (2013), s. 715-723 ISSN 0894-3230 Grant - others:GA ČR(CZ) GAP108/12/1356; GA ČR(CZ) GAP207/11/0338 Institutional support: RVO:61388963 Keywords : BINOL * copper * cross-coupling * DFT calculations * mass spectrometry * reaction mechanisms Subject RIV: CC - Organic Chemistry Impact factor: 1.229, year: 2013

  9. Photoinduced C-C Cross-Coupling of Aryl Chlorides and Inert Arenes

    Directory of Open Access Journals (Sweden)

    Lele Wang

    2016-01-01

    Full Text Available Here we report a facile, efficient, and catalyst-free method to realize C-C cross-coupling of aryl chlorides and inert arenes under UV light irradiation. The aryl radical upon homolytic cleavage of C-Cl bond initiated the nucleophilic substitution reaction with inert arenes to give biaryl products. This mild reaction mode can also be applied to other synthetic reactions, such as the construction of C-N bonds and trifluoromethylated compounds.

  10. Merging Photoredox and Nickel Catalysis: Decarboxylative Cross-Coupling of Carboxylic Acids with Vinyl Halides

    Science.gov (United States)

    2015-01-01

    Decarboxylative cross-coupling of alkyl carboxylic acids with vinyl halides has been accomplished through the synergistic merger of photoredox and nickel catalysis. This new methodology has been successfully applied to a variety of α-oxy and α-amino acids, as well as simple hydrocarbon-substituted acids. Diverse vinyl iodides and bromides give rise to vinylation products in high efficiency under mild, operationally simple reaction conditions. PMID:25521443

  11. Recyclable polystyrene-supported siloxane-transfer agent for palladium-catalyzed cross-coupling reactions.

    Science.gov (United States)

    Nguyen, Minh H; Smith, Amos B

    2014-04-04

    The rational design, synthesis, and validation of a significantly improved insoluble polymer-supported siloxane-transfer agent has been achieved that permits efficient palladium-catalyzed cross-coupling reactions. The cross-linked polystyrene support facilitates product purification with excellent siloxane recycling. Drawbacks of a previous polymer-supported siloxane-transfer agent, relating to reaction efficiency and polymer stability after repeated cycles, have been addressed.

  12. The Suzuki–Miyaura Cross-Coupling as a Versatile Tool for Peptide Diversification and Cyclization

    Directory of Open Access Journals (Sweden)

    Tom Willemse

    2017-02-01

    Full Text Available The (site-selective derivatization of amino acids and peptides represents an attractive field with potential applications in the establishment of structure–activity relationships and labeling of bioactive compounds. In this respect, bioorthogonal cross-coupling reactions provide valuable means for ready access to peptide analogues with diversified structure and function. Due to the complex and chiral nature of peptides, mild reaction conditions are preferred; hence, a suitable cross-coupling reaction is required for the chemical modification of these challenging substrates. The Suzuki reaction, involving organoboron species, is appropriate given the stability and environmentally benign nature of these reactants and their amenability to be applied in (partial aqueous reaction conditions, an expected requirement upon the derivatization of peptides. Concerning the halogenated reaction partner, residues bearing halogen moieties can either be introduced directly as halogenated amino acids during solid-phase peptide synthesis (SPPS or genetically encoded into larger proteins. A reversed approach building in boron in the peptidic backbone is also possible. Furthermore, based on this complementarity, cyclic peptides can be prepared by halogenation, and borylation of two amino acid side chains present within the same peptidic substrate. Here, the Suzuki–Miyaura reaction is a tool to induce the desired cyclization. In this review, we discuss diverse amino acid and peptide-based applications explored by means of this extremely versatile cross-coupling reaction. With the advent of peptide-based drugs, versatile bioorthogonal conversions on these substrates have become highly valuable.

  13. Hypochlorite-induced oxidation of thiols

    DEFF Research Database (Denmark)

    Davies, Michael Jonathan; Hawkins, C L

    2000-01-01

    -, thermal- or UV light-catalysed decomposition of sulfenyl or sulfonyl chlorides which are postulated intermediates in thiol oxidation. In this study we show that thiyl radicals are generated on reaction of a number of low-molecular-weight thiols with HOCl. With sub-stoichiometric amounts of HOCl, relative...... to the thiol, thiyl radicals are the major species detected by EPR spin trapping. When the HOCl is present in excess over the thiol, additional radicals are detected with compounds which contain amine functions; these additional radicals are assigned to nitrogen-centered species. Evidence is presented...

  14. E-Z isomerization in Suzuki cross-couplings of haloenones: ligand effects and evidence for a separate catalytic cycle.

    Science.gov (United States)

    Chehal, Navneet K; Budzelaar, Peter H M; Hultin, Philip G

    2018-02-14

    Suzuki cross-coupling of haloalkenes is generally assumed to occur with retention of the alkene stereochemistry. While studying Suzuki cross-couplings on E-1,2-dichlorovinyl phenyl ketone, we were surprised to observe extensive isomerization. More surprisingly, the ligand employed strongly influenced the degree of isomerization: DPEphos and Xantphos led to 96% isomerized cross-coupled product whereas reactions in the absence of a phosphine ligand, or reactions employing t-BuXantphos, gave 94% retention of stereochemistry. While E-Z isomerization in Pd-catalyzed vinylic couplings has previously been attributed to events within the cross-coupling catalytic cycle, we present experimental and computational evidence for a separate Pd-catalyzed isomerization process in these reactions.

  15. Synthesis of C3-symmetric and C4-symmetric amino acid derivatives via Suzuki-Miyaura cross-coupling reaction.

    Science.gov (United States)

    Kotha, S; Shah, V R

    2008-06-01

    Various non-natural C(3)- and C(4)-symmetric alpha-amino acid derivatives have been synthesized via Suzuki-Miyaura cross-coupling reaction between aromatic iodides or bromide and a suitably protected DL-4-boronophenylalanine derivative.

  16. Configurationally stable, enantioenriched organometallic nucleophiles in stereospecific Pd-catalyzed cross-coupling reactions: an alternative approach to asymmetric synthesis

    Science.gov (United States)

    Wang, Chao-Yuan; Derosa, Joseph

    2015-01-01

    Several research groups have recently developed methods to employ configurationally stable, enantioenriched organometallic nucleophiles in stereospecific Pd-catalyzed cross-coupling reactions. By establishing the absolute configuration of a chiral alkyltin or alkylboron nucleophile prior to its use in cross-coupling reactions, new stereogenic centers may be rapidly and reliably generated with preservation of the known initial stereochemistry. While this area of research is still in its infancy, such stereospecific cross-coupling reactions may emerge as simple, general methods to access diverse, optically active products from common enantioenriched organometallic building blocks. This minireview highlights recent progress towards the development of general, stereospecific Pd-catalyzed cross-coupling reactions using configurationally stable organometallic nucleophiles. PMID:26388985

  17. Metallaphotoredox-catalysed sp3-sp3 cross-coupling of carboxylic acids with alkyl halides

    Science.gov (United States)

    Johnston, Craig P.; Smith, Russell T.; Allmendinger, Simon; MacMillan, David W. C.

    2016-08-01

    In the past 50 years, cross-coupling reactions mediated by transition metals have changed the way in which complex organic molecules are synthesized. The predictable and chemoselective nature of these transformations has led to their widespread adoption across many areas of chemical research. However, the construction of a bond between two sp3-hybridized carbon atoms, a fundamental unit of organic chemistry, remains an important yet elusive objective for engineering cross-coupling reactions. In comparison to related procedures with sp2-hybridized species, the development of methods for sp3-sp3 bond formation via transition metal catalysis has been hampered historically by deleterious side-reactions, such as β-hydride elimination with palladium catalysis or the reluctance of alkyl halides to undergo oxidative addition. To address this issue, nickel-catalysed cross-coupling processes can be used to form sp3-sp3 bonds that utilize organometallic nucleophiles and alkyl electrophiles. In particular, the coupling of alkyl halides with pre-generated organozinc, Grignard and organoborane species has been used to furnish diverse molecular structures. However, the manipulations required to produce these activated structures is inefficient, leading to poor step- and atom-economies. Moreover, the operational difficulties associated with making and using these reactive coupling partners, and preserving them through a synthetic sequence, has hindered their widespread adoption. A generically useful sp3-sp3 coupling technology that uses bench-stable, native organic functional groups, without the need for pre-functionalization or substrate derivatization, would therefore be valuable. Here we demonstrate that the synergistic merger of photoredox and nickel catalysis enables the direct formation of sp3-sp3 bonds using only simple carboxylic acids and alkyl halides as the nucleophilic and electrophilic coupling partners, respectively. This metallaphotoredox protocol is suitable for

  18. Suzuki-Miyaura cross-coupling reactions in aqueous media: green and sustainable syntheses of biaryls.

    Science.gov (United States)

    Polshettiwar, Vivek; Decottignies, Audrey; Len, Christophe; Fihri, Aziz

    2010-05-25

    Carbon-carbon cross-coupling reactions are among the most important processes in organic chemistry, and Suzuki-Miyaura reactions are among the most widely used protocols for the formation of carbon-carbon bonds. These reactions are generally catalyzed by soluble palladium complexes with various ligands. However, the use of toxic organic solvents remains a scientific challenge and an aspect of economical and ecological relevance. This Review will summarize various recently developed significant methods by which the Suzuki-Miyaura coupling was conducted in aqueous media, and analyzes if they are "real green" protocols.

  19. Copper(I) mediated cross-coupling of amino acid derived organozinc reagents with acid chlorides

    DEFF Research Database (Denmark)

    Hjelmgaard, Thomas; Tanner, David Ackland

    2006-01-01

    This paper describes the development of a straightforward experimental protocol for copper-mediated cross-coupling of amino acid derived beta-amido-alkylzinc iodides 1 and 3 with a range of acid chlorides. The present method uses CuCN center dot 2LiCl as the copper source and for organozinc reagent...... 1 the methodology appears to be limited to reaction with more stable acid chlorides, providing the desired products in moderate yields. When applied to organozinc reagent 3, however, the protocol is more general and provides the products in good yields in all but one of the cases tested....

  20. Modular approach to novel chiral aryl-ferrocenyl phosphines by Suzuki cross-coupling

    DEFF Research Database (Denmark)

    Jensen, Jakob Feldthusen; Søtofte, Inger; Sorensen, H.O.

    2002-01-01

    Two novel planar chiral and atropisomeric P,N and P,O aryl-ferrocenyl ligand systems have been developed. The strategy is short and involves a new synthetic approach to aryl-ferrocenyl compounds via a Suzuki cross-coupling procedure. The modular design can easily give access to variety of chiral ...... mono- and bidentate ligands. Two simple derivatives of a novel chiral bidenate P,N ligand belonging to the MOPF family have been synthesized and tested in the enantioselective copper-catalyzed addition of diethyl zinc to an enone and a "difficult" diester. Moderate to excellent yields...

  1. C-H to C-N Cross-Coupling of Sulfonamides with Olefins.

    Science.gov (United States)

    Ma, Rulin; White, M Christina

    2018-03-07

    Cross-coupling of nitrogen with hydrocarbons under fragment coupling conditions stands to significantly impact chemical synthesis. Herein, we disclose a C(sp 3 )-N fragment coupling reaction between terminal olefins and N-triflyl protected aliphatic and aromatic amines via Pd(II)/SOX (sulfoxide-oxazoline) catalyzed intermolecular allylic C-H amination. A range of (56) allylic amines are furnished in good yields (avg. 75%) and excellent regio- and stereoselectivity (avg. >20:1 linear:branched, >20:1 E: Z). Mechanistic studies reveal that the SOX ligand framework is effective at promoting functionalization by supporting cationic π-allyl Pd.

  2. Palladium-catalyzed cross-coupling reactions of aryl boronic acids with aryl halides in water.

    Science.gov (United States)

    Wang, Shaoyan; Zhang, Zhiqiang; Hu, Zhizhi; Wang, Yue; Lei, Peng; Chi, Haijun

    2009-01-01

    An efficient Suzuki cross-coupling reaction using a variety of aryl halides in neat water was developed. The Pd-catalyzed reaction between aryl bromides or chlorides and phenyl boronic acids was compatible with various functional groups and affords biphenyls in good to excellent yields without requirement of organic cosolvents. The air stability and solubility in water of the palladium-phosphinous acid complexes were considered to facilitate operation of the coupling reaction and product isolation. The reaction conditions including Pd catalyst selection, temperature, base and catalyst recoverability were also investigated.

  3. Suzuki-Miyaura cross-coupling reactions in aqueous media: Green and sustainable syntheses of biaryls

    KAUST Repository

    Polshettiwar, Vivek

    2010-02-28

    Carbon-carbon cross-coupling reactions are among the most important processes in organic chemistry, and Suzuki-Miyaura reactions are among the most widely used protocols for the formation of carbon-carbon bonds. These reactions are generally catalyzed by soluble palladium complexes with various ligands. However, the use of toxic organic solvents remains a scientific challenge and an aspect of economical and ecological relevance. This Review will summarize various recently developed significant methods by which the Suzuki-Miyaura coupling was conducted in aqueous media, and analyzes if they are "real green" protocols. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Cross-Coupling Reactions as Valuable Tool for the Preparation of PET Radiotracers

    Directory of Open Access Journals (Sweden)

    Marc Pretze

    2011-01-01

    Full Text Available The increasing application of positron emission tomography (PET in nuclear medicine has stimulated the extensive development of a multitude of new radiotracers and novel radiolabeling procedures with the most prominent short-lived positron emitters carbon-11 and fluorine-18. Radiolabeling with these radionuclides represents a remarkable challenge. Special attention has to be paid to synthesis time and specific labeling techniques due to the short physical half life of the respective radionuclides 11C (t1/2 = 20.4 min and 18F (t1/2 = 109.8 min. In the past, numerous transition metal-catalyzed reactions were employed in organic chemistry, even though only a handful of these coupling reactions were adopted in radiochemical practice. Thus, the implementation of modern synthesis methods like cross-coupling reactions offers the possibility to develop a wide variety of novel radiotracers. The introduction of catalysts based on transition metal complexes bears a high potential for rapid, efficient, highly selective and functional group-tolerating incorporation of carbon-11 and fluorine-18 into target molecules. This review deals with design, application and improvement of transition metal-mediated carbon-carbon as well as carbon-heteroatom cross-coupling reactions as a labeling feature with the focus on the preparation of radiolabeled compounds for molecular imaging.

  5. Suzuki–Miyaura Cross-Coupling of Aryl Carbamates and Sulfamates: Experimental and Computational Studies

    Science.gov (United States)

    Quasdorf, Kyle W.; Antoft-Finch, Aurora; Liu, Peng; Silberstein, Amanda L.; Komaromi, Anna; Blackburn, Tom; Ramgren, Stephen D.; Houk, K. N.; Snieckus, Victor; Garg, Neil K.

    2011-01-01

    The first Suzuki–Miyaura cross-coupling reactions of the synthetically versatile O-aryl carbamate and O-sulfamate groups is described. The transformations utilize the inexpensive, bench-stable catalyst NiCl2(PCy3)2 to furnish biaryls in good to excellent yields. A broad scope for this methodology has been demonstrated. Substrates with electron-donating and electron-withdrawing groups (EDGs, EWGs) are tolerated, in addition to those that possess ortho substitutents. Furthermore, heteroaryl substrates may be employed as coupling partners. A computational study providing the full catalytic cycles for these cross-coupling reactions is described. The oxidative additions with carbamates and sulfamates occur via a five-centered transition state, resulting in the exclusive cleavage of the Ar–O bond. Water is found to stabilize the Ni–carbamate catalyst resting state, and thus provides rationalization of the relative decreased rate of coupling of carbamates. Several synthetic applications are presented to showcase the utility of the methodology in the synthesis of polysubstituted aromatic compounds of natural product and bioactive molecule interest. PMID:21456551

  6. Optimization of an Efficient and Sustainable Sonogashira Cross-Coupling Protocol

    KAUST Repository

    Walter, Philipp E.

    2012-12-01

    Cross coupling reactions are a well-established tool in modern organic synthesis and play a crucial role in the synthesis of a high number of organic compounds. Their importance is highlighted by the Nobel Prize in chemistry to Suzuki, Heck and Negishi in 2010. The increasing importance of sustainability requirements in chemical production has furthermore promoted the development of cross-coupling protocols that comply with the principles of “Green Chemistry”1. The Sonogashira reaction is today the most versatile and powerful way to generate aryl alkynes, a moiety recurring in many pharmaceutical and natural products. Despite many improvements to the original reaction, reports on generally applicable protocols that work under sustainable conditions are scarce. Our group recently reported an efficient protocol for a copperfree Sonogashira cross-coupling at low temperature, in aqueous medium and with no addition of organic solvents or additives2. The goal of this work was to further investigate the effects of different reaction parameters on the catalytic activity in order to optimize the protocol. Limitations of the protocol were tested in respect to reaction temperature, heating method, atmosphere, base type and amount, catalyst loading, reaction time and work up procedure. The reaction worked successfully under air and results were not affected by the presence of oxygen in the water phase. Among a variety of bases tested, triethylamine was confirmed to give the best results and its required excess could be reduced from nine to four equivalents. Catalyst loading could also be reduced by up to 90%: Good to near quantitative yields for a broad range of substrates were achieved using a catalyst concentration of 0.25mol% and 5 eq of Et3N at 50°C while more reactive substrates could be coupled with a catalyst concentration as low as 0.025mol%. Filtration experiments showed the possibility of a simplified work up procedure and a protocol completely free of organic

  7. Predicting reaction performance in C-N cross-coupling using machine learning.

    Science.gov (United States)

    Ahneman, Derek T; Estrada, Jesús G; Lin, Shishi; Dreher, Spencer D; Doyle, Abigail G

    2018-02-15

    Machine learning methods are becoming integral to scientific inquiry in numerous disciplines. Here we demonstrate that machine learning can be used to predict the performance of a synthetic reaction in multidimensional chemical space using data obtained via high-throughput experimentation. We created scripts to compute and extract atomic, molecular, and vibrational descriptors for the components of a palladium-catalyzed Buchwald-Hartwig cross-coupling of aryl halides with 4-methylaniline in the presence of various potentially inhibitory additives. Using these descriptors as inputs and reaction yield as output, we show that a random forest algorithm provides significantly improved predictive performance over linear regression analysis. The random forest model was also successfully applied to sparse training sets and out-of-sample prediction, suggesting its value in facilitating adoption of synthetic methodology. Copyright © 2018, American Association for the Advancement of Science.

  8. An efficient protocol for the palladium-catalysed Suzuki-Miyaura cross-coupling

    KAUST Repository

    Marziale, Alexander N.

    2011-01-01

    The palladacyclic catalyst precursor received by ortho-palladation of ([1,1′-biphenyl]-2-yloxy)diisopropyl-phosphine represents a highly active system for Suzuki-Miyaura cross-coupling reactions when used in neat water. An efficient, broadly applicable and sustainable aqueous protocol was developed using 2.5 eq. of Na2CO3 as base, allowing the reaction to be performed under air and at ambient temperature with Pd loadings of 0.04 mol%. Coupling products are obtained in high yields and excellent purity by simple filtration with no organic solvents needed throughout the whole reaction. A broad variety of functional groups are tolerated and a large number of substrates can be applied with this protocol. The crystal structure of the palladacyclic catalyst precursor is presented as well as investigations targeting the nature of catalyst activation and the active catalytic species. © 2011 The Royal Society of Chemistry.

  9. Multimetallic catalysed cross-coupling of aryl bromides with aryl triflates

    Science.gov (United States)

    Ackerman, Laura K. G.; Lovell, Matthew M.; Weix, Daniel J.

    2015-08-01

    The advent of transition-metal catalysed strategies for forming new carbon-carbon bonds has revolutionized the field of organic chemistry, enabling the efficient synthesis of ligands, materials, and biologically active molecules. In cases where a single metal fails to promote a selective or efficient transformation, the synergistic cooperation of two distinct catalysts--multimetallic catalysis--can be used instead. Many important reactions rely on multimetallic catalysis, such as the Wacker oxidation of olefins and the Sonogashira coupling of alkynes with aryl halides, but this approach has largely been limited to the use of metals with distinct reactivities, with only one metal catalyst undergoing oxidative addition. Here, we demonstrate that cooperativity between two group 10 metal catalysts--(bipyridine)nickel and (1,3-bis(diphenylphosphino)propane)palladium--enables a general cross-Ullmann reaction (the cross-coupling of two different aryl electrophiles). Our method couples aryl bromides with aryl triflates directly, eliminating the use of arylmetal reagents and avoiding the challenge of differentiating between multiple carbon-hydrogen bonds that is required for direct arylation methods. Selectivity can be achieved without an excess of either substrate and originates from the orthogonal reactivity of the two catalysts and the relative stability of the two arylmetal intermediates. While (1,3-bis(diphenylphosphino)propane)palladium reacts preferentially with aryl triflates to afford a persistent intermediate, (bipyridine)nickel reacts preferentially with aryl bromides to form a transient, reactive intermediate. Although each catalyst forms less than 5 per cent cross-coupled product in isolation, together they are able to achieve a yield of up to 94 per cent. Our results reveal a new method for the synthesis of biaryls, heteroaryls, and dienes, as well as a general mechanism for the selective transfer of ligands between two metal catalysts. We anticipate that this

  10. Evaluation and Control of Thiol-ene/Thiol-epoxy Hybrid Networks

    OpenAIRE

    Carioscia, Jacquelyn A.; Stansbury, Jeffrey W.; Bowman, Christopher N.

    2007-01-01

    The development of thiol-ene/thiol-epoxy hybrid networks offers the advantage of tailorable polymerization kinetics while producing a highly crosslinked, high Tg polymer that has significantly reduced shrinkage stress. Stoichiometric mixtures of pentaerythritol tetra(3-mercaptopropionate) (PETMP)/triallyl-1,3,5-triazine-2,4,6-trione (TATATO) (thiol-ene, mixture 1) and PETMP/bisphenol a diglycidyl ether (BADGE) (thiol-epoxy, mixture 2) were prepared and hybrid mixtures of 75/25, 50/50, 25/75, ...

  11. Role of thiols in cellular response to radiation and drugs. Symposium: thiols

    International Nuclear Information System (INIS)

    Biaglow, J.E.; Varnes, M.E.; Clark, E.P.; Epp, E.R.

    1983-01-01

    Cellular nonprotein thiols (NPSH) consist of glutathione (GSH) and other low molecular weight species such as cysteine, cysteamine, and coenzyme. A GSH is usually less than the total cellular NPSH, and with thiol reactive agents, such as diethyl maleate (DEM), its rate of depletion is in part dependent upon the cellular capacity for its resynthesis. If resynthesis is blocked by buthionine-S,R-sulfoximine(BSO), the NPSH, including GSH, is depleted more rapidly, Cellular thiol depletion by diamide, N-ethylmaleimide, and BSO may render oxygenated cells more sensitive to radiation. These cells may or may not show a reduction in the oxygen enhancement ratio (OER). Human A549 lung carcinoma cells depleted of their NPSH either by prolonged culture or by BSO treatment do not show a reduced OER but do show increased aerobic responses to radiation. Other nitrocompounds, such as misonidazole, are activated under hypoxic conditions to radical intermediates. When cellular thiols are depleted peroxide is formed. Under hypoxic conditions thiols are depleted because metabolically reduced intermediates react with GSH instead of oxygen. Thiol depletion, under hypoxic conditions, may be the reason that misonidazole and other nitrocompounds show an extra enhancement ratio with hypoxic cells. Thiol depletion by DEM or BSO alters the radiation response of hypoxic cells to misonidazole. In conclusion, we propose an altered thiol model which includes a mechanism for thiol involvement in the aerobic radiation response of cells

  12. Role of thiols in cellular response to radiation and drugs. Symposium: thiols

    Energy Technology Data Exchange (ETDEWEB)

    Biaglow, J.E. (Case Western Reserve Univ. Medical School, Cleveland, OH); Varnes, M.E.; Clark, E.P.; Epp, E.R.

    1983-09-01

    Cellular nonprotein thiols (NPSH) consist of glutathione (GSH) and other low molecular weight species such as cysteine, cysteamine, and coenzyme. A GSH is usually less than the total cellular NPSH, and with thiol reactive agents, such as diethyl maleate (DEM), its rate of depletion is in part dependent upon the cellular capacity for its resynthesis. If resynthesis is blocked by buthionine-S,R-sulfoximine(BSO), the NPSH, including GSH, is depleted more rapidly, Cellular thiol depletion by diamide, N-ethylmaleimide, and BSO may render oxygenated cells more sensitive to radiation. These cells may or may not show a reduction in the oxygen enhancement ratio (OER). Human A549 lung carcinoma cells depleted of their NPSH either by prolonged culture or by BSO treatment do not show a reduced OER but do show increased aerobic responses to radiation. Other nitrocompounds, such as misonidazole, are activated under hypoxic conditions to radical intermediates. When cellular thiols are depleted peroxide is formed. Under hypoxic conditions thiols are depleted because metabolically reduced intermediates react with GSH instead of oxygen. Thiol depletion, under hypoxic conditions, may be the reason that misonidazole and other nitrocompounds show an extra enhancement ratio with hypoxic cells. Thiol depletion by DEM or BSO alters the radiation response of hypoxic cells to misonidazole. In conclusion, we propose an altered thiol model which includes a mechanism for thiol involvement in the aerobic radiation response of cells.

  13. Hypochlorite-induced oxidation of thiols

    DEFF Research Database (Denmark)

    Davies, Michael Jonathan; Hawkins, C L

    2000-01-01

    -molecular-weight thiols such as reduced glutathione (GSH), and sulfur-containing amino acids in proteins, are major targets for HOCl. Radicals have not generally been implicated as intermediates in thiol oxidation by HOCl, though there is considerable literature evidence for the involvement of radicals in the metal ion......-, thermal- or UV light-catalysed decomposition of sulfenyl or sulfonyl chlorides which are postulated intermediates in thiol oxidation. In this study we show that thiyl radicals are generated on reaction of a number of low-molecular-weight thiols with HOCl. With sub-stoichiometric amounts of HOCl, relative...... for the involvement of sulfenyl chlorides (RSCl) in the formation of these radicals, and studies with an authentic sulfenyl chloride have demonstrated that this compound readily decomposes in thermal-, metal-ion- or light-catalysed reactions to give thiyl radicals. The formation of thiyl radicals on oxidation...

  14. Thiol/disulfide homeostasis in postmenopausal osteoporosis.

    Science.gov (United States)

    Korkmaz, V; Kurdoglu, Z; Alisik, M; Turgut, E; Sezgın, O O; Korkmaz, H; Ergun, Y; Erel, O

    2017-04-01

    To evaluate the impact of postmenopausal osteoporosis on thiol/disulfide homeostasis. A total of 75 participants were divided into two groups: Group 1 (n = 40) was composed of healthy postmenopausal women, and group 2 (n = 35) was composed of women with postmenopausal osteoporosis. Clinical findings and thiol/disulfide homeostasis were compared between the two groups. The disulfide/native thiol ratio was 8.6% ± 3.6 in group 1 and 12.7% ± 8.4 in group 2 (p = 0.04). The disulfide/native thiol percent ratio was significantly higher in group 2 after adjustment for the years since menopause and age (p menopause and age (p menopause in postmenopausal osteoporosis.

  15. Urinary protein thiols in different grades of proteinuria

    OpenAIRE

    Prakash, Mungli; Shetty, Jeevan K.; Dash, Sambit; Barik, Bijay K.; Sarkar, Abhirup; Awanti, Sharanabasappa M.; Prabhu, Ravindra

    2008-01-01

    Total thiol status of plasma, especially thiol groups over protein contributes maximum to the plasma antioxidant status of the body. Serum protein thiols were found to be decreased in various disease conditions including chronic renal failure patients. Only few studies determined the levels of urinary protein thiols in disease conditions. The current study was designed to know the levels of urinary protein thiols in patients with different grades of proteinuria. The study was conducted on uri...

  16. Nickel-catalyzed enantioselective cross-couplings of racemic secondary electrophiles that bear an oxygen leaving group.

    Science.gov (United States)

    Oelke, Alexander J; Sun, Jianwei; Fu, Gregory C

    2012-02-15

    To date, effective nickel-catalyzed enantioselective cross-couplings of alkyl electrophiles that bear oxygen leaving groups have been limited to reactions of allylic alcohol derivatives with Grignard reagents. In this Communication, we establish that, in the presence of a nickel/pybox catalyst, a variety of racemic propargylic carbonates are suitable partners for asymmetric couplings with organozinc reagents. The method is compatible with an array of functional groups and utilizes commercially available catalyst components. The development of a versatile nickel-catalyzed enantioselective cross-coupling process for electrophiles that bear a leaving group other than a halide adds a significant new dimension to the scope of these reactions.

  17. A novel 4-aminoantipyrine-Pd(II complex catalyzes Suzuki–Miyaura cross-coupling reactions of aryl halides

    Directory of Open Access Journals (Sweden)

    Claudia A. Contreras-Celedón

    2014-12-01

    Full Text Available A simple and efficient catalytic system based on a Pd complex of 4-aminoantipyrine, 4-AAP–Pd(II, was found to be highly active for Suzuki–Miyaura cross-coupling of aryl iodides and bromides with phenylboronic acids under mild reaction conditions. Good to excellent product yields from the cross-coupling reaction can be achieved when the reaction is carried out in ethanol, in the open air, using low loading of 4-AAP–Pd(II as a precatalyst, and in the presence of aqueous K2CO3 as the base. A variety of functional groups are tolerated.

  18. Investigations of thiol-modified phenol derivatives for the use in thiol-ene photopolymerizations.

    Science.gov (United States)

    Reinelt, Sebastian; Tabatabai, Monir; Fischer, Urs Karl; Moszner, Norbert; Utterodt, Andreas; Ritter, Helmut

    2014-01-01

    Thiol-ene photopolymerizations gain a growing interest in academic research. Coatings and dental restoratives are interesting applications for thiol-ene photopolymerizations due to their unique features. In most studies the relative flexible and hydrophilic ester derivative, namely pentaerythritoltetra(3-mercaptopropionate) (PETMP), is investigated as the thiol component. Thus, in the present study we are encouraged to investigate the performance of more hydrophobic ester-free thiol-modified bis- and trisphenol derivatives in thiol-ene photopolymerizations. For this, six different thiol-modified bis- and trisphenol derivatives exhibiting four to six thiol groups are synthesized via the radical addition of thioacetic acid to suitable allyl-modified precursors and subsequent hydrolysis. Compared to PETMP better flexural strength and modulus of elasticity are achievable in thiol-ene photopolymerizations employing 1,3,5-triallyl-1,3,5-triazine-2,4,6-trione (TATATO) as the ene derivative. Especially, after storage in water, the flexural strength and modulus of elasticity is twice as high compared to the PETMP reference system.

  19. Evaluation and Control of Thiol-ene/Thiol-epoxy Hybrid Networks.

    Science.gov (United States)

    Carioscia, Jacquelyn A; Stansbury, Jeffrey W; Bowman, Christopher N

    2007-03-08

    The development of thiol-ene/thiol-epoxy hybrid networks offers the advantage of tailorable polymerization kinetics while producing a highly crosslinked, high T(g) polymer that has significantly reduced shrinkage stress. Stoichiometric mixtures of pentaerythritol tetra(3-mercaptopropionate) (PETMP)/triallyl-1,3,5-triazine-2,4,6-trione (TATATO) (thiol-ene, mixture 1) and PETMP/bisphenol a diglycidyl ether (BADGE) (thiol-epoxy, mixture 2) were prepared and hybrid mixtures of 75/25, 50/50, 25/75, and 10/90 w/w of mixtures 1 and 2 were polymerized using a combination of both radical and anionic initiation. The light exposure timing and the relative initiation conditions of the two types were used to control the order and relative rates of the radical and anionic polymerizations. The 50/50 w/w thiol-ene/thiol-epoxy hybrid material exhibited a final stress of only 0.2 MPa, which is 90 % lower than the stress developed in a control dimethacrylate resin. Kinetic analysis indicates composition affects network development in thiol-ene/thiol-epoxy hybrid networks and produces materials with robust mechanical properties.

  20. Determinants of Motion Sickness in Tilting Trains: Coriolis/Cross-Coupling Stimuli and Tilt Delay.

    Science.gov (United States)

    Bertolini, Giovanni; Durmaz, Meek Angela; Ferrari, Kim; Küffer, Alexander; Lambert, Charlotte; Straumann, Dominik

    2017-01-01

    Faster trains require tilting of the cars to counterbalance the centrifugal forces during curves. Motion sensitive passengers, however, complain of discomfort and overt motion sickness. A recent study comparing different control systems in a tilting train, suggested that the delay of car tilts relative to the curve of the track contributes to motion sickness. Other aspects of the motion stimuli, like the lateral accelerations and the car jitters, differed between the tested conditions and prevented a final conclusion on the role of tilt delay. Nineteen subjects were tested on a motorized 3D turntable that simulated the roll tilts during yaw rotations experienced on a tilting train, isolating them from other motion components. Each session was composed of two consecutive series of 12 ideal curves that were defined on the bases of recordings during an actual train ride. The simulated car tilts started either at the beginning of the curve acceleration phase (no-delay condition) or with 3 s of delay (delay condition). Motion sickness was self-assessed by each subject at the end of each series using an analog motion sickness scale. All subjects were tested in both conditions. Significant increases of motion sickness occurred after the first sequence of 12 curves in the delay condition, but not in the no-delay condition. This increase correlated with the sensitivity of motion sickness, which was self-assessed by each subject before the experiment. The second sequence of curve did not lead to a significant further increase of motion sickness in any condition. Our results demonstrate that, even if the speed and amplitude are as low as those experienced on tilting trains, a series of roll tilts with a delay relative to the horizontal rotations, isolated from other motion stimuli occurring during a travel, generate Coriolis/cross-coupling stimulations sufficient to rapidly induce motion sickness in sensitive individuals. The strength and the rapid onset of the motion

  1. Determinants of Motion Sickness in Tilting Trains: Coriolis/Cross-Coupling Stimuli and Tilt Delay

    Directory of Open Access Journals (Sweden)

    Giovanni Bertolini

    2017-05-01

    Full Text Available Faster trains require tilting of the cars to counterbalance the centrifugal forces during curves. Motion sensitive passengers, however, complain of discomfort and overt motion sickness. A recent study comparing different control systems in a tilting train, suggested that the delay of car tilts relative to the curve of the track contributes to motion sickness. Other aspects of the motion stimuli, like the lateral accelerations and the car jitters, differed between the tested conditions and prevented a final conclusion on the role of tilt delay. Nineteen subjects were tested on a motorized 3D turntable that simulated the roll tilts during yaw rotations experienced on a tilting train, isolating them from other motion components. Each session was composed of two consecutive series of 12 ideal curves that were defined on the bases of recordings during an actual train ride. The simulated car tilts started either at the beginning of the curve acceleration phase (no-delay condition or with 3 s of delay (delay condition. Motion sickness was self-assessed by each subject at the end of each series using an analog motion sickness scale. All subjects were tested in both conditions. Significant increases of motion sickness occurred after the first sequence of 12 curves in the delay condition, but not in the no-delay condition. This increase correlated with the sensitivity of motion sickness, which was self-assessed by each subject before the experiment. The second sequence of curve did not lead to a significant further increase of motion sickness in any condition. Our results demonstrate that, even if the speed and amplitude are as low as those experienced on tilting trains, a series of roll tilts with a delay relative to the horizontal rotations, isolated from other motion stimuli occurring during a travel, generate Coriolis/cross-coupling stimulations sufficient to rapidly induce motion sickness in sensitive individuals. The strength and the rapid onset

  2. A General Regioselective Synthesis of 2,4-Diarylpyrimidines from 2-Thiouracil through Two Orthogonal Cross-Coupling Reactions

    Czech Academy of Sciences Publication Activity Database

    Čerňová, Miroslava; Pohl, Radek; Klepetářová, Blanka; Hocek, Michal

    2012-01-01

    Roč. 23, č. 9 (2012), s. 1305-1308 ISSN 0936-5214 Grant - others:GA ČR(CZ) GAP207/12/0205 Institutional support: RVO:61388963 Keywords : pyrimidines * uracil * cross-coupling * palladium Subject RIV: CC - Organic Chemistry Impact factor: 2.655, year: 2012

  3. Sonogashira cross-coupling under non-basic conditions. Flow chemistry as a new paradigm in reaction control

    Czech Academy of Sciences Publication Activity Database

    Voltrová, Svatava; Šrogl, Jiří

    2014-01-01

    Roč. 1, č. 9 (2014), s. 1067-1071 ISSN 2052-4129 R&D Projects: GA MŠk LH12013 Institutional support: RVO:61388963 Keywords : Sonogashira * cross-coupling * flow chemistry Subject RIV: CC - Organic Chemistry

  4. Amide to Alkyne Interconversion via a Nickel/Copper-Catalyzed Deamidative Cross-Coupling of Aryl and Alkenyl Amides

    KAUST Repository

    Srimontree, Watchara

    2017-06-05

    A nickel-catalyzed deamidative cross-coupling reaction of amides with terminal alkynes as coupling partners was disclosed. This newly developed methodology allows the direct interconversion of amides to alkynes and enables a facile route for C(sp2)-C(sp) bond formation in a straightforward and mild fashion.

  5. Selective sp3 C-H alkylation via polarity-match-based cross-coupling

    Science.gov (United States)

    Le, Chip; Liang, Yufan; Evans, Ryan W.; Li, Ximing; MacMillan, David W. C.

    2017-07-01

    The functionalization of carbon-hydrogen (C-H) bonds is one of the most attractive strategies for molecular construction in organic chemistry. The hydrogen atom is considered to be an ideal coupling handle, owing to its relative abundance in organic molecules and its availability for functionalization at almost any stage in a synthetic sequence. Although many C-H functionalization reactions involve C(sp3)-C(sp2) coupling, there is a growing demand for C-H alkylation reactions, wherein sp3 C-H bonds are replaced with sp3 C-alkyl groups. Here we describe a polarity-match-based selective sp3 C-H alkylation via the combination of photoredox, nickel and hydrogen-atom transfer catalysis. This methodology simultaneously uses three catalytic cycles to achieve hydridic C-H bond abstraction (enabled by polarity matching), alkyl halide oxidative addition, and reductive elimination to enable alkyl-alkyl fragment coupling. The sp3 C-H alkylation is highly selective for the α-C-H of amines, ethers and sulphides, which are commonly found in pharmaceutically relevant architectures. This cross-coupling protocol should enable broad synthetic applications in de novo synthesis and late-stage functionalization chemistry.

  6. Selective sp3 C–H alkylation via polarity-match-based cross-coupling

    Science.gov (United States)

    Le, Chip; Liang, Yufan; Evans, Ryan W.; Li, Ximing; MacMillan, David W. C.

    2017-01-01

    The functionalization of carbon–hydrogen (C–H) bonds is one of the most attractive strategies for molecular construction in organic chemistry. The hydrogen atom is considered to be an ideal coupling handle, owing to its relative abundance in organic molecules and its availability for functionalization at almost any stage in a synthetic sequence1. Although many C–H functionalization reactions involve C(sp3)–C(sp2) coupling, there is a growing demand for C–H alkylation reactions, wherein sp3 C–H bonds are replaced with sp3 C–alkyl groups. Here we describe a polarity-match-based selective sp3 C–H alkylation via the combination of photoredox, nickel and hydrogen-atom transfer catalysis. This methodology simultaneously uses three catalytic cycles to achieve hydridic C–H bond abstraction (enabled by polarity matching), alkyl halide oxidative addition, and reductive elimination to enable alkyl–alkyl fragment coupling. The sp3 C–H alkylation is highly selective for the α-C–H of amines, ethers and sulphides, which are commonly found in pharmaceutically relevant architectures. This cross-coupling protocol should enable broad synthetic applications in de novo synthesis and late-stage functionalization chemistry. PMID:28636596

  7. Selective sp3 C-H alkylation via polarity-match-based cross-coupling.

    Science.gov (United States)

    Le, Chip; Liang, Yufan; Evans, Ryan W; Li, Ximing; MacMillan, David W C

    2017-07-06

    The functionalization of carbon-hydrogen (C-H) bonds is one of the most attractive strategies for molecular construction in organic chemistry. The hydrogen atom is considered to be an ideal coupling handle, owing to its relative abundance in organic molecules and its availability for functionalization at almost any stage in a synthetic sequence. Although many C-H functionalization reactions involve C(sp 3 )-C(sp 2 ) coupling, there is a growing demand for C-H alkylation reactions, wherein sp 3 C-H bonds are replaced with sp 3 C-alkyl groups. Here we describe a polarity-match-based selective sp 3 C-H alkylation via the combination of photoredox, nickel and hydrogen-atom transfer catalysis. This methodology simultaneously uses three catalytic cycles to achieve hydridic C-H bond abstraction (enabled by polarity matching), alkyl halide oxidative addition, and reductive elimination to enable alkyl-alkyl fragment coupling. The sp 3 C-H alkylation is highly selective for the α-C-H of amines, ethers and sulphides, which are commonly found in pharmaceutically relevant architectures. This cross-coupling protocol should enable broad synthetic applications in de novo synthesis and late-stage functionalization chemistry.

  8. Remote C−H Activation of Quinolines through Copper-Catalyzed Radical Cross-Coupling

    KAUST Repository

    Xu, Jun

    2016-01-12

    Achieving site selectivity in carbon-hydrogen (C-H) functionalization reactions is a formidable challenge in organic chemistry. Herein, we report a novel approach to activating remote C-H bonds at the C5 position of 8-aminoquinoline through copper-catalyzed sulfonylation under mild conditions. Our strategy shows high conversion efficiency, a broad substrate scope, and good toleration with different functional groups. Furthermore, our mechanistic investigations suggest that a single-electron-transfer process plays a vital role in generating sulfonyl radicals and subsequently initiating C-S cross-coupling. Importantly, our copper-catalyzed remote functionalization protocol can be expanded for the construction of a variety of chemical bonds, including C-O, C-Br, C-N, C-C, and C-I. These findings provide a fundamental insight into the activation of remote C-H bonds, while offering new possibilities for rational design of drug molecules and optoelectronic materials requiring specific modification of functional groups. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. DFT and AFIR Study on the Mechanism and the Origin of Enantioselectivity in Iron-Catalyzed Cross-Coupling Reactions.

    Science.gov (United States)

    Sharma, Akhilesh K; Sameera, W M C; Jin, Masayoshi; Adak, Laksmikanta; Okuzono, Chiemi; Iwamoto, Takahiro; Kato, Masako; Nakamura, Masaharu; Morokuma, Keiji

    2017-11-15

    The mechanism of the full catalytic cycle for Fe-chiral-bisphosphine-catalyzed cross-coupling reaction between alkyl halides and Grignard reagents (Nakamura and co-workers, J. Am. Chem. Soc. 2015, 137, 7128) was rationalized by using density functional theory (DFT) and multicomponent artificial force-induced reaction (MC-AFIR) methods. The computed mechanism consists of (a) C-Cl activation, (b) transmetalation, (c) C-Fe bond formation, and (d) C-C bond formation through reductive elimination. Our survey on the prereactant complexes suggested that formation of Fe II (BenzP*)Ph 2 and Fe I (BenzP*)Ph complexes are thermodynamically feasible. Fe I (BenzP*)Cl complex is the active intermediate for C-Cl activation. Fe II (BenzP*)Ph 2 complex can be formed if the concentration of Grignard reagent is high. However, it leads to biphenyl (byproduct) instead of the cross-coupling product. This explains why slow addition of Grignard reagent is critical for the cross-coupling reaction. The MC-AFIR method was used for systematic determination of transition states for C-Fe bond formation and C-C bond formation starting from the key intermediate Fe II (BenzP*)PhCl. According to our detailed analysis, C-C bond formation is the selectivity-determining step. The computed enantiomeric ratio of 95:5 is in good agreement with the experimental ratio (90:10). Energy decomposition analysis suggested that the origin of the enantioselectivity is the deformation of Ph-ligand in Fe-complex, which is induced by the bulky tert-butyl group of BenzP* ligand. Our study provides important mechanistic insights for the cross-coupling reaction between alkyl halides and Grignard reagents and guides the design of efficient Fe-based catalysts for cross-coupling reactions.

  10. Novel thermal curing of cycloaliphatic resins by thiol-epoxy click process with several multifunctional thiols

    OpenAIRE

    Guzman, Dailyn; Mateu, Blai; Fernández Francos, Xavier; Ramis Juan, Xavier; Serra Albet, Àngels

    2017-01-01

    Novel thermosets were prepared by the base-catalysed reaction between a cycloaliphatic resin (ECC) and various thiol crosslinkers. 4-(N,N-Dimethylaminopyridine) (DMAP) was used as base catalyst for the thiol–epoxy reaction. A commercial tetrathiol (PETMP) and three different thiols synthesized by us, 6SH-SQ, 3SH-EU and 3SH-ISO, were tested. 6SH-SQ and 3SH-EU were prepared from vinyl or allyl compounds from renewable resources such as squalene and eugenol, respectively. Thiol 3SH-ISO was prepa...

  11. Optical vibration measurements of cross coupling effects in capacitive micromachined ultrasonic transducer arrays

    Science.gov (United States)

    Leirset, Erlend; Aksnes, Astrid

    2011-05-01

    Optical vibration measurement systems are excellent tools for characterizing ultrasonic transducers. This paper presents measurements on immersed arrays of capacitive ultrasonic transducers (CMUTs) using a heterodyne interferometer. The interferometer allows measurements of vibrations from DC up to 1 GHz with a noise floor of ~1pm/√Hz. Previously CMUTs have been characterized in air. The transducer is intended for intravascular use. Therefore the CMUTs were characterized in the transparent fluids kerosene and rapeseed oil that have acoustic properties closer to blood. The optical measurements on immersed CMUTs were validated by assessing the measurement errors caused by the acousto optic effects in the fluid. When immersed there is significant cross coupling between individual CMUTs within an array. Simulations presented here indicate that this causes an acoustic wave mode that is bound to the interface between the CMUTs and the fluid. This is confirmed by measurements of the phase velocity and attenuation coefficient of this wave. The measurement results indicate that the wave exists up to a maximum frequency and that the attenuation constant increases with increasing frequency. Rapeseed oil causes a significantly larger attenuation coefficient than kerosene, which most probably is due to a considerable difference in fluid viscosities. There was a mismatch between the simulated and measured phase velocity for low frequencies. It is likely that the cause of this is coupling between the fluid CMUT interface waves and Lamb waves in the substrate of the CMUT array. Measurements performed with the heterodyne interferometer have confirmed the presence of dispersive waves bound to the surface of the transducer by directly showing their propagation along the array. The setup has also characterized the bound waves by measuring dispersion relations.

  12. Cross-coupling effects in chemically non-equilibrium viscous compressible flows

    International Nuclear Information System (INIS)

    Kustova, E.V.; Giordano, D.

    2011-01-01

    Graphical abstract: Self-cosistent kinetic-theory description of chemical-reaction rates and mean normal stress in one-temperature viscous compressible gas flows. Reaearch highlights: → In chemically non-equilibrium viscous compressible flows, the rate of each reaction depends on the velocity divergence and rates of all other reactions. → Cross effects between the rates of chemical reactions and normal mean stress can be found in the symmetric form and expressed in terms of the reaction affinities. → In the case of small affinities, the entropy production is unconditionally non-negative; in the case of finite affinities, the entropy production related to the scalar forces has no definite sign. - Abstract: A closed self-consistent description of a one-temperature non-equilibrium reacting flow is presented on the basis of the kinetic theory methods. A general case including internal degrees of freedom, dissociation-recombination and exchange reactions, and arbitrary values of affinities of chemical reactions is considered. Chemical-reaction rates and mean normal stress in viscous compressible flows are studied and a symmetric cross coupling between these terms is found. It is shown that the rate of each chemical reaction and the mean normal stress depend on velocity divergence and affinities of all chemical reactions; the law of mass action is violated in viscous flows. The results obtained in the frame of linear irreversible thermodynamics can be deduced from the proposed model for the particular case of small affinities. The reciprocal Onsager-Casimir relations are verified, the symmetry of kinetic coefficients is demonstrated, and the entropy production in a viscous flow is studied.

  13. Total Thiols: Biomedical Importance And Their Alteration In Various Disorders

    Directory of Open Access Journals (Sweden)

    Mungli Prakash

    2009-09-01

    Full Text Available Thiols are the organic compounds that contain a sulphydryl group. Among all the antioxidants that are available in the body, thiols constitute the major portion of the total body antioxidants and they play a significant role in defense against reactive oxygen species. Total thiols composed of both intracellular and extracellular thiols either in the free form as oxidized or reduced glutathione, or thiols bound to proteins. Among the thiols that are bound to proteins, albumin makes the major portion of the protein bound thiols, which binds to sufhydryl group at its cysteine-34 portion. Apart from their role in defense against free radicals, thiols share significant role in detoxification, signal transduction, apoptosis and various other functions at molecular level. The thiol status in the body can be assessed easily by determining the serum levels of thiols. Decreased levels of thiols has been noted in various medical disorders including chronic renal failure and other disorders related to kidney, cardiovascular disorders, stroke and other neurological disorders, diabetes mellitus, alcoholic cirrhosis and various other disorders. Therapy using thiols has been under investigation for certain disorders.

  14. Fabrication and bonding of thiol-ene-based microfluidic devices

    DEFF Research Database (Denmark)

    Sikanen, Tiina M; Lafleur, Josiane P.; Moilanen, Maria-Elisa

    2013-01-01

    In this work, the bonding strength of microchips fabricated by thiol-ene free-radical polymerization was characterized in detail by varying the monomeric thiol/allyl composition from the stoichiometric ratio (1:1) up to 100% excess of thiol (2:1) or allyl (1:2) functional groups. Four different...

  15. A Search for Interstellar Monohydric Thiols

    Energy Technology Data Exchange (ETDEWEB)

    Gorai, Prasanta; Das, Ankan; Das, Amaresh; Chakrabarti, Sandip K. [Indian Centre for Space Physics, 43 Chalantika, Garia Station Rd., Kolkata, 700084 (India); Sivaraman, Bhalamurugan [Atomic Molecular and Optical Physics Division, Physical Research Laboratory, Ahmedabad, 380009 (India); Etim, Emmanuel E., E-mail: ankan.das@gmail.com [Indian Institute of Science Bangalore, 560012 (India)

    2017-02-10

    It has been pointed out by various astronomers that a very interesting relationship exists between interstellar alcohols and the corresponding thiols (sulfur analog of alcohols) as far as the spectroscopic properties and chemical abundances are concerned. Monohydric alcohols such as methanol and ethanol are widely observed and 1-propanol was recently claimed to have been seen in Orion KL. Among the monohydric thiols, methanethiol (chemical analog of methanol) has been firmly detected in Orion KL and Sgr B2(N2) and ethanethiol (chemical analog of ethanol) has been observed in Sgr B2(N2), though the confirmation of this detection is yet to come. It is very likely that higher order thiols could be observed in these regions. In this paper, we study the formation of monohydric alcohols and their thiol analogs. Based on our quantum chemical calculation and chemical modeling, we find that the Tg conformer of 1-propanethiol is a good candidate of astronomical interest. We present various spectroscopically relevant parameters of this molecule to assist in its future detection in the interstellar medium.

  16. Regioselective synthesis and slow-release Suzuki-Miyaura cross-coupling of MIDA boronate-functionalized isoxazoles and triazoles.

    Science.gov (United States)

    Grob, Jonathan E; Nunez, Jill; Dechantsreiter, Michael A; Hamann, Lawrence G

    2011-12-16

    The efficient preparation of heterocycles with a range of substitutions ortho to heteroatoms remains as a challenge in organic synthesis, particularly relevant to the construction of druglike molecules due to the ubiquitous presence of such moieties in that chemical space. Modular installation of heterocyclic building blocks using Suzuki-Miyaura cross-coupling is a conceptually useful strategy to address this challenge, though this has historically been met with technical difficulty due to issues of inaccessibility and instability of the requisite heterocyclic boronates. Herein we report a mild and highly regioselective cycloaddition approach which affords convenient access to stable MIDA boronate-functionalized isoxazoles and triazoles and their subsequent efficient Suzuki-Miyaura cross-coupling. This methodology is then further applied to a set of druglike compounds in an efficient one-pot telescoped sequence in line with green chemistry principles.

  17. Cross-coupling reactions of nucleoside triphosphates followed by polymerase incorporation. Construction and applications of base-functionalized nucleic acids.

    Science.gov (United States)

    Hocek, Michal; Fojta, Miroslav

    2008-07-07

    Construction of functionalized nucleic acids (DNA or RNA) via polymerase incorporation of modified nucleoside triphosphates is reviewed and selected applications of the modified nucleic acids are highlighted. The classical multistep approach for the synthesis of modified NTPs by triphosphorylation of modified nucleosides is compared to the novel approach consisting of direct aqueous cross-coupling reactions of unprotected halogenated nucleoside triphosphates. The combination of cross-coupling of NTPs with polymerase incorporation gives an efficient and straightforward two-step synthesis of modified nucleic acids. Primer extension using biotinylated templates followed by separation using streptavidine-coated magnetic beads and DNA duplex denaturation is used for preparation of modified single stranded oligonucleotides. Examples of using this approach for electrochemical DNA labelling and bioanalytical applications are given.

  18. Electron transfer-induced four-membered cyclic intermediate formation: Olefin cross-coupling vs. olefin cross-metathesis

    International Nuclear Information System (INIS)

    Okada, Yohei; Chiba, Kazuhiro

    2011-01-01

    An electron transfer-induced four-membered cyclic intermediate, formed between a radical cation of an enol ether and an unactivated olefin, played a key role in the pathway toward either cross-coupling or cross-metathesis. The presence of an alkoxy group on the phenyl ring of the olefin entirely determined the synthetic outcome of the reaction, which mirrored the efficiency of the intramolecular electron transfer.

  19. Reactions of nitroxides 15. Cinnamates bearing a nitroxyl moiety synthesized using a Mizoroki–Heck cross-coupling reaction

    Directory of Open Access Journals (Sweden)

    Jerzy Zakrzewski

    2015-07-01

    Full Text Available Cinnamic acid derivatives bearing a nitroxyl moiety (2,2,6,6-tetramethyl-1-oxyl-4-piperidyl 3-E-aryl acrylates were synthesized in 30–100% yield using a Mizoroki–Heck cross-coupling reaction between 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl and iodobenzene derivatives in the presence of palladium(II acetate coordinated with a tri(o-tolylphosphine ligand immobilized in a polyurea matrix.

  20. A well-defined (POCOP)Rh catalyst for the coupling of aryl halides with thiols.

    Science.gov (United States)

    Timpa, Samuel D; Pell, Christopher J; Ozerov, Oleg V

    2014-10-22

    This article describes a well-defined pincer-Rh catalyst for C-S cross-coupling reactions. (POCOP)Rh(H)(Cl) serves as an active precatalyst for the coupling of aryl chlorides and bromides with aryl and alkyl thiols under reasonable conditions (3% mol cat., 110 °C, 2-24 h, >90% yield). For select substrates, >90% yields were obtained with catalyst loading as low as 0.1%. Key mechanistic intermediates have been isolated and fully characterized, including (POCOP)Rh(Ph)(SPh) (6a) and (POCOP)Rh(SPh2) (6b). The aryl/bis(phosphinite) (POCOP)Rh system has been shown to favor aryl thiolate reductive elimination at elevated temperatures and in some cases at room temperature, compared with the analogous diarylamido/bis(phosphine) (PNP)Rh pincer system. Concerted reductive elimination has been studied with 6a directly and in the presence of aryl bromide and aryl chloride traps. This investigation demonstrates a clear rate dependence on aryl chloride concentration during catalysis, a dependence that is absent when using aryl bromides. The rate of catalysis is dramatically reduced or brought to zero for ortho-tolyl halides, which can be traced to slower C-S coupling and slower carbon-halogen oxidative addition for ortho-substituted aryls. The influence of the sterics in the thiol component is less straightforward. The S-H oxidative addition product (POCOP)Rh(H)(SPh) (16) has been fully characterized and its reactivity has been examined, resulting in the isolation of the sodium-thiolate adduct (POCOP)Rh(NaSPh) (19). The solid-state structure of 19 shows Na interactions not only with sulfur, but also with a neighboring Rh and the chelating aryl carbon of the pincer framework. The reactivity of 16 and 19 indicates that these potential side products should not hinder catalysis.

  1. How low does iron go? Chasing the active species in fe-catalyzed cross-coupling reactions.

    Science.gov (United States)

    Bedford, Robin B

    2015-05-19

    The catalytic cross-coupling reactions of organic halides or related substrates with organometallic nucleophiles form the cornerstone of many carbon-carbon bond-forming processes. While palladium-based catalysts typically mediate such reactions, there are increasing concerns about the long-term sustainability of palladium in synthesis. This is due to the high cost of palladium, coupled with its low natural abundance, environmentally deleterious extraction (∼6 g of metal are produced per ton of ore), toxicity, and competition for its use from the automotive and consumer electronics sectors. Therefore, there is a growing interest in replacing palladium-based catalysts with those incorporating more earth-abundant elements. With its low cost, high natural abundance, and low toxicity, iron makes a particularly appealing alternative, and accordingly, the development of iron-catalyzed cross-coupling is undergoing explosive growth. However, our understanding of the mechanisms that underpin the iron-based catalytic cycles is still very much in its infancy. Mechanistic insight into catalytic reactions is not only academically important but also allows us to maximize the efficiency of processes or even to develop entirely new transformations. Key to the development of robust mechanistic models for cross-coupling is knowing the lowest oxidation state in the cycle. Once this is established, we can explore subsequent redox processes and build the catalytic manifold. Until we know with confidence what the lowest oxidation state is, any cycles proposed are largely just guesswork. To date, Fe(-II), Fe(-I), Fe(0), Fe(I), and Fe(II) have been proposed as contenders for the lowest-oxidation-state species in the cycle in iron-catalyzed cross-coupling; the aim of this Account is to pull together the various pieces of evidence in support, or otherwise, of each of these suggestions in turn. There currently exists no direct evidence that oxidation states below Fe(0) are active in the

  2. Diversity-oriented approach to macrocyclic cyclophane derivatives by Suzuki-Miyaura cross-coupling and olefin metathesis as key steps.

    Science.gov (United States)

    Kotha, Sambasivarao; Chavan, Arjun S; Shaikh, Mobin

    2012-01-06

    Palladium-catalyzed Suzuki-Miyaura (SM) cross-coupling reaction with allylboronic acid pinacol ester and titanium assisted cross-metathesis (CM)/ring-closing metathesis (RCM) cascade has been used to synthesize macrocyclic cyclophane derivatives.

  3. Kerr-effect analysis in a three-level negative index material under magneto cross-coupling

    Science.gov (United States)

    Boutabba, N.

    2018-02-01

    We discuss the feasibility of the Kerr effect in negative refractive index materials under magneto cross-coupling and reservoir interaction. The considered medium is a typical three-level atomic system where we derive both the refractive and the gain spectrum. The profiles are analyzed for a weak probe field, and for varying strengths of the strong control field. The considered scheme shows an enhancement of the Kerr nonlinearity which we attribute to the contribution of the electromagnetic components of the fields. For more realistic experimental conditions, we discuss the dependence of the Kerr effect on different thermal bath coupling constants.

  4. Glycosyl Cross-Coupling of Anomeric Nucleophiles: Scope, Mechanism, and Applications in the Synthesis of Aryl C-Glycosides.

    Science.gov (United States)

    Zhu, Feng; Rodriguez, Jacob; Yang, Tianyi; Kevlishvili, Ilia; Miller, Eric; Yi, Duk; O'Neill, Sloane; Rourke, Michael J; Liu, Peng; Walczak, Maciej A

    2017-12-13

    Stereoselective manipulations at the C1 anomeric position of saccharides are one of the central goals of preparative carbohydrate chemistry. Historically, the majority of reactions forming a bond with anomeric carbon has focused on reactions of nucleophiles with saccharide donors equipped with a leaving group. Here, we describe a novel approach to stereoselective synthesis of C-aryl glycosides capitalizing on the highly stereospecific reaction of anomeric nucleophiles. First, methods for the preparation of anomeric stannanes have been developed and optimized to afford both anomers of common saccharides in high anomeric selectivities. We established that oligosaccharide stannanes could be prepared from monosaccharide stannanes via O-glycosylation with Schmidt-type donors, glycal epoxides, or under dehydrative conditions with C1 alcohols. Second, we identified a general set of catalytic conditions with Pd 2 (dba) 3 (2.5 mol%) and a bulky ligand (JackiePhos, 10 mol%) controlling the β-elimination pathway. We demonstrated that the glycosyl cross-coupling resulted in consistently high anomeric selectivities for both anomers with mono- and oligosaccharides, deoxysugars, saccharides with free hydroxyl groups, pyranose, and furanose substrates. The versatility of the glycosyl cross-coupling reaction was probed in the total synthesis of salmochelins (siderophores) and commercial anti-diabetic drugs (gliflozins). Combined experimental and computational studies revealed that the β-elimination pathway is suppressed for biphenyl-type ligands due to the shielding of Pd(II) by sterically demanding JackiePhos, whereas smaller ligands, which allow for the formation of a Pd-F complex, predominantly result in a glycal product. Similar steric effects account for the diminished rates of cross-couplings of 1,2-cis C1-stannanes with aryl halides. DFT calculations also revealed that the transmetalation occurs via a cyclic transition state with retention of configuration at the anomeric

  5. New air-stable planar chiral ferrocenyl monophosphine ligands: Suzuki cross-coupling of aryl chlorides and bromides

    DEFF Research Database (Denmark)

    Jensen, Jakob Feldthusen; Johannsen, Mogens

    2003-01-01

    GraphicA novel class of planar chiral electron-rich monophosphine ligands has been developed. The modular design allows a short and efficient synthesis of an array of aryl-ferrocenyl derivatives carrying the donating bis(dicyclohexyl)phosphino moiety. These new ligands have successfully been appl...... applied in the palladium-catalyzed Suzuki cross-coupling of activated as well as nonactivated aryl chlorides at room temperature. The asymmetric coupling of an aryl bromide and an aryl boronic acid was also tested, giving ees up to 54%....

  6. Compensation of Cross-Coupling Stiffness and Increase of Direct Damping in Multirecess Journal Bearings using Active Hybrid Lubrication

    DEFF Research Database (Denmark)

    Santos, Ilmar; Watanabe, F.Y.

    2004-01-01

    Fluid film forces are generated in hydrostatic journal bearings by two types of lubrication mechanisms: the hydrostatic lubrication in the bearing recesses and hydrodynamic lubrication in the bearing lands, when operating in rotation. The combination of both lubrication mechanisms leads to hybrid...... journal bearings (HJB). When part of hydrostatic pressure is also dynamically modified by means of hydraulic control systems, one refers to the active lubrication. The main contribution of the present theoretical work is to show that it is possible to reduce cross-coupling stiffness and increase...

  7. Effect of δ meson and ρ-ω cross couplings in effective field theory motivated Lagrangian approach

    International Nuclear Information System (INIS)

    Jagota, R.K.; Dhiman, S.K.; Sharma, B.K.; Arumugam, P.; Patra, S.K.

    2005-01-01

    It is shown that the self and cross couplings of ω meson plays an important role to make the nuclear equation of state (EOS) softer. The parameter set G2, obtained from the effective field theory motivated Lagrangian (E-RMF) approach, is very successful to reproduce the nuclear matter properties including the structure of neutron star as well as of finite nuclei. The motivation of the present report is to see the effects of these terms in the E-RMF Lagrangian on infinite nuclear matter as well as finite nuclei

  8. An efficient protocol for copper-free palladium-catalyzed Sonogashira cross-coupling in aqueous media at low temperatures

    KAUST Repository

    Marziale, Alexander N.

    2011-11-01

    A thorough study on copper-free Sonogashira cross-couplings in water was carried out using the palla-dacycle, [{Pd(μ-Cl){K2-P,C-P(iPr) 2(OC6H3-2-Ph)}}2] as pre-catalyst with different bases and palladium concentrations. The highly active pre-catalyst imparts good to near quantitative yields using a concentration of 0.25 mol % at 40 °C. This broadly applicable protocol exhibits high tolerance of functional groups and substitution patterns. © 2011 Elsevier Ltd. All rights reserved.

  9. Cross-coupling reactions of nucleoside triphosphates followed by polymerase incorporation. Construction and applications of base-functionalized nucleic acids

    Czech Academy of Sciences Publication Activity Database

    Hocek, Michal; Fojta, Miroslav

    2008-01-01

    Roč. 6, č. 13 (2008), s. 2233-2241 ISSN 1477-0520 R&D Projects: GA ČR GA203/05/0043; GA ČR GA203/07/1195; GA MŠk LC512; GA MŠk(CZ) LC06035 Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z50040507 Keywords : DNA * nucleotides * cross-coupling reactions Subject RIV: CC - Organic Chemistry Impact factor: 3.550, year: 2008

  10. Urinary protein thiols in different grades of proteinuria.

    Science.gov (United States)

    Prakash, Mungli; Shetty, Jeevan K; Dash, Sambit; Barik, Bijay K; Sarkar, Abhirup; Awanti, Sharanabasappa M; Prabhu, Ravindra

    2008-10-01

    Total thiol status of plasma, especially thiol groups over protein contributes maximum to the plasma antioxidant status of the body. Serum protein thiols were found to be decreased in various disease conditions including chronic renal failure patients. Only few studies determined the levels of urinary protein thiols in disease conditions. The current study was designed to know the levels of urinary protein thiols in patients with different grades of proteinuria. The study was conducted on urine of 40 healthy controls and 61 cases with proteinuria. Based on proteinuria cases were further divided into two groups; group I - microproteinuria (150-300 mg protein/d), 32 cases, group II - frank proteinuria (>300 mg protein/d), 29 cases. Urinary thiol levels were determined by spectrophotometric method using dithionitrobenzoic acid. A significant decrease (pproteinuria.

  11. Hybrid Organic/Inorganic Thiol-ene-Based Photopolymerized Networks

    OpenAIRE

    Schreck, Kathleen M.; Leung, Diana; Bowman, Christopher N.

    2011-01-01

    The thiol-ene reaction serves as a more oxygen tolerant alternative to traditional (meth)acrylate chemistry for forming photopolymerized networks with numerous desirable attributes including energy absorption, optical clarity, and reduced shrinkage stress. However, when utilizing commercially available monomers, many thiol-ene networks also exhibit decreases in properties such as glass transition temperature (Tg) and crosslink density. In this study, hybrid organic/inorganic thiol-ene resins ...

  12. Quantifying the global cellular thiol-disulfide status

    DEFF Research Database (Denmark)

    Hansen, Rosa E; Roth, Doris; Winther, Jakob R

    2009-01-01

    It is widely accepted that the redox status of protein thiols is of central importance to protein structure and folding and that glutathione is an important low-molecular-mass redox regulator. However, the total cellular pools of thiols and disulfides and their relative abundance have never been...... cell types. However, when cells are exposed to a sublethal dose of the thiol-specific oxidant diamide, PSSG levels increase to >15% of all protein cysteine. Glutathione is typically characterized as the "cellular redox buffer"; nevertheless, our data show that protein thiols represent a larger active...

  13. Decarbonylative Cross-Couplings: Nickel Catalyzed Functional Group Interconversion Strategies for the Construction of Complex Organic Molecules

    KAUST Repository

    Guo, Lin

    2018-04-13

    The utilization of carboxylic acid esters as electrophiles in metal-catalyzed cross-coupling reactions is increasingly popular, as environmentally friendly and readily available ester derivatives can be powerful alternatives to the commonly used organohalides. However, key challenges associated with the use of these chemicals remain to be addressed, including the stability of ester substrates and the high energy barrier associated with their oxidative addition to low-valent metal species. Due to recent developments in nickel catalysis that make it easier to perform oxidative additions, chemists have become interested in applying less reactive electrophiles as coupling counterparts in nickel-catalyzed transformations. Hence, our group and others have independently investigated various ester group substitutions and functionalizations enabled by nickel catalysis. Such methods are of great interest as they enable the exchange of ester groups, which can be used as directing groups in metal-catalyzed C-H functionalizations prior to their replacement. Here, we summarize our recent efforts toward the development of nickel-catalyzed decarbonylative cross-coupling reactions of carboxylic esters. Achievements accomplished by other groups in this area are also included. To this day, a number of new transformations have been successfully developed, including decarbonylative arylations, alkylations, cyanations, silylations, borylations, aminations, thioetherifications, stannylations, and hydrogenolysis reactions. These transformations proceed via a nickel-catalyzed decarbonylative pathway and have shown a high degree of reactivity and chemoselectivity, as well as several other unique advantages in terms of substrate availability, due to the use of esters as coupling partners. Although the mechanisms of these reactions have not yet been fully understood, chemists have already provided some important insights. For example, Yamamoto explored the stoichiometric nickel

  14. Role of endogenous thiols in protection

    Science.gov (United States)

    Vos, O.

    Aminothiols represent the most important group of radioprotective compounds. The most effective compounds administered at an optimal dose and time before irradiation are able to provide a protection in mice with a dose reduction factor (DRF) of about 2-2.5. The working mechanism can partly be explained as a scavenging process of radicals induced in water and partly as a chemical repair process of injured DNA. The endogenous aminothiol which has far-out the highest intracellular concentration is glutathione (GSH). The importance of intracellular GSH in determining cellular radiosensitivity has been shown by irradiating cells that had very low GSH levels. Such cells appear to have a high radiosensitivity, especially in hypoxic conditions. On the other hand, it has been demonstrated that induction of a high GSH level (100-200% above the normal level) provides only a small protection. In vitro experiments with DNA indicate that thiols with a high positive charge condense in the vicinity of DNA and are effective protectors, whereas thiols with a negative charge are kep away from it and are poor protectors. In comparison with the most effective exogenous aminothiols like cysteamine and WR1065, GSH is not an effective radioprotector. Putative explanations for this relatively poor protective ability of GSH are presented.

  15. Photoinduced formation of thiols in human hair.

    Science.gov (United States)

    Fedorkova, M V; Brandt, N N; Chikishev, A Yu; Smolina, N V; Balabushevich, N G; Gusev, S A; Lipatova, V A; Botchey, V M; Dobretsov, G E; Mikhalchik, E V

    2016-11-01

    Raman, scanning electron, and optical microscopy of hair and spectrophotometry of soluble hair proteins are used to study the effect of UV-vis radiation on white hair. The samples of a healthy subject are irradiated using a mercury lamp and compared with non-irradiated (control) hair. The cuticle damage with partial exfoliation is revealed with the aid of SEM and optical microscopy of semifine sections. Gel filtration chromatography shows that the molecular weight of soluble proteins ranges from 5 to 7kDa. Absorption spectroscopy proves an increase in amount of thiols in a heavier fraction of the soluble proteins of irradiated samples under study. Raman data indicate a decrease in the amount of SS and CS bonds in cystines and an increase in the amount of SH bonds due to irradiation. Such changes are more pronounced in peripheral regions of hair. Conformational changes of hair keratins presumably related to the cleavage of disulfide bonds, follow from variations in amide I and low-frequency Raman bands. An increase in the content of thiols in proteins revealed by both photometric data on soluble proteins and Raman microspectroscopy of hair cuts can be used to develop a protocol of the analysis of photoinduced hair modification. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Thiol/disulfide homeostasis in untreated schizophrenia patients.

    Science.gov (United States)

    Topcuoglu, Canan; Bakirhan, Abdurrahim; Yilmaz, Fatma Meric; Neselioglu, Salim; Erel, Ozcan; Sahiner, Safak Yalcin

    2017-05-01

    The aim of the study was to investigate dynamic thiol/disulfide (SH/SS) homeostasis in untreated schizophrenia. Blood thiol/disulfide homeostasis status, which reflects native thiol-disulfide exchanges, was investigated in 87 untreated patients (52 males, 35 females), and the obtained results were compared with 86 healthy controls. Blood serum native thiol and total thiol (ToSH) concentrations were measured in a paired test. The half value of the difference between native thiol and ToSH concentrations was calculated as the disulfide bond amount. SH and ToSH concentrations were found to be significantly lower (pschizophrenia compared with the control group, whereas disulfide levels were significantly higher (pSchizophrenia patients had significantly higher SS/ToSH and SS/SH ratios and a significantly lower SH/ToSH ratio compared to those of healthy individuals. SH and ToSH amounts were found to be insufficient in untreated schizophrenia patients. Additionally, according to the results of the study, thiol/disulfide homeostasis was also disturbed by a shift to the disulfide bond formation side. This might affect the neurotransmission processes, which are known to be related with many symptoms observed in schizophrenia. The replacement of the thiol gap and the reduction of excess SS amounts might have a positive effect in supporting therapy for schizophrenia patients. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

  17. QuadraPure-Supported Palladium Nanocatalysts for Microwave-Promoted Suzuki Cross-Coupling Reaction under Aerobic Condition

    Directory of Open Access Journals (Sweden)

    Kin Hong Liew

    2014-01-01

    Full Text Available Cross-linked resin-captured palladium (XL-QPPd was readily prepared by simple physical adsorption onto the high loading QuadraPure macroporous resin and a subsequent reduction process. To enhance the mechanical stability, entrapped palladium nanocatalysts were cross-linked with succinyl chloride. Both transmission electron microscopy images and X-ray diffraction analysis revealed that the palladium nanoparticles were well dispersed with diameters ranging in 4–10 nm. The catalyst performed good catalytic activity in microwave-promoted Suzuki cross-coupling reactions in water under aerobic condition with mild condition by using various aryl halides and phenylboronic acid. In addition, the catalyst showed an excellent recyclability without significant loss of catalytic activity.

  18. Pd Metal Catalysts for Cross-Couplings and Related Reactions in the 21st Century: A Critical Review.

    Science.gov (United States)

    Biffis, Andrea; Centomo, Paolo; Del Zotto, Alessandro; Zecca, Marco

    2018-02-28

    Cross-couplings and related reactions are a class of highly efficient synthetic protocols that are generally promoted by molecular Pd species as catalysts. However, catalysts based on more or less highly dispersed Pd metal have been also employed for this purpose, and their use, which was largely limited to the Heck reaction until the turn of the century, has been extended in recent years to most reactions of this class. This review provides a critical overview on these recent applications of Pd metal catalysts. Particular attention is devoted to the discussion of the mechanistic pathways that have been proposed to explain the catalytic role of Pd metal. Furthermore, the most outstanding Pd metal based catalytic systems that have emerged are illustrated, together with the development of novel approaches to boost the reactivity of Pd metal. A section summarizing the current industrial applications of Pd metal catalyzed reactions of this kind concludes the review.

  19. An Iron-Catalyzed Bond-Making/Bond-Breaking Cascade Merges Cycloisomerization and Cross-Coupling Chemistry.

    Science.gov (United States)

    Echeverria, Pierre-Georges; Fürstner, Alois

    2016-09-05

    Treatment of readily available enynes with alkyl-Grignard reagents in the presence of catalytic amounts of Fe(acac)3 engenders a remarkably facile and efficient reaction cascade that results in the net formation of two new C-C bonds while a C-Z bond in the substrate backbone is broken. Not only does this new manifold lend itself to the extrusion of heteroelements (Z=O, NR), but it can even be used for the cleavage of activated C-C bonds. The reaction likely proceeds via metallacyclic intermediates, the iron center of which gains ate character before reductive elimination occurs. The overall transformation represents a previously unknown merger of cycloisomerization and cross-coupling chemistry. It provides ready access to highly functionalized 1,3-dienes comprising a stereodefined tetrasubstituted alkene unit, which are difficult to make by conventional means. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Nickel-Catalyzed Suzuki-Miyaura Cross-Coupling in a Green Alcohol Solvent for an Undergraduate Organic Chemistry Laboratory.

    Science.gov (United States)

    Hie, Liana; Chang, Jonah J; Garg, Neil K

    2015-03-10

    A modern undergraduate organic chemistry laboratory experiment involving the Suzuki-Miyaura coupling is reported. Although Suzuki-Miyaura couplings typically employ palladium catalysts in environmentally harmful solvents, this experiment features the use of inexpensive nickel catalysis, in addition to a "green" alcohol solvent. The experiment employs heterocyclic substrates, which are important pharmaceutical building blocks. Thus, this laboratory procedure exposes students to a variety of contemporary topics in organic chemistry, including transition metal-catalyzed cross-couplings, green chemistry, and the importance of heterocycles in drug discovery, none of which are well represented in typical undergraduate organic chemistry curricula. The experimental protocol uses commercially available reagents and is useful in both organic and inorganic instructional laboratories.

  1. Dynamic thiol-disulfide homeostasis in hyperemesis gravidarum.

    Science.gov (United States)

    Ergin, M; Cendek, B D; Neselioglu, S; Avsar, A F; Erel, O

    2015-10-01

    To determine serum thiol-disulfide homeostasis in hyperemesis gravidarum. Twenty-six pregnant women with hyperemesis gravidarum and 37 healthy pregnant women were included in the study. Native thiol, disulfide and total thiol concentrations were measured with a novel automated method. Serum disulfide levels were 15.68±4.41 μmol l(-1) in the hyperemesis gravidarum group and 13.49±2.81 μmol l(-1) in the healthy group (P=0.031). Native thiol levels were 213.86±26.29 μmol l(-1) in the hyperemesis gravidarum group and 232.18±19.21 μmol l(-1) in healthy group (P=0.004), and total thiol levels were 245.23±28.58 μmol l(-1) in the hyperemesis gravidarum group and 259.17±19.94 μmol l(-1) in the healthy group (P=0.038). Native and total thiol were deficient in the hyperemesis gravidarum group and this deficiency was correlated with the severity of the disease. The thiol-disulfide balance has shifted to the oxidative side. This metabolic disturbance may have a role in the pathogenesis of hyperemesis gravidarum.

  2. Photopolymerized Thiol-Ene Systems as Shape Memory Polymers

    Science.gov (United States)

    Nair, Devatha P.; Cramer, Neil B.; Scott, Timothy F.; Bowman, Christopher N.; Shandas, Robin

    2010-01-01

    In this study we introduce the use of thiol-ene photopolymers as shape memory polymer systems. The thiol-ene polymer networks are compared to a commonly utilized acrylic shape memory polymer and shown to have significantly improved properties for two different thiol-ene based polymer formulations. Using thermomechanical and mechanical analysis, we demonstrate that thiol-ene based shape memory polymer systems have comparable thermomechanical properties while also exhibiting a number of advantageous properties due to the thiol-ene polymerization mechanism which results in the formation of a homogenous polymer network with low shrinkage stress and negligible oxygen inhibition. The resulting thiol-ene shape memory polymer systems are tough and flexible as compared to the acrylic counterparts. The polymers evaluated in this study were engineered to have a glass transition temperature between 30 and 40 °C, exhibited free strain recovery of greater than 96% and constrained stress recovery of 100%. The thiol-ene polymers exhibited excellent shape fixity and a rapid and distinct shape memory actuation response. PMID:21072253

  3. Impaired Thiol-Disulfide Balance in Acute Brucellosis.

    Science.gov (United States)

    Kolgelier, Servet; Ergin, Merve; Demir, Lutfi Saltuk; Inkaya, Ahmet Cagkan; Aktug Demir, Nazlim; Alisik, Murat; Erel, Ozcan

    2017-05-24

    The objective of this study was to examine a novel profile: thiol-disulfide homeostasis in acute brucellosis. The study included 90 patients with acute brucellosis, and 27 healthy controls. Thiol-disulfide profile tests were analyzed by a recently developed method, and ceruloplasmin levels were determined. Native thiol levels were 256.72 ± 48.20 μmol/L in the acute brucellosis group and 461.13 ± 45.37 μmol/L in the healthy group, and total thiol levels were 298.58 ± 51.78 μmol/L in the acute brucellosis group and 504.83 ± 51.05 μmol/L in the healthy group (p brucellosis than in the healthy controls (p brucellosis. The strong associations between thiol-disulfide parameters and a positive acute-phase reactant reflected the disruption of the balance between the antioxidant and oxidant systems. Since thiol groups act as anti-inflammatory mediators, the alteration in the thiol-disulfide homeostasis may be involved in brucellosis.

  4. Thiol/disulphide homeostasis as a novel indicator of oxidative stress in sudden sensorineural hearing loss.

    Science.gov (United States)

    Dinc, M E; Ulusoy, S; Is, A; Ayan, N N; Avincsal, M O; Bicer, C; Erel, O

    2016-05-01

    To investigate a novel oxidative stress marker, thiol/disulphide literature homeostasis, in patients with idiopathic sudden sensorineural hearing loss, and to compare the results with healthy controls for the first time. Thirty-two patients with idiopathic sudden sensorineural hearing loss and 30 healthy individuals were included in the study. Serum native thiol, total thiol and disulphide levels were measured, and disulphide/native thiol and disulphide/total thiol ratios were determined in all subjects. Serum native thiol and total thiol levels were significantly lower in patients with sudden sensorineural hearing loss compared with controls (p sudden sensorineural hearing loss in those patients.

  5. Radical Scavenging Efficacy of Thiol Capped Silver Nanoparticles

    Indian Academy of Sciences (India)

    OH) ... nents involved in redox homeostasis. Nature of bonding ..... study provides valuable and fundamental information about the scavenging behavior of thiol capped AgNPs in biological system. Supplementary Information. All additional ...

  6. Facially amphiphilic thiol capped gold and silver nanoparticles

    Indian Academy of Sciences (India)

    Abstract. A series of bile acid-derived facially amphiphilic thiols have been used to cap sliver and gold nanoparticles. The self-assembling properties of these steroid-capped nanoparticles have been investigated and reported in this article.

  7. Intracellular thiols: involvement in drug metabolism and radiation response

    International Nuclear Information System (INIS)

    Astor, M.

    1983-01-01

    Nitro compunds are activated by coupled enzyme reactions to oxygen reactive intermediates leading to the formation of peroxide, under aerobic conditions, and to the depletion of thiols, under anaerobic conditions. Some nitro compounds as substrates for glutathione-S-transferase, show peroxide production without prior thiol removal. Other drugs reacting spontaneouly with glutathione also produce peroxide. Glutathione plays an important role in the metabolism of the nitrocompounds either by directly reacting with them or their reduced intermediates such as the nitroso, nitro and hydroxyl radical. In the case of misonidazole, protection against their cytotoxic effects can be achieved by the addition of exogenous thiols such as glutathione or cysteamine. Results indicate that oxygen and peroxide electrodes provide convenient means for measuring the products of metabolic activation of nitro compounds. Mechanisms are proposed whereby protein, nonprotein and glutathione thiols can interact with drug radicals or with DNA radicals. 60 references, 14 figures, 5 tables

  8. Reversible inactivation of CO dehydrogenase with thiol compounds

    Energy Technology Data Exchange (ETDEWEB)

    Kreß, Oliver [Department of Microbiology, University of Bayreuth, 95440 Bayreuth (Germany); Gnida, Manuel [Department of Chemistry, University of Paderborn, 33098 Paderborn (Germany); Pelzmann, Astrid M. [Department of Microbiology, University of Bayreuth, 95440 Bayreuth (Germany); Marx, Christian [Institute of Biochemistry and Biophysics, Friedrich-Schiller-University of Jena, 07745 Jena (Germany); Meyer-Klaucke, Wolfram [Department of Chemistry, University of Paderborn, 33098 Paderborn (Germany); Meyer, Ortwin, E-mail: Ortwin.Meyer@uni-bayreuth.de [Department of Microbiology, University of Bayreuth, 95440 Bayreuth (Germany)

    2014-05-09

    Highlights: • Rather large thiols (e.g. coenzyme A) can reach the active site of CO dehydrogenase. • CO- and H{sub 2}-oxidizing activity of CO dehydrogenase is inhibited by thiols. • Inhibition by thiols was reversed by CO or upon lowering the thiol concentration. • Thiols coordinate the Cu ion in the [CuSMo(=O)OH] active site as a third ligand. - Abstract: Carbon monoxide dehydrogenase (CO dehydrogenase) from Oligotropha carboxidovorans is a structurally characterized member of the molybdenum hydroxylase enzyme family. It catalyzes the oxidation of CO (CO + H{sub 2}O → CO{sub 2} + 2e{sup −} + 2H{sup +}) which proceeds at a unique [CuSMo(=O)OH] metal cluster. Because of changing activities of CO dehydrogenase, particularly in subcellular fractions, we speculated whether the enzyme would be subject to regulation by thiols (RSH). Here we establish inhibition of CO dehydrogenase by thiols and report the corresponding K{sub i}-values (mM): L-cysteine (5.2), D-cysteine (9.7), N-acetyl-L-cysteine (8.2), D,L-homocysteine (25.8), L-cysteine–glycine (2.0), dithiothreitol (4.1), coenzyme A (8.3), and 2-mercaptoethanol (9.3). Inhibition of the enzyme was reversed by CO or upon lowering the thiol concentration. Electron paramagnetic resonance spectroscopy (EPR) and X-ray absorption spectroscopy (XAS) of thiol-inhibited CO dehydrogenase revealed a bimetallic site in which the RSH coordinates to the Cu-ion as a third ligand ([Mo{sup VI}(=O)OH{sub (2)}SCu{sup I}(SR)S-Cys]) leaving the redox state of the Cu(I) and the Mo(VI) unchanged. Collectively, our findings establish a regulation of CO dehydrogenase activity by thiols in vitro. They also corroborate the hypothesis that CO interacts with the Cu-ion first. The result that thiol compounds much larger than CO can freely travel through the substrate channel leading to the bimetallic cluster challenges previous concepts involving chaperone function and is of importance for an understanding how the sulfuration step in

  9. Synthesis of 2'-deoxyadenosine nucleosides bearing bipyridine-type ligands and their Ru-complexes in position 8 through cross-coupling reactions

    Czech Academy of Sciences Publication Activity Database

    Vrábel, Milan; Pohl, Radek; Klepetářová, Blanka; Votruba, Ivan; Hocek, Michal

    2007-01-01

    Roč. 5, č. 17 (2007), s. 2849-2857 ISSN 1477-0520 R&D Projects: GA MŠk LC512; GA ČR GA203/05/0043 Institutional research plan: CEZ:AV0Z40550506 Keywords : nucleosides * purines * cross-coupling * ruthenium Subject RIV: CC - Organic Chemistry Impact factor: 3.167, year: 2007

  10. Pyrazine-functionalized calix[4]arenes: synthesis by palladium-catalyzed cross-coupling with phosphorus pronucleophiles and metal ion extraction properties

    NARCIS (Netherlands)

    Nikishkin, N.; Huskens, Jurriaan; Ansari, S.A.; Mohapatra, P.K.; Verboom, Willem

    2013-01-01

    A series of pyrazine-based calix[4]arene extractants was prepared by a stepwise functionalization, comprising palladium-catalyzed exhaustive cross-coupling of di- and tetrasubstituted calix[4]arenes bearing chloropyrazine moieties. The extraction behavior of the synthesized ligands was studied on

  11. Preparation of 5-acyl- and 5-aryl-substituted 1-(benzyloxy)pyrazoles via directed ortho-lithiation/transmetalation and palladium catalyzed cross- coupling

    DEFF Research Database (Denmark)

    Kristensen, Jesper Langgaard; Begtrup, M.; Vedsø, P.

    1998-01-01

    Palladium(0) catalyzed cross-coupling of 1-(benzyloxy)pyrazol-5-ylzinc halides 3a,b, prepared by transmetalation of 1-(benzyloxy)-5-lithiopyrazole (2), with acyl chlorides produced 5 acyl-1-(benzyloxy)pyrazoles 4a-d in high yields. Similar coupling of the pyrazol-5-ylzinc halide with amino-, hydr...

  12. Synthesis of (purin-6-yl)acetates and 6-(2-hydroxyethyl)purines via cross-couplings of 6-chloropurines with the Reformatsky reagent

    Czech Academy of Sciences Publication Activity Database

    Hasník, Zbyněk; Šilhár, Peter; Hocek, Michal

    2007-01-01

    Roč. 48, č. 32 (2007), s. 5589-5592 ISSN 0040-4039 R&D Projects: GA MŠk 1M0508; GA AV ČR 1QS400550501 Institutional research plan: CEZ:AV0Z40550506 Keywords : purin es * nucleosides * cross-coupling reactions Subject RIV: CC - Organic Chemistry Impact factor: 2.615, year: 2007

  13. Oxidative Photoredox-Catalytic Activation of Aliphatic Nucleophiles for C(sp3)-C(sp2) Cross-Coupling Reactions

    Czech Academy of Sciences Publication Activity Database

    Jahn, Emanuela; Jahn, Ullrich

    2014-01-01

    Roč. 53, č. 49 (2014), s. 13326-13328 ISSN 1433-7851 Institutional support: RVO:61388963 Keywords : amino acids * cross-coupling * nickel * persistent radical effect * photoredox catalysis Subject RIV: CC - Organic Chemistry Impact factor: 11.261, year: 2014

  14. An efficient method for the construction of functionalized DNA bearing amino acid groups through cross-coupling reactions of nucleoside triphosphates followed by primer extension or PCR

    Czech Academy of Sciences Publication Activity Database

    Čapek, Petr; Cahová, Hana; Pohl, Radek; Hocek, Michal; Gloeckner, Ch.; Marx, A.

    2007-01-01

    Roč. 13, č. 21 (2007), s. 6196-6203 ISSN 0947-6539 R&D Projects: GA MŠk LC512; GA ČR GA203/05/0043 Institutional research plan: CEZ:AV0Z40550506 Keywords : nucleoside triphosphates * cross-coupling * DNA Subject RIV: CC - Organic Chemistry Impact factor: 5.330, year: 2007

  15. A green-LED driven source of hydrated electrons characterized from microseconds to hours and applied to cross couplings.

    Science.gov (United States)

    Naumann, Robert; Goez, Martin

    2018-03-12

    We present a novel photoredox catalytic system that delivers synthetically useable concentrations of hydrated electrons when illuminated with a green light-emitting diode (LED). The catalyst is a ruthenium complex protected by an anionic micelle, and the urate dianion serves as sacrificial donor confined to the aqueous bulk. Through its chemical properties, that donor not only suppresses charge recombination that would limit the electron yield but also enables this system to perform cross couplings via hydrated electrons, for which we report the first examples. We have investigated the kinetics of all the steps involving the electron and its direct precursor in a comparative study by using laser flash photolysis and by monitoring product formation during LED photolysis. Despite the differences in timescales, each approach on its own already gives a complete picture of the reaction over a temporal range ten orders of magnitude wide. Noticeable discrepancies between the kinetic parameters obtained with the two complementary techniques can be rationalized with the slow secondary chemistry of the system; they reveal that the product-based method provides a more accurate description because it responds also to the changes of the system composition during a synthesis; hence, they demonstrate that in complex systems the timescale of the experimental observation should be matched to that of the actual application. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Cationic Pd(II-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies

    Directory of Open Access Journals (Sweden)

    Takashi Nishikata

    2016-05-01

    Full Text Available Cationic palladium(II complexes have been found to be highly reactive towards aromatic C–H activation of arylureas at room temperature. A commercially available catalyst [Pd(MeCN4](BF42 or a nitrile-free cationic palladium(II complex generated in situ from the reaction of Pd(OAc2 and HBF4, effectively catalyzes C–H activation/cross-coupling reactions between aryl iodides, arylboronic acids and acrylates under milder conditions than those previously reported. The nature of the directing group was found to be critical for achieving room temperature conditions, with the urea moiety the most effective in promoting facile coupling reactions at an ortho C–H position. This methodology has been utilized in a streamlined and efficient synthesis of boscalid, an agent produced on the kiloton scale annually and used to control a range of plant pathogens in broadacre and horticultural crops. Mechanistic investigations led to a proposed catalytic cycle involving three steps: (1 C–H activation to generate a cationic palladacycle; (2 reaction of the cationic palladacycle with an aryl iodide, arylboronic acid or acrylate, and (3 regeneration of the active cationic palladium catalyst. The reaction between a cationic palladium(II complex and arylurea allowed the formation and isolation of the corresponding palladacycle intermediate, characterized by X-ray analysis. Roles of various additives in the stepwise process have also been studied.

  17. Nonsymmetrical 3,4-dithienylmaleimides by cross-coupling reactions with indium organometallics: synthesis and photochemical studies.

    Science.gov (United States)

    Mosquera, Angeles; Férnandez, M Isabel; Canle Lopez, Moisés; Pérez Sestelo, José; Sarandeses, Luis A

    2014-10-27

    The synthesis and photochemical study of novel nonsymmetrical 1,2-dithienylethenes (DTEs) with a maleimide bridge have been carried out. The synthetic approach to the DTEs was based on successive selective palladium-catalyzed cross-coupling reactions of 5-susbtituted-2-methyl-3-thiophenyl indium reagents with 3,4-dichloromaleimides. The required organoindium reagents were prepared from 2-methyl-3,5-dibromothiophene by a selective (C-5) coupling reaction with triorganoindium compounds (R3 In) and subsequent metal-halogen exchange. The coupling reactions usually gave good yields and have a high atom economy with substoichiometric amounts of R3 In. The results of photochemical studies show that these novel dithienylmaleimides undergo a photocyclization reaction upon irradiation in the UV region and a photocycloreversion after excitation in the visible region, thus they can be used as photochemical switches. ON-OFF operations can be repeated in successive cycles without appreciable loss of effectiveness in the process. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. A Maximum Efficiency Point Tracking Control Scheme Based on Different Cross Coupling of Dual-Receiver Inductive Power Transfer System

    Directory of Open Access Journals (Sweden)

    Ruikun Mai

    2017-02-01

    Full Text Available One of the most promising inductive power transfer applications is the wireless power supply for locomotives which may cancel the need for pantographs. In order to meet the dynamic and high power demands of wireless power supplies for locomotives, a relatively long transmitter track and multiple receivers are usually adopted. However, during the dynamic charging, the mutual inductances between the transmitter and receivers vary and the load of the locomotives also changes randomly, which dramatically affects the system efficiency. A maximum efficiency point tracking control scheme is proposed to improve the system efficiency against the variation of the load and the mutual inductances between the transmitter and receivers while considering the cross coupling between receivers. Firstly, a detailed theoretical analysis on dual receivers is carried out. Then a control scheme with three control loops is proposed to regulate the receiver currents to be the same, to regulate the output voltage and to search for the maximum efficiency point. Finally, a 2 kW prototype is established to validate the performance of the proposed method. The overall system efficiency (DC-DC efficiency reaches 90.6% at rated power and is improved by 5.8% with the proposed method under light load compared with the traditional constant output voltage control method.

  19. Protein Thiols as an Indication of Oxidative Stress

    Directory of Open Access Journals (Sweden)

    Yousef Rezaei Chianeh

    2014-06-01

    Full Text Available Thiol is an organic compound that contain sulphhydryl group that have a critical role in preventing any involvement of oxidative stress in the cell. These defensive functions are generally considered to be carried out by the low molecular weight thiol glutathione and by cysteine residues in the active sites of proteins such as thioredoxin and peroxiredoxin. In addition, there are thiols exposed on protein surfaces that are not directly involved with protein function, although they can interact with the intracellular environment.The process of protection of the cell against an oxidative damage occur by thiol and cystein residue that has a low molecular weight. These residue are present in the active sites of a protein like, peroxiredoxin and thioredoxin. Apart from intracellular antioxidant defense mechanism by protein thiol, there are presence of thiol in outer surface of protein that are not involved with the function of protein, even though they can interact with intracellular part of the cell. [Archives Medical Review Journal 2014; 23(3.000: 443-456

  20. Quantifying Reversible Oxidation of Protein Thiols in Photosynthetic Organisms

    Science.gov (United States)

    Slade, William O.; Werth, Emily G.; McConnell, Evan W.; Alvarez, Sophie; Hicks, Leslie M.

    2015-04-01

    Photosynthetic organisms use dynamic post-translational modifications to survive and adapt, which include reversible oxidative modifications of protein thiols that regulate protein structure, function, and activity. Efforts to quantify thiol modifications on a global scale have relied upon peptide derivatization, typically using isobaric tags such as TMT, ICAT, or iTRAQ that are more expensive, less accurate, and provide less proteome coverage than label-free approaches—suggesting the need for improved experimental designs for studies requiring maximal coverage and precision. Herein, we present the coverage and precision of resin-assisted thiol enrichment coupled to label-free quantitation for the characterization of reversible oxidative modifications on protein thiols. Using C. reinhardtii and Arabidopsis as model systems for algae and plants, we quantified 3662 and 1641 unique cysteinyl peptides, respectively, with median coefficient of variation (CV) of 13% and 16%. Further, our method is extendable for the detection of protein abundance changes and stoichiometries of cysteine oxidation. Finally, we demonstrate proof-of-principle for our method, and reveal that exogenous hydrogen peroxide treatment regulates the C. reinhardtii redox proteome by increasing or decreasing the level of oxidation of 501 or 67 peptides, respectively. As protein activity and function is controlled by oxidative modifications on protein thiols, resin-assisted thiol enrichment coupled to label-free quantitation can reveal how intracellular and environmental stimuli affect plant survival and fitness through oxidative stress.

  1. Metallophilic interactions in polymeric group 11 thiols

    Science.gov (United States)

    Kolari, Kalle; Sahamies, Joona; Kalenius, Elina; Novikov, Alexander S.; Kukushkin, Vadim Yu.; Haukka, Matti

    2016-10-01

    Three polymeric group 11 transition metal polymers featuring metallophilic interactions were obtained directly via self-assembly of metal ions and 4-pyridinethiol ligands. In the cationic [Cu2(S-pyH)4]n2+ with [ZnCl4]n2- counterion (1) and in the neutral [Ag(S-py) (S-pyH)]n (2) 4-pyridinethiol (S-pyH) and its deprotonated form (S-py) are coordinated through the sulfur atom. Both ligands are acting as bridging ligands linking the metal centers together. In the solid state, the gold(I) polymer [Au(S-pyH)2]Cl (3) consists of the repeating cationic [Au(S-pyH)2]+ units held together by aurophilic interactions. Compound 1 is a zig-zag chain, whereas the metal chains in the structures of 2 and 3 are linear. The protonation level of the thiol ligand had an impact on the crystallization of polymers. Both nature of the metal center and reaction conditions affected the polymerization. QTAIM analysis confirmed direct metal-metal contacts only in polymers 1 and 3. In polymer 2, no theoretical evidence of argentophilic contacts was obtained even though the AgṡṡṡAg distance was found to be less than sum of the Bondi's van der Waals radius of silver.

  2. Thiol-yne/thiol-epoxy hybrid crosslinked materials based on propargyl modified hyperbranched poly(ethyleneimine) and diglycidylether of bisphenol A resins

    OpenAIRE

    Acebo Gorostiza, Cristina; Fernández Francos, Xavier; Ramis Juan, Xavier; Serra Albet, Àngels

    2016-01-01

    A novel curing methodology based on the combination of thiol-yne and thiol-epoxy click reactions has been developed. The curing process consists of a first photoinitiated thiol-yne reaction, followed by a thermal thiol-epoxy process. As alkyne substrate a new propargyl terminated hyperbranched poly(ethyleneimine) (PEIyne) has been synthesized from the reaction of commercial poly(ethylenimine) (PEI) and glycidyl propargyl ether. The evolution of the curing of different mixtures of PEIyne and d...

  3. Polymer surface engineering via thiol-mediated reactions

    Science.gov (United States)

    Hensarling, Ryan Matthew

    Synthesis of polymer brushes to decorate a surface with desired functionality typically involves surface-initiated polymerization (SIP) of functional, but non-reactive monomers. This approach suffers major drawbacks associated with synthesizing sufficiently thick polymer brushes containing surface-attached polymer chains of high molecular weight at high grafting density (i.e. cost, synthetic effort and functional group intolerance during polymerization). The research herein seeks to circumvent these limitations by the decoration of surfaces with polymer chains bearing specific pendent functional groups amenable to post-polymerization modification (PPM). In particular, this dissertation leverages PPM via a specific class of click reactions - thiol-click - that 1) enables the rapid generation of a diverse library of functional surfaces from a single substrates precursor, 2) utilizes a structurally diverse range of commercially available or easily attainable reagents, 3) proceeds rapidly to quantitative conversions under mild conditions and 4) opens the door to orthogonal and site-selective functionalization. In the first two studies, radical-mediated thiol-yne and base-catalyzed thiol-isocyanate reactions are demonstrated as modular platforms for the rapid and practical fabrication of highly functional, multicomponent surfaces under ambient conditions. Brush surfaces expressing a three-dimensional configuration of alkyne or isocyanate functionalities were modified with high efficiency and short reaction times using a library of commercially available thiols. In the third study, two routes to multifunctional brush surfaces were demonstrated utilizing orthogonal thiol-click reactions. In the first approach, alkyne-functionalized homopolymer brushes were modified with multiple thiols via a statistical, radical-mediated thiol-yne co-click reaction; and in the second approach, statistical copolymer brushes carrying two distinctly-addressable reactive moieties were

  4. Designed Chemical Intervention with Thiols for Prophylactic Contraception.

    Science.gov (United States)

    Sharma, Monika; Kumar, Lokesh; Jain, Ashish; Verma, Vikas; Sharma, Vikas; Kushwaha, Bhavana; Lal, Nand; Kumar, Lalit; Rawat, Tara; Dwivedi, Anil K; Maikhuri, Jagdamba P; Sharma, Vishnu L; Gupta, Gopal

    2013-01-01

    Unlike somatic cells, sperm have several-fold more available-thiols that are susceptible to redox-active agents. The present study explains the mechanism behind the instant sperm-immobilizing and trichomonacidal activities of pyrrolidinium pyrrolidine-1-carbodithioate (PPC), a novel thiol agent rationally created for prophylactic contraception by minor chemical modifications of some known thiol drugs. PPC, and its three derivatives (with potential active-site blocked by alkylation), were synthesized and evaluated against live human sperm and metronidazole-susceptible and resistant Trichomonas vaginalis, in vitro. Sperm hexokinase activity was evaluated by coupled enzyme assay. PPC irreversibly immobilized 100% human sperm in ∼30 seconds and totally eliminated Trichomonas vaginalis more efficiently than nonoxynol-9 and metronidazole. It significantly inhibited (Pspermicidal and microbicidal activities (in vitro), and contraceptive efficacy in rabbits. PPC remained fully active in quick-dissolving, mucoadhesive vaginal-film formulation, and these PPC-films significantly reduced pregnancy and fertility rates in rabbits. The films released ∼90% of PPC in simulated vaginal fluid (pH 4.2) at 37°C in 5 minutes, in vitro. We have thus discovered a common target (reactive thiols) on chiefly-anaerobic, redox-sensitive cells like sperm and Trichomonas, which is susceptible to designed chemical interference for prophylactic contraception. The active thiol in PPC inactivates sperm and Trichomonas via interference with crucial sulfhydryl-disulfide based reactions, e.g. hexokinase activation in human sperm. In comparison to non-specific surfactant action of OTC spermicide nonoxynol-9, the action of thiol-active PPC is apparently much more specific, potent and safe. PPC presents a proof-of-concept for prophylactic contraception via manipulation of thiols in vagina for selective targeting of sperm and Trichomonas, and qualifies as a promising lead for the development of dually

  5. Designed Chemical Intervention with Thiols for Prophylactic Contraception.

    Directory of Open Access Journals (Sweden)

    Monika Sharma

    Full Text Available Unlike somatic cells, sperm have several-fold more available-thiols that are susceptible to redox-active agents. The present study explains the mechanism behind the instant sperm-immobilizing and trichomonacidal activities of pyrrolidinium pyrrolidine-1-carbodithioate (PPC, a novel thiol agent rationally created for prophylactic contraception by minor chemical modifications of some known thiol drugs. PPC, and its three derivatives (with potential active-site blocked by alkylation, were synthesized and evaluated against live human sperm and metronidazole-susceptible and resistant Trichomonas vaginalis, in vitro. Sperm hexokinase activity was evaluated by coupled enzyme assay. PPC irreversibly immobilized 100% human sperm in ∼30 seconds and totally eliminated Trichomonas vaginalis more efficiently than nonoxynol-9 and metronidazole. It significantly inhibited (P<0.001 thiol-sensitive sperm hexokinase. However, the molecule completely lost all its biological activities once its thiol group was blocked by alkylation. PPC was subsequently formulated into a mucoadhesive vaginal film using GRaS excipients and evaluated for spermicidal and microbicidal activities (in vitro, and contraceptive efficacy in rabbits. PPC remained fully active in quick-dissolving, mucoadhesive vaginal-film formulation, and these PPC-films significantly reduced pregnancy and fertility rates in rabbits. The films released ∼90% of PPC in simulated vaginal fluid (pH 4.2 at 37°C in 5 minutes, in vitro. We have thus discovered a common target (reactive thiols on chiefly-anaerobic, redox-sensitive cells like sperm and Trichomonas, which is susceptible to designed chemical interference for prophylactic contraception. The active thiol in PPC inactivates sperm and Trichomonas via interference with crucial sulfhydryl-disulfide based reactions, e.g. hexokinase activation in human sperm. In comparison to non-specific surfactant action of OTC spermicide nonoxynol-9, the action of

  6. Protection by thiols against poisoning by radiomimetic agents. Chapter 8

    International Nuclear Information System (INIS)

    Bacq, Z.M.

    1975-01-01

    A review is presented of reports of studies aimed at detecting a protective effect of thiols against radiomimetic alkylating agents such as those used in cancer therapy (nitrogen mustards (HN2), sarcolysine, busulfan, etc.). Protection by thiols against alkylating agents has been observed in mammals, plant cells, bacteria, isolated mammalian cells and in model systems. The lack of correlation between the protective power of various thiols against radiomimetic agents and ionizing radiations indicates that different mechanisms are involved. Studies have been made of the toxicity of the protector and the competition factor, increased excretion of detoxication products of alkylating agents, decreased alkylation of DNA and RNA both in vivo and in vitro, the protection of hematopoietic tissues, tumours and the adrenal cortex, and the modification of the effects of nitrosoalkylamines, carbon tetrachloride and fungistatics by thiols. The restriction of DNA alkylation by the competitive removal of radiomimetic agents is thought to account for the protective effect of thiols against radiomimetic agents. (U.K.)

  7. Mesoporous silicabis(ethylsulfanyl)propane palladium catalysts for hydrogenation and one-pot two-step Suzuki cross-coupling followed by hydrogenation.

    Science.gov (United States)

    Qazi, Asma; Sullivan, Alice

    2011-10-28

    The solid phase catalytic activity of mesoporous silicabis(ethylsulfanyl)propane palladium catalysts for hydrogenation and novel one-pot two-step Suzuki cross-coupling followed by hydrogenation is described. The efficiency of catalytic hydrogenation was measured for substrate nitrobenzene with 5, 7 and 14 nm average pore diameter materials. The 5 nm pore material performed best and was also very effective in the catalytic hydrogenation of alkene, nitrile and imine substrates. Novel one-pot two-step Suzuki cross-coupling and hydrogenation was demonstrated using bromonitro- and bromodinitrobenzene and phenylboronic acid as substrates with conversion to the corresponding coupled amino compounds. As a consequence of the high affinity of the sulfur ligands for palladium, none was detected in leaching tests and the catalyst is easily separated and recycled.

  8. A Physical-Inorganic Approach for the Elucidation of Active Iron Species and Mechanism in Iron-Catalyzed Cross-Coupling.

    Science.gov (United States)

    Carpenter, Stephanie H; Neidig, Michael L

    2017-12-01

    Detailed studies of iron speciation and mechanism in iron-catalyzed cross-coupling reactions are critical for providing the necessary fundamental insight to drive new reaction development. However, such insight is challenging to obtain due to the prevalence of mixtures of unstable, paramagnetic organoiron species that can form in this chemistry. A physical-inorganic research approach combining freeze-trapped inorganic spectroscopic studies, organometallic synthesis and GC/kinetic studies provides a powerful method for studying such systems. Mössbauer, EPR and MCD spectroscopy enable the direct investigation of in situ formed iron species and, combined with GC analysis, the direct correlation of reactions of specific iron species to the generation of organic products. This review focuses on a description of the key methods involved in this physical-inorganic approach, as well as examples of its application to investigations of iron-SciOPP catalyzed cross-coupling catalysis.

  9. Effect of Oral Zinc Supplementation on the Thiol Oxido-Reductive Index and Thiol-Related Enzymes in Seminal Plasma and Spermatozoa of Iraqi Asthenospermic Patients.

    Science.gov (United States)

    Alsalman, Abdul Razzaq S; Almashhedy, Lamia A; Hadwan, Mahmoud Hussein

    2017-12-08

    A thiol group plays an essential role in sperm metabolism and the antioxidative defense state. Zinc is the second most abundant element in the human body, following iron. The present study was conducted to study the effect of zinc supplementation on the characteristics of semen along with thiol and thiol-related enzymes in semen of asthenospermic patients. Semen samples were obtained from 60 fertile and 60 asthenospermic men, from couples who had consulted the infertility clinic of Babil Hospital (Hillah city, Iraq). The subfertile group was treated with zinc; every participant took two 220 mg capsules of zinc sulfate per day for 3 months. Semen samples were obtained (before and after zinc supplementation). The levels of reduced thiol, oxidized thiol, thiol oxido-reductive index, and thiol-related enzymes activities were determined in spermatozoa and seminal plasma of patients and healthy groups. Oxidized thiol levels were significantly higher in the infertile patients compared to that in the fertile group. Conversely, reduced thiol level, sulfhydryl oxidase activity, and glutathione peroxidase activity significantly decreased in the infertile patients compared to that in the fertile group. Oxidized thiol levels, reduced thiol levels, and thiol-related enzymes activities of the infertile patients were restored to normal values after treatment with zinc. However, reduced and oxidized thiol levels in spermatozoa did not change significantly in the group treated with zinc. The quantitative values for RSH/RSSR and thiol-related enzymes may provide useful means to qualitatively express the oxidant/antioxidant balance in clinical and epidemiologic studies. ClinicalTrials.gov Identifier: NCT02985905.

  10. Improving the throughput of batch photochemical reactions using flow: Dual photoredox and nickel catalysis in flow for C(sp2)C(sp3) cross-coupling.

    Science.gov (United States)

    Abdiaj, Irini; Alcázar, Jesús

    2017-12-01

    We report herein the transfer of dual photoredox and nickel catalysis for C(sp 2 )C(sp 3 ) cross coupling form batch to flow. This new procedure clearly improves the scalability of the previous batch reaction by the reactor's size and operating time reduction, and allows the preparation of interesting compounds for drug discovery in multigram amounts. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Copper-catalyzed decarboxylative C-P cross-coupling of alkynyl acids with H-phosphine oxides: a facile and selective synthesis of (E)-1-alkenylphosphine oxides.

    Science.gov (United States)

    Hu, Gaobo; Gao, Yuxing; Zhao, Yufen

    2014-09-05

    A novel and efficient copper-catalyzed decarboxylative cross-coupling of alkynyl acids for the stereoselective synthesis of E-alkenylphosphine oxides has been developed. In the presence of 10 mol % of CuCl without added ligand, base, and additive, various alkynyl acids reacted with H-phosphine oxides to afford E-alkenylphosphine oxides with operational simplicity, broad substrate scope, and the stereoselectivity for E-isomers.

  12. Tetra- and mono-organotin reagents in palladium-mediated cross-coupling reactions for the labeling with carbon-11 of PET tracers

    Energy Technology Data Exchange (ETDEWEB)

    Bourdier, T.; Huiban, M.; Sobrio, F.; Perrio, C.; Barre, E. [Groupe de Dev Methodol en Tomographie par Emission de Positons, UMR CEA 2E, Universite deCaen, Centre Cyceron, F-14070 Caen Cedex (France); Fouquet, A.; Huet, A. [Laboratoire de Chimie Organique et Organometallique, UMR CNRS 3802, Univ Bordeaux I, F-33405 Talence Cedex (France)

    2008-07-01

    The palladium-catalyzed cross-coupling reactions between a (trimethylstannyl)arene and [{sup 11}C]methyl iodide (Stille reaction) or between an aryl halide and a [{sup 11}C]monomethyltin reagent issued from Lappert's stannylene, were developed for the synthesis of polyfunctional [{sup 11}C]methyl quinolines and quinoline-imides as potential tracers for positron emission tomography (PET). (authors)

  13. Nickel-catalyzed Suzuki-Miyaura type cross-coupling reactions of (2,2-difluorovinyl)benzene derivatives with arylboronic acids.

    Science.gov (United States)

    Xiong, Yang; Huang, Tao; Ji, Xinfei; Wu, Jingjing; Cao, Song

    2015-07-21

    An unprecedented highly stereoselective example of nickel-catalyzed Suzuki-Miyaura type cross-coupling reactions of (2,2-difluorovinyl)benzene derivatives with arylboronic acids was developed. The reaction proceeded efficiently in the presence of 5 mol% NiCl2(PCy3)2 and K3PO4, affording the Z-fluorostyrene derivatives in good to high yields with excellent regioselectivity.

  14. Cysteine-functional polymers via thiol-ene conjugation.

    Science.gov (United States)

    Kuhlmann, Matthias; Reimann, Oliver; Hackenberger, Christian P R; Groll, Jürgen

    2015-03-01

    A thiofunctional thiazolidine is introduced as a new low-molar-mass building block for the introduction of cysteine residues via a thiol-ene reaction. Allyl-functional polyglycidol (PG) is used as a model polymer to demonstrate polymer-analogue functionalization through reaction with the unsaturated side-chains. A modified trinitrobenzenesulfonic acid (TNBSA) assay is used for the redox-insensitive quantification and a precise final cysteine content can be predetermined at the polymerization stage. Native chemical ligation at cysteine-functional PG is performed as a model reaction for a chemoselective peptide modification of this polymer. The three-step synthesis of the thiofunctional thiazolidine reactant, together with the standard thiol-ene coupling and the robust quantification assay, broadens the toolbox for thiol-ene chemistry and offers a generic and straightforward approach to cysteine-functional materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Highly tailorable thiol-ene based emulsion-templated monoliths

    DEFF Research Database (Denmark)

    Lafleur, J. P.; Kutter, J. P.

    2014-01-01

    The attractive surface properties of thiol-ene polymers combined with their ease of processing make them ideal substrates in many bioanalytical applications. We report the synthesis of highly tailorable emulsion-templated porous polymers and beads in microfluidic devices based on off-stoichiometr......The attractive surface properties of thiol-ene polymers combined with their ease of processing make them ideal substrates in many bioanalytical applications. We report the synthesis of highly tailorable emulsion-templated porous polymers and beads in microfluidic devices based on off......-stoichiometry thiolene chemistry. The method allows monolith synthesis and anchoring inside thiol-ene microchannels in a single step. Variations in the monomer stoichiometric ratios and/or amount of porogen used allow for the creation of extremely varied polymer morphologies, from foam-like materials to dense networks...

  16. Resistivity of thiol-modified gold thin films

    International Nuclear Information System (INIS)

    Correa-Puerta, Jonathan; Del Campo, Valeria; Henríquez, Ricardo; Häberle, Patricio

    2014-01-01

    In this work, we study the effect of thiol self assembled monolayers on the electrical resistivity of metallic thin films. The analysis is based on the Fuchs–Sondheimer–Lucas theory and on electrical transport measurements. We determined resistivity change due to dodecanethiol adsorption on gold thin films. For this purpose, we controlled the deposition and annealing temperatures of the films to change the surface topography and to diminish the effect of electron grain boundary scattering. Results show that the electrical response to the absorption of thiols strongly depends on the initial topography of the surface. - Highlights: • We study the effect of self assembled monolayers on the resistivity of thin films. • Fuchs–Sondheimer theory reproduces the resistivity increase due to thiol deposition. • We determined resistivity change due to dodecanethiol deposition on gold thin films. • The electrical response strongly depends on the substrate surface topography

  17. Mechanism of the Suzuki–Miyaura Cross-Coupling Reaction Mediated by [Pd(NHC)(allyl)Cl] Precatalysts

    KAUST Repository

    Meconi, Giulia Magi

    2017-05-24

    Density functional theory calculations have been used to investigate the activation mechanism for the precatalyst series [Pd]-X-1–4 derived from [Pd(IPr)(R-allyl)X] species by substitutions at the terminal position of the allyl moiety ([Pd] = Pd(IPr); R = H (1), Me (2), gem-Me2 (3), Ph (4), X = Cl, Br). Next, we have investigated the Suzuki–Miyaura cross-coupling reaction for the active catalyst species IPr-Pd(0) using 4-chlorotoluene and phenylboronic acid as substrates and isopropyl alcohol as a solvent. Our theoretical findings predict an upper barrier trend, corresponding to the activation mechanism for the [Pd]-Cl-1–4 series, in good agreement with the experiments. They indeed provide a quantitative explanation of the low yield (12%) displayed by [Pd]-Cl-1 species (ΔG⧧ ≈ 30.0 kcal/mol) and of the high yields (≈90%) observed in the case of [Pd]-Cl-2–4 complexes (ΔG⧧ ≈ 20.0 kcal/mol). Additionally, the studied Suzuki–Miyaura reaction involving the IPr-Pd(0) species is calculated to be thermodynamically favorable and kinetically facile. Similar investigations for the [Pd]-Br-1–4 series, derived from [Pd(IPr)(R-allyl)Br], indicate that the oxidative addition step for IPr-Pd(0)-mediated catalysis with 4-bromotoluene is kinetically more favored than that with 4-chlorotoluene. Finally, we have explored the potential of Ni-based complexes [Ni((IPr)(R-allyl)X] (X = Cl, Br) as Suzuki–Miyaura reaction catalysts. Apart from a less endergonic reaction energy profile for both precatalyst activation and catalytic cycle, a steep increase in the predicted upper energy barriers (by 2.0–15.0 kcal/mol) is calculated in the activation mechanism for the [Ni]-X-1–4 series compared to the [Pd]-X-1–4 series. Overall, these results suggest that Ni-based precatalysts are expected to be less active than the Pd-based precatalysts for the studied Suzuki–Miyaura reaction.

  18. 5-Furan-2yl[1,3,4]oxadiazole-2-thiol, 5-Furan-2yl-4H [1,2,4] triazole-3-thiol and Their Thiol-Thione Tautomerism

    Directory of Open Access Journals (Sweden)

    A. Cansız

    2005-02-01

    Full Text Available 5-Furan-2-yl[1,3,4]oxadiazole-2-thiol (Ia and 5-furan-2-yl-4H-[1,2,4]-triazole-3-thiol (Ib were synthesized from furan-2-carboxylic acid hydrazide. Mannich basesand methyl derivatives were then prepared. The structures of the synthesized compoundswere confirmed by elemental analyses, IR and 1H-NMR spectra. Their thiol-thione tautomericequilibrium is described.

  19. Kinetic and Thermodynamic Aspects of Cellular Thiol-Disulfide Redox Regulation

    DEFF Research Database (Denmark)

    Jensen, Kristine Steen; Hansen, Rosa Erritzøe; Winther, Jakob R

    2009-01-01

    that affect the rate of thiol-disulfide exchange and stability of disulfide bonds are discussed within the framework of the underlying chemical foundations. This includes the effect of thiol acidity (pKa), the local electrostatic environment, molecular strain and entropy. Even though a thiol...

  20. Ground-State Distortion in N-Acyl-tert-butyl-carbamates (Boc) and N-Acyl-tosylamides (Ts): Twisted Amides of Relevance to Amide N-C Cross-Coupling.

    Science.gov (United States)

    Szostak, Roman; Shi, Shicheng; Meng, Guangrong; Lalancette, Roger; Szostak, Michal

    2016-09-02

    Amide N-C(O) bonds are generally unreactive in cross-coupling reactions employing low-valent transition metals due to nN → π*C═O resonance. Herein we demonstrate that N-acyl-tert-butyl-carbamates (Boc) and N-acyl-tosylamides (Ts), two classes of acyclic amides that have recently enabled the development of elusive amide bond N-C cross-coupling reactions with organometallic reagents, are intrinsically twisted around the N-C(O) axis. The data have important implications for the design of new amide cross-coupling reactions with the N-C(O) amide bond cleavage as a key step.

  1. Metal-free oxidative coupling of thiols to disulfides using ...

    Indian Academy of Sciences (India)

    Abstract. Efficient combination of nitro urea or guanidinium nitrate and silica sulfuric acid (SiO2OSO3H) as a new oxidizing system is able to oxidize a variety of aliphatic or aromatic thiols to the corresponding disulfides. The process reported here is operationally simple, environmentally benign and reactions have been ...

  2. Hybrid Organic/Inorganic Thiol-ene-Based Photopolymerized Networks.

    Science.gov (United States)

    Schreck, Kathleen M; Leung, Diana; Bowman, Christopher N

    2011-09-15

    The thiol-ene reaction serves as a more oxygen tolerant alternative to traditional (meth)acrylate chemistry for forming photopolymerized networks with numerous desirable attributes including energy absorption, optical clarity, and reduced shrinkage stress. However, when utilizing commercially available monomers, many thiol-ene networks also exhibit decreases in properties such as glass transition temperature (T(g)) and crosslink density. In this study, hybrid organic/inorganic thiol-ene resins incorporating silsesquioxane (SSQ) species into the photopolymerized networks were investigated as a route to improve these properties. Thiol- and ene-functionalized SSQs (SH-SSQ and allyl-SSQ, respectively) were synthesized via alkoxysilane hydrolysis/condensation chemistry, using a photopolymerizable monomer [either pentaerythriol tetrakis(3-mercaptopropionate) (PETMP) or 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATATO)] as the reaction solvent. The resulting SSQ-containing solutions (SSQ-PETMP and SSQ-TATATO) were characterized, and their incorporation into photopolymerized networks was evaluated.

  3. Are free radicals involved in thiol-based redox signaling?

    Science.gov (United States)

    Winterbourn, Christine C

    2015-03-01

    Cells respond to many stimuli by transmitting signals through redox-regulated pathways. It is generally accepted that in many instances signal transduction is via reversible oxidation of thiol proteins, although there is uncertainty about the specific redox transformations involved. The prevailing view is that thiol oxidation occurs by a two electron mechanism, most commonly involving hydrogen peroxide. Free radicals, on the other hand, are considered as damaging species and not generally regarded as important in cell signaling. This paper examines whether it is justified to dismiss radicals or whether they could have a signaling role. Although there is no direct evidence that radicals are involved in transmitting thiol-based redox signals, evidence is presented that they are generated in cells when these signaling pathways are activated. Radicals produce the same thiol oxidation products as two electron oxidants, although by a different mechanism, and at this point radical-mediated pathways should not be dismissed. There are unresolved issues about how radical mechanisms could achieve sufficient selectivity, but this could be possible through colocalization of radical-generating and signal-transducing proteins. Colocalization is also likely to be important for nonradical signaling mechanisms and identification of such associations should be a priority for advancing the field. Copyright © 2014 Elsevier Inc. All rights reserved.

  4. Facially amphiphilic thiol capped gold and silver nanoparticles

    Indian Academy of Sciences (India)

    Wintec

    Jawaharlal Nehru Centre for Advanced Scientific Research,. Bangalore 560 064. Facially amphiphilic thiol capped gold and silver nanoparticles. †. SHREEDHAR BHAT a and UDAY MAITRA*. Department of Organic Chemistry, Indian Institute of Science, Bangalore 560 012 a. Current address: ISM, University of Bordeaux, ...

  5. Capillary electrophoresis in the analysis of biologically important thiols

    Czech Academy of Sciences Publication Activity Database

    Lačná, J.; Kubáň, Petr; Foret, František

    Roč. 38, č. 1 ( 2017 ), s. 203-222 ISSN 0173-0835 Institutional support: RVO:68081715 Keywords : biological thiols * capillary electrophoresis * clinical applications Subject RIV: CB - Analytical Chemistry, Separation OBOR OECD: Analytical chemistry Impact factor: 2.744, year: 2016

  6. Facially amphiphilic thiol capped gold and silver nanoparticles

    Indian Academy of Sciences (India)

    Wintec

    *For correspondence. Also at the Chemical Biology Unit,. Jawaharlal Nehru Centre for Advanced Scientific Research,. Bangalore 560 064. Facially amphiphilic thiol capped gold and silver nanoparticles. †. SHREEDHAR BHAT a and UDAY MAITRA*. Department of Organic Chemistry, Indian Institute of Science, Bangalore ...

  7. Metal-free oxidative coupling of thiols to disulfides using ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 123; Issue 4. Metal-free oxidative coupling of thiols to disulfides using guanidinium nitrate or nitro urea in the presence of silica sulfuric acid. Arash Ghorbani-Choghamarani Mohsen Nikoorazm Hamid Goudarziafshar Alireza Shokr Hosein Almasi. Volume 123 Issue 4 ...

  8. Capillary electrophoresis in the analysis of biologically important thiols

    Czech Academy of Sciences Publication Activity Database

    Lačná, J.; Kubáň, Petr; Foret, František

    2017-01-01

    Roč. 38, č. 1 (2017), s. 203-222 ISSN 0173-0835 Institutional support: RVO:68081715 Keywords : biological thiols * capillary electrophoresis * clinical applications Subject RIV: CB - Analytical Chemistry, Separation OBOR OECD: Analytical chemistry Impact factor: 2.744, year: 2016

  9. Radical Scavenging Efficacy of Thiol Capped Silver Nanoparticles

    Indian Academy of Sciences (India)

    J. Chem. Sci. Vol. 127, No. 12, December 2015, pp. 2183–2191. c Indian Academy of Sciences. DOI 10.1007/s12039-015-0968-x. Radical Scavenging Efficacy of Thiol ... aSchool of Studies in Chemistry, Pt. Ravishankar Shukla University, Raipur 492 010, India ..... Authors are thankful to sophisticated analytical instru-.

  10. Effect of thione–thiol tautomerism on the inhibition of ...

    Indian Academy of Sciences (India)

    WINTEC

    Abstract. The keto-enol type tautomerism in anti-thyroid drugs and their selenium analogues are de- scribed. The commonly used anti-thyroid drug methimazole exists predominantly in its thione form, whereas its selenium analogue exists in a zwitterionic form. To understand the effect of thione/thiol and selone/selenol ...

  11. Thiol-containing polymeric embedding materials for nanoskiving

    NARCIS (Netherlands)

    Mays, Robin L.; Pourhossein, Parisa; Savithri, Dhanalekshmi; Genzer, Jan; Chiechi, Ryan C.; Dickey, Michael D.

    2013-01-01

    This paper describes the characterization of new embedding resins for nanoskiving (ultramicrotomy) that contain thiols. Nanoskiving is a technique to produce nanoscale structures using an ultramicrotome to section thin films of materials (e. g., gold) embedded in polymer. Epoxies are used typically

  12. Surface functionalized thiol-ene waveguides for fluorescence biosensing in microfluidic devices

    DEFF Research Database (Denmark)

    Feidenhans'l, Nikolaj Agentoft; Lafleur, Josiane P.; Jensen, Thomas Glasdam

    2013-01-01

    -ene materials vary considerably with variations in stoichiometric composition, their optical properties remain mostly unchanged with an average refractive index value of 1.566 ± 0.008 for thiol-ene substrates encompassing a range from 150% excess ene to 90% excess thiol. Microfluidic chips featuring thiol......Thiol-ene polymers possess physical, optical, and chemical characteristics thatmake them ideal substrates for the fabrication of optofluidic devices. In this work, thiol-ene polymers are used to simultaneously create microfluidic channels and optical waveguides in one simple moulding step...

  13. [PdA (IPr*) (cinnamyl)Cl]: An efficient pre-catalyst for the preparation of tetra-ortho-substituted biaryls by Suzuki-Miyaura cross-coupling

    KAUST Repository

    Chartoire, Anthony

    2012-03-13

    The bigger the better: The new well-defined [Pd(IPr*)(cin)Cl] pre-catalyst is described (see scheme). This complex proves to be highly active in the Suzuki-Miyaura cross-coupling for the synthesis of tetra-ortho- substituted biaryls under mild conditions. IPr* is reported as the largest N-heterocyclic carbene (NHC) to date for [Pd(NHC)(cin)Cl] complexes, explaining the high reactivity observed for this complex in this challenging transformation. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Co-catalyzed cross-coupling of alkyl halides with tertiary alkyl Grignard reagents using a 1,3-butadiene additive.

    Science.gov (United States)

    Iwasaki, Takanori; Takagawa, Hiroaki; Singh, Surya P; Kuniyasu, Hitoshi; Kambe, Nobuaki

    2013-07-03

    The cobalt-catalyzed cross-coupling of alkyl (pseudo)halides with alkyl Grignard reagents in the presence of 1,3-butadiene as a ligand precursor and LiI is described. Sterically congested quaternary carbon centers could be constructed by using tertiary alkyl Grignard reagents. This reaction proceeds via an ionic mechanism with inversion of stereochemistry at the reacting site of the alkyl halide and is compatible with various functional groups. The use of both 1,3-butadiene and LiI was essential for achieving high yields and high selectivities.

  15. An efficient process for pd-catalyzed C-N cross-coupling reactions of aryl iodides: insight into controlling factors.

    Science.gov (United States)

    Fors, Brett P; Davis, Nicole R; Buchwald, Stephen L

    2009-04-29

    An investigation into Pd-catalyzed C-N cross-coupling reactions of aryl iodides is described. NaI is shown to have a significant inhibitory effect on these processes. By switching to a solvent system in which the iodide byproduct was insoluble, reactions of aryl iodides were accomplished with the same efficiencies as aryl chlorides and bromides. Using catalyst systems based on certain biarylphosphine ligands, aryl iodides were successfully reacted with an array of primary and secondary amines in high yields. Lastly, reactions of heteroarylamines and heteroaryliodides were also conducted in high yields.

  16. Comparative Analyses of Phase Noise in 28 nm CMOS LC Oscillator Circuit Topologies: Hartley, Colpitts, and Common-Source Cross-Coupled Differential Pair

    Science.gov (United States)

    Chlis, Ilias

    2014-01-01

    This paper reports comparative analyses of phase noise in Hartley, Colpitts, and common-source cross-coupled differential pair LC oscillator topologies in 28 nm CMOS technology. The impulse sensitivity function is used to carry out both qualitative and quantitative analyses of the phase noise exhibited by each circuit component in each circuit topology with oscillation frequency ranging from 1 to 100 GHz. The comparative analyses show the existence of four distinct frequency regions in which the three oscillator topologies rank unevenly in terms of best phase noise performance, due to the combined effects of device noise and circuit node sensitivity. PMID:24683340

  17. Comparative analyses of phase noise in 28 nm CMOS LC oscillator circuit topologies: Hartley, Colpitts, and common-source cross-coupled differential pair.

    Science.gov (United States)

    Chlis, Ilias; Pepe, Domenico; Zito, Domenico

    2014-01-01

    This paper reports comparative analyses of phase noise in Hartley, Colpitts, and common-source cross-coupled differential pair LC oscillator topologies in 28 nm CMOS technology. The impulse sensitivity function is used to carry out both qualitative and quantitative analyses of the phase noise exhibited by each circuit component in each circuit topology with oscillation frequency ranging from 1 to 100 GHz. The comparative analyses show the existence of four distinct frequency regions in which the three oscillator topologies rank unevenly in terms of best phase noise performance, due to the combined effects of device noise and circuit node sensitivity.

  18. Synthesis and Characterization of Graphene and Graphene Oxide Based Palladium Nanocomposites and Their Catalytic Applications in Carbon-Carbon Cross-Coupling Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Minjae [Kunsan National Univ., Gunsan (Korea, Republic of); Kim, Bohyun; Lee, Yuna; Kim, Beomtae; Park, Joon B. [Chonbuk National Univ., Jeonju (Korea, Republic of)

    2014-07-15

    We have developed an efficient method to generate highly active Pd and PdO nanoparticles (NPs) dispersed on graphene and graphene oxide (GO) by an impregnation method combined with thermal treatments in H{sub 2} and O{sub 2} gas flows, respectively. The Pd NPs supported on graphene (Pd/G) and the PdO NPs supported on GO (PdO/GO) demonstrated excellent carbon-carbon cross-coupling reactions under a solvent-free, environmentally-friendly condition. The morphological and chemical structures of PdO/GO and Pd/G were fully characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). We found that the remarkable reactivity of the Pd/G and PdO/GO catalysts toward the cross-coupling reaction is attributed to the high degree of dispersion of the Pd and PdO NPs while the oxidative states of Pd and the oxygen functionalities of graphene oxide are not critical for their catalytic performance.

  19. Synthesis and Characterization of Graphene and Graphene Oxide Based Palladium Nanocomposites and Their Catalytic Applications in Carbon-Carbon Cross-Coupling Reactions

    International Nuclear Information System (INIS)

    Lee, Minjae; Kim, Bohyun; Lee, Yuna; Kim, Beomtae; Park, Joon B.

    2014-01-01

    We have developed an efficient method to generate highly active Pd and PdO nanoparticles (NPs) dispersed on graphene and graphene oxide (GO) by an impregnation method combined with thermal treatments in H 2 and O 2 gas flows, respectively. The Pd NPs supported on graphene (Pd/G) and the PdO NPs supported on GO (PdO/GO) demonstrated excellent carbon-carbon cross-coupling reactions under a solvent-free, environmentally-friendly condition. The morphological and chemical structures of PdO/GO and Pd/G were fully characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). We found that the remarkable reactivity of the Pd/G and PdO/GO catalysts toward the cross-coupling reaction is attributed to the high degree of dispersion of the Pd and PdO NPs while the oxidative states of Pd and the oxygen functionalities of graphene oxide are not critical for their catalytic performance

  20. Functional Conducting Polymers via Thiol-ene Chemistry

    OpenAIRE

    Feldman, Kathleen E.; Martin, David C.

    2012-01-01

    We demonstrate here that thiol-ene chemistry can be used to provide side-chain functionalized monomers based on 3,4-propylenedioxythiophene (ProDOT) containing ionic, neutral, hydrophobic, and hydrophilic side chains. All reactions gave high yields and purification could generally be accomplished through precipitation. These monomers were polymerized either chemically or electro-chemically to give soluble materials or conductive films, respectively. This strategy provides for facile tuning of...

  1. Investigation of thiol derivatized gold nanoparticle sensors for gas analysis

    Science.gov (United States)

    Stephens, Jared S.

    Analysis of volatile organic compounds (VOCs) in air and exhaled breath by sensor array is a very useful testing technique. It can provide non-invasive, fast, inexpensive testing for many diseases. Breath analysis has been very successful in identifying cancer and other diseases by using a chemiresistor sensor or array with gold nanoparticles to detect biomarkers. Acetone is a biomarker for diabetes and having a portable testing device could help to monitor diabetic and therapeutic progress. An advantage to this testing method is it is conducted at room temperature instead of 200 degrees Celsius. 3. The objective of this research is to determine the effect of thiol derivatized gold nanoparticles based on sensor(s) detection of VOCs. The VOCs to be tested are acetone, ethanol, and a mixture of acetone and ethanol. Each chip is tested under all three VOCs and three concentration levels (0.1, 1, and 5.0 ppm). VOC samples are used to test the sensors' ability to detect and differentiate VOCs. Sensors (also referred to as a chip) are prepared using several types of thiol derivatized gold nanoparticles. The factors are: thiol compound and molar volume loading of the thiol in synthesis. The average resistance results are used to determine the VOC selectivity of the sensors tested. The results show a trend of increasing resistance as VOC concentration is increased relative to dry air; which is used as baseline for VOCs. Several sensors show a high selectivity to one or more VOCs. Overall the 57 micromoles of 4-methoxy-toluenethiol sensor shows the strongest selectivity for VOCs tested. 3. Gerfen, Kurt. 2012. Detection of Acetone in Air Using Silver Ion Exchanged ZSM-5 and Zinc Oxide Sensing Films. Master of Science thesis, University of Louisville.

  2. Simple preparation of thiol-ene particles in glycerol and surface functionalization by thiol-ene chemistry (TEC) and surface chain transfer free radical polymerization (SCT-FRP)

    DEFF Research Database (Denmark)

    Hoffmann, Christian; Chiaula, Valeria; Pinelo, Manuel

    2018-01-01

    functionalization of excess thiol groups via photochemical thiol-ene chemistry (TEC) resulting in a functional monolayer. In addition, surface chain transfer free radical polymerization (SCT-FRP) was used for the first time to introduce a thicker polymer layer on the particle surface. The application potential...

  3. Investigation and Demonstration of Catalyst/Initiator-Driven Selectivity in Thiol-Michael Reactions.

    Science.gov (United States)

    Frayne, Stephen H; Murthy, Raghavendra R; Northrop, Brian H

    2017-08-04

    Thiol-Michael "click" reactions are essential synthetic tools in the preparation of various materials including polymers, dendrimers, and other macromolecules. Despite increasing efforts to apply thiol-Michael chemistry in a controlled fashion, the selectivity of base- or nucleophile-promoted thiol-Michael reactions in complex mixtures of multiple thiols and/or acceptors remains largely unknown. Herein, we report a thorough fundamental study of the selectivity of thiol-Michael reactions through a series of 270 ternary reactions using 1 H NMR spectroscopy to quantify product selectivity. The varying influences of different catalysts/initiators are explored using ternary reactions between two Michael acceptors and a single thiol or between a single Michael acceptor and two thiols using three different catalysts/initiators (triethylamine, DBU, and dimethylphenylphosphine) in chloroform. The results from the ternary reactions provide a platform from which sequential quaternary, one-pot quaternary, and sequential senary thiol-Michael reactions were designed and their selectivities quantified. These results provide insights into the design of selective thiol-Michael reactions that can be used for the synthesis and functionalization of multicomponent polymers and further informs how catalyst/initiator choice influences the reactivity between a given thiol and Michael acceptor.

  4. Organized thiol functional groups in mesoporous core shell colloids

    Energy Technology Data Exchange (ETDEWEB)

    Marchena, Martin H. [Gerencia Quimica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), Avda. Gral. Paz 1499, B1650KNA Buenos Aires (Argentina); Granada, Mara [Centro Atomico Bariloche-CNEA, 8400 San Carlos de Bariloche (Argentina); Instituto Balseiro-Centro Atomico Bariloche-CNEA, San Carlos de Bariloche 8400 (Argentina); Bordoni, Andrea V. [Gerencia Quimica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), Avda. Gral. Paz 1499, B1650KNA Buenos Aires (Argentina); Joselevich, Maria [Asociacion Civil Expedicion Ciencia, Cabrera 4948, C1414BGP Buenos Aires (Argentina); Troiani, Horacio [Centro Atomico Bariloche-CNEA, 8400 San Carlos de Bariloche (Argentina); Instituto Balseiro-Centro Atomico Bariloche-CNEA, San Carlos de Bariloche 8400 (Argentina); Williams, Federico J. [DQIAQyF-INQUIMAE FCEN, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon II, C1428EHA Buenos Aires (Argentina); Wolosiuk, Alejandro, E-mail: wolosiuk@cnea.gov.ar [Gerencia Quimica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), Avda. Gral. Paz 1499, B1650KNA Buenos Aires (Argentina)

    2012-03-15

    The co-condensation in situ of tetraethoxysilane (TEOS) and mercaptopropyltrimethoxysilane (MPTMS) using cetyltrimethylammonium bromide (CTAB) as a template results in the synthesis of multilayered mesoporous structured SiO{sub 2} colloids with 'onion-like' chemical environments. Thiol groups were anchored to an inner selected SiO{sub 2} porous layer in a bilayered core shell particle producing different chemical regions inside the colloidal layered structure. X-Ray Photoelectron Spectroscopy (XPS) shows a preferential anchoring of the -SH groups in the double layer shell system, while porosimetry and simple chemical modifications confirm that pores are accessible. We can envision the synthesis of interesting colloidal objects with defined chemical environments with highly controlled properties. - Graphical abstract: Mesoporous core shell SiO{sub 2} colloids with organized thiol groups. Highlights: Black-Right-Pointing-Pointer Double shell mesoporous silica colloids templated with CTAB. Black-Right-Pointing-Pointer Sequential deposition of mesoporous SiO{sub 2} layers with different chemistries. Black-Right-Pointing-Pointer XPS shows the selective functionalization of mesoporous layers with thiol groups.

  5. Kinetics of deuterium isotope exchange between 2-methylpropane-2-thiol and propane-2-thiol in aprotic solvents

    International Nuclear Information System (INIS)

    Wawer, A.

    1986-01-01

    The rate constants for bimolecular deuterium isotope exchange between 2-methylpropane-2-thiol and propane-2-thiol in C 6 D1 2 , CCl 4 , (CD 3 ) 2 CO, HCON(CH 3 ) 2 , (CD 2 ) 4 O, and (CH 3 ) 2 SO solutions were determined by use of H n.m.r. analysis. The rate constants, k, and activation enthalpy, ΔH decrease, and entropy, -ΔS, increases, with increase in ability of the solvents to form hydrogen bonds with alkanethiols. The rate constant of concerted hydrogen transfer inside the cyclic dimer of alkanethiols with two H-bonds, k 3 , increases with increasing dielectric constant of the solvent. (author)

  6. Inhibition of the Vacuolar-like ATPase from Halobacterium saccharovorum by Thiol Reagents: Evidence for Different Functional Thiols

    Science.gov (United States)

    Hochstein, L. I.; Stanlotter, H.; Emrich, E.; Morrison, David (Technical Monitor)

    1994-01-01

    N-Ethylmaleimide (NEM) inhibited the vacuolar-like ATPase from Halobacterium saccharovorum (K(sub i) approximately 1 mM) by modifying one or more of the thiols located on the largest of the subunit. ATP protected against inhibition and coincidentally prevented NEM binding which suggested that NEM acts at or near the catalytic site. p-Chloromercuriphenylsulfonate (PCMS) also inhibited this ATPase (K(sub i) approximately 90 microM). ATP did not protect against PCMS inhibition. Dithiothreitol (DTT) partially reversed PCMS inhibition and restored approximately half of the initial activity of 90% inhibited enzyme. DTT did not restore activity of the NEM-inhibited enzyme or the PCMS-inhibited enzyme when it was subsequently incubated with NEM. The failure of ATP to protect against PCMS inhibition and the inability of DTT to restore activity of enzyme incubated in the presence of PCMS and NEM suggests these reagents react with different thiols and that the PCMS-sensitive thiol may have a structural role.

  7. Simulation studies on structural and thermal properties of alkane thiol capped gold nanoparticles.

    Science.gov (United States)

    Devi, J Meena

    2017-06-01

    The structural and thermal properties of the passivated gold nanoparticles were explored employing molecular dynamics simulation for the different surface coverage densities of the self-assembled monolayer (SAM) of alkane thiol. The structural properties of the monolayer protected gold nanoparticles such us overall shape, organization and conformation of the capping alkane thiol chains were found to be influenced by the capping density. The structural order of the thiol capped gold nanoparticles enhances with the increase in the surface coverage density. The specific heat capacity of the alkane thiol capped gold nanoparticles was found to increase linearly with the thiol coverage density. This may be attributed to the enhancement in the lattice vibrational energy. The present simulation results suggest, that the structural and thermal properties of the alkane thiol capped gold nanoparticles may be modified by the suitable selection of the SAM coverage density. Copyright © 2017 Elsevier Inc. All rights reserved.

  8. Ester-free Thiol-X Resins: New Materials with Enhanced Mechanical Behavior and Solvent Resistance

    OpenAIRE

    Podgórski, Maciej; Becka, Eftalda; Chatani, Shunsuke; Claudino, Mauro; Bowman, Christopher N.

    2015-01-01

    A series of thiol-Michael and radical thiol-ene network polymers were successfully prepared from ester-free as well as ester-containing monomer formulations. Polymerization reaction rates, dynamic mechanical analysis, and solvent resistance experiments were performed and compared between compositions with varied ester loading. The incorporation of ester-free alkyl thiol, vinyl sulfone and allylic monomers significantly improved the mechanical properties when compared with commercial, mercapto...

  9. Palladium Nanoparticles Immobilized on Poly(vinyl chloride-Supported Pyridinium as an Efficient and Recyclable Catalyst for Suzuki-Miyaura Cross-Coupling Reaction

    Directory of Open Access Journals (Sweden)

    Bo Zhou

    2011-01-01

    Full Text Available The palladium nanoparticles immobilized on the polymeric surface of poly(vinyl chloride-supported pyridinium (PVC-Py-Pd0 were achieved by a simple procedure by applying the corresponding functionalized polymer and palladium chloride in ethanol solution. The as-prepared catalyst (PVC-Py-Pd0 was found to be air and moisture stable and exhibits significant catalytic activity for Suzuki-Miyaura cross-coupling reaction of various aryl halides and phenylboronic acid under milder operating conditions. The procedure presented here showed several merits such as short reaction time, simple experimental and isolated procedure and excellent yields of products. Furthermore, the catalyst can be easily recovered and reused for at least six times with consistent activities.

  10. Efficient Synthesis of 2-Amino-6-Arylbenzothiazoles via Pd(0 Suzuki Cross Coupling Reactions: Potent Urease Enzyme Inhibition and Nitric Oxide Scavenging Activities of the Products

    Directory of Open Access Journals (Sweden)

    Md. Saiful Islam

    2013-07-01

    Full Text Available In general, benzothiazole derivatives have attracted great interest due to thier pharmaceutical and biological importance. New 2-amino-6-arylbenzothiazoles were synthesized in moderate to excellent yields via Suzuki cross coupling reactions using various aryl boronic acids and aryl boronic acid pinacol esters and the antiurease and nitric oxide (NO scavenging activity of the products were also examined. The most active compound concerning urease enzyme inhibition was 6-phenylbenzo[d]thiazole-2-amine 3e, with an IC50 value of 26.35 µg/mL. Compound 3c, 6-(4-methoxyphenyl benzo[d]thiazole-2-amine, exhibited the highest nitric oxide percentage scavenging at 100µg/mL.

  11. Consecutive cross-coupling reactions of 2,2-difluoro-1-iodoethenyl tosylate with boronic acids: efficient synthesis of 1,1-diaryl-2,2-difluoroethenes

    Directory of Open Access Journals (Sweden)

    Ju Hee Kim

    2013-11-01

    Full Text Available The cross-coupling reactions of 2,2-difluoro-1-iodoethenyl tosylate (2 with 2 equiv of boronic acids in the presence of catalytic amounts of Pd(OAc2 and Na2CO3 afforded the mono-coupled products 3 and 5 in high yields. The use of 4 equiv of boronic acids in the presence of catalytic amount of Pd(PPh32Cl2 and Na2CO3 in this reaction resulted in the formation of symmetrical di-coupled products 4 in high yields. Unsymmetrical di-coupled products 4 were obtained in high yields from the reactions of 3 with 2 equiv of boronic acids in the presence of catalytic amounts of Pd(OAc2 and Na2CO3.

  12. Quantification of protein-derived thiols during atmosphere-controlled brewing in laboratory scale

    DEFF Research Database (Denmark)

    Murmann, Anne Nordmark; Andersen, Preben; Mauch, Alexander

    2016-01-01

    An atmosphere-controlled brewing system was built to study thiol oxidation during brewing in laboratory scale under conditions with limited oxygen exposure. Quantification of free and total thiols and protein showed that thiols were lost during wort boiling possibly owing to protein precipitation...... was more pronounced at longer incubation times. However, the reduction of the pool of oxidized thiols by sulfite was inefficient for sulfite concentrations typically found in beer, and the reaction was found to be relatively slow compared with reduction by tris(carboxyethyl)phosphine....

  13. Elastomeric and degradable polyanhydride network polymers by step-growth thiol-ene photopolymerization.

    Science.gov (United States)

    Shipp, Devon A; McQuinn, Christopher W; Rutherglen, Broden G; McBath, Ryan A

    2009-11-14

    Linear and crosslinked polyanhydrides can be made using photoinitiated thiol-ene chemistry, a simple and effective method of making crosslinked structures that have surface degradation characteristics.

  14. Transsulfuration pathway thiols and methylated arginines: the Hunter Community Study.

    Directory of Open Access Journals (Sweden)

    Arduino A Mangoni

    Full Text Available Serum homocysteine, when studied singly, has been reported to be positively associated both with the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine [ADMA, via inhibition of dimethylarginine dimethylaminohydrolase (DDAH activity] and with symmetric dimethylarginine (SDMA. We investigated combined associations between transsulfuration pathway thiols, including homocysteine, and serum ADMA and SDMA concentrations at population level.Data on clinical and demographic characteristics, medication exposure, C-reactive protein, serum ADMA and SDMA (LC-MS/MS, and thiols (homocysteine, cysteine, taurine, glutamylcysteine, total glutathione, and cysteinylglycine; capillary electrophoresis were collected from a sample of the Hunter Community Study on human ageing [n = 498, median age (IQR = 64 (60-70 years].REGRESSION ANALYSIS SHOWED THAT: a age (P = 0.001, gender (P = 0.03, lower estimated glomerular filtration rate (eGFR, P = 0.08, body mass index (P = 0.008, treatment with beta-blockers (P = 0.03, homocysteine (P = 0.02, and glutamylcysteine (P = 0.003 were independently associated with higher ADMA concentrations; and b age (P = 0.001, absence of diabetes (P = 0.001, lower body mass index (P = 0.01, lower eGFR (P<0.001, cysteine (P = 0.007, and glutamylcysteine (P < 0.001 were independently associated with higher SDMA concentrations. No significant associations were observed between methylated arginines and either glutathione or taurine concentrations.After adjusting for clinical, demographic, biochemical, and pharmacological confounders the combined assessment of transsulfuration pathway thiols shows that glutamylcysteine has the strongest and positive independent associations with ADMA and SDMA. Whether this reflects a direct effect of glutamylcysteine on DDAH activity (for ADMA and/or cationic amino acid transport requires further investigations.

  15. Involvement of thiol-based mechanisms in plant development.

    Science.gov (United States)

    Rouhier, Nicolas; Cerveau, Delphine; Couturier, Jérémy; Reichheld, Jean-Philippe; Rey, Pascal

    2015-08-01

    Increasing knowledge has been recently gained regarding the redox regulation of plant developmental stages. The current state of knowledge concerning the involvement of glutathione, glutaredoxins and thioredoxins in plant development is reviewed. The control of the thiol redox status is mainly ensured by glutathione (GSH), a cysteine-containing tripeptide and by reductases sharing redox-active cysteines, glutaredoxins (GRXs) and thioredoxins (TRXs). Indeed, thiol groups present in many regulatory proteins and metabolic enzymes are prone to oxidation, ultimately leading to post-translational modifications such as disulfide bond formation or glutathionylation. This review focuses on the involvement of GSH, GRXs and TRXs in plant development. Recent studies showed that the proper functioning of root and shoot apical meristems depends on glutathione content and redox status, which regulate, among others, cell cycle and hormone-related processes. A critical role of GRXs in the formation of floral organs has been uncovered, likely through the redox regulation of TGA transcription factor activity. TRXs fulfill many functions in plant development via the regulation of embryo formation, the control of cell-to-cell communication, the mobilization of seed reserves, the biogenesis of chloroplastic structures, the metabolism of carbon and the maintenance of cell redox homeostasis. This review also highlights the tight relationships between thiols, hormones and carbon metabolism, allowing a proper development of plants in relation with the varying environment and the energy availability. GSH, GRXs and TRXs play key roles during the whole plant developmental cycle via their antioxidant functions and the redox-regulation of signaling pathways. This article is part of a Special Issue entitled Redox regulation of differentiation and de-differentiation. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Fractionation and purification of the thiol proteinases from papaya latex.

    Science.gov (United States)

    Dekeyser, P M; De Smedt, S; Demeester, J; Lauwers, A

    1994-06-03

    Three cysteine proteinases, i.e. chymopapain, papaya proteinase IV and proteinase III, were purified to homogeneity from papaya latex using a combination of ion-exchange chromatography and hydrophobic interaction chromatography. During the purification procedure, the thiol-groups of the active center were reversibly blocked as mixed disulfides with 2-thiopyridone. Homogeneity was proved electrophoretically by native polyacrylamide gel electrophoresis (PAGE), sodium dodecyl sulfate (SDS)-PAGE and rechromatography on a Mono S 5/5 column at pH 5.0.

  17. Rapid Access to Phospholipid Analogs Using Thiol-yne Chemistry

    Science.gov (United States)

    2015-05-19

    7–8 min 100% Phase B to 50% Phase B in Phase A (Phase A: H2O with 0.1% formic acid , Phase B: MeOH with 0.1% formic acid ). Anisotropy Measurements...1,3,6-trisulfonic acid (HPTS) in H2O, pH ¼ 7.4) was added to 100 mL of lipid solution. Themixture was icked to form an emulsion. The emulsion was...discussion The mechanism of thiol-yne click chemistry has been previ- ously elucidated.52 The addition of a thiyl radical to an alkyne results in a carbon

  18. Chiral liquid crystalline thiols for preparation of polybutadiene diols

    Czech Academy of Sciences Publication Activity Database

    Bubnov, Alexej; Kašpar, Miroslav; Sedláková, Zdeňka; Ilavský, Michal

    2008-01-01

    Roč. 35, č. 5 (2008), s. 653-660 ISSN 0267-8292 R&D Projects: GA ČR GA202/05/0431; GA MŠk OC 175; GA AV ČR IAA4112401; GA AV ČR IAA100100710 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z40500505 Keywords : monomers * liquid crystal * polybutadiene s * chiral thiol Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.132, year: 2008

  19. Protein and low molecular mass thiols as targets and inhibitors of glycation reactions.

    Science.gov (United States)

    Zeng, Jingmin; Davies, Michael J

    2006-12-01

    Protein glycation has been implicated in the aging process as well as the complications of diabetes (retinopathy, neuropathy, nephropathy, and atherosclerosis). The nitrogen substituents of Lys, Arg, and His residues and the N-terminus of proteins are known to be readily glycated. As the thiol group of Cys is a powerful nucleophile, we hypothesized that Cys residues should also be targets of glycation and that low molecular mass thiols may act as protective agents. In this study the role of thiol glycation, induced by dicarbonyls, in protein cross-link formation and damage prevention is examined. It is shown that incubation of creatine kinase with glyoxal results in protein cross-link formation, with this occurring concurrently with loss of thiol groups, enzyme inactivation, and formation of S-carboxymethylcysteine, a product of glyoxal adduction to Cys residues. Cross-links have also been detected between N-acetylcysteine and the Lys-rich protein histone H1, demonstrating the formation of thiol-glyoxal-amine cross-links. Mass spectrometry has been used to characterize some of these cross-links as 2-(alkylthio)acetamides. A range of low molecular mass thiols have been shown to inhibit dicarbonyl adduction to, and cross-linking of, the thiol-free protein lysozyme, consistent with these thiols being alternative (sacrificial) targets of glycation. Some of these thiols are more efficient modulators of glycation than established glycation inhibitors such as aminoguanidine. These data demonstrate that thiols are facile targets of glycation and that low molecular mass thiols are potent glycation inhibitors. These data may aid the design of therapeutic agents for the treatment of the complications of diabetes.

  20. The role of thiols in cellular response to radiation and drugs.

    Science.gov (United States)

    Biaglow, J E; Varnes, M E; Clark, E P; Epp, E R

    1983-09-01

    Cellular nonprotein thiols (NPSH) consist of glutathione (GSH) and other low molecular weight species such as cysteine, cysteamine, and coenzyme A. GSH is usually less than the total cellular NPSH, and with thiol reactive agents, such as diethyl maleate (DEM), its rate of depletion is in part dependent upon the cellular capacity for its resynthesis. If resynthesis is blocked by buthionine-S,R-sulfoximine(BSO), the NPSH, including GSH, is depleted more rapidly, Cellular thiol depletion by diamide, N-ethylmaleimide, and BSO may render oxygenated cells more sensitive to radiation. These cells may or may not show a reduction in the oxygen enhancement ratio (OER). Human A549 lung carcinoma cells depleted of their NPSH either by prolonged culture or by BSO treatment do not show a reduced OER but do show increased aerobic responses to radiation. Some nitroheterocyclic radiosensitizing drugs also deplete cellular thiols under aerobic conditions. Such reactivity may be the reason that they show anomalous radiation sensitization (i.e., better than predicted on the basis of electron affinity). Other nitrocompounds, such as misonidazole, are activated under hypoxic conditions to radical intermediates. When cellular thiols are depleted peroxide is formed. Under hypoxic conditions thiols are depleted because metabolically reduced intermediates react with GSH instead of oxygen. Thiol depletion, under hypoxic conditions, may be the reason that misonidazole and other nitrocompounds show an extra enhancement ratio with hypoxic cells. Thiol depletion by DEM or BSO alters the radiation response of hypoxic cells to misonidazole. In conclusion, we propose an altered thiol model which includes a mechanism for thiol involvement in the aerobic radiation response of cells. This mechanism involves both thiol-linked hydrogen donation to oxygen radical adducts to produce hydroperoxides followed by a GSH peroxidase-catalyzed reduction of the hydroperoxides to intermediates entering into

  1. Non-protein thiol imaging and quantification in live cells with a novel benzofurazan sulfide triphenylphosphonium fluorogenic compound.

    Science.gov (United States)

    Yang, Yang; Guan, Xiangming

    2017-05-01

    Thiols (-SH) play various roles in biological systems. They are divided into protein thiols (PSH) and non-protein thiols (NPSH). Due to the significant roles thiols play in various physiological/pathological functions, numerous analytical methods have been developed for thiol assays. Most of these methods are developed for glutathione, the major form of NPSH. Majority of these methods require tissue/cell homogenization before analysis. Due to a lack of effective thiol-specific fluorescent/fluorogenic reagents, methods for imaging and quantifying thiols in live cells are limited. Determination of an analyte in live cells can reveal information that cannot be revealed by analysis of cell homogenates. Previously, we reported a thiol-specific thiol-sulfide exchange reaction. Based on this reaction, a benzofurazan sulfide thiol-specific fluorogenic reagent was developed. The reagent was able to effectively image and quantify total thiols (PSH+NPSH) in live cells through fluorescence microscopy. The reagent was later named as GUALY's reagent. Here we would like to report an extension of the work by synthesizing a novel benzofurazan sulfide triphenylphosphonium derivative [(((7,7'-thiobis(benzo[c][1,2,5]oxadiazole-4,4'-sulfonyl))bis(methylazanediyl))bis(butane-4,1-diyl))bis(triphenylphosphonium) (TBOP)]. Like GUALY's reagent, TBOP is a thiol-specific fluorogenic agent that is non-fluorescent but forms fluorescent thiol adducts in a thiol-specific fashion. Different than GUALY's reagent, TBOP reacts only with NPSH but not with PSH. TBOP was effectively used to image and quantify NPSH in live cells using fluorescence microscopy. TBOP is a complementary reagent to GUALY's reagent in determining the roles of PSH, NPSH, and total thiols in thiol-related physiological/pathological functions in live cells through fluorescence microscopy. Graphical Abstract Live cell imaging and quantification of non-protein thiols by TBOP.

  2. Stoichiometry of mercury-thiol complexes on bacterial cell envelopes

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, Bhoopesh; Shoenfelt, Elizabeth; Yu, Qiang; Yee, Nathan; Fein, Jeremy B.; Myneni, Satish C. B.

    2017-08-01

    We have examined the speciation of Hg(II) complexed with intact cell suspensions (1013 cells L- 1) of Bacillus subtilis, a common gram-positive soil bacterium, Shewanella oneidensis MR-1, a facultative gram-negative aquatic organism, and Geobacter sulfurreducens, a gram-negative anaerobic bacterium capable of Hg-methylation at Hg(II) loadings spanning four orders of magnitude (120 nM to 350 μM) at pH 5.5 (± 0.2). The coordination environments of Hg on bacterial cells were analyzed using synchrotron based X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy at the Hg LIII edge. The abundance of thiols on intact cells was determined by a fluorescence-spectroscopy based method using a soluble bromobimane, monobromo(trimethylammonio)bimane (qBBr) to block thiol sites, and potentiometric titrations of biomass with and without qBBr treatment. The chemical forms of S on intact bacterial cells were determined using S k-edge XANES spectroscopy.

  3. Novel Thiol-Ene Hybrid Coating for Metal Protection

    Directory of Open Access Journals (Sweden)

    Mona Taghavikish

    2016-04-01

    Full Text Available A novel hybrid anticorrosion coating with dual network of inorganic (Si–O–Si and organic bonds (C–S–C was prepared on metal through an in situ sol-gel and thiol-ene click reaction. This novel interfacial thin film coating incorporates (3-mercaptopropyl trimethoxysilane (MPTS and 1,4-di(vinylimidazolium butane bisbromide based polymerizable ionic liquid (PIL to form a thiol-ene based photo-polymerized film, which on subsequent sol-gel reaction forms a thin hybrid interfacial layer on metal surface. On top of this PIL hybrid film, a self-assembled nanophase particle (SNAP coating was employed to prepare a multilayer thin film coating for better corrosion protection and barrier performance. The novel PIL hybrid film was characterised for structure and properties using Fourier transform infrared spectroscopy (FTIR, differential scanning calorimetry (DSC, and thermogravimetric analysis (TGA. The corrosion protection performance of the multilayer coating was examined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS. The results reveal that this novel double layer coating on metal offers excellent protection against corrosion and has remarkably improved the barrier effect of the coating.

  4. Impairment of thiol-disulfide homeostasis in preeclampsia.

    Science.gov (United States)

    Korkmaz, Vakkas; Kurdoglu, Zehra; Alisik, Murat; Cetin, Orkun; Korkmaz, Hilal; Surer, Hatice; Erel, Ozcan

    2016-12-01

    To investigate the effects of severity of preeclampsia on thiol-disulfide homeostasis (TDH). A total of 108 participants were divided into three groups: Group 1 was composed of pregnant women with no obstetric complications, Group 2 included pregnant women with mild preeclampsia, and Group 3 consisted of pregnant women with severe preeclampsia. TDH parameters were determined, and comparisons of clinical and routine laboratory test findings were made in all groups. The serum native thiol level was 347.9 ± 27.4 in the control group, 237.2 ± 44.2 in the mild preeclampsia group, and 227.9 ± 53.1 in the severe preeclampsia group (p preeclampsia group, and 248.3 ± 57.4 in the severe preeclampsia group (p preeclampsia group, and 10.2 ± 4.8 in the severe preeclampsia group (p = 0.001). A significant correlation between impairment in degree of TDH and severity of preeclampsia was observed. TDH was impaired in women with preeclampsia, and this impairment increased with disease severity. Therefore, impaired TDH may have a role in the etiopathogenesis of the disease.

  5. Surfactant-free coating of thiols on gold nanoparticles using sonochemistry: a study of competing processes.

    Science.gov (United States)

    Pallipurath, Anuradha; Nicoletti, Olivia; Skelton, Jonathan M; Mahajan, Sumeet; Midgley, Paul A; Elliott, Stephen R

    2014-09-01

    A method for the surfactant-free coating of gold nanoparticles with thiols using sonochemistry is presented. The gold nanoparticles were prepared by a modified Zsigmondy method, affording good control over the particle-size distribution, and the thiol coating was performed by the sonication of a biphasic system consisting of a nanoparticle suspension in water and thiols in toluene. The effects of two important reaction parameters on the particle morphology, viz. sonication time and thiol concentration, were investigated in detail using transmission electron microscopy. The effect of the thiol chain length was also studied. We show that the morphology of the coated particles is determined through a competition between two opposing effects: particle fusion, due to the sonication conditions, and digestive ripening, due to the action of the thiols. Additionally, we illustrate the utility of our technique for various applications, including surface-enhanced Raman scattering from bound molecules, and further functionalization using a thiol-exchange reaction. Our technique paves the way for an efficient synthesis of thiol-coated AuNPs of different shapes and sizes, suitable for a range of diverse applications. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. A fluorescent probe which allows highly specific thiol labeling at low pH

    DEFF Research Database (Denmark)

    Nielsen, Jonas W.; Jensen, Kristine Steen; Hansen, Rosa E.

    2012-01-01

    Determination of the thiol-disulfide status in biological systems is challenging as redox pools are easily perturbed during sample preparation. This is particularly pertinent under neutral to mildly alkaline conditions typically required for alkylation of thiols. Here we describe the synthesis an...

  7. Orented immobilization of farnesylated proteins by the thiol-ene reaction

    NARCIS (Netherlands)

    Weinrich, Dirk; Lin, Po-Chiao; Jonkheijm, Pascal; Nguyen, Uyen T.T.; Schröder, Hendrik; Niemeyer, Christof M.; Alexandrov, Kirill; Goody, Roger; Waldmann, Herbert

    2010-01-01

    Anchoring the protein: Proteins were immobilized rapidly under mild conditions by thiol-ene photocoupling between S-farnesyl groups attached to a genetically encodable “CAAX-box” tetrapeptide sequence (A is aliphatic) at the C terminus of the protein and surface-exposed thiols (see scheme). This

  8. EFFECTS OF ATMOSPHERIC H2S ON THIOL COMPOSITION OF CROP PLANTS

    NARCIS (Netherlands)

    BUWALDA, F; DE KOK, LJ; Stulen, I.

    Exposure of crop plants to H2S resulted in an increase in thiol level and a change in the composition of the thiol pool. Non-leguminous species accumulated cysteine and glutathione in the light, whereas in the dark, substantial amounts of gamma-glutamyl-cysteine were also detected. In leguminous

  9. Rapid photochemical surface patterning of proteins in thiol-ene based microfluidic devices

    DEFF Research Database (Denmark)

    Lafleur, Josiane P.; Kwapiszewski, Radoslaw; Jensen, Thomas Glasdam

    2012-01-01

    ” and “ene” monomers present in the microfluidic chip bulk material provides a simple and efficient way of tuning the chip’s surface chemistry. Here, thiol-ene chips displaying an excess of functional thiol groups at their surfaces are functionalized with biotin and streptavidin in a controlled fashion using...

  10. Determination of thiol groups and disulphide bonds in wheat flour and dough

    NARCIS (Netherlands)

    Graveland, A.; Bosveld, P.; Marseille, J.P.

    1978-01-01

    A study was made of the conditions for determining all thiol (SH) groups and disulphide (S—S) bonds in wheat flour and dough. Thiol groups were determined by amperometric titration with Ag2SO4, the flour or dough which contains proteins and peptides being suspended in a solution of 6 m urea and 10−4

  11. The role of thiols in cellular response to radiation and drugs

    International Nuclear Information System (INIS)

    Biaglow, J.E.; Varnes, M.E.; Clark, E.P.; Epp, E.R.

    1983-01-01

    Cellular nonprotein thiols (NPSH) consist of glutathione (GSH) and other low molecular weight species such as cysteine, cysteamine, and coenzyme A. GSH is usually less than the total cellular NPSH, and with thiol reactive agents, such as diethyl maleate (DEM), its rate of depletion is in part dependent upon the cellular capacity for its resynthesis. If resynthesis is blocked by buthionine-S,R-sulfoximine(BSO), the NPSH, including GSH, is depleted more rapidly, Cellular thiol depletion by diamide, N-ethylmaleimide, and BSO may render oxygenated cells more sensitive to radiation. These cells may or may not show a reduction in the oxygen enhancement ratio (OER). Human A549 lung carcinoma cells depleted of their NPSH either by prolonged culture or by BSO treatment do not show a reduced OER but do show increased aerobic responses to radiation. Some nitroheterocyclic radiosensitizing drugs also deplete cellular thiols under aerobic conditions. Such reactivity may be the reason that they show anomalous radiation sensitization (i.e., better than predicted on the basis of electron affinity). Other nitrocompounds, such as misonidazole, are activated under hypoxic conditions to radical intermediates. When cellular thiols are depleted peroxide is formed. Under hypoxic conditions thiols are depleted because metabolically reduced intermediates react with GSH instead of oxygen. Thiol depletion, under hypoxic conditions, may be the reason that misonidazole and other nitrocompounds show an extra enhancement ratio with hypoxic cells. Thiol depletion by DEM or BSO alters the radiation response of hypoxic cells to misonidazole

  12. The role of thiols in cellular response to radiation and drugs

    Energy Technology Data Exchange (ETDEWEB)

    Biaglow, J.E.; Varnes, M.E.; Clark, E.P.; Epp, E.R.

    1983-09-01

    Cellular nonprotein thiols (NPSH) consist of glutathione (GSH) and other low molecular weight species such as cysteine, cysteamine, and coenzyme A. GSH is usually less than the total cellular NPSH, and with thiol reactive agents, such as diethyl maleate (DEM), its rate of depletion is in part dependent upon the cellular capacity for its resynthesis. If resynthesis is blocked by buthionine-S,R-sulfoximine(BSO), the NPSH, including GSH, is depleted more rapidly, Cellular thiol depletion by diamide, N-ethylmaleimide, and BSO may render oxygenated cells more sensitive to radiation. These cells may or may not show a reduction in the oxygen enhancement ratio (OER). Human A549 lung carcinoma cells depleted of their NPSH either by prolonged culture or by BSO treatment do not show a reduced OER but do show increased aerobic responses to radiation. Some nitroheterocyclic radiosensitizing drugs also deplete cellular thiols under aerobic conditions. Such reactivity may be the reason that they show anomalous radiation sensitization (i.e., better than predicted on the basis of electron affinity). Other nitrocompounds, such as misonidazole, are activated under hypoxic conditions to radical intermediates. When cellular thiols are depleted peroxide is formed. Under hypoxic conditions thiols are depleted because metabolically reduced intermediates react with GSH instead of oxygen. Thiol depletion, under hypoxic conditions, may be the reason that misonidazole and other nitrocompounds show an extra enhancement ratio with hypoxic cells. Thiol depletion by DEM or BSO alters the radiation response of hypoxic cells to misonidazole.

  13. Equilibrium mercury isotope fractionation between dissolved Hg(II) species and thiol-bound Hg

    NARCIS (Netherlands)

    Wiederhold, Jan G.; Cramer, Christopher J.; Daniel, Kelly; Infante, Ivan; Bourdon, Bernard; Kretzschmar, Ruben

    2010-01-01

    Stable Hg isotope ratios provide a new tool to trace environmental Hg cycling. Thiols (-SH) are the dominant Hg-binding groups in natural organic matter. Here, we report experimental and computational results on equilibrium Hg isotope fractionation between dissolved Hg(II) species and thiol-bound

  14. A method for site-specific labeling of multiple protein thiols

    NARCIS (Netherlands)

    Kuiper, Johanna M.; Pluta, Radek; Huibers, Wim H. C.; Fusetti, Fabrizia; Geertsma, Eric R.; Poolman, Bert

    We present a generic method for the site-specific and differential labeling of multiple cysteine residues in one protein. Phenyl arsenic oxide has been employed as a protecting group of two closely spaced thiols, allowing first labeling of a single thiol. Subsequently, the protecting group is

  15. Preparation and Preliminary Dielectric Characterization of Structured C60-Thiol-Ene Polymer Nanocomposites Assembled Using the Thiol-Ene Click Reaction

    OpenAIRE

    Ahmed, Hanaa M.; Windham, Amber D.; Al-Ejji, Maryam M.; Al-Qahtani, Noora H.; Hassan, Mohammad K.; Mauritz, Kenneth A.; Buchanan, Randy K.; Buchanan, J. Paige

    2015-01-01

    Fullerene-containing materials have the ability to store and release electrical energy. Therefore, fullerenes may ultimately find use in high-voltage equipment devices or as super capacitors for high electric energy storage due to this ease of manipulating their excellent dielectric properties and their high volume resistivity. A series of structured fullerene (C60) polymer nanocomposites were assembled using the thiol-ene click reaction, between alkyl thiols and allyl functionalized C60 deri...

  16. ?Grafting to? of RAFTed Responsive Polymers to Glass Substrates by Thiol?Ene and Critical Comparison to Thiol?Gold Coupling

    OpenAIRE

    Biggs, Caroline I.; Walker, Marc; Gibson, Matthew I.

    2016-01-01

    Surface-grafted polymers have been widely applied to modulate biological interfaces and introduce additional functionality. Polymers derived from reversible addition?fragmentation transfer (RAFT) polymerization have a masked thiol at the ?-chain end providing an anchor point for conjugation and in particular displays high affinity for gold surfaces (both flat and particulate). In this work, we report the direct grafting of RAFTed polymers by a ?thiol?ene click? (Michael addition) onto glass s...

  17. Quantitation Method for Polyfunctional Thiols in Hops (Humulus lupulus L.) and Beer Using Specific Extraction of Thiols and Gas Chromatography-Tandem Mass Spectrometry.

    Science.gov (United States)

    Takazumi, Koji; Takoi, Kiyoshi; Koie, Koichiro; Tuchiya, Youichi

    2017-11-07

    A method for the quantitation of six polyfunctional thiols, 4-methyl-4-sulfanylpentan-2-one (4MSP), 3-sulfanyl-4-methylpentan-1-ol (3S4MP), 3-sulfanyl-4-methylpentyl acetate (3S4MPA), 3-sulfanyl-3-methylbutan-1-ol (3S3MB), 3-sulfanylhexan-1-ol (3SH), and 3-sulfanylhexyl acetate (3SHA), in hops and beer without organic mercury compounds was developed. The method employed specific extraction of thiols using a silver ion solid phase extraction (SPE) cartridge and gas chromatography-tandem mass spectrometry (GC-MS/MS). For all thiols analyzed, good linearity was achieved by adding thioglycerol as an analyte protectant. Recoveries for both hops (74-100%) and beer (79-113%) were acceptable, and the repeatability for both was also good (relative standard deviations of 2.8-8.4%). The limits of detection for the six polyfunctional thiols were below their odor thresholds in beer. The method was applied to quantitation of hops and beer flavored with thiol-containing hop varieties. Due to their detected levels and level variations in different beers, 4MSP and 3S4MP are thought to be important polyfunctional thiols for the characteristic flavor of hop varieties.

  18. Ester-free Thiol-X Resins: New Materials with Enhanced Mechanical Behavior and Solvent Resistance.

    Science.gov (United States)

    Podgórski, Maciej; Becka, Eftalda; Chatani, Shunsuke; Claudino, Mauro; Bowman, Christopher N

    A series of thiol-Michael and radical thiol-ene network polymers were successfully prepared from ester-free as well as ester-containing monomer formulations. Polymerization reaction rates, dynamic mechanical analysis, and solvent resistance experiments were performed and compared between compositions with varied ester loading. The incorporation of ester-free alkyl thiol, vinyl sulfone and allylic monomers significantly improved the mechanical properties when compared with commercial, mercaptopropionate-based thiol-ene or thiol-Michael networks. For polymers with no hydrolytically degradable esters, glass transition temperatures (T g 's) as high as 100 °C were achieved. Importantly, solvent resistance tests demonstrated enhanced stability of ester-free formulations over PETMP-based polymers, especially in concentrated basic solutions. Kinetic analysis showed that glassy step-growth polymers are readily formed at ambient conditions with conversions reaching 80% and higher.

  19. Thiol-ene click chemistry: a biocompatible way for orthogonal bioconjugation of colloidal nanoparticles.

    Science.gov (United States)

    Liu, Yuan; Hou, Weijia; Sun, Hao; Cui, Cheng; Zhang, Liqin; Jiang, Ying; Wu, Yongxiang; Wang, Yanyue; Li, Juan; Sumerlin, Brent S; Liu, Qiaoling; Tan, Weihong

    2017-09-01

    Bioconjugation based on crosslinking primary amines to carboxylic acid groups has found broad applications in protein modification, drug development, and nanomaterial functionalization. However, proteins, which are made up of amino acids, typically give nonselective bioconjugation when using primary amine-based crosslinking. In order to control protein orientation and activity after conjugation, selective bioconjugation is desirable. We herein report an efficient and cysteine-selective thiol-ene click reaction-based bioconjugation strategy using colloidal nanoparticles. The resulting thiol-ene based aptamer and enzyme nanoconjugates demonstrated excellent target binding ability and enzymatic activity, respectively. Thus, thiol-ene click chemistry can provide a stable and robust crosslinker in a biocompatible manner for bioconjugation of any thiol-containing biomolecule with nanomaterials. This will open more opportunities for applications of thiol-ene reactions and functional colloidal nanoparticles in chemical biology.

  20. The Role of Follicular Fluid Thiol/Disulphide Homeostasis in Polycystic Ovary Syndrome.

    Science.gov (United States)

    Tola, Esra Nur; Köroğlu, Nadiye; Ergin, Merve; Oral, Hilmi Baha; Turgut, Abdülkadir; Erel, Özcan

    2018-04-04

    Oxidative stress is suggested as a potential triggering factor in the etiopathogenesis of Polycystic ovary syndrome related infertility. Thiol/disulphide homeostasis, a recently oxidative stress marker, is one of the antioxidant mechanism in human which have critical roles in folliculogenesis and ovulation. The aim of our study is to investigate follicular fluid thiol/disulphide homeostasis in the etiopathogenesis of Polycystic ovary syndrome and to determine its' association with in vitro fertilization outcome. The study procedures were approved by local ethic committee. Cross sectional design Methods: Follicular fluid of twenty-two Polycystic ovary syndrome women and twenty ovulatory controls undergoing in vitro fertilization treatment were recruited. Thiol/disulphide homeostasis was analyzed via a novel spectrophotometric method. Follicular native thiol levels were found to be lower in Polycystic ovary syndrome group than non- Polycystic ovary syndrome group (p=0.041) as well as native thiol/total thiol ratio (pPolycystic ovary syndrome group (pPolycystic ovary syndrome patients was found. A positive predictive effect of native thiol on fertilization rate among Polycystic ovary syndrome group was also found (p=0.03, β=0.45, 95% CI=0.031-0.643). Deterioration in thiol/disulphide homeostasis, especially elevated disulphide levels could be one of the etiopathogenetic mechanism in Polycystic ovary syndrome. Increased native thiol levels is related to fertilization rate among Polycystic ovary syndrome patients and also positive predictor marker of fertilization rate among Polycystic ovary syndrome patients. Improvement of thiol/disulphide homeostasis could be of importance in the treatment of Polycystic ovary syndrome to increase in vitro fertilization success in Polycystic ovary syndrome.

  1. Chemoselective Synthesis of 4,5-Diarylpyrrolo[2,3-d]pyrimidines (6,7-Diaryl-7-deazapurines) by Consecutive Suzuki and Liebeskind-Srogl Cross-Couplings

    Czech Academy of Sciences Publication Activity Database

    Krömer, M.; Klečka, Martin; Slavětínská, Lenka; Klepetářová, Blanka; Hocek, Michal

    Roč. 2014 , č. 32 ( 2014 ), s. 7203-7210 ISSN 1434-193X Grant - others:GA ČR(CZ) GAP207/12/0205 Institutional support: RVO:61388963 Keywords : synthetic methods * chemoselectivity * cross-coupling * palladium * nitrogen heterocycles Subject RIV: CC - Organic Chemistry Impact factor: 3.065, year: 2014

  2. One-Pot Three-Step Synthesis of 1,2,3-Triazoles by Copper-Catalyzed Cycloaddition of Azides with Alkynes formed by a Sonogashira Cross-Coupling and Desilylation

    Science.gov (United States)

    Friscourt, Frédéric; Boons, Geert-Jan

    2010-01-01

    A microwave-assisted one-pot, three-step Sonogashira cross coupling-desilylation-cycloaddition sequence was developed for the convenient preparation of 1,4-disubstituted 1,2,3-triazoles starting from a range of halides, acyl chlorides, ethynyltrimethylsilane and azides. PMID:20942390

  3. Synthesis of Fluorescent 2-Substituted 6-(Het)aryl-7-deazapurine Bases {4-(Het)aryl-pyrrolo[2,3-d]pyrimidines} by Aqueous Suzuki-Miyaura Cross-Coupling Reactions

    Czech Academy of Sciences Publication Activity Database

    Sabat, Nazarii; Nauš, Petr; Matyašovský, Ján; Dziuba, Dmytro; Poštová Slavětínská, Lenka; Hocek, Michal

    2016-01-01

    Roč. 48, č. 7 (2016), s. 1029-1045 ISSN 0039-7881 R&D Projects: GA ČR GAP207/11/0344 Institutional support: RVO:61388963 Keywords : nucleobases * deazapurines * pyrrolo[2,3-d]pyrimidines * Suzuki cross-coupling * arylation Subject RIV: CC - Organic Chemistry Impact factor: 2.650, year: 2016

  4. Modification of Pyrrolo[2,3-d]pyrimidines by C-H Borylation Followed by Cross-Coupling or Other Transformations: Synthesis of 6,8-Disubstituted 7-Deazapurine Bases

    Czech Academy of Sciences Publication Activity Database

    Klečka, Martin; Poštová Slavětínská, Lenka; Hocek, Michal

    2015-01-01

    Roč. 2015, č. 36 (2015), s. 7943-7961 ISSN 1434-193X Institutional support: RVO:61388963 Keywords : synthetic methods * cross-coupling * C-H activation * nitrogen heterocycles * nucleobases * deazapurines Subject RIV: CC - Organic Chemistry Impact factor: 3.068, year: 2015

  5. Impaired Tilt Suppression of Post-Rotatory Nystagmus and Cross-Coupled Head-Shaking Nystagmus in Cerebellar Lesions: Image Mapping Study.

    Science.gov (United States)

    Lee, Sun-Uk; Choi, Jeong-Yoon; Kim, Hyo-Jung; Park, Jeong-Jin; Zee, David S; Kim, Ji-Soo

    2017-02-01

    We sought to determine the cerebellar structures responsible for tilt suppression of post-rotatory nystagmus. We investigated ocular motor findings and MRI lesions in 73 patients with isolated cerebellar lesions who underwent recording of the vestibulo-ocular reflex (VOR) using rotatory chair tests. Tilt suppression of post-rotatory nystagmus was diminished in 27 patients (27/73, 37.0 %). The gains of the VOR and the TCs of per- and post-rotatory nystagmus did not differ between the patients with diminished and with normal tilt suppression. The patients with impaired tilt suppression showed perverted ("cross-coupled") head-shaking nystagmus (pHSN) and central positional nystagmus (CPN) more frequently than those with normal responses. Tilt suppression was impaired in five (71.4 %) of the seven patients with isolated nodulus and uvular infarction. Probabilistic lesion-mapping analysis showed that the nodulus and uvula are responsible for tilt suppression. Impaired tilt suppression may be ascribed to disruption of cerebellar contribution to the vestibular velocity-storage mechanism, which integrates information from the semicircular canals and otolith organs to help derive the brain's estimate of the head orientation relative to the pull of gravity.

  6. Synthesis of zwitterionic palladium complexes and their application as catalysts in cross-coupling reactions of aryl, heteroaryl and benzyl bromides with organoboron reagents in neat water.

    Science.gov (United States)

    Ramakrishna, V; Dastagiri Reddy, N

    2017-07-04

    N-(3-Chloro-2-quinoxalinyl)-N'-arylimidazolium salts (aryl = 2,6-diisopropylphenyl [HL1Cl]Cl, aryl = mesityl [HL2Cl]Cl) have been synthesized by treating 2,3-dichloroquinoxaline with the corresponding N'-arylimidazole in neat water. Facile reactions of these imidazolium salts with Pd(PPh 3 ) 4 and Pd 2 (dba) 3 /PPh 3 (dba = dibenzyledene acetone) at 50 °C have afforded zwitterionic palladium(ii) complexes [Pd(HL1)(PPh 3 )Cl 2 ] (I) and [Pd(HL2)(PPh 3 )Cl 2 ] (II) in excellent yields. I and II have been tested for their ability to catalyze Suzuki-Miyaura cross coupling (SMC) reactions in neat water/K 2 CO 3 and are found to be highly active for carrying out these reactions between aryl bromides and organoboron reagents. Furthermore, the scope of the catalyst I was also examined by employing (hetero)aryl bromides, hydrophilic aryl bromides, benzyl bromides and various organoboron reagents. More than 80 aryl/benzyl bromide-arylboronic acid combinations were screened in neat water/K 2 CO 3 and it was found that I was a versatile catalyst, which produced biaryls/diarylmethanes in excellent yields. A TON of 82 000 was achieved by using I. Studies on the mechanism have also been carried out to investigate the involvement of carbene complexes in the catalytic path. Poison tests and a two-phase test were also conducted and the results are reported.

  7. Palladium nanoparticle-decorated reduced graphene oxide sheets synthesized using Ficus carica fruit extract: A catalyst for Suzuki cross-coupling reactions.

    Science.gov (United States)

    Anasdass, Jaculin Raiza; Kannaiyan, Pandian; Raghavachary, Raghunathan; Gopinath, Subash C B; Chen, Yeng

    2018-01-01

    We present a biogenic method for the synthesis of palladium nanoparticle (PdNP)-modified by reducing graphene oxide sheets (rGO) in a one-pot strategy using Ficus carica fruit juice as the reducing agent. The synthesized material was well characterized by morphological and structural analyses, including, Ultraviolet-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Transmission Electron Microscopy (TEM) and Raman spectroscopy. The results revealed that the PdNP modified GO are spherical in shape and estimated to be a dimension of ~0.16 nm. The PdNP/graphene exhibits a great catalytic activity in Suzuki cross-coupling reactions for the synthesis of biaryl compounds with various substrates under both aqueous and aerobic conditions. The catalyst can be recovered easily and is suitable for repeated use because it retains its original catalytic activity. The PdNP/rGO catalyst synthesized by an eco-friendly protocol was used for the Suzuki coupling reactions. The method offers a mild and effective substitute to the existing methods and may significantly contribute to green chemistry.

  8. Atypical McMurry Cross-Coupling Reactions Leading to a New Series of Potent Antiproliferative Compounds Bearing the Key [Ferrocenyl-Ene-Phenol] Motif

    Directory of Open Access Journals (Sweden)

    Pascal Pigeon

    2014-07-01

    Full Text Available In the course of the preparation of a series of ferrocenyl derivatives of diethylstilbestrol (DES, in which one of the 4-hydroxyphenyl moieties was replaced by a ferrocenyl group, the McMurry reaction of chloropropionylferrocene with a number of mono-aryl ketones unexpectedly yielded the hydroxylated ferrocenyl DES derivatives, 5a–c, in poor yields (10%–16%. These compounds showed high activity on the hormone-independent breast cancer cell line MDA-MB-231 with IC50 values ranging from 0.14 to 0.36 µM. Surprisingly, non-hydroxylated ferrocenyl DES, 4, showed only an IC50 value of 1.14 µM, illustrating the importance of the hydroxyethyl function in this promising new series. For comparison, McMurry reactions of the shorter chain analogue chloroacetylferrocene were carried out to see the difference in behaviour with mono-aryl ketones versus a diaryl ketone. The effect of changing the length of the alkyl chain adjacent to the phenolic substituent of the hydroxylated ferrocenyl DES was studied, a mechanistic rationale to account for the unexpected products is proposed, and the antiproliferative activities of all of these compounds on MDA-MB-231 cells lines were measured and compared. X-ray crystal structures of cross-coupled products and of pinacol-pinacolone rearrangements are reported.

  9. Key role of Ti(IV) in the selective radical-radical cross-coupling mediated by the Ingold-Fischer effect.

    Science.gov (United States)

    Spaccini, Raffaele; Pastori, Nadia; Clerici, Angelo; Punta, Carlo; Porta, Ombretta

    2008-12-31

    We report an innovative approach for the selective synthesis of polyfunctional derivatives by cross-combination of different radicals generated under mild conditions. The coordinating effect of Ti(IV) plays a key role in the reaction mechanism: due to its chelating action on the hydroxyl groups, it promotes the homolytic C-C bond cleavage of alpha,beta-dihydroxy ketones by enhancing the captodative effect and the consequent stabilization of the corresponding alpha-hydroxy-alpha-carbonyl radicals. When these radicals are generated in the presence of stoichiometric amounts of TiCl(4) and 2,2'-azo-bis-isobutyronitrile (AIBN) is employed as a source of alpha-cyanoisopropyl radicals, the selective radical-radical cross-coupling is observed, affording the corresponding beta-hydroxynitriles in high yields. This innovative methodology allows application of the well-known Ingold-Fischer effect to a wider range of stabilized carbon-centered radicals, whose formation derives from the chelating action of Ti(IV).

  10. Palladium nanoparticle-decorated reduced graphene oxide sheets synthesized using Ficus carica fruit extract: A catalyst for Suzuki cross-coupling reactions.

    Directory of Open Access Journals (Sweden)

    Jaculin Raiza Anasdass

    Full Text Available We present a biogenic method for the synthesis of palladium nanoparticle (PdNP-modified by reducing graphene oxide sheets (rGO in a one-pot strategy using Ficus carica fruit juice as the reducing agent. The synthesized material was well characterized by morphological and structural analyses, including, Ultraviolet-Visible spectroscopy (UV-Vis, X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FT-IR and Transmission Electron Microscopy (TEM and Raman spectroscopy. The results revealed that the PdNP modified GO are spherical in shape and estimated to be a dimension of ~0.16 nm. The PdNP/graphene exhibits a great catalytic activity in Suzuki cross-coupling reactions for the synthesis of biaryl compounds with various substrates under both aqueous and aerobic conditions. The catalyst can be recovered easily and is suitable for repeated use because it retains its original catalytic activity. The PdNP/rGO catalyst synthesized by an eco-friendly protocol was used for the Suzuki coupling reactions. The method offers a mild and effective substitute to the existing methods and may significantly contribute to green chemistry.

  11. Thiol-Disulfide Exchange between Glutaredoxin and Glutathione

    DEFF Research Database (Denmark)

    Iversen, Rasmus; Andersen, Peter Anders; Jensen, Kristine Steen

    2010-01-01

    Glutaredoxins are ubiquitous thiol-disulfide oxidoreductases which catalyze the reduction of glutathione-protein mixed disulfides. Belonging to the thioredoxin family, they contain a conserved active site CXXC motif. The N-proximal active site cysteine can form a mixed disulfide with glutathione ...... has been replaced with serine. The exchange reaction between the reduced protein and oxidized glutathione leading to formation of the mixed disulfide could readily be monitored by isothermal titration calorimetry (ITC) due to the enthalpic contributions from the noncovalent interactions...... and the protonation of glutathione thiolate. An algorithm for the analysis of this type of reaction by ITC was developed and showed that the interaction is enthalpy driven with a large entropy penalty. The applicability of the method was verified by a mass spectrometry-based approach, which gave a standard reduction...

  12. Cross-coupled doa trackers

    OpenAIRE

    Pérez Neira, Ana Isabel; Lagunas Hernandez, Miguel A.; Kirlin, R L

    1997-01-01

    A new robust, low complexity algorithm for multiuser tracking is proposed, modifying the two-stage parallel architecture of the estimate-maximize (EM) algorithm. The algorithm copes with spatially colored noise, large differences in source powers, multipath, and crossing trajectories. Following a discussion on stability, the simulations demonstrate an asymptotic and tracking behavior that neither the EM nor a nonparallelized tracker can emulate. Peer Reviewed

  13. Mercury Binding Sites in Thiol-Functionalized Mesostructured Silica

    International Nuclear Information System (INIS)

    Billinge, Simon J.L.; McKimmey, Emily J.; Shatnawi, Mouath; Kim, HyunJeong; Petkov, Valeri; Wermeille, Didier; Pinnavaia, Thomas J.

    2005-01-01

    Thiol-functionalized mesostructured silica with anhydrous compositions of (SiO 2 ) 1-x (LSiO 1.5 ) x , where L is a mercaptopropyl group and x is the fraction of functionalized framework silicon centers, are effective trapping agents for the removal of mercuric(II) ions from water. In the present work, we investigate the mercury-binding mechanism for representative thiol-functionalized mesostructures by atomic pair distribution function (PDF) analysis of synchrotron X-ray powder diffraction data and by Raman spectroscopy. The mesostructures with wormhole framework structures and compositions corresponding to x = 0.30 and 0.50 were prepared by direct assembly methods in the presence of a structure-directing amine porogen. PDF analyses of five mercury-loaded compositions with Hg/S ratios of 0.50-1.30 provided evidence for the bridging of thiolate sulfur atoms to two metal ion centers and the formation of chain structures on the pore surfaces. We find no evidence for Hg-O bonds and can rule out oxygen coordination of the mercury at greater than the 10% level. The relative intensities of the PDF peaks corresponding to Hg-S and Hg-Hg atomic pairs indicate that the mercury centers cluster on the functionalized surfaces by virtue of thiolate bridging, regardless of the overall mercury loading. However, the Raman results indicate that the complexation of mercury centers by thiolate depends on the mercury loading. At low mercury loadings (Hg/S (le) 0.5), the dominant species is an electrically neutral complex in which mercury most likely is tetrahedrally coordinated to bridging thiolate ligands, as in Hg(SBu t ) 2 . At higher loadings (Hg/S 1.0-1.3), mercury complex cations predominate, as evidenced by the presence of charge-balancing anions (nitrate) on the surface. This cationic form of bound mercury is assigned a linear coordination to two bridging thiolate ligands.

  14. Endothelium-dependent vasorelaxation in inhibited by in vivo depletion of vascular thiol levels

    DEFF Research Database (Denmark)

    Laursen, J B; Boesgaard, S; Trautner, S

    2001-01-01

    Thiols like glutathione may serve as reducing cofactors in the production of nitric oxide (NO) and protect NO from inactivation by radical oxygen species. Depletion of thiol compounds reduces NO-mediated vascular effects in vitro and in vivo. The mechanisms underlying these actions are not clear...... superoxide anion (O2.-) production in conscious chronically catheterized rats. Thiol depletion induced by buthionine sulfoximine (BSO, 1 g i.p. within 24 h) decreased the hypotensive effect of Ach by 30% (MAP reduction before BSO 27 +/- 3 mmHg, 19 +/- 3 mmHg after BSO, (mean +/- SEM), p

  15. Preparation and Characterization of Fluorinated Hydrophobic UV-Crosslinkable Thiol-Ene Polyurethane Coatings

    Directory of Open Access Journals (Sweden)

    Wenjing Xia

    2017-08-01

    Full Text Available The polyurethane prepolymer terminated with a double bond was synthesized using isophorone diisocyanate (IPDI, hydroxyl terminated polybutadiene (HTPB, 1,4-butanediol (BDO, and 2-hydroxyethyl acrylate (HEA. Then, a series of innovative UV-curable polyurethane coatings were prepared by blending ene-terminated polyurethane, fluoroacrylate monomer, and multifunctional thiol crosslinker upon UV exposure. The incorporation of fluoroacrylate monomer and multifunctional thiols into polyurethane coatings significantly enhanced the hydrophobic property, mechanical property, pencil hardness, and glossiness of the polyurethane coatings. This method of preparing UV crosslinkable, hydrophobic polyurethane coatings based on thiol-ene chemistry exhibited numerous advantages over other UV photocuring systems.

  16. Quinoline-2-thiol Derivatives as Fluorescent Sensors for Metals, pH and HNO

    Directory of Open Access Journals (Sweden)

    Naphtali A. O’Connor

    2014-06-01

    Full Text Available A tautomeric equilibrium exists for quinoline-2-thiol and quinoline-2(1H-thione. Quantum mechanical calculations predict the thione is the major tautomer and this is confirmed by the absorption spectra. The utility of quinolone-2-thiol/quinoline-2(1H-thione as a chromophore for developing fluorescent sensors is explored. No fluorescence is observed when excited at absorption maxima, however a fluorescence increase is observed when exposed to HNO, a molecule of import as a cardiovascular therapeutic. Alkylated quinoline-2-thiol derivatives are found to be fluorescent and show a reduction in fluorescence when exposed to metals and changes in pH.

  17. Preparation and Preliminary Dielectric Characterization of Structured C60-Thiol-Ene Polymer Nanocomposites Assembled Using the Thiol-Ene Click Reaction.

    Science.gov (United States)

    Ahmed, Hanaa M; Windham, Amber D; Al-Ejji, Maryam M; Al-Qahtani, Noora H; Hassan, Mohammad K; Mauritz, Kenneth A; Buchanan, Randy K; Buchanan, J Paige

    2015-11-18

    Fullerene-containing materials have the ability to store and release electrical energy. Therefore, fullerenes may ultimately find use in high-voltage equipment devices or as super capacitors for high electric energy storage due to this ease of manipulating their excellent dielectric properties and their high volume resistivity. A series of structured fullerene (C 60 ) polymer nanocomposites were assembled using the thiol-ene click reaction, between alkyl thiols and allyl functionalized C 60 derivatives. The resulting high-density C 60 -urethane-thiol-ene (C 60 -Thiol-Ene) networks possessed excellent mechanical properties. These novel networks were characterized using standard techniques, including infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermal gravimetric analysis (TGA). The dielectric spectra for the prepared samples were determined over a broad frequency range at room temperature using a broadband dielectric spectrometer and a semiconductor characterization system. The changes in thermo-mechanical and electrical properties of these novel fullerene-thiol-ene composite films were measured as a function of the C 60 content, and samples characterized by high dielectric permittivity and low dielectric loss were produced. In this process, variations in chemical composition of the networks were correlated to performance characteristics.

  18. Preparation and Preliminary Dielectric Characterization of Structured C60-Thiol-Ene Polymer Nanocomposites Assembled Using the Thiol-Ene Click Reaction

    Directory of Open Access Journals (Sweden)

    Hanaa M. Ahmed

    2015-11-01

    Full Text Available Fullerene-containing materials have the ability to store and release electrical energy. Therefore, fullerenes may ultimately find use in high-voltage equipment devices or as super capacitors for high electric energy storage due to this ease of manipulating their excellent dielectric properties and their high volume resistivity. A series of structured fullerene (C60 polymer nanocomposites were assembled using the thiol-ene click reaction, between alkyl thiols and allyl functionalized C60 derivatives. The resulting high-density C60-urethane-thiol-ene (C60-Thiol-Ene networks possessed excellent mechanical properties. These novel networks were characterized using standard techniques, including infrared spectroscopy (FTIR, differential scanning calorimetry (DSC, dynamic mechanical analysis (DMA, and thermal gravimetric analysis (TGA. The dielectric spectra for the prepared samples were determined over a broad frequency range at room temperature using a broadband dielectric spectrometer and a semiconductor characterization system. The changes in thermo-mechanical and electrical properties of these novel fullerene-thiol-ene composite films were measured as a function of the C60 content, and samples characterized by high dielectric permittivity and low dielectric loss were produced. In this process, variations in chemical composition of the networks were correlated to performance characteristics.

  19. Responses of Monolayer Membrances of Thiol-Containing Lipids to Odor Substances

    Science.gov (United States)

    Miyazaki, Yoshio; Hayashi, Kenshi; Toko, Kiyoshi; Yamafuji, Kaoru; Nakashima, Naotoshi

    1992-05-01

    It is known that thiol-containing compounds form monolayer membranes on a gold surface via chemisorption from organic solvents in terms of a strong connection ability between thiol and the metal. Here we prepared different kinds of thiol-containing lipids and fabricated monolayer membranes on the gold disk electrode whose surface structures were similar to biological membranes. Responses of this lipid-coated electrode to odor substances were examined by an electrochemical method of a cyclic voltammetry. Blocking ability for the redox reaction of Fe(CN)63- was found to change upon adsorption of odor substances into monolayer membranes. The order of threshold values to detect the odorants was β-iononeamyl acetate; this order was the same as that in the human olfactory sense. The present study indicates that the monolayer membrane of thiol-containing lipids can be useful as a transducer of an odor sensor.

  20. Mass Spectrometry in Studies of Protein Thiol Chemistry and Signaling: Opportunities and Caveats

    Science.gov (United States)

    Devarie Baez, Nelmi O.; Reisz, Julie A.; Furdui, Cristina M.

    2014-01-01

    Mass spectrometry (MS) has become a powerful and widely utilized tool in the investigation of protein thiol chemistry, biochemistry, and biology. Very early biochemical studies of metabolic enzymes have brought to light the broad spectrum of reactivity profiles that distinguish cysteine thiols with functions in catalysis and protein stability from other cysteine residues in proteins. The development of MS methods for the analysis of proteins using electrospray ionization (ESI) or matrix-assisted laser desorption/ionization (MALDI) coupled with the emergence of high-resolution mass analyzers have been instrumental in advancing studies of thiol modifications, both in single proteins and within the cellular context. This article reviews MS instrumentation and methods of analysis employed in investigations of thiols and their reactivity toward a range of small biomolecules. A selected number of studies are detailed to highlight the advantages brought about by the MS technologies along with the caveats associated with these analyses. PMID:25261734

  1. Epidithiodiketopiperazines: Strain-Promoted Thiol-Mediated Cellular Uptake at the Highest Tension.

    Science.gov (United States)

    Zong, Lili; Bartolami, Eline; Abegg, Daniel; Adibekian, Alexander; Sakai, Naomi; Matile, Stefan

    2017-05-24

    The disulfide dihedral angle in epidithiodiketopiperazines (ETPs) is near 0°. Application of this highest possible ring tension to strain-promoted thiol-mediated uptake results in efficient delivery to the cytosol and nucleus. Compared to the previous best asparagusic acid (AspA), ring-opening disulfide exchange with ETPs occurs more efficiently even with nonactivated thiols, and the resulting thiols exchange rapidly with nonactivated disulfides. ETP-mediated cellular uptake is more than 20 times more efficient compared to AspA, occurs without endosomal capture, depends on temperature, and is "unstoppable" by inhibitors of endocytosis and conventional thiol-mediated uptake, including siRNA against the transferrin receptor. These results suggest that ETP-mediated uptake not only maximizes delivery to the cytosol and nucleus but also opens the door to a new multitarget hopping mode of action.

  2. AFM-assisted fabrication of thiol SAM pattern with alternating quantified surface potential

    Directory of Open Access Journals (Sweden)

    Simons Janet

    2011-01-01

    Full Text Available Abstract Thiol self-assembled monolayers (SAMs are widely used in many nano- and bio-technology applications. We report a new approach to create and characterize a thiol SAMs micropattern with alternating charges on a flat gold-coated substrate using atomic force microscopy (AFM and Kelvin probe force microscopy (KPFM. We produced SAMs-patterns made of alternating positively charged, negatively charged, and hydrophobic-terminated thiols by an automated AFM-assisted manipulation, or nanografting. We show that these thiol patterns possess only small topographical differences as revealed by AFM, and distinguished differences in surface potential (20-50 mV, revealed by KPFM. The pattern can be helpful in the development of biosensor technologies, specifically for selective binding of biomolecules based on charge and hydrophobicity, and serve as a model for creating surfaces with quantified alternating surface potential distribution.

  3. Investigations of thiol-modified phenol derivatives for the use in thiol–ene photopolymerizations

    OpenAIRE

    Sebastian Reinelt; Monir Tabatabai; Urs Karl Fischer; Norbert Moszner; Andreas Utterodt; Helmut Ritter

    2014-01-01

    Summary Thiol–ene photopolymerizations gain a growing interest in academic research. Coatings and dental restoratives are interesting applications for thiol–ene photopolymerizations due to their unique features. In most studies the relative flexible and hydrophilic ester derivative, namely pentaerythritoltetra(3-mercaptopropionate) (PETMP), is investigated as the thiol component. Thus, in the present study we are encouraged to investigate the performance of more hydrophobic ester-free thiol-m...

  4. Content of endogenous thiols and radioresistance of gemmating cells of Saccharomyces ellipsoideus and Saccharomyces cerevisiale yeasts

    International Nuclear Information System (INIS)

    Simonyan, N.V.; Avakyan, Ts.M.; Dzhanpoladyan, N.L.; Stepanyan, L.G.

    1983-01-01

    It has been shown that gemmating cells of ''wild type'' yeasts are more radioresistant and contain more endogenous thiols, than resting cells. Gemmating cells of Saccharomyces cerevisial yeasts, carrying the mutation rad 51, as to radioresistance and content of SH groups do not differ from resting cells. The results obtained testify to a connec-- tion between increased radioresistance of the yeast gemmating cells and increased content of endogenous thiols in them

  5. Glutathione-S-Transferase and Thiol Stress in patients with acute renal failure

    Directory of Open Access Journals (Sweden)

    Mungli Prakash

    2010-07-01

    Full Text Available Introduction: Tubular damage is common finding in acute renal failure (ARF. Various etiologies have been put forth to explain the tubular damage in ARF, one important mechanism among them is oxidative damage to renal tubules. Several biomolecules including low-molecular weight peptides and enzymes in urine have been proposed as early markers of renal failure. Current study has been undertaken to study the thiol stress and glutathione-S-transferase (GST levels in ARF patients. Method: 58 ARF patients and 55 healthy controls were selected based on inclusion and exclusion criteria. Serum thiols, GST, malanoldehyde (MDA and urine thiols were determined by spectrophotometer based methods. Results: Serum thiols and urine thiols were significantly decreased (p<0.0001, and serum GST and MDA levels were significantly increased (p<0.0001 in ARF patients compared to healthy controls. Serum GST and MDA correlated positively in ARF cases (r2 = 0.6938, p<0.0001. Conclusion: There is significant thiol stress and increased lipid peroxidation in ARF patients which leads to tubular cell membrane damage and release of GST into blood stream and into urine. This may be possible mechanism for the increased presence of GST in urine (enzymuria found in other studies.

  6. Electrical resistivity of nanoporous gold modified with thiol self-assembled monolayers

    International Nuclear Information System (INIS)

    Hakamada, Masataka; Kato, Naoki; Mabuchi, Mamoru

    2016-01-01

    Highlights: • Nanoporous gold is modified with thiol-containing self-assembled monolayers. • The electrical resistivity of the thiol-modified nanoporous gold increases. • The electrical resistivity increases with increasing thiol concentration. • Monolayer tail groups enhance the atmosphere dependence of electrical resistivity. - Abstract: The electrical resistivity of nanoporous gold (NPG) modified with thiol self-assembled monolayers (SAMs) has been measured at 298 K using a four-probe method. We found that the adsorption of thiol SAMs increases the electrical resistivity of NPG by up to 22.2%. Dependence of the electrical resistivity on the atmosphere (air or water) was also observed in SAMs-modified NPG, suggesting that the electronic states of the tail groups affect the electrons of the binding sulfur and adjacent surface gold atoms. The present results suggest that adsorption of thiol molecules can influence the behavior of the conducting electrons in NPG and that modification of NPG with SAMs may be useful for environmental sensing.

  7. Electrical resistivity of nanoporous gold modified with thiol self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Hakamada, Masataka, E-mail: hakamada.masataka.3x@kyoto-u.ac.jp; Kato, Naoki, E-mail: katou.naoki.75w@st.kyoto-u.ac.jp; Mabuchi, Mamoru, E-mail: mabuchi@energy.kyoto-u.ac.jp

    2016-11-30

    Highlights: • Nanoporous gold is modified with thiol-containing self-assembled monolayers. • The electrical resistivity of the thiol-modified nanoporous gold increases. • The electrical resistivity increases with increasing thiol concentration. • Monolayer tail groups enhance the atmosphere dependence of electrical resistivity. - Abstract: The electrical resistivity of nanoporous gold (NPG) modified with thiol self-assembled monolayers (SAMs) has been measured at 298 K using a four-probe method. We found that the adsorption of thiol SAMs increases the electrical resistivity of NPG by up to 22.2%. Dependence of the electrical resistivity on the atmosphere (air or water) was also observed in SAMs-modified NPG, suggesting that the electronic states of the tail groups affect the electrons of the binding sulfur and adjacent surface gold atoms. The present results suggest that adsorption of thiol molecules can influence the behavior of the conducting electrons in NPG and that modification of NPG with SAMs may be useful for environmental sensing.

  8. Thiol/disulphide homeostasis in Bell's palsy as a novel pathogenetic marker.

    Science.gov (United States)

    Babademez, M A; Gul, F; Kale, H; Muderris, T; Bayazit, Y; Ergin, M; Erel, O; Kiris, M

    2017-04-01

    The aim of this study was to investigate the relationship between Bell's palsy and a novel oxidative stress parameter, thiol/disulphide homeostasis. A prospective study evaluating oxidative stress in Bell's palsy. This research took place in the department of Otorhinolaryngology, Ataturk Training and Research Hospital. Totally, 77 patients with Bell's palsy and 38 healthy controls were included in this study. The blood levels of total and native thiol and disulphide activity were assessed, and their levels were compared in the patients and controls. There were statistically significant differences between the patients and controls regarding thiol/disulphide parameters. The mean native thiol and total thiol were significantly lower and disulphide levels were higher in the Bell's palsy than controls. On binary logistic regression analysis, the created model showed 45.3% variation. The cut-off value was 18.95 for disulphides. Native and total thiol levels were low in the Bell's palsy. This metabolic disturbance may have a role in the pathogenesis of Bell's palsy. © 2016 John Wiley & Sons Ltd.

  9. Integration of the thiol redox status with cytokine response to physical training in professional basketball players.

    Science.gov (United States)

    Zembron-Lacny, A; Slowinska-Lisowska, M; Ziemba, A

    2010-01-01

    The present study was designed to evaluate the plasma markers of reactive oxygen species (ROS) activity and cytokines, and their relationship with thiol redox status of basketball players during training. Sixteen professional players of the Polish Basketball Extraleague participated in the study. The study was performed during the preparatory period and the play-off round. Markers of ROS activity (lipid peroxidation TBARS, protein carbonylation PC) and reduced glutathione (GSH) demonstrated regularity over time, i.e. TBARS, PC and GSH were elevated at the beginning and decreased at the end of training periods. Oxidized glutathione (GSSG) was not affected by exercise training. Thiol redox status (GSH(total)-2GSSG/GSSG) correlated with TBARS and PC in both training periods. The level of interleukin-6 (IL-6) was increased and positively correlated with thiol redox (r=0.423) in the preparatory period, whereas tumor necrosis factor alpha (TNFalpha) was increased and inversely correlated with thiol redox (r= 0.509) in the play-off round. The present study showed significant shifts in markers of ROS activity, thiol redox status and inflammatory mediators (IL-6, TNFalpha) following professional sport training as well as correlation between changes in thiol redox and cytokine response.

  10. Immediate stabilization of human blood for delayed quantification of endogenous thiols and disulfides

    Science.gov (United States)

    Giustarini, Daniela; Galvagni, Federico; Orlandini, Maurizio; Fanti, Paolo; Rossi, Ranieri

    2016-01-01

    Endogenous thiols undergo rapid and reversible oxidation to disulfides when exposed to oxidants and are, therefore, suitable biomarkers of oxidative stress. However, accurate analysis of thiols in blood is frequently compromised by their artifactual oxidation during sample manipulation, which spuriously elevates the disulfide levels. Here, we describe a validated pre-analytical procedure that prevents both artifactual oxidation of thiols during sample manipulation and their oxidative decay for months in biosamples that are stored at −80°C. Addition of N-ethylmaleimide to blood samples from healthy donors was used to stabilize whole blood, red blood cells, platelets and plasma disulfides, whereas addition of citrate buffer followed by dilution of plasma with H2O was used to stabilize plasma thiols. The concentrations of thiols and disulfides were stable in all biosamples for at least 6 months when analyzed by UV/Vis HPLC at regular intervals. Only 3 ml of blood were needed to perform the analyses of thiols and disulfides in the different blood fractions. This pre-analytical procedure is reliable for use in both animal and human prospective studies. Its ease of implementation makes the method suitable for application to multicenter studies where blood samples are collected by different sites and personnel and are shipped to specific specialized laboratories. PMID:26896310

  11. Nickel-Catalyzed Diaryl Ketone Synthesis by N-C Cleavage: Direct Negishi Cross-Coupling of Primary Amides by Site-Selective N,N-Di-Boc Activation.

    Science.gov (United States)

    Shi, Shicheng; Szostak, Michal

    2016-11-18

    A general Negishi acylation of primary amides enabled by a combination of site-selective N,N-di-Boc activation and nickel catalysis is reported for the first time. The reaction is promoted by a bench-stable, inexpensive Ni catalyst. The reaction shows excellent functional group compatibility, affording functionalized diaryl ketones by selective N-C cleavage. Most notably, this protocol represents the first amide cross-coupling by direct metal insertion of simple and readily available primary amides. The overall strategy by N,N-di-Boc activation/metal insertion is suitable for a broad range of coupling protocols via acylmetals. Mechanistic experiments suggest high reactivity of N,N-di-Boc activated 1° amides in direct amide C-N cross-couplings.

  12. Adlayers of dimannoside thiols on gold: surface chemical analysis.

    Science.gov (United States)

    Dietrich, Paul M; Horlacher, Tim; Girard-Lauriault, Pierre-Luc; Gross, Thomas; Lippitz, Andreas; Min, Hyegeun; Wirth, Thomas; Castelli, Riccardo; Seeberger, Peter H; Unger, Wolfgang E S

    2011-04-19

    Carbohydrate films on gold based on dimannoside thiols (DMT) were prepared, and a complementary surface chemical analysis was performed in detail by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), near-edge X-ray absorption fine structure (NEXAFS), FT-IR, and contact angle measurements in order to verify formation of ω-carbohydrate-functionalized alkylthiol films. XPS (C 1s, O 1s, and S 2p) reveals information on carbohydrate specific alkoxy (C-O) and acetal moieties (O-C-O) as well as thiolate species attached to gold. Angle-resolved synchrotron XPS was used for chemical speciation at ultimate surface sensitivity. Angle-resolved XPS analysis suggests the presence of an excess top layer composed of unbound sulfur components combined with alkyl moieties. Further support for DMT attachment on Au is given by ToF-SIMS and FT-IR analysis. Carbon and oxygen K-edge NEXAFS spectra were interpreted by applying the building block model supported by comparison to data of 1-undecanethiol, poly(vinyl alcohol), and polyoxymethylene. No linear dichroism effect was observed in the angle-resolved C K-edge NEXAFS. © 2011 American Chemical Society

  13. Thiol-linked alkylation of RNA to assess expression dynamics.

    Science.gov (United States)

    Herzog, Veronika A; Reichholf, Brian; Neumann, Tobias; Rescheneder, Philipp; Bhat, Pooja; Burkard, Thomas R; Wlotzka, Wiebke; von Haeseler, Arndt; Zuber, Johannes; Ameres, Stefan L

    2017-12-01

    Gene expression profiling by high-throughput sequencing reveals qualitative and quantitative changes in RNA species at steady state but obscures the intracellular dynamics of RNA transcription, processing and decay. We developed thiol(SH)-linked alkylation for the metabolic sequencing of RNA (SLAM seq), an orthogonal-chemistry-based RNA sequencing technology that detects 4-thiouridine (s 4 U) incorporation in RNA species at single-nucleotide resolution. In combination with well-established metabolic RNA labeling protocols and coupled to standard, low-input, high-throughput RNA sequencing methods, SLAM seq enabled rapid access to RNA-polymerase-II-dependent gene expression dynamics in the context of total RNA. We validated the method in mouse embryonic stem cells by showing that the RNA-polymerase-II-dependent transcriptional output scaled with Oct4/Sox2/Nanog-defined enhancer activity, and we provide quantitative and mechanistic evidence for transcript-specific RNA turnover mediated by post-transcriptional gene regulatory pathways initiated by microRNAs and N 6 -methyladenosine. SLAM seq facilitates the dissection of fundamental mechanisms that control gene expression in an accessible, cost-effective and scalable manner.

  14. Thiol passivation of MWIR type II superlattice photodetectors

    Science.gov (United States)

    Salihoglu, O.; Muti, A.; Aydinli, A.

    2013-06-01

    Poor passivation on photodetectors can result in catastrophic failure of the device. Abrupt termination of mesa side walls during pixel definition generates dangling bonds that lead to inversion layers and surface traps leading to surface leakage currents that short circuit diode action. Good passivation, therefore, is critical in the fabrication of high performance devices. Silicondioxide has been the main stay of passivation for commercial photodetectors, deposited at high temperatures and high RF powers using plasma deposition techniques. In photodetectors based on III-V compounds, sulphur passivation has been shown to replace oxygen and saturate the dangling bonds. Despite its effectiveness, it degrades over time. More effort is required to create passivation layers which eliminate surface leakage current. In this work, we propose the use of sulphur based octadecanethiol (ODT), CH3(CH2)17SH, as a passivation layer for the InAs/GaSb superlattice photodetectors that acts as a self assembled monolayer (SAM). ODT SAMs consist of a chain of 18 carbon atoms with a sulphur atom at its head. ODT Thiol coating is a simple process that consist of dipping the sample into the solution for a prescribed time. Excellent electrical performance of diodes tested confirm the effectiveness of the sulphur head stabilized by the intermolecular interaction due to van der Walls forces between the long chains of ODT SAM which results in highly stable ultrathin hydrocarbon layers without long term degradation.

  15. Surface Eroding, Semicrystalline Polyanhydrides via Thiol-Ene "Click" Photopolymerization.

    Science.gov (United States)

    Poetz, Katie L; Mohammed, Halimatu S; Shipp, Devon A

    2015-05-11

    Surface eroding and semicrystalline polyanhydrides, with tunable erosion times and drug delivery pharmacokinetics largely dictated by erosion, are produced easily with thiol-ene "click" polymerization. This strategy yields both linear and cross-linked network polyanhydrides that are readily and fully cured within minutes using photoinitiation, can contain up to 60% crystallinity, and have tensile moduli up to 25 MPa for the compositions studied. Since they readily undergo hydrolysis and exhibit the oft-preferred surface erosion mechanism, they may be particularly useful in drug delivery applications. The polyanhydrides were degraded under pseudophysiological conditions and cylindrical samples (10 mm diameter × 5 mm height) were completely degraded within ∼10 days, with the mass-time profile being linear for much of this time after a ∼24 h induction period. Drug release studies, using lidocaine as a model, showed pharmacokinetics that displayed a muted burst release in the early stages of erosion, but then a delayed release profile that is closely correlated to the erosion kinetics. Furthermore, cytotoxicity studies of the linear and cross-linked semicrystalline polyanhydrides, and degradation products, against fibroblast cells indicate that the materials have good cytocompatibility. Overall, cells treated with up to 2500 mg/L of the semicrystalline polyanhydrides and degradation products show >90% human dermal fibroblast adult (HDFa) cell viability indicative of good cytocompatibility.

  16. Thiol-redox antioxidants protect against lung vascular endothelial cytoskeletal alterations caused by pulmonary fibrosis inducer, bleomycin: comparison between classical thiol-protectant, N-acetyl-l-cysteine, and novel thiol antioxidant, N,N′-bis-2-mercaptoethyl isophthalamide

    Science.gov (United States)

    Patel, Rishi B.; Kotha, Sainath R.; Sauers, Lynn A.; Malireddy, Smitha; Gurney, Travis O.; Gupta, Niladri N.; Elton, Terry S.; Magalang, Ulysses J.; Marsh, Clay B.; Haley, Boyd E.; Parinandi, Narasimham L.

    2012-01-01

    Lung vascular alterations and pulmonary hypertension associated with oxidative stress have been reported to be involved in idiopathic lung fibrosis (ILF). Therefore, here, we hypothesize that the widely used lung fibrosis inducer, bleomycin, would cause cytoskeletal rearrangement through thiol-redox alterations in the cultured lung vascular endothelial cell (EC) monolayers. We exposed the monolayers of primary bovine pulmonary artery ECs to bleomycin (10 µg) and studied the cytotoxicity, cytoskeletal rearrangements, and the macromolecule (fluorescein isothiocyanate-dextran, 70,000 mol. wt.) paracellular transport in the absence and presence of two thiol-redox protectants, the classic water-soluble N-acetyl-l-cysteine (NAC) and the novel hydrophobic N,N′-bis-2-mercaptoethyl isophthalamide (NBMI). Our results revealed that bleomycin induced cytotoxicity (lactate dehydrogenase leak), morphological alterations (rounding of cells and filipodia formation), and cytoskeletal rearrangement (actin stress fiber formation and alterations of tight junction proteins, ZO-1 and occludin) in a dose-dependent fashion. Furthermore, our study demonstrated the formation of reactive oxygen species, loss of thiols (glutathione, GSH), EC barrier dysfunction (decrease of transendothelial electrical resistance), and enhanced paracellular transport (leak) of macromolecules. The observed bleomycin-induced EC alterations were attenuated by both NAC and NBMI, revealing that the novel hydrophobic thiol-protectant, NBMI, was more effective at µM concentrations as compared to the water-soluble NAC that was effective at mM concentrations in offering protection against the bleomycin-induced EC alterations. Overall, the results of the current study suggested the central role of thiol-redox in vascular EC dysfunction associated with ILF. PMID:22409285

  17. Synthesis, Characterization and Microwave-Promoted Catalytic Activity of Novel N-phenylbenzimidazolium Salts in Heck-Mizoroki and Suzuki-Miyaura Cross-Coupling Reactions under Mild Conditions

    Directory of Open Access Journals (Sweden)

    Ülkü Yılmaz

    2013-02-01

    Full Text Available A number of novel benzimidazolium salts having aryl substituents such as N-phenyl, 4-chlorophenyl and various alkyl substituents were synthesized. Their microwave-assisted catalytic activities were evaluated in Heck-Mizoroki and Suzuki-Miyaura cross-coupling reactions using a catalytic system consisting of Pd(OAc2/K2CO3 in DMF/H2O under mild reaction conditions with consistent high yields, except those of 2-bromopyridine.

  18. Cross-coupling reactions of unprotected halopurine bases, nucleosides, nucleotides and nucleoside triphosphates with 4-boronophenylalanine in water. Synthesis of (purin-8-yl)- and (purin-6-yl)phenylalanines

    Czech Academy of Sciences Publication Activity Database

    Čapek, Petr; Pohl, Radek; Hocek, Michal

    2006-01-01

    Roč. 4, č. 11 (2006), s. 2278-2284 ISSN 1477-0520 R&D Projects: GA AV ČR(CZ) 1QS400550501; GA MŠk(CZ) 1M0508 Institutional research plan: CEZ:AV0Z40550506 Keywords : amino acids * purines * nucleosides * cross-coupling reactions Subject RIV: CC - Organic Chemistry Impact factor: 2.874, year: 2006

  19. Thiol-ene immobilisation of carbohydrates onto glass slides as a simple alternative to gold-thiol monolayers, amines or lipid binding.

    Science.gov (United States)

    Biggs, Caroline I; Edmondson, Steve; Gibson, Matthew I

    2015-01-01

    Carbohydrate arrays are a vital tool in studying infection, probing the mechanisms of bacterial, viral and toxin adhesion and the development of new treatments, by mimicking the structure of the glycocalyx. Current methods rely on the formation of monolayers of carbohydrates that have been chemically modified with a linker to enable interaction with a functionalised surface. This includes amines, biotin, lipids or thiols. Thiol-addition to gold to form self-assembled monolayers is perhaps the simplest method for immobilisation as thiolated glycans are readily accessible from reducing carbohydrates in a single step, but are limited to gold surfaces. Here we have developed a quick and versatile methodology which enables the use of thiolated carbohydrates to be immobilised as monolayers directly onto acrylate-functional glass slides via a 'thiol-ene'/Michael-type reaction. By combining the ease of thiol chemistry with glass slides, which are compatible with microarray scanners this offers a cost effective, but also useful method to assemble arrays.

  20. A Study of Functional Polymer Colloids Prepared Using Thiol-Ene/Yne Click Chemistry

    Science.gov (United States)

    Durham, Olivia Z.

    This project demonstrates the first instance of thiol-ene chemistry as the polymerization method for the production of polymer colloids in two-phase heterogeneous suspensions, miniemulsions, and emulsions. This work was also expanded to thiol-yne chemistry for the production of polymer particles containing increased crosslinking density. The utility of thiol-ene and thiol-yne chemistries for polymerization and polymer modification is well established in bulk systems. These reactions are considered 'click' reactions, which can be defined as processes that are both facile and simple, offering high yields with nearly 100% conversion, no side products, easy product separation, compatibility with a diverse variety of commercially available starting materials, and orthogonality with other chemistries. In addition, thiol-ene and thiol-yne chemistry follow a step-growth mechanism for the development of highly uniform polymer networks, where polymer growth is dependent on the coupling of functional groups. These step-growth polymerization systems are in stark contrast to the chain-growth mechanisms of acrylic and styrenic monomers that have dominated the field of conventional heterogeneous polymerizations. Preliminary studies evaluated the mechanism of particle production in suspension and miniemulsion systems. Monomer droplets were compared to the final polymer particles to confirm that particle growth occurred through the polymerization of monomer droplets. Additional parameters examined include homogenization energy (mechanical mixing), diluent species and concentration, and monomer content. These reactions were conducted using photoinitiation to yield particles in a matter of minutes with diameters in the size range of several microns to hundreds of microns in suspensions or submicron particles in miniemulsions. Improved control over the particle size and size distribution was examined through variation of reaction parameters. In addition, a method of seeded suspension

  1. Electrochemistry behavior of endogenous thiols on fluorine doped tin oxide electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Rojas, Luciana; Molero, Leonard; Tapia, Ricardo A.; Rio, Rodrigo del; Valle, M. Angelica del; Antilen, Monica [Departamento de Quimica Inorganica, Facultad de Quimica, Pontificia Universidad Catolica de Chile, Av Vicuna Mackenna 4860, Casilla 306, Correo 22, Macul, Santiago (Chile); Armijo, Francisco, E-mail: jarmijom@uc.cl [Departamento de Quimica Inorganica, Facultad de Quimica, Pontificia Universidad Catolica de Chile, Av Vicuna Mackenna 4860, Casilla 306, Correo 22, Macul, Santiago (Chile)

    2011-10-01

    Highlights: > The first time that fluorine doped tin oxide electrodes are used for the electrooxidation of endogenous thiols. > Low potentials of electrooxidation were obtained for the different thiols. > The electrochemical behavior of thiols depends on the pH and the ionic electroactive species, the electrooxidation proceeds for a process of adsorption of electroactive species on FTO and high values the heterogeneous electron tranfer rate constant of the reaction were obtained. - Abstract: In this work the electrochemical behavior of different thiols on fluorine doped tin oxide (FTO) electrodes is reported. To this end, the mechanism of electrochemical oxidation of glutathione (GSH), cysteine (Cys), homocysteine (HCys) and acetyl-cysteine (ACys) at different pH was investigated. FTO showed electroactivity for the oxidation of the first three thiols at pH between 2.0 and 4.0, but under these conditions no acetyl-cysteine oxidation was observed on FTO. Voltammetric studies of the electro-oxidation of GSH, Cys and HCys showed peaks at about 0.35, 0.29, and 0.28 V at optimum pH 2.4, 2.8 and 3.4, respectively. In addition, this study demonstrated that GSH, Cys and HCys oxidation occurs when the zwitterion is the electro-active species that interact by adsorption on FTO electrodes. The overall reaction involves 4e{sup -}/4H{sup +} and 2e{sup -}/2H{sup +}, respectively, for HCys and for GSH and Cys and high heterogeneous electron transfer rate constants. Besides, the use of FTO for the determination of different thiols was evaluated. Experimental square wave voltammetry shows a linear current vs. concentrations response between 0.1 and 1.0 mM was found for HCys and GSH, indicating that these FTO electrodes are promising candidates for the efficient electrochemical determination of these endogenous thiols.

  2. Detoxification of Atrazine by Low Molecular Weight Thiols in Alfalfa (Medicago sativa).

    Science.gov (United States)

    Zhang, Jing Jing; Xu, Jiang Yan; Lu, Feng Fan; Jin, She Feng; Yang, Hong

    2017-10-16

    Low molecular weight (LMW) thiols in higher plants are a group of sulfur-rich nonprotein compounds and play primary and multiple roles in cellular redox homeostasis, enzyme activities, and xenobiotics detoxification. This study focused on identifying thiols-related protein genes from the legume alfalfa exposed to the herbicide atrazine (ATZ) residues in environment. Using high-throughput RNA-sequencing, a set of ATZ-responsive thiols-related protein genes highly up-regulated and differentially expressed in alfalfa was identified. Most of the differentially expressed genes (DEGs) were involved in regulation of biotic and abiotic stress responses. By analyzing the genes involved in thiols-mediated redox homeostasis, we found that many of them were thiols-synthetic enzymes such as γ-glutamylcysteine synthase (γECS), homoglutathione synthetase (hGSHS), and glutathione synthetase (GSHS). Using liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS), we further characterized a group of ATZ-thiols conjugates, which are the detoxified forms of ATZ in plants. Cysteine S-conjugate ATZ-HCl+Cys was the most important metabolite detected by MS. Several other ATZ-conjugates were also examined as ATZ-detoxified metabolites. Such results were validated by characterizing their analogs in rice. Our data showed that some conjugates under ATZ stress were detected in both plants, indicating that some detoxified mechanisms and pathways can be shared by the two plant species. Overall, these results indicate that LMW thiols play critical roles in detoxification of ATZ in the plants.

  3. Bucillamine, a thiol antioxidant, prevents transplantation-associated reperfusion injury

    Science.gov (United States)

    Amersi, Farin; Nelson, Sally K.; Shen, Xiu Da; Kato, Hirohisa; Melinek, Judy; Kupiec-Weglinski, Jerzy W.; Horwitz, Lawrence D.; Busuttil, Ronald W.; Horwitz, Marcus A.

    2002-01-01

    Ischemia/reperfusion (I/R) injury is a serious potential threat to outcomes in organ transplantation and other clinical arenas in which there is temporary interruption of blood flow. I/R is a frequent cause of primary failure in organ transplantation. We hypothesized that the antioxidant bucillamine, a potent sulfhydryl donor, would protect against I/R injury in high-risk organ transplants. Because livers subjected to prolonged ischemia and very fatty livers are highly susceptible to severe I/R injury, we studied the effect of bucillamine in three animal models of liver transplantation: two ex vivo models of isolated perfused livers, either normal or fatty rat livers, and an in vivo model of syngenic orthotopic liver transplants in rats. In all models, livers were deprived of oxygen for 24 h before either ex vivo reperfusion or transplantation. In the ex vivo models, bucillamine treatment significantly improved portal vein blood flow and bile production, preserved normal liver architecture, and significantly reduced liver enzyme release and indices of oxidative stress. Moreover, bucillamine treatment significantly increased levels of reduced glutathione in the liver and lowered levels of oxidized glutathione in both liver and blood. In rats subjected to liver transplants, bucillamine significantly enhanced survival and protected against hepatic injury. Possible mechanisms of this protection include prevention of excessive accumulation of toxic oxygen species, interruption of redox signaling in hepatocytes, and inhibition of macrophage activation. This study demonstrates the potential utility of bucillamine or other cysteine-derived thiol donors for improving outcomes in organ transplantation and other clinical settings involving I/R injury. PMID:12084933

  4. Rapid and simple preparation of thiol-ene emulsion-templated monoliths and their application as enzymatic microreactors

    DEFF Research Database (Denmark)

    Lafleur, Josiane P; Senkbeil, Silja; Novotny, Jakub

    2015-01-01

    A novel, rapid and simple method for the preparation of emulsion-templated monoliths in microfluidic channels based on thiol-ene chemistry is presented. The method allows monolith synthesis and anchoring inside thiol-ene microchannels in a single photoinitiated step. Characterization by scanning...... electron microscopy showed that the methanol-based emulsion templating process resulted in a network of highly interconnected and regular thiol-ene beads anchored solidly inside thiol-ene microchannels. Surface area measurements indicate that the monoliths are macroporous, with no or little micro...

  5. Visualizing and quantifying oxidized protein thiols in tissue sections: a comparison of dystrophic mdx and normal skeletal mouse muscles.

    Science.gov (United States)

    Iwasaki, Tomohito; Terrill, Jessica; Shavlakadze, Tea; Grounds, Miranda D; Arthur, Peter G

    2013-12-01

    Reactive oxygen species (ROS) are not only a cause of oxidative stress in a range of disease conditions but are also important regulators of physiological pathways in vivo. One mechanism whereby ROS can regulate cell function is by modification of proteins through the reversible oxidation of their thiol groups. An experimental challenge has been the relative lack of techniques to probe the biological significance of protein thiol oxidation in complex multicellular tissues and organs. We have developed a sensitive and quantitative fluorescence labeling technique to detect and localize protein thiol oxidation in histological tissue sections. In our technique, reduced and oxidized protein thiols are visualized and quantified on two consecutive tissue sections and the extent of protein thiol oxidation is expressed as a percentage of total protein thiols (reduced plus oxidized). We tested the application of this new technique using muscles of dystrophic (mdx) and wild-type C57Bl/10Scsn (C57) mice. In mdx myofibers, protein thiols were consistently more oxidized (19 ± 3%) compared with healthy myofibers (10 ± 1%) in C57 mice. A striking observation was the localization of intensive protein thiol oxidation (70 ± 9%) within myofibers associated with necrotic damage. Oxidative stress is an area of active investigation in many fields of research, and this technique provides a useful tool for locating and further understanding protein thiol oxidation in normal, damaged, and diseased tissues. © 2013 Published by Elsevier Inc.

  6. Low molecular weight thiols and thioredoxins are important players in Hg(II) resistance in Thermus thermophilus HB27.

    Science.gov (United States)

    Norambuena, J; Wang, Y; Hanson, T; Boyd, J M; Barkay, T

    2017-11-17

    Mercury (Hg), one of the most toxic and widely distributed heavy metals, has a high affinity for thiol groups. Thiol groups reduce and sequester Hg. Therefore, low molecular weight and protein thiols may be important cell components used in Hg resistance. To date, the role of low molecular weight thiols in Hg-detoxification remains understudied. The mercury resistance ( mer ) operon of Thermus thermophilus suggests an evolutionary link between Hg(II) resistance and low molecular weight thiol metabolism. This mer operon encodes for an enzyme involved in methionine biosynthesis, Oah. Challenge with Hg(II) resulted in increased expression of genes involved in the biosynthesis of multiple low molecular weight thiols (cysteine, homocysteine, and bacillithiol), as well as the thioredoxin system. Phenotypic analysis of gene replacement mutants indicated that Oah contributes to Hg resistance under sulfur limiting conditions, and strains lacking bacillithiol and/or thioredoxins are more sensitive to Hg(II) than the wild type. Growth in presence of either a thiol oxidizing agent or a thiol alkylating agent increased sensitivity to Hg(II). Furthermore, exposure to 3 μM Hg(II) consumed all intracellular reduced bacillithiol and cysteine. Database searches indicate that oah2 is present in all Thermus spp. mer operons. The presence of a thiol related gene was also detected in some alphaprotobacterial mer operons, in which a glutathione reductase gene was present, supporting the role of thiols in Hg(II) detoxification. These results have led to a working model in which LMW thiols act as Hg(II) buffering agents while Hg is reduced by MerA. Importance The survival of microorganisms in presence of toxic metals is central to life's sustainability. The affinity of thiol groups to toxic heavy metals drives microbe-metal interactions and modulate metal toxicity. Mercury detoxification ( mer ) genes likely originated early in microbial evolution among geothermal environments. Little is

  7. Thiol groups controls on arsenite binding by organic matter: new experimental and modeling evidence.

    Science.gov (United States)

    Catrouillet, Charlotte; Davranche, Mélanie; Dia, Aline; Bouhnik-Le Coz, Martine; Pédrot, Mathieu; Marsac, Rémi; Gruau, Gérard

    2015-12-15

    Although it has been suggested that several mechanisms can describe the direct binding of As(III) to organic matter (OM), more recently, the thiol functional group of humic acid (HA) was shown to be an important potential binding site for As(III). Isotherm experiments on As(III) sorption to HAs, that have either been grafted with thiol or not, were thus conducted to investigate the preferential As(III) binding sites. There was a low level of binding of As(III) to HA, which was strongly dependent on the abundance of the thiols. Experimental datasets were used to develop a new model (the modified PHREEQC-Model VI), which defines HA as a group of discrete carboxylic, phenolic and thiol sites. Protonation/deprotonation constants were determined for each group of sites (pKA=4.28±0.03; ΔpKA=2.13±0.10; pKB=7.11±0.26; ΔpKB=3.52±0.49; pKS=5.82±0.052; ΔpKS=6.12±0.12 for the carboxylic, phenolic and thiols sites, respectively) from HAs that were either grafted with thiol or not. The pKS value corresponds to that of single thiol-containing organic ligands. Two binding models were tested: the Mono model, which considered that As(III) is bound to the HA thiol site as monodentate complexes, and the Tri model, which considered that As(III) is bound as tridentate complexes. A simulation of the available literature datasets was used to validate the Mono model, with logKMS=2.91±0.04, i.e. the monodentate hypothesis. This study highlighted the importance of thiol groups in OM reactivity and, notably, determined the As(III) concentration bound to OM (considering that Fe is lacking or at least negligible) and was used to develop a model that is able to determine the As(III) concentrations bound to OM. Copyright © 2015. Published by Elsevier Inc.

  8. Heavy metal ion removal by thiol functionalized aluminum oxide hydroxide nanowhiskers

    Science.gov (United States)

    Xia, Zhiyong; Baird, Lance; Zimmerman, Natasha; Yeager, Matthew

    2017-09-01

    In this study, we developed a cost effective method of using thiol functionalized γ-aluminum oxide hydroxide (γ-AlOOH) filters for removing three key heavy metals from water: mercury, lead, and cadmium under non-concomitant conditions. Compared to non-thiol treated γ-AlOOH filters, the introduction of thiol functional groups greatly improved the heavy metal removal efficiency under both static and dynamic filtration conditions. The adsorption kinetics of thiol functionalized γ-AlOOH were investigated using the Lagergren first order and pseudo-second order kinetics models; whereas the isothermal adsorption behavior of these membranes was revealed through the Langmuir and Freundlich models. Heavy metal concentration was quantified by Inductively Coupled Plasma-Mass Spectroscopy, and the thiol level on γ-AlOOH surface was measured by a colorimetric assay using Ellman's reagent. X-ray photoelectron spectroscopy was used to further address the surface sulfur state on the membranes after heavy metal exposure. Mechanisms for heavy metal adsorption were also discussed.

  9. The synthesis of novel hybrid thiol-functionalized nano-structured SBA-15

    International Nuclear Information System (INIS)

    Hoang, Van Duc; Dang, Tuyet Phuong; Dinh, Quang Khieu; Vu, Anh Tuan; Nguyen, Huu Phu

    2010-01-01

    Mesoporous thiol-functionalized SBA-15 has been directly synthesized by co-condensation of tetraethyl orthosilicate (TEOS) and 3-mercaptopropyltrimethoxysilane (MPTMS) with triblock copolymer P123 as-structure-directing agent under hydrothermal conditions. Surfactant removal was performed by Soxhlet ethanol extraction. These materials have been characterized by powder x-ray diffraction (XRD), nitrogen adsorption/desorption (BET model), transmission electron microscopy (TEM), thermal analysis, infrared spectroscopy (IR) and energy-dispersive x-ray spectroscopy (EDX). The main parameters, such as the initial molar ratio of MPTMS to TEOS, the time of adding MPTMS to synthesized gel and the Soxhlet ethanol extraction on the thiol functionalized SBA-15 with high thiol content and highly ordered hexagonal mesostructure, were investigated and evaluated. The adsorption capacity of the thiol-functionalized and non-functionalized SBA-15 materials for Pb 2+ ion from aqueous solution was tested. It was found that the Pb 2+ adsorption capacity of the thiol functionalized SBA-15 is three times higher than that of non-functionalized SBA-15

  10. Near-Edge X-ray Absorption Fine Structure Spectroscopy of Diamondoid Thiol Monolayers on Gold

    Energy Technology Data Exchange (ETDEWEB)

    Willey, T M; Fabbri, J; Lee, J I; Schreiner, P; Fokin, A A; Tkachenko, B A; Fokina, N A; Dahl, J; Carlson, B; Vance, A L; Yang, W; Terminello, L J; van Buuren, T; Melosh, N

    2007-11-27

    Diamondoids, hydrocarbon molecules with cubic-diamond-cage structures, have unique properties with potential value for nanotechnology. The availability and ability to selectively functionalize this special class of nanodiamond materials opens new possibilities for surface-modification, for high-efficiency field emitters in molecular electronics, as seed crystals for diamond growth, or as robust mechanical coatings. The properties of self-assembled monolayers (SAMs) of diamondoids are thus of fundamental interest for a variety of emerging applications. This paper presents the effects of thiol substitution position and polymantane order on diamondoid SAMs on gold using near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray photoelectron spectroscopy (XPS). A framework to determine both molecular tilt and twist through NEXAFS is presented and reveals highly ordered diamondoid SAMs, with the molecular orientation controlled by the thiol location. C 1s and S 2p binding energies are lower in adamantane thiol than alkane thiols on gold by 0.67 {+-} 0.05 eV and 0.16 {+-} 0.04 eV respectively. These binding energies vary with diamondoid monolayer structure and thiol substitution position, consistent with different amounts of steric strain and electronic interaction with the substrate. This work demonstrates control over the assembly, in particular the orientational and electronic structure, providing a flexible design of surface properties with this exciting new class of diamond clusters.

  11. The Reducing Capacity of Thioredoxin on Oxidized Thiols in Boiled Wort

    DEFF Research Database (Denmark)

    Murmann, Anne N.; Hägglund, Per; Svensson, Birte

    2017-01-01

    Free thiol-containing proteins are suggested to work as antioxidants in beer, but the majority of thiols in wort are present in their oxidized form as disulfides and are therefore not active as antioxidants. Thioredoxin, a disulfide-reducing protein, is released into the wort from some yeast...... and fluorescence detection of thiol-derivatives. When boiled wort was incubated with all components of the thioredoxin system at pH 7.0 and 25 °C for 60 min under anaerobic conditions, the free thiol concentration increased from 25 to 224 μM. At pH values similar to wort (pH 5.7) and beer (pH 4.5), the thioredoxin...... system was also capable of increasing the free thiol concentration, although with lower efficiency to 187 and 170 μM, respectively. The presence of sulfite, an important antioxidant in beer secreted by the yeast during fermentation, was found to inactivate thioredoxin by sulfitolysis. Reduction...

  12. Self-Healing Photocurable Epoxy/thiol-ene Systems Using an Aromatic Epoxy Resin

    Directory of Open Access Journals (Sweden)

    Ricardo Acosta Ortiz

    2016-01-01

    Full Text Available A rapid and efficient method to obtain self-healing epoxy resins is discussed. This method is based on the use of a thiol-disulfide oligomer obtained by partial oxidation of a multifunctional thiol using a hypervalent iodine (III compound as oxidant. The oligomer was characterized by Fourier transform infrared spectroscopy (FTIR, Raman and nuclear magnetic resonance spectroscopies, and gel permeation chromatography (GPC. The oligomer was a joint component of the thiol-ene system along with a tetra-allyl-functionalized curing agent. The kinetics of the photopolymerization of diglycidylether of bisphenol A (DGEBA revealed that conversions of the epoxy groups as high as 80% were achieved in only 15 minutes by increasing the concentration of the thiol-ene system in the formulation. The disulfide bonds introduced in the copolymer using the thiol-disulfide oligomer allowed the repairing of the test specimens in as little as 10 minutes when the specimens were heated at 80°C or for 500 minutes at room temperature. The analysis of the mechanical properties using dynamic mechanical analysis (DMA showed that the specimens displayed a healing efficiency up to 111% compared with the unhealed specimens, depending on the amount of polythioethers present in the copolymer.

  13. Monocyte activation drives preservation of membrane thiols by promoting release of oxidised membrane moieties via extracellular vesicles.

    Science.gov (United States)

    Szabó-Taylor, K É; Tóth, E Á; Balogh, A M; Sódar, B W; Kádár, L; Pálóczi, K; Fekete, N; Németh, A; Osteikoetxea, X; Vukman, K V; Holub, M; Pállinger, É; Nagy, Gy; Winyard, P G; Buzás, E I

    2017-07-01

    The redox state of cellular exofacial molecules is reflected by the amount of available thiols. Furthermore, surface thiols can be considered as indicators of immune cell activation. One group of thiol containing proteins, peroxiredoxins, in particular, have been associated with inflammation. In this study, we assessed surface thiols of the U937 and Thp1 monocyte cell lines and primary monocytes in vitro upon inflammatory stimulation by irreversibly labelling the cells with a fluorescent derivative of maleimide. We also investigated exofacial thiols on circulating blood mononuclear cells in patients with rheumatoid arthritis and healthy controls. When analysing extracellular vesicles, we combined thiol labelling with the use of antibodies to specific CD markers to exclude extracellular vesicle mimicking signals from thiol containing protein aggregates. Furthermore, differential detergent lysis was applied to confirm the vesicular nature of the detected extracellular events in blood plasma. We found an increase in exofacial thiols on monocytes upon in vitro stimulation by LPS or TNF, both in primary monocytes and monocytic cell lines (pextracellular vesicles showed a decrease in their exofacial thiols compared with those from unstimulated cells (pextracellular vesicles of isolated CD14 + cells from rheumatoid arthritis patients had decreased thiol levels compared with healthy subjects (pextracellular vesicles was increased in rheumatoid arthritis blood plasma (pextracellular vesicle-enriched preparations from blood plasma. Our data show that cell surface thiols play a protective role and reflect oxidative stress resistance state in activated immune cells. Furthermore, they support a role of extracellular vesicles in the redox regulation of human monocytes, possibly representing an antioxidant mechanism. Copyright © 2017. Published by Elsevier Inc.

  14. Redox regulation of Rac1 by thiol oxidation

    Science.gov (United States)

    Hobbs, G. Aaron; Mitchell, Lauren E.; Arrington, Megan E.; Gunawardena, Harsha P.; DeCristo, Molly J.; Loeser, Richard F.; Chen, Xian; Cox, Adrienne D.; Campbell, Sharon L.

    2016-01-01

    The Rac1 GTPase is an essential and ubiquitous protein that signals through numerous pathways to control critical cellular processes, including cell growth, morphology, and motility. Rac1 deletion is embryonic lethal, and its dysregulation or mutation can promote cancer, arthritis, cardiovascular disease, and neurological disorders. Rac1 activity is highly regulated by modulatory proteins and posttranslational modifications. Whereas much attention has been devoted to guanine nucleotide exchange factors that act on Rac1 to promote GTP loading and Rac1 activation, cellular oxidants may also regulate Rac1 activation by promoting guanine nucleotide exchange. Herein, we show that Rac1 contains a redox-sensitive cysteine (Cys18) that can be selectively oxidized at physiological pH because of its lowered pKa. Consistent with these observations, we show that Rac1 is glutathiolated in primary chondrocytes. Oxidation of Cys18 by glutathione greatly perturbs Rac1 guanine nucleotide binding and promotes nucleotide exchange. As aspartate substitutions have been previously used to mimic cysteine oxidation, we characterized the biochemical properties of Rac1C18D. We also evaluated Rac1C18S as a redox-insensitive variant and found that it retains structural and biochemical properties similar to those of Rac1WT but is resistant to thiol oxidation. In addition, Rac1C18D, but not Rac1C18S, shows greatly enhanced nucleotide exchange, similar to that observed for Rac1 oxidation by glutathione. We employed Rac1C18D in cell-based studies to assess whether this fast-cycling variant, which mimics Rac1 oxidation by glutathione, affects Rac1 activity and function. Expression of Rac1C18D in Swiss 3T3 cells showed greatly enhanced GTP-bound Rac1 relative to Rac1WT and the redox-insensitive Rac1C18S variant. Moreover, expression of Rac1C18D in HEK-293T cells greatly promoted lamellipodia formation. Our results suggest that Rac1 oxidation at Cys18 is a novel posttranslational modification that

  15. Enzymatic Continuous Flow Synthesis of Thiol-Terminated Poly(δ-Valerolactone) and Block Copolymers.

    Science.gov (United States)

    Zhu, Ning; Huang, Weijun; Hu, Xin; Liu, Yihuan; Fang, Zheng; Guo, Kai

    2018-04-01

    Thiol-terminated poly(δ-valerolactone) is directly synthesized via enzymatic 6-mercapto-1-hexanol initiated ring-opening polymerization in both batch and microreactor. By using Candida antartica Lipase B immobilized tubular reactor, narrowly dispersed poly(δ-valerolactone) with higher thiol fidelity is more efficiently prepared in contrast to the batch reactor. Moreover, the integrated enzyme packed tubular reactor system is established to perform the chain extension experiments. Thiol-terminated poly(δ-valerolactone)-block-poly(ε-caprolactone) and poly(ε-caprolactone)-block-poly(δ-valerolactone) are easily prepared by modulating the monomer introduction sequence. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Diamond surface functionalization with biomimicry – Amine surface tether and thiol moiety for electrochemical sensors

    Energy Technology Data Exchange (ETDEWEB)

    Sund, James B., E-mail: jim@jamessund.com [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Causey, Corey P. [Departments of Chemistry and Biochemistry, Duke University, Durham, NC (United States); Wolter, Scott D. [Department of Physics, Elon University, Elon, NC 27244 (United States); Parker, Charles B., E-mail: charles.parker@duke.edu [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Stoner, Brian R. [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Research Triangle Institute (RTI) International, Research Triangle Park, NC (United States); Toone, Eric J. [Departments of Chemistry and Biochemistry, Duke University, Durham, NC (United States); Glass, Jeffrey T. [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States)

    2014-05-01

    Highlights: • Diamond surfaces were functionalized with organic molecules using a novel approach. • Used biomimicry to select a molecule to bind NO, similar to the human body. • Molecular orbital theory predicted the molecule-analyte oxidation behavior. • A thiol moiety was attached to an amine surface tether on the diamond surface. • XPS analysis verified each surface functionalization step. - Abstract: The surface of conducting diamond was functionalized with a terminal thiol group that is capable of binding and detecting nitrogen–oxygen species. The functionalization process employed multiple steps starting with doped diamond films grown by plasma enhanced chemical vapor deposition followed by hydrogen termination and photochemical attachment of a chemically protected amine alkene. The surface tether was deprotected to reveal the amine functionality, which enabled the tether to be extended with surface chemistry to add a terminal thiol moiety for electrochemical sensing applications. Each step of the process was validated using X-ray photoelectron spectroscopy analysis.

  17. Preparation of photochromic silk fabrics based on thiol-halogen click chemistry

    Science.gov (United States)

    Fan, Ji; Wang, Wei; Yu, Dan

    2018-02-01

    In this study, we have synthesized a photochromic compound 9‧-(2-bromo-2-methylethoxycarbonyl)-1,3,3-trimethyl-spiro[2H-indole-2,3‧-[3H]naphtha[2,1-b] [1,4]oxazine] and applied it to the silk fabric to acquire photochromic properties. First, tris (2-carboxyethyl) phosphine (TCEP) was used as a reducing agent to produce thiol groups on the surface of silk fabric. Then, these thiol groups will react with -Br groups of the spirooxazine via thiol-halogen click chemistry. The spirooxazine was characterized by FTIR and UV. And the color change properties of the as-prepared silk fabrics were evaluated by the color measurement methods. The results indicated that treated silk fabric has excellent photochromic properties.

  18. Thiol peptides induction in the seagrass Thalassia testudinum (Banks ex Koenig) in response to cadmium exposure

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez-Legorreta, Teresa [Departamento de Recursos del Mar, CINVESTAV-IPN, Unidad Merida, Apdo. Postal 73-Cordemex, Merida, Yucatan 97310 (Mexico); Mendoza-Cozatl, David; Moreno-Sanchez, Rafael [Departamento de Bioquimica, Instituto Nacional de Cardiologia, Mexico D.F. 14080 (Mexico); Gold-Bouchot, Gerardo [Departamento de Recursos del Mar, CINVESTAV-IPN, Unidad Merida, Apdo. Postal 73-Cordemex, Merida, Yucatan 97310 (Mexico)], E-mail: gold@mda.cinvestav.mx

    2008-01-20

    Trace metal accumulation and thiol compounds synthesis as induced by cadmium exposure was studied in the seagrass Thalassia testudinum. Shoots were exposed for 24, 48, 96 and 144 h to several CdCl{sub 2} concentrations (0, 30, 50 and 70 {mu}M). Levels of cadmium, cysteine, glutathione (GSH), {gamma}-glutamylcysteine ({gamma}-EC), and phytochelatin-like peptides were determined in green blades, live sheaths and root/rhizomes tissues. Metal accumulation was dependent on Cd concentration and type of tissue, with green blades showing the highest content followed by live sheaths and root/rhizomes. All tissues experienced an increase in thiol-containing compounds as a response to cadmium exposure. Live sheaths showed the highest levels of cysteine, GSH and {gamma}-EC. This is the first report of induction of thiol peptides, presumably phytochelatins, by a trace metal in a sea grass species.

  19. Protein Thiol Oxidation in Murine Airway Epithelial Cells in Response to Naphthalene or Diethyl Maleate

    Science.gov (United States)

    Spiess, Page C.; Morin, Dexter; Williams, Chase R.; Buckpitt, Alan R.

    2010-01-01

    Naphthalene (NA) is a semivolatile aromatic hydrocarbon to which humans are exposed from a variety of sources. NA results in acute cytotoxicity to respiratory epithelium in rodents. Cytochrome P450-dependent metabolic activation to form reactive intermediates and loss of soluble cellular thiols (glutathione) are critical steps in NA toxicity, but the precise mechanisms by which this chemical results in cellular injury remain unclear. Protein thiols are likely targets of reactive NA metabolites. Loss of these, through adduction or thiol oxidation mechanisms, may be important underlying mechanisms for NA toxicity. To address the hypothesis that loss of thiols on specific cellular proteins is critical to NA-induced cytotoxicity, we compared reduced to oxidized thiol ratios in airway epithelial cell proteins isolated from lungs of mice treated with NA or the nontoxic glutathione depletor, diethyl maleate (DEM). At 300 mg/kg doses, NA administration resulted in a greater than 85% loss of glutathione levels in the airway epithelium, which is similar to the loss observed after DEM treatment. Using differential fluorescent maleimide labeling followed by 2DE separation of proteins, we identified more than 35 unique proteins that have treatment-specific differential sulfhydryl oxidation. At doses of NA and DEM that produce similar levels of glutathione depletion, Cy3/Cy5 labeling ratios were statistically different for 16 nonredundant proteins in airway epithelium. Proteins identified include a zinc finger protein, several aldehyde dehydrogenase variants, β-actin, and several other structural proteins. These studies show distinct patterns of protein thiol alterations with the noncytotoxic DEM and the cytotoxic NA. PMID:19843705

  20. Coordination chemistry controls the thiol oxidase activity of the B12-trafficking protein CblC.

    Science.gov (United States)

    Li, Zhu; Shanmuganathan, Aranganathan; Ruetz, Markus; Yamada, Kazuhiro; Lesniak, Nicholas A; Kräutler, Bernhard; Brunold, Thomas C; Koutmos, Markos; Banerjee, Ruma

    2017-06-09

    The cobalamin or B 12 cofactor supports sulfur and one-carbon metabolism and the catabolism of odd-chain fatty acids, branched-chain amino acids, and cholesterol. CblC is a B 12 -processing enzyme involved in an early cytoplasmic step in the cofactor-trafficking pathway. It catalyzes the glutathione (GSH)-dependent dealkylation of alkylcobalamins and the reductive decyanation of cyanocobalamin. CblC from Caenorhabditis elegans ( ce CblC) also exhibits a robust thiol oxidase activity, converting reduced GSH to oxidized GSSG with concomitant scrubbing of ambient dissolved O 2 The mechanism of thiol oxidation catalyzed by ce CblC is not known. In this study, we demonstrate that novel coordination chemistry accessible to ce CblC-bound cobalamin supports its thiol oxidase activity via a glutathionyl-cobalamin intermediate. Deglutathionylation of glutathionyl-cobalamin by a second molecule of GSH yields GSSG. The crystal structure of ce CblC provides insights into how architectural differences at the α- and β-faces of cobalamin promote the thiol oxidase activity of ce CblC but mute it in wild-type human CblC. The R161G and R161Q mutations in human CblC unmask its latent thiol oxidase activity and are correlated with increased cellular oxidative stress disease. In summary, we have uncovered key architectural features in the cobalamin-binding pocket that support unusual cob(II)alamin coordination chemistry and enable the thiol oxidase activity of ce CblC. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  1. Surface modification of cyclomatrix polyphosphazene microsphere by thiol-ene chemistry and lectin recognition

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chen; Zhu, Xue-yan; Gao, Qiao-ling; Fang, Fei; Huang, Xiao-jun, E-mail: hxjzxh@zju.edu.cn

    2016-11-30

    Graphical abstract: A new synthetic route leading to polyphosphazene cyclomatrix microsphere with various functional groups has achieved via thiol-ene click modification. Herein, hexacholorocyclophosphazene (HCCP) crosslinked with bisphenol-S and 4,4′-diallyl bisphenol-S to generate broadly dispersed microspheres. Thiol-ene modification under UV irradiation not only presented high efficiency and flexibility for post-functionalization, but also imposed no harm on global morphology and crosslinked skeleton of such microspheres. - Highlights: • Functional polyphosphazene microspheres with high chemical flexibility were synthesized by thiol-ene modification. • Polyphosphazene microspheres possessed high thermal stability. • Glycosylated polyphosphazene microspheres showed affinity to lectin Con-A, which inferred potential application in biomedicine. - Abstract: A new synthetic route leading to functional polyphosphazene cyclomatrix microsphere has been developed via thiol-ene click modification. Hexacholorocyclophosphazene (HCCP) was crosslinked with both bisphenol-S and 4,4′-diallyl bisphenol-S to obtain vinyl polyphosphazene microspheres (VPZM) in order to ensure high crosslinking degree and introduce vinyl moieties. Compared to the microspheres obtained by HCCP and bisphenol-S, the size of VPZM was broadly dispersed from 400 nm to 1.40 μm. Thiol-ene click reactions were carried out to attach functional groups, such as glucosyl, carboxyl, ester and dodecyl groups onto polyphosphazene microspheres, which demonstrated no change in morphology and size after modification. Solid state NMR (SSNMR) and Fourier transform infrared spectoscopy (FT-IR) results showed that the vinyl moieties were introduced in the period of crosslinking and functionalization was also successful via click reactions. Moreover, the microspheres presented a little difference in thermal properties after modification. Concanavalin A (Con-A) fluorescent adsorption was also observed for

  2. Protein thiol oxidation in murine airway epithelial cells in response to naphthalene or diethyl maleate.

    Science.gov (United States)

    Spiess, Page C; Morin, Dexter; Williams, Chase R; Buckpitt, Alan R

    2010-09-01

    Naphthalene (NA) is a semivolatile aromatic hydrocarbon to which humans are exposed from a variety of sources. NA results in acute cytotoxicity to respiratory epithelium in rodents. Cytochrome P450-dependent metabolic activation to form reactive intermediates and loss of soluble cellular thiols (glutathione) are critical steps in NA toxicity, but the precise mechanisms by which this chemical results in cellular injury remain unclear. Protein thiols are likely targets of reactive NA metabolites. Loss of these, through adduction or thiol oxidation mechanisms, may be important underlying mechanisms for NA toxicity. To address the hypothesis that loss of thiols on specific cellular proteins is critical to NA-induced cytotoxicity, we compared reduced to oxidized thiol ratios in airway epithelial cell proteins isolated from lungs of mice treated with NA or the nontoxic glutathione depletor, diethyl maleate (DEM). At 300 mg/kg doses, NA administration resulted in a greater than 85% loss of glutathione levels in the airway epithelium, which is similar to the loss observed after DEM treatment. Using differential fluorescent maleimide labeling followed by 2DE separation of proteins, we identified more than 35 unique proteins that have treatment-specific differential sulfhydryl oxidation. At doses of NA and DEM that produce similar levels of glutathione depletion, Cy3/Cy5 labeling ratios were statistically different for 16 nonredundant proteins in airway epithelium. Proteins identified include a zinc finger protein, several aldehyde dehydrogenase variants, beta-actin, and several other structural proteins. These studies show distinct patterns of protein thiol alterations with the noncytotoxic DEM and the cytotoxic NA.

  3. Redox regulation of mitochondrial proteins and proteomes by cysteine thiol switches.

    Science.gov (United States)

    Nietzel, Thomas; Mostertz, Jörg; Hochgräfe, Falko; Schwarzländer, Markus

    2017-03-01

    Mitochondria are hotspots of cellular redox biochemistry. Respiration as a defining mitochondrial function is made up of a series of electron transfers that are ultimately coupled to maintaining the proton motive force, ATP production and cellular energy supply. The individual reaction steps involved require tight control and flexible regulation to maintain energy and redox balance in the cell under fluctuating demands. Redox regulation by thiol switching has been a long-standing candidate mechanism to support rapid adjustment of mitochondrial protein function at the posttranslational level. Here we review recent advances in our understanding of cysteine thiol switches in the mitochondrial proteome with a focus on their operation in vivo. We assess the conceptual basis for thiol switching in mitochondria and discuss to what extent insights gained from in vitro studies may be valid in vivo, considering thermodynamic, kinetic and structural constraints. We compare functional proteomic approaches that have been used to assess mitochondrial protein thiol switches, including thioredoxin trapping, redox difference gel electrophoresis (redoxDIGE), isotope-coded affinity tag (OxICAT) and iodoacetyl tandem mass tag (iodoTMT) labelling strategies. We discuss conditions that may favour active thiol switching in mitochondrial proteomes in vivo, and appraise recent advances in dissecting their impact using combinations of in vivo redox sensing and quantitative redox proteomics. Finally we focus on four central facets of mitochondrial biology, aging, carbon metabolism, energy coupling and electron transport, exemplifying the current emergence of a mechanistic understanding of mitochondrial regulation by thiol switching in living plants and animals. Copyright © 2016 Elsevier B.V. and Mitochondria Research Society. All rights reserved.

  4. Stretching of BDT-gold molecular junctions: Thiol or thiolate termination?

    KAUST Repository

    Souza, Amaury De Melo

    2014-01-01

    It is often assumed that the hydrogen atoms in the thiol groups of a benzene-1,4-dithiol dissociate when Au-benzene-1,4-dithiol-Au junctions are formed. We demonstrate, by stability and transport property calculations, that this assumption cannot be made. We show that the dissociative adsorption of methanethiol and benzene-1,4-dithiol molecules on a flat Au(111) surface is energetically unfavorable and that the activation barrier for this reaction is as high as 1 eV. For the molecule in the junction, our results show, for all electrode geometries studied, that the thiol junctions are energetically more stable than their thiolate counterparts. Due to the fact that density functional theory (DFT) within the local density approximation (LDA) underestimates the energy difference between the lowest unoccupied molecular orbital and the highest occupied molecular orbital by several electron-volts, and that it does not capture the renormalization of the energy levels due to the image charge effect, the conductance of the Au-benzene-1,4-dithiol-Au junctions is overestimated. After taking into account corrections due to image charge effects by means of constrained-DFT calculations and electrostatic classical models, we apply a scissor operator to correct the DFT energy level positions, and calculate the transport properties of the thiol and thiolate molecular junctions as a function of the electrode separation. For the thiol junctions, we show that the conductance decreases as the electrode separation increases, whereas the opposite trend is found for the thiolate junctions. Both behaviors have been observed in experiments, therefore pointing to the possible coexistence of both thiol and thiolate junctions. Moreover, the corrected conductance values, for both thiol and thiolate, are up to two orders of magnitude smaller than those calculated with DFT-LDA. This brings the theoretical results in quantitatively good agreement with experimental data.

  5. Preparation of new biobased coatings from a triglycidyl eugenol derivative through thiol-epoxy click reaction

    OpenAIRE

    Guzman, Dailyn; Ramis Juan, Xavier; Fernández Francos, Xavier; de la Flor1 López, Sílvia; Serra Albet, Àngels

    2018-01-01

    © 2017 Elsevier B.V. A new triglycidyl eugenol derivative (3EPO-EU) was synthesized and characterized by spectroscopic techniques, and used as starting monomer in the preparation of novel bio-based thiol-epoxy thermosets. As thiols, commercially available tetrathiol derived from pentaerythritol (PETMP), a trithiol derived from eugenol (3SH-EU) and the hexathiol derived from squalene (6SH-SQ) were used in the presence of 4-(N,N-dimethylamino)pyridine as the basic catalyst. A flexible diglycidy...

  6. A robust and versatile mass spectrometry platform for comprehensive assessment of the thiol redox metabolome

    Directory of Open Access Journals (Sweden)

    T.R. Sutton

    2018-06-01

    Full Text Available Several diseases are associated with perturbations in redox signaling and aberrant hydrogen sulfide metabolism, and numerous analytical methods exist for the measurement of the sulfur-containing species affected. However, uncertainty remains about their concentrations and speciation in cells/biofluids, perhaps in part due to differences in sample processing and detection principles. Using ultrahigh-performance liquid chromatography in combination with electrospray-ionization tandem mass spectrometry we here outline a specific and sensitive platform for the simultaneous measurement of 12 analytes, including total and free thiols, their disulfides and sulfide in complex biological matrices such as blood, saliva and urine. Total assay run time is < 10 min, enabling high-throughput analysis. Enhanced sensitivity and avoidance of artifactual thiol oxidation is achieved by taking advantage of the rapid reaction of sulfhydryl groups with N-ethylmaleimide. We optimized the analytical procedure for detection and separation conditions, linearity and precision including three stable isotope labelled standards. Its versatility for future more comprehensive coverage of the thiol redox metabolome was demonstrated by implementing additional analytes such as methanethiol, N-acetylcysteine, and coenzyme A. Apparent plasma sulfide concentrations were found to vary substantially with sample pretreatment and nature of the alkylating agent. In addition to protein binding in the form of mixed disulfides (S-thiolation a significant fraction of aminothiols and sulfide appears to be also non-covalently associated with proteins. Methodological accuracy was tested by comparing the plasma redox status of 10 healthy human volunteers to a well-established protocol optimized for reduced/oxidized glutathione. In a proof-of-principle study a deeper analysis of the thiol redox metabolome including free reduced/oxidized as well as bound thiols and sulfide was performed

  7. On the reaction of thiols with primary radiation lesions in bacteriophage

    International Nuclear Information System (INIS)

    Korystov, Yu.N.; Veksler, A.M.; Ehjdus, L.Kh.

    1982-01-01

    In order to answer the question in which form, RSH of RS-, thiols react with the target responsible for reproductive cell death a study was made of the pH dependence (4.7-8.2) of the radioprotective effect of mercaptoethanol and cysteamine on the bacteriophage T 4 under the anoxic conditions. It was shown that the protective effect does not depend upon pH. Since the concentration of RSH, within the studied range of pH values, remains virtually invariable, and RS - concentration sharply changes, the obtained results indicate that the RSH is the form in which thiols react with primary radiation damages to the phage [ru

  8. Diamond surface functionalization with biomimicry - Amine surface tether and thiol moiety for electrochemical sensors

    Science.gov (United States)

    Sund, James B.; Causey, Corey P.; Wolter, Scott D.; Parker, Charles B.; Stoner, Brian R.; Toone, Eric J.; Glass, Jeffrey T.

    2014-05-01

    The surface of conducting diamond was functionalized with a terminal thiol group that is capable of binding and detecting nitrogen-oxygen species. The functionalization process employed multiple steps starting with doped diamond films grown by plasma enhanced chemical vapor deposition followed by hydrogen termination and photochemical attachment of a chemically protected amine alkene. The surface tether was deprotected to reveal the amine functionality, which enabled the tether to be extended with surface chemistry to add a terminal thiol moiety for electrochemical sensing applications. Each step of the process was validated using X-ray photoelectron spectroscopy analysis.

  9. Thiol-catalyzed formation of lactate and glycerate from glyceraldehyde. [significance in molecular evolution

    Science.gov (United States)

    Weber, A. L.

    1983-01-01

    The rate of lactate formation from glyceraldehyde, catalyzed by N-acetyl-cysteine at ambient temperature in aqueous sodium phosphate (pH 7.0), is more rapid at higher sodium phosphate concentrations and remains essentially the same in the presence and absence of oxygen. The dramatic increase in the rate of glycerate formation that is brought about by this thiol, N-acetylcysteine, is accompanied by commensurate decreases in the rates of glycolate and formate production. It is suggested that the thiol-dependent formation of lactate and glycerate occurs by way of their respective thioesters. Attention is given to the significance of these reactions in the context of molecular evolution.

  10. XAFS study on structural order in highly monodispersed thiol-stabilized Au nanoparticles

    International Nuclear Information System (INIS)

    Huang, Y; Liu, W; Yang, L; Huang, T; Jiang, Y; Yao, T; Wei, S

    2016-01-01

    Understanding the influence of thiol on nanoparticle size and structure is essential for the fundamental and applied researches. Here, using x-ray absorption fine structure (XAFS) spectroscopy, we investigate the structural order of Au nanoparticles (NPs) in the protection of thiol ligands with different contents. We found that besides protecting Au NPs against aggregation and growth, thiolates can effectively eliminate the dangling bonds of unsaturated Au atoms, and thus increase the structural order. This work enriches our knowledge of Au-S interface interaction and guides the way towards preparing size-controllable nanoparticles with specific physical/chemical properties. (paper)

  11. Multifunctional monomers based on vinyl sulfonates and vinyl sulfonamides for crosslinking thiol-Michael polymerizations: monomer reactivity and mechanical behavior.

    Science.gov (United States)

    Sinha, Jasmine; Podgórski, Maciej; Huang, Sijia; Bowman, Christopher N

    2018-03-25

    Multifunctional vinyl sulfonates and vinyl sulfonamides were conveniently synthesized and assessed in thiol-Michael crosslinking polymerizations. The monomer reactivities, mechanical behavior and hydrolytic properties were analyzed and compared with those of analogous thiol-acrylate polymerizations. Materials with a broad range of mechanical properties and diverse hydrolytic stabilities were obtained.

  12. Formation of Underbrushes on thiolated Poly (ethylene glycol) PEG monolayers by Oligoethylene glycol (OEG) terminated Alkane Thiols on Gold

    DEFF Research Database (Denmark)

    Lokanathan, Arcot R.

    2011-01-01

    of the molecule in superior resistance towards protein adsorption. The surfaces with underbrushes were imaged using atomic force microscopy (AFM) to detect any changes in mechanical properties of PEG thiol covered surfaces upon addition of OEG thiol. References: 1. Katsumi Uchida, Yuki Hoshino, Atsushi Tamura...

  13. Negishi Cross-Coupling Is Compatible with a Reactive B-Cl Bond: Development of a Versatile Late-Stage Functionalization of 1,2-Azaborines and Its Application to the Synthesis of New BN Isosteres of Naphthalene and Indenyl.

    Science.gov (United States)

    Brown, Alec N; Li, Bo; Liu, Shih-Yuan

    2015-07-22

    The compatibility of the Negishi cross-coupling reaction with the versatile B-Cl functionality has been demonstrated in the context of late-stage functionalization of 1,2-azaborines. Alkyl-, aryl-, and alkenylzinc reagents have been utilized for the functionalization of the triply orthogonal precursor 3-bromo-1-(tert-butyldimethylsilyl)-2-chloro-1,2-dihydro-1,2-azaborine (2) to furnish new 2,3-substituted monocyclic 1,2-azaborines. This methodology has enabled the synthesis of previously elusive BN-naphthalene and BN-indenyl structures from a common intermediate.

  14. Cross-coupling reactions of unprotected halopurine bases, nucleosides, nucleotides and nucleoside triphosphates with 4-boronophenylalanine in water. Synthesis of (purin-8-yl)- and (purin-6-yl)phenylalanines.

    Science.gov (United States)

    Capek, Petr; Pohl, Radek; Hocek, Michal

    2006-06-07

    An expeditious and highly efficient single-step methodology for the introduction of a phenylalanine moiety into position 8 and 6 of the purine scaffold was developed based on aqueous-phase Pd-catalysed Suzuki-Miyaura cross-coupling reactions of unprotected 4-boronophenylalanine with 8-bromo- or 6-chloropurines. The scope of the methodology was demonstrated by syntheses of unprotected (adenin-8-yl)phenylalanine base, nucleosides, nucleotides and nucleoside triphosphates as well as (purin-6-yl)phenylalanine base and nucleosides. All these products were obtained in high yields and in optically pure form.

  15. "Grafting to" of RAFTed Responsive Polymers to Glass Substrates by Thiol-Ene and Critical Comparison to Thiol-Gold Coupling.

    Science.gov (United States)

    Biggs, Caroline I; Walker, Marc; Gibson, Matthew I

    2016-08-08

    Surface-grafted polymers have been widely applied to modulate biological interfaces and introduce additional functionality. Polymers derived from reversible addition-fragmentation transfer (RAFT) polymerization have a masked thiol at the ω-chain end providing an anchor point for conjugation and in particular displays high affinity for gold surfaces (both flat and particulate). In this work, we report the direct grafting of RAFTed polymers by a "thiol-ene click" (Michael addition) onto glass substrates rather than gold, which provides a more versatile surface for subsequent array-based applications but retains the simplicity. The immobilization of two thermoresponsive polymers are studied here, poly[oligo(ethylene glycol) methyl ether methacrylate] (pOEGMA) and poly(N-isopropylacrylamide) (pNIPAM). Using a range of surface analysis techniques the grafting efficiency was compared to thiol-gold and was quantitatively compared to the gold alternative using quartz crystal microbalance. It is shown that this method gives easy access to grafted polymer surfaces with pNIPAM resulting in significantly increased surface coverage compared to pOEGMA. The nonfouling (protein resistance) character of these surfaces is also demonstrated.

  16. Simple Preparation of Thiol-Ene Particles in Glycerol and Surface Functionalization by Thiol-Ene Chemistry (TEC) and Surface Chain Transfer Free Radical Polymerization (SCT-FRP).

    Science.gov (United States)

    Hoffmann, Christian; Chiaula, Valeria; Yu, Liyun; Pinelo, Manuel; Woodley, John M; Daugaard, Anders E

    2018-01-01

    Thiol-ene (TE)-based polymer particles are traditionally prepared via emulsion polymerization in water (using surfactants, stabilizers, and cosolvents). Here, a green and simple alternative is presented with excellent control over particle size, while avoiding the addition of stabilizers. Glycerol is applied as a dispersing medium for the preparation of off-stoichiometric TE microparticles, where sizes in the range of 40-400 µm are obtained solely by changing the mixing speed of the emulsions prior to crosslinking. Control over surface chemistry is achieved by surface functionalization of excess thiol groups via photochemical thiol-ene chemistry resulting in a functional monolayer. In addition, surface chain transfer free radical polymerization is used for the first time to introduce a thicker polymer layer on the particle surface. The application potential of the system is demonstrated by using functional particles as adsorbent for metal ions and as a support for immobilized enzymes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Multiple shape memory polymers based on laminates formed from thiol-click chemistry based polymerizations.

    Science.gov (United States)

    Podgórski, M; Wang, C; Bowman, C N

    2015-09-14

    This investigation details the formation of polymer network trilayer laminates formed by thiol-X click chemistries, and their subsequent implementation and evaluation for quadruple shape memory behavior. Thiol-Michael addition and thiol-isocyanate-based crosslinking reactions were employed to fabricate each of the laminate's layers with independent control of the chemistry and properties of each layer and outstanding interlayer adhesion and stability. The characteristic features of step-growth thiol-X reactions, such as excellent network uniformity and narrow thermal transitions as well as their stoichiometric nature, enabled fabrication of trilayer laminates with three distinctly different glass transition temperatures grouped within a narrow range of 100 °C. Through variations in the layer thicknesses, a step-wise modulus drop as a function of temperature was achieved. This behavior allowed multi-step programming and the demonstration and quantification of quadruple shape memory performance. As is critical for this performance, the interface connecting the layers was evaluated in stoichiometric as well as off-stoichiometric systems. It was shown that the laminated structures exhibit strong interfacial binding and hardly suffer any delamination during cyclic material testing and deformation.

  18. Thiol-ene reaction as tool for crosslinking of polynorbornene micelles in the nanoscale

    Science.gov (United States)

    Rupp, Barbara; Bauer, Thomas; Slugovc, Christian

    2009-08-01

    The thiol-ene reaction is a established photoreaction of multifunctional thiols and enes. Virtually any type of ene will participate in a free radical polymerisation process with a thiol. An advantage over many other photochemical reactions is that the reaction proceeds almost as rapidly in ambient conditions as in inert atmosphere. In this work we introduce the UV-crosslinking of polynorbornenes made by ring opening metathesis polymerization making use of the residual double bond in the polymer backbone. The crosslinking experiments were done in thin films and were followed by FTIR measurements, to proof the accessibility of double-bonds in the polymers for the addition of the thiols. As a result of these pre-experiments we created flexible and light transmitting films. To further increase the scope of this reaction, amphiphilic block copolymers were prepared and used to form block copolymer micelles in a selective solvent, which were subsequently crosslinked with pentaerythritol tetra(3-mercaptopropionate) (PETMP). FT-IR, DLS and SEM-measurements were used to prove the successful crosslinking and thus nanoparticle formation.

  19. Investigations of thiol-modified phenol derivatives for the use in thiol–ene photopolymerizations

    Science.gov (United States)

    Reinelt, Sebastian; Tabatabai, Monir; Fischer, Urs Karl; Moszner, Norbert; Utterodt, Andreas

    2014-01-01

    Summary Thiol–ene photopolymerizations gain a growing interest in academic research. Coatings and dental restoratives are interesting applications for thiol–ene photopolymerizations due to their unique features. In most studies the relative flexible and hydrophilic ester derivative, namely pentaerythritoltetra(3-mercaptopropionate) (PETMP), is investigated as the thiol component. Thus, in the present study we are encouraged to investigate the performance of more hydrophobic ester-free thiol-modified bis- and trisphenol derivatives in thiol–ene photopolymerizations. For this, six different thiol-modified bis- and trisphenol derivatives exhibiting four to six thiol groups are synthesized via the radical addition of thioacetic acid to suitable allyl-modified precursors and subsequent hydrolysis. Compared to PETMP better flexural strength and modulus of elasticity are achievable in thiol–ene photopolymerizations employing 1,3,5-triallyl-1,3,5-triazine-2,4,6-trione (TATATO) as the ene derivative. Especially, after storage in water, the flexural strength and modulus of elasticity is twice as high compared to the PETMP reference system. PMID:25161731

  20. Investigations of thiol-modified phenol derivatives for the use in thiol–ene photopolymerizations

    Directory of Open Access Journals (Sweden)

    Sebastian Reinelt

    2014-07-01

    Full Text Available Thiol–ene photopolymerizations gain a growing interest in academic research. Coatings and dental restoratives are interesting applications for thiol–ene photopolymerizations due to their unique features. In most studies the relative flexible and hydrophilic ester derivative, namely pentaerythritoltetra(3-mercaptopropionate (PETMP, is investigated as the thiol component. Thus, in the present study we are encouraged to investigate the performance of more hydrophobic ester-free thiol-modified bis- and trisphenol derivatives in thiol–ene photopolymerizations. For this, six different thiol-modified bis- and trisphenol derivatives exhibiting four to six thiol groups are synthesized via the radical addition of thioacetic acid to suitable allyl-modified precursors and subsequent hydrolysis. Compared to PETMP better flexural strength and modulus of elasticity are achievable in thiol–ene photopolymerizations employing 1,3,5-triallyl-1,3,5-triazine-2,4,6-trione (TATATO as the ene derivative. Especially, after storage in water, the flexural strength and modulus of elasticity is twice as high compared to the PETMP reference system.

  1. Sytematic Study of the Adsorption of Thiol Molecules on Noble-Metal Nanoparticles

    Science.gov (United States)

    Barron, H.; Hidalgo, F.; Fernandez-Seivane, L.; Noguez, C.; Lopez-Lozano, X.

    2012-03-01

    The study of the interaction between nanoparticles and different types of ligands has been intensively investigated in the last years due to the potential contribution of their properties to the nanotechnology device design. These properties have opened new research fields like plasmonics, with interesting applications in optics, electronics, biophysics, medicine, pharmacology and materials science. Self-assembly monolayers have been thoroughly studied at experimental and theoretical level on extended (111) gold and silver surfaces. However, nanoparticle and molecule properties after the adsorption are still not well understood due to the different factors involved in this process such as the adsorption sites, size and element type of the nanoparticle. In this work we have performed a systematic study of the adsorption of methyl-thiol molecules on Au55 and Ag55 clusters through density functional theory calculations with the SIESTA code. Different adsorption modes of the methyl-thiol molecule on Au55 and Ag55 were considered. In general, for both type of nanoparticles, the methyl-thiol molecule prefers to be adsorbed on the Bridge sites. These results provide valuable information of the structural and electronic properties of methyl-thiol passivated Au and Ag nanoparticles.

  2. Factors influencing the oxidation of cysteamine and other thiols: implications for hyperthermic sensitization and radiation protection

    International Nuclear Information System (INIS)

    Biaglow, J.E.; Issels, R.W.; Gerweck, L.E.; Varnes, M.E.; Jacobson, B.; Mittchell, J.B.; Russo, A.

    1984-01-01

    Some of the factors influencing the oxygen uptake and peroxide formation for cysteamine (MEA) and other thiols in serum-supplemented modified McCoy's 5A, a well-known medium used to cultivate a variety of cells in vitro, have been studied. The oxidation of MEA and cysteine in modified McCoy's 5A has been compared with that in Ham's F-12, MEM, and phosphate-buffered saline. The ability to produce peroxide is dependent upon the temperature, the concentration of thiol, the presence of copper ions, and pH of the medium. Catalase also reduces the oxygen uptake for all thiols. Superoxide dismutase (SOD) was found to stimulate the oxygen uptake in the case of MEA and cysteine, but had little or no effect with DTT and glutathione. The combined presence of SOD and catalase resulted in less inhibition of oxygen uptake than that obtained by catalase alone. Alkaline pH was found to enhance the oxidation of cysteine and MEA. The results indicate that many problems may arise when thiols are added to various media. A major consideration is concerned with the production of peroxide, superoxide, and reduced trace metal intermediates. The presence of these intermediates may result in the production of hydroxyl radical intermediates as well as the eventual oxygen depletion from the medium

  3. Chemical groups and structural characterization of lignin via thiol-mediated demethylation

    Science.gov (United States)

    Lihong Hu; Hui Pan; Yonghong Zhou; Chung-Yun Hse; Chengguo Liu; Baofang Zhang; Bin Xu

    2014-01-01

    A new approach to increase the reactivity of lignin by thiol-mediated demethylation was investigated in this study. Demethylated lignin was characterized by the changes in its hydroxyl and methoxyl groups, molecular weight, and other properties using titration and spectroscopy methods including FT-IR, 1H NMR, UV,and GPC. The total...

  4. NitroxylFluor: A Thiol-Based Fluorescent Probe for Live-Cell Imaging of Nitroxyl.

    Science.gov (United States)

    Pino, Nicholas W; Davis, Jerome; Yu, Zhengxin; Chan, Jefferson

    2017-12-27

    Detection of nitroxyl (HNO), the transient one-electron reduced form of nitric oxide, is a significant challenge owing to its high reactivity with biological thiols (with rate constants as high as 10 9  M -1 s -1 ). To address this, we report a new thiol-based HNO-responsive trigger that can compete against reactive thiols for HNO. This process forms a common N-hydroxysulfenamide intermediate that cyclizes to release a masked fluorophore leading to fluorescence enhancement. To ensure that the cyclization step is rapid, our design capitalizes on two established physical organic phenomena; the alpha-effect and the Thorpe-Ingold effect. Using this new trigger, we developed NitroxylFluor, a selective HNO-responsive fluorescent probe. Treatment of NitroxylFluor with an HNO donor results in a 16-fold turn-on. This probe also exhibits excellent selectivity over various reactive nitrogen, oxygen, and sulfur species and efficacy in the presence of thiols (e.g., glutathione in mM concentrations). Lastly, we successfully performed live cell imaging of HNO using NitroxylFluor.

  5. Thimerosal Exposure and the Role of Sulfation Chemistry and Thiol Availability in Autism

    Directory of Open Access Journals (Sweden)

    Mark R. Geier

    2013-08-01

    Full Text Available Autism spectrum disorder (ASD is a neurological disorder in which a significant number of the children experience a developmental regression characterized by a loss of previously acquired skills and abilities. Typically reported are losses of verbal, nonverbal, and social abilities. Several recent studies suggest that children diagnosed with an ASD have abnormal sulfation chemistry, limited thiol availability, and decreased glutathione (GSH reserve capacity, resulting in a compromised oxidation/reduction (redox and detoxification capacity. Research indicates that the availability of thiols, particularly GSH, can influence the effects of thimerosal (TM and other mercury (Hg compounds. TM is an organomercurial compound (49.55% Hg by weight that has been, and continues to be, used as a preservative in many childhood vaccines, particularly in developing countries. Thiol-modulating mechanisms affecting the cytotoxicity of TM have been identified. Importantly, the emergence of ASD symptoms post-6 months of age temporally follows the administration of many childhood vaccines. The purpose of the present critical review is provide mechanistic insight regarding how limited thiol availability, abnormal sulfation chemistry, and decreased GSH reserve capacity in children with an ASD could make them more susceptible to the toxic effects of TM routinely administered as part of mandated childhood immunization schedules.

  6. Heat- and light-induced thiol-ene oligomerization of soybean oil-based polymercaptan

    Science.gov (United States)

    Polymercaptanized soybean oil (PMSO), the product of a thiol-ene reaction between soybean oil and hydrogen sulfide, is a material of interest as a lubricant additive and polymer precursor. We investigated with gel permeation chromatography, nuclear magnetic resonance (one-dimensional and two-dimensi...

  7. Gold Nanoparticles Protected with Thiol-Derivatized Amphiphilic Poly(epsilon-caprolactone)-b-poly(acrylic acid)

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli; Hvilsted, Søren

    2009-01-01

    ) of tent-butyl acrylate (tBA) in a controlled fashion by use of NiBr2(PPh3)(2) catalyst to produce Prot-PCL-b-PtBA with narrow polydispersities (1.17-1.39). Subsequent mild deprotection protocols provided HS-PCL-b-PAA. Reduction of a gold salt in the presence of this macroligand under thiol...

  8. Gold Nanoparticles Protected with Thiol-Derivatized Amphiphilic Poly( -caprolactone)-b-poly(acrylic acid)

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli; Hvilsted, Søren

    2008-01-01

    distribution (1.09). The hydroxy chain end of Br-PCL-OR was modified by reacting with a-(2,4-dinitrophenylthio)acetic acid or a-(4methoxytritylthio) acetic acid resulting in heterotelechelic PCL incorporating protected thiol and bromoester functionalities. It was then employed as macroinitiator in NiBr2(PPh3...

  9. Thiol-reducing agents prevent sulforaphane-induced growth inhibition in ovarian cancer cells.

    Science.gov (United States)

    Kim, Seung Cheol; Choi, Boyun; Kwon, Youngjoo

    2017-01-01

    The inhibitory potential of sulforaphane against cancer has been suggested for different types of cancer, including ovarian cancer. We examined whether this effect is mediated by mitogen-activated protein kinase (MAPK) and reactive oxygen species (ROS), important signaling molecules related to cell survival and proliferation, in ovarian cancer cells. Sulforaphane at a concentration of 10 μM effectively inhibited the growth of cancer cells. Use of specific inhibitors revealed that activation of MAPK pathways by sulforaphane is unlikely to mediate sulforaphane-induced growth inhibition. Sulforaphane did not generate significant levels of intracellular ROS. Pretreatment with thiol reducers, but not ROS scavengers, prevented sulforaphane-induced growth inhibition. Furthermore, diamide, a thiol-oxidizing agent, enhanced both growth inhibition and cell death induced by sulforaphane, suggesting that the effect of sulforaphane on cell growth may be related to oxidation of protein thiols or change in cellular redox status. Our data indicate that supplementation with thiol-reducing agents should be avoided when sulforaphane is used to treat cancer.

  10. Effect of thione-thiol tautomerism on the inhibition of lactoperoxidase ...

    Indian Academy of Sciences (India)

    The keto-enol type tautomerism in anti-thyroid drugs and their selenium analogues are described. The commonly used anti-thyroid drug methimazole exists predominantly in its thione form, whereas its selenium analogue exists in a zwitterionic form. To understand the effect of thione/thiol and selone/selenol tautomerism on ...

  11. Quantitative interpretation of the transition voltages in gold-poly(phenylene) thiol-gold molecular junctions

    KAUST Repository

    Wu, Kunlin

    2013-01-01

    The transition voltage of three different asymmetric Au/poly(phenylene) thiol/Au molecular junctions in which the central molecule is either benzene thiol, biphenyl thiol, or terphenyl thiol is investigated by first-principles quantum transport simulations. For all the junctions, the calculated transition voltage at positive polarity is in quantitative agreement with the experimental values and shows weak dependence on alterations of the Au-phenyl contact. When compared to the strong coupling at the Au-S contact, which dominates the alignment of various molecular orbitals with respect to the electrode Fermi level, the coupling at the Au-phenyl contact produces only a weak perturbation. Therefore, variations of the Au-phenyl contact can only have a minor influence on the transition voltage. These findings not only provide an explanation to the uniformity in the transition voltages found for π-conjugated molecules measured with different experimental methods, but also demonstrate the advantage of transition voltage spectroscopy as a tool for determining the positions of molecular levels in molecular devices. © 2013 AIP Publishing LLC.

  12. Aroma extraction dilution analysis of Sauternes wines. Key role of polyfunctional thiols.

    Science.gov (United States)

    Bailly, Sabine; Jerkovic, Vesna; Marchand-Brynaert, Jacqueline; Collin, Sonia

    2006-09-20

    The aim of the present work was to investigate Sauternes wine aromas. In all wine extracts, polyfunctional thiols were revealed to have a huge impact. A very strong bacon-petroleum odor emerged at RI = 845 from a CP-Sil5-CB column. Two thiols proved to participate in this perception: 3-methyl-3-sulfanylbutanal and 2-methylfuran-3-thiol. A strong synergetic effect was evidenced between the two compounds. The former, never mentioned before in wines, and not found in the musts of this study, is most probably synthesized during fermentation. 3-Methylbut-2-ene-1-thiol, 3-sulfanylpropyl acetate, 3-sulfanylhexan-1-ol, and 3-sulfanylheptanal also contribute to the global aromas of Sauternes wines. Among other key odorants, the presence of a varietal aroma (alpha-terpineol), sotolon, fermentation alcohols (3-methylbutan-1-ol and 2-phenylethanol) and esters (ethyl butyrate, ethyl hexanoate, and ethyl isovalerate), carbonyls (trans-non-2-enal and beta-damascenone), and wood flavors (guaiacol, vanillin, eugenol, beta-methyl-gamma-octalactone, and Furaneol) is worth stressing.

  13. The reaction of cinnamaldehyde and cinnam(oyl derivatives with thiols

    Directory of Open Access Journals (Sweden)

    Alessandro Autelitano

    2017-07-01

    Full Text Available Spurred by the alleged relevance of the thia-Michael reaction in the bioactivity of various classes of cinnam(oyl natural products and by the development of a quick NMR assay to study this reaction, we have carried out a systematic study of the “native” reactivity of these compounds with dodecanethiol and cysteamine as models, respectively, of simple thiols and reactive protein thiols that can benefit from iminium ion catalysis in Michael reactions. Cinnamoyl esters and amides, as well as cinnamyl ketones and oximes, did not show any reactivity with the two probe thiols, while cinnamaldehyde (1a reacted with cysteamine to afford a mixture of a thiazoline derivative and compounds of multiple addition, and with aliphatic thiols to give a single bis-dithioacetal (6. Chalchones and their vinylogous C5-curcuminoid derivatives were the only cinnamoyl derivatives that gave a thia-Michael reaction. From a mechanistic standpoint, loss of conjugation in the adduct might underlie the lack of a native Michael reactivity. This property is restored by the presence of another conjugating group on the carbonyl, as in chalcones and C5-curcuminoids. A critical mechanistic revision of the chemical and biomedical literature on cinnamaldehyde and related compounds seems therefore required.

  14. Thiol-functionalized silica colloids, grains, and membranes for irreversible adsorption of metal(oxide) nanoparticles

    NARCIS (Netherlands)

    Claesson, E.M.; Philipse, A.P.

    2007-01-01

    Thiol-functionalization is described for silica surfaces from diverging origin, including commercial silica nanoparticles and St¨ober silica as well as silica structures provided by porous glasses and novel polymer-templated silica membranes. The functionalization allows in all cases for the

  15. Monitoring of Saccharomyces cerevisiae cell proliferation on thiol-modified planar gold microelectrodes using impedance spectroscopy

    DEFF Research Database (Denmark)

    Heiskanen, Arto; Spegel, Christer F; Kostesha, Natalie

    2008-01-01

    An impedance spectroscopic study of the interaction between thiol-modified Au electrodes and Saccharomyces cerevisiae of strain EBY44 revealed that the cells formed an integral part of the interface, modulating the capacitive properties until a complete monolayer was obtained, whereas the charge ...

  16. Cooperative functions of manganese and thiol redox system against oxidative stress in human spermatozoa

    Directory of Open Access Journals (Sweden)

    Amrit Kaur Bansal

    2009-01-01

    Full Text Available Aims: In this study, the effects of 0.1 mM Mn 2+ on thiol components (total thiols [TSH], glutathione reduced [GSH], glutathione oxidized [GSSG] and redox ratio [GSH/ GSSG] have been determined in human spermatozoa. Settings and Design: The subjects of the study were healthy males having more than 75% motility and 80 x 10 6 sperms/mL. Materials and Methods: Fresh semen was suspended in phosphate-buffered saline (PBS (pH 7.2 and this suspension was divided into eight equal fractions. All fractions, control (containing PBS and experimental (treated/untreated with [ferrous ascorbate, FeAA - 200 FeSO 4 μM, 1000 μM ascorbic acid, nicotine (0.5 mM and FeAA + nicotine], supplemented/unsupplemented with Mn 2+ [0.1 mM], were incubated for 2 h at 378C. These fractions were assessed for determining the thiol components. Statistical Analysis: The data were statistically analyzed by Students " t" test. Results and Conclusions: Ferrous ascorbate, nicotine and ferrous ascorbate + nicotine induced oxidative stress and decreased GSH and redox ratio (GSH/GSSG ratio but increased the TSH and GSSG levels. Mn 2+ supplementation improved TSH, GSH and redox ratio (GSH/GSSG but decreased the GSSG level under normal and oxidative stress conditions. Thiol groups serve as defense mechanisms of sperm cells to fight against oxidative stress induced by stress inducers such as ferrous ascorbate, nicotine and their combination (ferrous ascorbate + nicotine. In addition, Mn 2+ supplementation maintains the thiol level by reducing oxidative stress.

  17. Mitochondrial thiol modification by a targeted electrophile inhibits metabolism in breast adenocarcinoma cells by inhibiting enzyme activity and protein levels

    Directory of Open Access Journals (Sweden)

    M. Ryan Smith

    2016-08-01

    Full Text Available Many cancer cells follow an aberrant metabolic program to maintain energy for rapid cell proliferation. Metabolic reprogramming often involves the upregulation of glutaminolysis to generate reducing equivalents for the electron transport chain and amino acids for protein synthesis. Critical enzymes involved in metabolism possess a reactive thiolate group, which can be modified by certain oxidants. In the current study, we show that modification of mitochondrial protein thiols by a model compound, iodobutyl triphenylphosphonium (IBTP, decreased mitochondrial metabolism and ATP in MDA-MB 231 (MB231 breast adenocarcinoma cells up to 6 days after an initial 24 h treatment. Mitochondrial thiol modification also depressed oxygen consumption rates (OCR in a dose-dependent manner to a greater extent than a non-thiol modifying analog, suggesting that thiol reactivity is an important factor in the inhibition of cancer cell metabolism. In non-tumorigenic MCF-10A cells, IBTP also decreased OCR; however the extracellular acidification rate was significantly increased at all but the highest concentration (10 µM of IBTP indicating that thiol modification can have significantly different effects on bioenergetics in tumorigenic versus non-tumorigenic cells. ATP and other adenonucleotide levels were also decreased by thiol modification up to 6 days post-treatment, indicating a decreased overall energetic state in MB231 cells. Cellular proliferation of MB231 cells was also inhibited up to 6 days post-treatment with little change to cell viability. Targeted metabolomic analyses revealed that thiol modification caused depletion of both Krebs cycle and glutaminolysis intermediates. Further experiments revealed that the activity of the Krebs cycle enzyme, aconitase, was attenuated in response to thiol modification. Additionally, the inhibition of glutaminolysis corresponded to decreased glutaminase C (GAC protein levels, although other protein levels were

  18. Functionalization of embedded thiol-ene waveguides for evanescent wave-induced fluorescence detection in a microfluidic device

    DEFF Research Database (Denmark)

    Feidenhans, Nikolaj A.; Jensen, Thomas Glasdam; Lafleur, Josiane P.

    2013-01-01

    functionalized with biotin using photografting. The biotin was used for immobilization of fluorescently labelled streptavidin, and experiments revealed a linear correlation between streptavidin concentration and fluorescent intensity. To further demonstrate the attractiveness of using thiol-ene for optofluidic...

  19. Nitroolefin-based BODIPY as a novel water-soluble ratiometric fluorescent probe for detection of endogenous thiols

    Science.gov (United States)

    Kang, Jin; Huo, Fangjun; Chao, Jianbin; Yin, Caixia

    2018-04-01

    Small molecule biothiols, including cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play many crucial roles in physiological processes. In this work, we have prepared a nitroolefin-based BODIPY fluorescent probe with excellent water solubility for detection thiols, which displayed ratiometric fluorescent signal for thiols. Incorporation of a nitroolefin unit to the BODIPY dye would transform it into a strong Michael acceptor, which would be highly susceptible to sulfhydryl nucleophiles. This probe shows an obvious ratio change upon response with thiols, an increase of the emission at 517 nm along with a concomitant decrease of fluorescence peak at 573 nm. Moreover, these successes of intracellular imaging experiments in A549 cells indicated that this probe is suitable for imaging of ex-/endogenous thiols in living cells.

  20. Thiol- and Biotin-Labeled Probes for Oligonucleotide Quartz Crystal Microbalance Biosensors of Microalga Alexandrium Minutum

    Directory of Open Access Journals (Sweden)

    Mathieu Lazerges

    2012-07-01

    Full Text Available Two quartz crystal microbalance oligonucleotide biosensors of a toxic microalga gene sequence (Alexandrium Minutum have been designed. Grafting on a gold surface of 20-base thiol- or biotin-labeled probe, and selective hybridization with the complementary 20-base target, have been monitored in situ with a 27 MHz quartz crystal microbalance under controlled hydrodynamic conditions. The frequency of the set up is stable to within a few hertz, corresponding to the nanogram scale, for three hour experiments. DNA recognition by the two biosensors is efficient and selective. Hybridization kinetic curves indicate that the biosensor designed with the thiol-labeled probe is more sensitive, and that the biosensor designed with the biotin-labeled probe has a shorter time response and a higher hybridization efficiency.

  1. Field effect on digestive ripening of thiol-capped gold nanoparticles

    International Nuclear Information System (INIS)

    Lin, Meng-Lin; Peng, J. S.; Lee, Sanboh; Yang, Fuqian

    2014-01-01

    We studied the digestive ripening of thiol-capped gold nanoparticles under simultaneous action of electric field and reflux heating in a silicone oil bath at 130 °C, using transmission electron microscopy. Observation revealed that a polydispersed gold nanoparticle system reached the state of nearly monodispersity under the action of an electric field and the thiol-capped gold nanoparticles carried negative charges. The electric field caused the increase of the particle size for the nearly monodispersed gold nanoparticle system. The self-assembly of the nearly monodisperse gold nanoparticles under the action of an electric field of a high field intensity was observed. The gold nanoparticles tended to form self-assembled nanostructures of six-fold symmetry. This study provides a new route for system engineering to control the particle size of metallic nanoparticles by electric field and digestive ripening

  2. Synthesis and Biological Evaluation of Novel Benzothiazole-2-thiol Derivatives as Potential Anticancer Agents

    Directory of Open Access Journals (Sweden)

    Luo-Ting Yu

    2012-03-01

    Full Text Available A series of novel benzothiazole-2-thiol derivatives were synthesized and their structures determined by 1H-NMR, 13C-NMR and HRMS (ESI. The effects of all compounds on a panel of different types of human cancer cell lines were investigated. Among them, pyridinyl-2-amine linked benzothiazole-2-thiol compounds 7d, 7e, 7f and 7i exhibited potent and broad-spectrum inhibitory activities. Compound 7e displayed the most potent anticancer activity on SKRB-3 (IC50 = 1.2 nM, SW620 (IC50 = 4.3 nM, A549 (IC50 = 44 nM and HepG2 (IC50 = 48 nM and was found to induce apoptosis in HepG2 cancer cells.

  3. Pre-fermentation addition of grape tannin increases the varietal thiols content in wine.

    Science.gov (United States)

    Larcher, Roberto; Tonidandel, Loris; Román Villegas, Tomás; Nardin, Tiziana; Fedrizzi, Bruno; Nicolini, Giorgio

    2015-01-01

    The recent finding that grape tannin may contain significant amount of S-glutathionylated (GSH-3MH) and S-cysteinylated (Cys-3MH) precursors of the varietal thiols 3-mercapto-1-hexanol and 3-mercaptohexyl acetate, characteristic of Sauvignon blanc wines, offers new opportunities for enhancing the tropical aroma in fermented beverages. In this study this new hypothesis was investigated: Müller Thurgau (17 samples) and Sauvignon blanc (15 samples) grapes were fermented with and without addition of a selected grape tannin. As expected, the tannin-added juices were higher in precursors, and they produced wines with increased free thiols. Preliminary informal sensory tests confirmed that in particular the Sauvignon wines produced with the tannin addition were often richer with increased "fruity/green" notes than the corresponding reference wines. This outcome confirms that grape tannin addition prior to fermentation can fortify the level of these compounds. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. On the Reactions of Thiols, Sulfenic Acids, and Sulfinic Acids with Hydrogen Peroxide.

    Science.gov (United States)

    Chauvin, Jean-Philippe R; Pratt, Derek A

    2017-05-22

    The reaction of thiols with H 2 O 2 is central to many processes essential to life, from protein folding to redox signaling. The initial products are assumed to be sulfenic acids, but their observation, and the kinetic and mechanistic characterization of their subsequent reactions, has proven challenging. The introduction of a 9-fluorotriptycene substituent enabled the use of 19 F NMR to directly monitor the reaction of a thiol with H 2 O 2 to yield a sulfenic acid, and its subsequent oxidation to sulfinic and sulfonic acids. The oxidations are specific base catalyzed, as revealed by the lack of isotope effects and the dependence of the kinetics on pH but not buffer concentration. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Highly stretchable thermoset fibers and nonwovens using thiol-ene photopolymerization.

    Science.gov (United States)

    Shanmuganathan, Kadhiravan; Elliot, Steven M; Lane, Austin P; Ellison, Christopher J

    2014-08-27

    In this report, we describe the preparation and characterization of a new class of thermoset fibers with high elongation and elastic recovery. Integrating UV-activated thiol-ene photopolymerization and electrospinning, we demonstrate an environmentally friendly single step approach to convert small monomeric precursor molecules into highly elastic fibers and nonwoven mats. The fibers were derived by in situ photopolymerization of a trifunctional vinyl ether monomer and a tetrafunctional thiol. Although thermosets often offer good chemical and thermal stability, these fibers also have a high average elongation at break of 62%. The elastomeric nature of these vinyl-ether based fibers can be partly attributed to their subambient Tg and partly to the cross-link density, monomer structure, and resulting network homogeneity. Nonwoven mats of these fibers were also stretchable and exhibited a much higher elongation at break of about 85%. These thermoset stretchable fibers could have potential applications as textile, biomedical, hot chemical filtration, and composite materials.

  6. Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction

    OpenAIRE

    Saed, Mohand O.; Torbati, Amir H.; Nair, Devatha P.; Yakacki, Christopher M.

    2016-01-01

    This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline elastomers (LCEs) with facile control over network structure and programming of an aligned monodomain. Tailored LCE networks were synthesized using routine mixing of commercially available starting materials and pouring monomer solutions into molds to cure. An initial polydomain LCE network is formed via a self-limiting thiol-acrylate Michael-addi...

  7. Contribution of captopril thiol group to the prevention of spontaneous hypertension

    Czech Academy of Sciences Publication Activity Database

    Pecháňová, Olga

    2007-01-01

    Roč. 56, Suppl.2 (2007), S41-S48 ISSN 0862-8408 Grant - others:VEGA(SK) 2/6148/26; VEGA(SK) 1/3429/06; APPV(SK) 0586-06 Institutional research plan: CEZ:AV0Z50110509 Keywords : captopril and enalapril * thiols * spontaneous hypertension Subject RIV: FA - Cardiovascular Diseases incl. Cardiotharic Surgery Impact factor: 1.505, year: 2007

  8. Ruthenium(III Chloride Catalyzed Acylation of Alcohols, Phenols, and Thiols in Room Temperature Ionic Liquids

    Directory of Open Access Journals (Sweden)

    Mingzhong Cai

    2009-09-01

    Full Text Available Ruthenium(III chloride-catalyzed acylation of a variety of alcohols, phenols, and thiols was achieved in high yields under mild conditions (room temperature in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]. The ionic liquid and ruthenium catalyst can be recycled at least 10 times. Our system not only solves the basic problem of ruthenium catalyst reuse, but also avoids the use of volatile acetonitrile as solvent.

  9. Programmable Liquid Crystal Elastomers Prepared by Thiol-Ene Photopolymerization (Postprint)

    Science.gov (United States)

    2015-08-17

    hierarchical) orientation of liquid crystal polymers can be used to generate bending and torsional deflections.20 Hierarchical variation is...mercaptopropionate), which has a molecular weight per thiol of 122 g/mol. These formulations did not exhibit the required combination of a readily alignable nematic...nematic director to the long axis of the sample by 30° (Figure S1) produces torsional deformations. On heating, the sample morphs from flat to a twisted

  10. Functionalized 3D Architected Materials via Thiol-Michael Addition and Two-Photon Lithography.

    Science.gov (United States)

    Yee, Daryl W; Schulz, Michael D; Grubbs, Robert H; Greer, Julia R

    2017-04-01

    Fabrication of functionalized 3D architected materials is achieved by a facile method using functionalized acrylates synthesized via thiol-Michael addition, which are then polymerized using two-photon lithography. A wide variety of functional groups can be attached, from Boc-protected amines to fluoroalkanes. Modification of surface wetting properties and conjugation with fluorescent tags are demonstrated to highlight the potential applications of this technique. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Resin-assisted enrichment of thiols as a general strategy for proteomic profiling of cysteine-based reversible modifications

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Jia [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Gaffrey, Matthew J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Su, Dian [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Genentech Inc., South San Francisco, CA (United States); Liu, Tao [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Camp, David G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Smith, Richard D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Qian, Weijun [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2013-12-12

    Reversible modifications on cysteine thiols play a significant role in redox signaling and regulation. A number of reversible redox modifications, including disulfide formation, S-nitrosylation, and S-glutathionylation, have been recognized for their significance in various physiological and pathological processes. Here we describe in detail a resin-assisted thiol-affinity enrichment protocol for both biochemical and proteomics applications. This protocol serves as a general approach for specific isolation of thiol-containing proteins or peptides derived from reversible redox-modified proteins. This approach utilizes thiol-affinity resins to directly capture thiol-containing proteins or peptides through a disulfide exchange reaction followed by on-resin protein digestion and on-resin multiplexed isobaric labeling to facilitate LC-MS/MS based quantitative site-specific analysis of redox modifications. The overall approach requires a much simpler workflow with increased specificity compared to the commonly used biotin switch technique. By coupling different selective reduction strategies, the resin-assisted approach provides the researcher with a useful tool capable of enriching different types of reversible modifications on protein thiols. Procedures for selective enrichment and analyses of S-nitrosylation and total reversible cysteine oxidation are presented to demonstrate the utility of this general strategy.

  12. Improvement of aromatic thiol release through the selection of yeasts with increased β-lyase activity.

    Science.gov (United States)

    Belda, Ignacio; Ruiz, Javier; Navascués, Eva; Marquina, Domingo; Santos, Antonio

    2016-05-16

    The development of a selective medium for the rapid differentiation of yeast species with increased aromatic thiol release activity has been achieved. The selective medium was based on the addition of S-methyl-l-cysteine (SMC) as β-lyase substrate. In this study, a panel of 245 strains of Saccharomyces cerevisiae strains was tested for their ability to grow on YCB-SMC medium. Yeast strains with an increased β-lyase activity grew rapidly because of their ability to release ammonium from SMC in comparison to others, and allowed for the easy isolation and differentiation of yeasts with promising properties in oenology, or another field, for aromatic thiol release. The selective medium was also helpful for the discrimination between those S. cerevisiae strains, which present a common 38-bp deletion in the IRC7 sequence (present in around 88% of the wild strains tested and are likely to be less functional for 4-mercapto-4-methylpentan-2-one (4MMP) production), and those S. cerevisiae strains homozygous for the full-length IRC7 allele. The medium was also helpful for the selection of non-Saccharomyces yeasts with increased β-lyase activity. Based on the same medium, a highly sensitive, reproducible and non-expensive GC-MS method for the evaluation of the potential volatile thiol release by different yeast isolates was developed. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Superhydrophobic hybrid inorganic-organic thiol-ene surfaces fabricated via spray-deposition and photopolymerization.

    Science.gov (United States)

    Sparks, Bradley J; Hoff, Ethan F T; Xiong, Li; Goetz, James T; Patton, Derek L

    2013-03-13

    We report a simple and versatile method for the fabrication of superhydrophobic inorganic-organic thiol-ene coatings via sequential spray-deposition and photopolymerization under ambient conditions. The coatings are obtained by spray-deposition of UV-curable hybrid inorganic-organic thiol-ene resins consisting of pentaerythritol tetra(3-mercaptopropionate) (PETMP), triallyl isocyanurate (TTT), 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (TMTVSi), and hydrophobic fumed silica nanoparticles. The spray-deposition process and nanoparticle agglomeration/dispersion provide surfaces with hierarchical morphologies exhibiting both micro- and nanoscale roughness. The wetting behavior, dependent on the concentration of TMTVSi and hydrophobic silica nanoparticles, can be varied over a broad range to ultimately provide coatings with high static water contact angles (>150°), low contact angle hysteresis, and low roll off angles (<5°). The cross-linked thiol-ene coatings are solvent resistant, stable at low and high pH, and maintain superhydrophobic wetting behavior after extended exposure to elevated temperatures. We demonstrate the versatility of the spray-deposition and UV-cure process on a variety of substrate surfaces including glass, paper, stone, and cotton fabric.

  14. Characterization of plasma thiol redox potential in a common marmoset model of aging

    Directory of Open Access Journals (Sweden)

    James R. Roede

    2013-01-01

    Full Text Available Due to its short lifespan, ease of use and age-related pathologies that mirror those observed in humans, the common marmoset (Callithrix jacchus is poised to become a standard nonhuman primate model of aging. Blood and extracellular fluid possess two major thiol-dependent redox nodes involving cysteine (Cys, cystine (CySS, glutathione (GSH and glutathione disulfide (GSSG. Alteration in these plasma redox nodes significantly affects cellular physiology, and oxidation of the plasma Cys/CySS redox potential (EhCySS is associated with aging and disease risk in humans. The purpose of this study was to determine age-related changes in plasma redox metabolites and corresponding redox potentials (Eh to further validate the marmoset as a nonhuman primate model of aging. We measured plasma thiol redox states in marmosets and used existing human data with multivariate adaptive regression splines (MARS to model the relationships between age and redox metabolites. A classification accuracy of 70.2% and an AUC of 0.703 were achieved using the MARS model built from the marmoset redox data to classify the human samples as young or old. These results show that common marmosets provide a useful model for thiol redox biology of aging.

  15. Limiting the Hydrolysis and Oxidation of Maleimide-Peptide Adducts Improves Detection of Protein Thiol Oxidation.

    Science.gov (United States)

    Boyatzis, Amber E; Bringans, Scott D; Piggott, Matthew J; Duong, Marisa N; Lipscombe, Richard J; Arthur, Peter G

    2017-05-05

    Oxidative stress, caused by reactive oxygen and nitrogen species (RONS), is important in the pathophysiology of many diseases. A key target of RONS is the thiol group of protein cysteine residues. Because thiol oxidation can affect protein function, mechanistic information about how oxidative stress affects tissue function can be ascertained by identifying oxidized proteins. The probes used must be specific and sensitive, such as maleimides for the alkylation of reduced cysteine thiols. However, we find that maleimide-alkylated peptides (MAPs) are oxidized and hydrolyzed under sample preparation conditions common for proteomic studies. This can result in up to 90% of the MAP signal being converted to oxidized or hydrolyzed MAPs, decreasing the sensitivity of the analysis. A substantial portion of these modifications were accounted for by Coomassie "blue silver" staining (∼14%) of gels and proteolytic digestion buffers (∼20%). More than 40% of the MAP signal can be retained with the use of thioglycolic acid during gel electrophoresis, trichloroethanol-UV protein visualization in gels, and proteolytic digestion buffer of pH 7.0 TRIS. This work demonstrates that it is possible to decrease modifications to MAPs through changes to the sample preparation workflow, enhancing the potential usefulness of maleimide in identifying oxidized peptides.

  16. Quantification of Polyfunctional Thiols in Wine by HS-SPME-GC-MS Following Extractive Alkylation.

    Science.gov (United States)

    Musumeci, Lauren E; Ryona, Imelda; Pan, Bruce S; Loscos, Natalia; Feng, Hui; Cleary, Michael T; Sacks, Gavin L

    2015-07-06

    Analyses of key odorous polyfunctional volatile thiols in wines (3-mercaptohexanol (3-MH), 3-mercaptohexylacetate (3-MHA), and 4-mercapto-4-methyl-2-pentanone (4-MMP)) are challenging due to their high reactivity and ultra-trace concentrations, especially when using conventional gas-chromatography electron impact mass spectrometry (GC-EI-MS). We describe a method in which thiols are converted to pentafluorobenzyl (PFB) derivatives by extractive alkylation and the organic layer is evaporated prior to headspace solid phase microextraction (HS-SPME) and GC-EI-MS analysis. Optimal parameters were determined by response surface area modeling. The addition of NaCl solution to the dried SPME vials prior to extraction resulted in up to less than fivefold improvement in detection limits. Using 40 mL wine samples, limits of detection for 4-MMP, 3-MH, and 3-MHA were 0.9 ng/L, 1 ng/L, and 17 ng/L, respectively. Good recovery (90%-109%) and precision (5%-11% RSD) were achieved in wine matrices. The new method was used to survey polyfunctional thiol concentrations in 61 commercial California and New York State wines produced from V. vinifera (Riesling, Gewürztraminer, Cabernet Sauvignon, Sauvignon blanc and non-varietal rosé wines), V. labruscana (Niagara), and Vitis spp. (Cayuga White). Mean 4-MMP concentrations in New York Niagara (17 ng/L) were not significantly different from concentrations in Sauvignon blanc, but were significantly higher than 4-MMP in other varietal wines.

  17. Thiol-Functionalized Mesoporous Silica for Effective Trap of Mercury in Rats

    Directory of Open Access Journals (Sweden)

    Wei Zhao

    2016-01-01

    Full Text Available The chance of exposure to heavy metal for human being rises severely today due to the increasing water contamination and air pollution. Here, we prepared a series of thiol-functionalized mesoporous silica as oral formulation for the prevention and treatment of heavy metal poisoning. The successful incorporation of thiol was verified by the FTIR spectra. SBA15-SH-10 was used for the study as it is of uniform mesopores and fine water dispersibility. In simulated gastrointestinal fluid, the thiol-functionalized mesoporous silica can selectively capture heavy metal, showing a very high affinity for inorganic mercury (II. The blood and urine mercury levels of rats fed with a diet containing Hg (II and material were significantly lower than those of rats fed with the metal-rich diet only. On the contrary, the mercury content in fecal excretion of the treatment group increased more than twice as much as that of the control group. This result indicated that SBA15-SH-10 could effectively remove mercury (II in vivo and the mercury loaded on SBA15-SH-10 would be excreted out. Hence, SBA15-SH-10 has potential application in preventing and treating heavy metal poisoning via digestive system.

  18. Endoplasmic Reticulum Thiol Oxidase Deficiency Leads to Ascorbic Acid Depletion and Noncanonical Scurvy in Mice

    Science.gov (United States)

    Zito, Ester; Hansen, Henning Gram; Yeo, Giles S.H.; Fujii, Junichi; Ron, David

    2012-01-01

    Summary Endoplasmic reticulum (ER) thiol oxidases initiate a disulfide relay to oxidatively fold secreted proteins. We found that combined loss-of-function mutations in genes encoding the ER thiol oxidases ERO1α, ERO1β, and PRDX4 compromised the extracellular matrix in mice and interfered with the intracellular maturation of procollagen. These severe abnormalities were associated with an unexpectedly modest delay in disulfide bond formation in secreted proteins but a profound, 5-fold lower procollagen 4-hydroxyproline content and enhanced cysteinyl sulfenic acid modification of ER proteins. Tissue ascorbic acid content was lower in mutant mice, and ascorbic acid supplementation improved procollagen maturation and lowered sulfenic acid content in vivo. In vitro, the presence of a sulfenic acid donor accelerated the oxidative inactivation of ascorbate by an H2O2-generating system. Compromised ER disulfide relay thus exposes protein thiols to competing oxidation to sulfenic acid, resulting in depletion of ascorbic acid, impaired procollagen proline 4-hydroxylation, and a noncanonical form of scurvy. PMID:22981861

  19. Thiol-Ene Based Polymer Waveguides Fabricated By Uv-Assisted Soft Lithography For Optofluidic Applications

    DEFF Research Database (Denmark)

    Zhuang, Guisheng; Jensen, Thomas Glasdam; Kutter, Jörg Peter

    2011-01-01

    In this paper, a thiol-ene based polymer waveguide, defined by UV-assisted soft lithography, is designed, fabricated and characterized. Waveguides are formed by filling microfluidic channels with a high refractive index liquid mixture of ‘thiol’ and ‘ene’ monomers (e.g., trimethylolpropane tris(3...... thiol-ene based polymers as waveguide core materials for potential optofluidic applications.......In this paper, a thiol-ene based polymer waveguide, defined by UV-assisted soft lithography, is designed, fabricated and characterized. Waveguides are formed by filling microfluidic channels with a high refractive index liquid mixture of ‘thiol’ and ‘ene’ monomers (e.g., trimethylolpropane tris(3......-mercaptopropionate) = ‘thiol’, and 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione = ‘ene’), which can be cured by UV exposure into a solid polymer. The waveguides demonstrated good confinement of light, and a propagation loss of 0.5 dB/cm was obtained. To our best knowledge, this is the first report to employ...

  20. The chemical foundations of nitroalkene fatty acid signaling through addition reactions with thiols.

    Science.gov (United States)

    Turell, Lucía; Steglich, Martina; Alvarez, Beatriz

    2018-03-22

    Nitroalkene fatty acids can be formed in vivo and administered exogenously. They exert pleiotropic signaling actions with cytoprotective and antiinflammatory effects. The presence of the potent electron withdrawing nitro group confers electrophilicity to the adjacent β-carbon. Thiols (precisely, thiolates) are strong nucleophiles and can react with nitroalkene fatty acids through reversible Michael addition reactions. In addition, nitroalkene fatty acids can undergo several other processes including metabolic oxidation, reduction, esterification, nitric oxide release and partition into hydrophobic compartments. The signaling actions of nitroalkenes are mainly mediated by reactions with critical thiols in regulatory proteins. Thus, the thio-Michael addition reaction provides a framework for understanding the molecular basis of the biological effects of nitroalkene fatty acids at the crossroads of thiol signaling and electrophilic lipid signaling. In this review, we describe the reactions of nitroalkene fatty acids in biological contexts. We focus on the thio-Michael addition reaction and its mechanism, and extrapolate kinetic and thermodynamic considerations to in vivo settings. Copyright © 2018. Published by Elsevier Inc.

  1. The maize benzoxazinone DIMBOA reacts with glutathione and other thiols to form spirocyclic adducts.

    Science.gov (United States)

    Dixon, David P; Sellars, Jonathan D; Kenwright, Alan M; Steel, Patrick G

    2012-05-01

    Maize, wheat and other grasses synthesise large quantities of benzoxazinones and their glucosides, which act as antifeedant and allelopathic agents. These activities are probably due to the electrophilic nature of the aglycones, however, the mechanism of their action is unclear. In biological systems, glutathione (GSH) is the major electrophile-reactive compound so the reaction of the major maize benzoxazinone DIMBOA with GSH was studied. GSH reacts with DIMBOA to form eight isomeric mono-conjugates and eight isomeric di-conjugates. Through NMR studies with the model thiol 2-mercaptoethanol, these were structurally elucidated as unusual spirocycles. Similar reactivity was observed with proteins, with cysteinyl thiols being modified by DIMBOA. The thioether bonds formed were stable and not easily reduced to the parent thiol. DIMBOA can therefore readily deplete GSH levels and irreversibly inactivate enzymes with active-site cysteine residues, with clear implications for potentially toxic effects when young grasses are ingested, whether by insect pests or humans. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. In situ photopolymerization of biomaterials by thiol-yne click chemistry.

    Science.gov (United States)

    Lomba, Miguel; Oriol, Luis; Alcalá, Rafael; Sánchez, Carlos; Moros, María; Grazú, Valeria; Serrano, José Luis; De la Fuente, Jesús M

    2011-11-10

    The thiol-yne click chemistry reaction has been used for the in situ photocrosslinking of an aliphatic hyperbranched polyester. The biocompatibility of the resulting networks has been studied and marked cytotoxicity was not found for HeLa (human cervical carcinoma) tumoral cells and COS7 fibroblasts. The photoinduced thiol-yne process allows the generation of patterned structures with different geometries in films by DLW and these materials can be used as substrates for cell adhesion. The influence of the substrate geometry on cell adhesion has been studied by culturing cells onto these substrates and a preference for the photopatterned polymeric material can be seen in some of the structures by contrast phase microscopy. Actin and vinculin fluorescent staining revealed different adhesion behavior for HeLa cells and COS7 fibroblasts and this could be assigned to the different motility of cells. The thiol-yne photoreaction has proven to be an attractive approach for the preparation of micropatterned biomaterials. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Design, Synthesis, and Characterization of Novel Thiol-Derivatized Ibuprofen Monolayer Protected Gold Clusters

    International Nuclear Information System (INIS)

    Lee, K.H.; Lee, K.H.; Lin, Y.Sh.; Huang, P.J.

    2013-01-01

    A series of new thiol-derivatized ibuprofen monolayer protected gold clusters have been prepared by amidation of ibuprofen with alkyl alcohol or aminophenol affording the carboxamide, N-hydroxyalkyl amide 2, and N-hydroxyphenyl amide 6, which were then tosylate with p-toluenesulfonyl chloride at hydroxyl group to give 3 and 7. Reactions of 3 and 7 with NaSH afforded the mercapto derivatives 4 and 8. Conducting Brust’s reaction with a 3:1 mole ratio of thiolate ibuprofen/ AuCl 4 - yielded polydisperse thiol-derivatized ibuprofen-MPCs 5 and 9. All compounds have been identified by NMR, MS, UV, and IR spectroscopies. Compounds 4 and 8 and the MPCs 5 and 9 have been investigated by using the method of 1 H NMR spectroscopy. The broadening of the signals from 0.8 to 2.0 ppm in 1 H NMR spectrum of MPCs 5 and 9 confirmed the success of the conjugation of thiol-containing derivatives with nano gold cluster.

  4. Catalytic effects by thioltransferase on the transfer of methylmercury and p-mercuribenzoate from macromolecules to low molecular weight thiol compounds

    Energy Technology Data Exchange (ETDEWEB)

    Eriksson, S.; Svenson, A.

    1978-01-01

    Thiol agarose and glyceraldehyde-3-phosphate dehydrogenase were blocked with methylmercury or p-mercuribenzoate. The exchange of mercurials between the thiol-containing polymers and glutathione or dithioerythritol was investigated. The activity of glyceraldehyde-3-phosphate dehydrogenase was inhibited by blocking thiol-groups with the mercury compounds. Inhibition was reversible when a short period of inactivation was used. Inactivation for longer periods resulted in reduced regain of enzyme activity. The activity was in part regained when either of the 2 thiol compounds was added. Thioltransferase, known to catalyze thiol-disulfide exchange reactions, increased the regain of glyceraldehyde-3-phosphate dehydrogenase activity to nearly the original value. Here, thioltransferase is proposed to catalyze the transfer of organomercurial from one thiol complex to another. Some consequences of the observations in vivo are discussed.

  5. Photoreduction of Hg(II) and photodemethylation of methylmercury: the key role of thiol sites on dissolved organic matter

    Science.gov (United States)

    Jeremiason, Jeffrey D.; Portner, Joshua C.; Aiken, George R.; Hiranaka, Amber J.; Dvorak, Michelle T.; Tran, Khuyen T.; Latch, Douglas E.

    2015-01-01

    This study examined the kinetics of photoreduction of Hg(II) and photodemethylation of methylmercury (MeHg+) attached to, or in the presence of, dissolved organic matter (DOM). Both Hg(II) and MeHg+ are principally bound to reduced sulfur groups associated with DOM in many freshwater systems. We propose that a direct photolysis mechanism is plausible for reduction of Hg(II) bound to reduced sulfur groups on DOM while an indirect mechanism is supported for photodemethylation of MeHg+ bound to DOM. UV spectra of Hg(II) and MeHg+ bound to thiol containing molecules demonstrate that the Hg(II)–S bond is capable of absorbing UV-light in the solar spectrum to a much greater extent than MeHg+–S bonds. Experiments with chemically distinct DOM isolates suggest that concentration of DOM matters little in the photochemistry if there are enough reduced S sites present to strongly bind MeHg+ and Hg(II); DOM concentration does not play a prominent role in photodemethylation other than to screen light, which was demonstrated in a field experiment in the highly colored St. Louis River where photodemethylation was not observed at depths ≥10 cm. Experiments with thiol ligands yielded slower photodegradation rates for MeHg+ than in experiments with DOM and thiols; rates in the presence of DOM alone were the fastest supporting an intra-DOM mechanism. Hg(II) photoreduction rates, however, were similar in experiments with only DOM, thiols plus DOM, or only thiols suggesting a direct photolysis mechanism. Quenching experiments also support the existence of an intra-DOM photodemethylation mechanism for MeHg+. Utilizing the difference in photodemethylation rates measured for MeHg+ attached to DOM or thiol ligands, the binding constant for MeHg+ attached to thiol groups on DOM was estimated to be 1016.7.

  6. Molecular Characterization of Thiols in Fossil Fuels by Michael Addition Reaction Derivatization and Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry.

    Science.gov (United States)

    Wang, Meng; Zhao, Suoqi; Liu, Xuxia; Shi, Quan

    2016-10-04

    Thiols widely occur in sediments and fossil fuels. However, the molecular composition of these compounds is unclear due to the lack of appropriate analytical methods. In this work, a characterization method for thiols in fossil fuels was developed on the basis of Michael addition reaction derivatization followed by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). Model thiol compound studies showed that thiols were selectively reacted with phenylvinylsulfone and transformed to sulfones with greater than 98% conversions. This method was applied to a coker naphtha, light and heavy gas oils, and crude oils from various geological sources. The results showed that long alkyl chain thiols are readily present in petroleum, which have up to 30 carbon atoms. Large DBE dispersity of thiols indicates that naphthenic and aromatic thiols are also present in the petroleum. This method is capable of detecting thiol compounds in the part per million range by weight. This method allows characterization of thiols in a complex hydrocarbon matrix, which is complementary to the comprehensive analysis of sulfur compounds in fossil fuels.

  7. Synthesis and characterization of thiol-ene functionalized siloxanes and evaluation of their polymerization kinetics, network properties, and dental applications

    Science.gov (United States)

    Cole, Megan A.

    We explored formation-structure-property relationships in thiol-ene functionalized oligosiloxanes to create crosslinked networks. Specifically, nine oligomers were synthesized, three with thiol-functional silane repeats and three with allyl-functional silane repeats. Structural variations in each oligomer were systematically induced through the incorporation of non-reactive repeats bearing either diphenyl or di-n-octyl moieties, and the oligomer molecular weight was limited by the presence of monofunctional silane condensation species. The molecular weights and chain compositions of all oligomers were ascertained and subsequently used in the evaluation of network properties formed upon photopolymerization of thiol- and ene-functional reactants. Polymerization kinetics of the thiol-ene functionalized siloxanes were also investigated using photoinitiation owing to the spatial and temporal control afforded by this technique. In particular, the effects of the viscosity of the ene-functionalized oligomer and the degree of thiol functionalization on the observed polymerization rate were determined. Results showed that the speed of polymerization varied with changes to the rate-limiting step, which was heavily influenced by neighboring non-reactive functionalities. Moreover, the thiol-ene reaction was found to exhibity unimolecular termination exclusively in siloxane-based systems. Proposed use of the thiol-ene functionalized siloxane system as a dental impression material necessitated the development of a redox initiation scheme. Evaluation of the benzoylperoxide/dimethyl-p-toluidine redox pair in traditional systems showed bulk thiol-ene polymerizations comparable to photoinitiation with the added advantage of uninhibited depth control, as also demonstrated in small molecule thiol-ene coupling reactions initiated by this same redox system. Application of the redox pair to the siloxane system allowed for the viscoelastic properties as well as the feature replication

  8. Reactivity of volatile thiols with polyphenols in a wine-model medium: impact of oxygen, iron, and sulfur dioxide.

    Science.gov (United States)

    Nikolantonaki, Maria; Chichuc, Igor; Teissedre, Pierre-Louis; Darriet, Philippe

    2010-02-15

    As volatile thiols are nucleophiles, they are capable of additional reactions with electrophiles. In enology, this concerns reactions between volatile or non-volatile thiols and oxidized phenolic compounds. Initial studies concerning the reactivity of volatile thiols with polyphenols showed that (+)-catechin played a detrimental role in the level of 3-sulfanylhexan-1-ol (3SH), in the absence of sulfur dioxide. Our experiment revealed that (-)-epicatechin was more reactive with volatile thiols than (+)-catechin. Furthermore, Fe (III) was shown to play a crucial role in catalyzing polyphenol oxidation reactions, by affecting the direct reaction of phenolic compounds with oxygen. It was noted that, even if the volatile thiols studied were members of the same chemical family, they exhibited a different behavior pattern under oxidation conditions. 2-furanmethanethiol (2FMT) was more reactive than 3-sulfanylhexan-1-ol with both (+)-catechin and (-)-epicatechin. In contrast, 4-methyl-4-sulfanylpentan-2-one (4MSP) was less reactive with these phenolics. Additionally, the vital role of sulfur dioxide in protecting 3-sulfanylhexan-1-ol, 2-furanmethanethiol, and 4-methyl-4-sulfanylpentan-2-one was demonstrated in the model medium. Copyright 2009 Elsevier B.V. All rights reserved.

  9. Oral-Fluid Thiol-Detection Test Identifies Underlying Active Periodontal Disease Not Detected by the Visual Awake Examination.

    Science.gov (United States)

    Queck, Katherine E; Chapman, Angela; Herzog, Leslie J; Shell-Martin, Tamara; Burgess-Cassler, Anthony; McClure, George David

    2018-03-20

    Periodontal disease in dogs is highly prevalent but can only be accurately diagnosed by performing an anesthetized oral examination with periodontal probing and dental radiography. In this study, 114 dogs had a visual awake examination of the oral cavity and were administered an oral-fluid thiol-detection test prior to undergoing a a full-mouth anesthetized oral examination and digital dental radiographs. The results show the visual awake examination underestimated the presence and severity of active periodontal disease. The thiol-detection test was superior to the visual awake examination at detecting the presence and severity of active periodontal disease and was an indicator of progression toward alveolar bone loss. The thiol-detection test detected active periodontal disease at early stages of development, before any visual cues were present, indicating the need for intervention to prevent periodontal bone loss. Early detection is important because without intervention, dogs with gingivitis (active periodontal disease) progress to irreversible periodontal bone loss (stage 2+). As suggested in the current AAHA guidelines, a thiol-detection test administered in conjunction with the visual awake examination during routine wellness examinations facilitates veterinarian-client communication and mitigates under-diagnosis of periodontal disease and underutilization of dental services. The thiol-detection test can be used to monitor the periodontal health status of the conscious patient during follow-up examinations based on disease severity.

  10. Synthesis and Optical Properties of Thiol Functionalized CdSe/ZnS (Core/Shell Quantum Dots by Ligand Exchange

    Directory of Open Access Journals (Sweden)

    Huaping Zhu

    2014-01-01

    Full Text Available The colloidal photoluminescent quantum dots (QDs of CdSe (core and CdSe/ZnS (core/shell were synthesized at different temperatures with different growth periods. Optical properties (i.e., UV/Vis spectra and photoluminescent emission spectra of the resulting QDs were investigated. The shell-protected CdSe/ZnS QDs exhibited higher photoluminescent (PL efficiency and stability than their corresponding CdSe core QDs. Ligand exchange with various thiol molecules was performed to replace the initial surface passivation ligands, that is, trioctylphosphine oxide (TOPO and trioctylphosphine (TOP, and the optical properties of the surface-modified QDs were studied. The thiol ligand molecules in this study included 1,4-benzenedimethanethiol, 1,16-hexadecanedithiol, 1,11-undecanedithiol, biphenyl-4,4′-dithiol, 11-mercapto-1-undecanol, and 1,8-octanedithiol. After the thiol functionalization, the CdSe/ZnS QDs exhibited significantly enhanced PL efficiency and storage stability. Besides surface passivation effect, such enhanced performance of thiol-functionalized QDs could be due to cross-linked assembly formation of dimer/trimer clusters, in which QDs are linked by dithiol molecules. Furthermore, effects of ligand concentration, type of ligand, and heating on the thiol stabilization of QDs were also discussed.

  11. The Synthesis of a Coumarin Carbohydrazide Dinuclear Copper Complex Based Fluorescence Probe and Its Detection of Thiols.

    Directory of Open Access Journals (Sweden)

    Guangjie He

    Full Text Available Small-molecule thiols, such as cysteine (CYS and glutathione (GSH, are essential for maintaining the cellular redox environment and play important roles in regulating various cellular physiological functions. A fluorescence probe (compound 1-Cu2+ for thiols based on coumarin carbohydrazide dinuclear copper complex was developed. Compound 1 was synthesized from the reaction of 7-(diethylamino-2-oxo-2H-chromene-3-carbohydrazide with 4-tert-butyl-2,6- diformylphenol. Accordingly, the copper complex (compound 1-Cu2+ was prepared by mixing compound 1 with 2 equivalents copper ions. Compound 1 had strong fluorescence while compound 1-Cu2+ hardly possessed fluorescence owing to the quenching nature of paramagnetism Cu2+ to the fluorescence molecule excited state. However, the fluorescence intensity of compound 1-Cu2+ was increased dramatically after the addition of thiol-containing amino acids, but not the other non-sulfhydryl amino acids. UV-vis absorption and fluorescence spectra indicated that compound 1-Cu2+ had good selectivity and sensitivity for thiols such as glutathione in CH3CN:H2O (3:2, v/v PBS solution. The fluorescence imaging experiments implied that compound 1-Cu2+ has potential application in thiol-containing amino acids detection in living cells.

  12. Mn2+-ZnSe/ZnS@SiO2 Nanoparticles for Turn-on Luminescence Thiol Detection

    Directory of Open Access Journals (Sweden)

    Mohammad S. Yazdanparast

    2017-08-01

    Full Text Available Biological thiols are antioxidants essential for the prevention of disease. For example, low levels of the tripeptide glutathione are associated with heart disease, cancer, and dementia. Mn2+-doped wide bandgap semiconductor nanocrystals exhibit luminescence and magnetic properties that make them attractive for bimodal imaging. We found that these nanocrystals and silica-encapsulated nanoparticle derivatives exhibit enhanced luminescence in the presence of thiols in both organic solvent and aqueous solution. The key to using these nanocrystals as sensors is control over their surfaces. The addition of a ZnS barrier layer or shell produces more stable nanocrystals that are isolated from their surroundings, and luminescence enhancement is only observed with thinner, intermediate shells. Tunability is demonstrated with dodecanethiol and sensitivities decrease with thin, medium, and thick shells. Turn-on nanoprobe luminescence is also generated by several biological thiols, including glutathione, N-acetylcysteine, cysteine, and dithiothreitol. Nanoparticles prepared with different ZnS shell thicknesses demonstrated varying sensitivity to glutathione, which allows for the tuning of particle sensitivity without optimization. The small photoluminescence response to control amino acids and salts indicates selectivity for thiols. Preliminary magnetic measurements highlight the challenge of optimizing sensors for different imaging modalities. In this work, we assess the prospects of using these nanoparticles as luminescent turn-on thiol sensors and for MRI.

  13. Investigations of step-growth thiol-ene polymerizations for novel dental restoratives.

    Science.gov (United States)

    Lu, Hui; Carioscia, Jacquelyn A; Stansbury, Jeffery W; Bowman, Christopher N

    2005-12-01

    The goal of this work was to investigate the feasibility of formulating novel dental restorative materials that utilize a step-growth thiol-ene photopolymerization. Particularly, we are aiming to significantly reduce the polymerization shrinkage and shrinkage stress while retaining adequate physical properties as compared to current dimethacrylatre-based systems. The thiol-ene system is composed of a 4:3 molar mixture of triallyl-1,3,5-triazine-2,4,6-trione (TATATO) and pentaerythritol tetramercaptopropionate (PETMP). The simultaneous measurement of shrinkage stress and functional group conversion was performed. Solvent extraction of unreacted monomers and dynamic mechanical analysis on the polymer networks that were formed were also studied. Flexural strength was measured for both filled and unfilled PETMP/TATATO and Bis-GMA/TEGDMA systems. Photopolymerization of PETMP/TATATO occurs at a much higher rate, with the maximum polymerization rate six times faster, than Bis-GMA/TEGDMA cured under the identical conditions. The results from the simultaneous measurement of shrinkage stress and conversion showed that the onset of shrinkage stress coincides with the delayed gel point conversion, which is predicted to be 41% for the 3:4 stoichiometric PETMP/TATATO resin composition. The maximum shrinkage stress developed for PETMP/TATATO was about 0.4 MPa, which was only approximately 14% of the maximum shrinkage stress of the Bis-GMA/TEGDMA system. Adequate flexural strength and flexural modulus values were obtained for both filled and unfilled PETMP/TATATO systems. The dramatically reduced shrinkage stress, increased polymerization rate, significance increased functional group conversion, and decreased leachable species are all benefits for the use-of thiol-ene systems as potential dental restorative materials.

  14. Thiol changes during epididymal maturation: a link to flagellar angulation in mouse spermatozoa?

    Science.gov (United States)

    Ijiri, T W; Vadnais, M L; Huang, A P; Lin, A M; Levin, L R; Buck, J; Gerton, G L

    2014-01-01

    Caput epididymal wild-type spermatozoa and cauda epididymal spermatozoa from mice null for the adenylyl cyclase Adcy10 gene are immotile unless stimulated by a membrane-permeant cyclic AMP analogue. Both types of spermatozoa exhibit flagellar angulation where the head folds back under these conditions. As sperm proteins undergo oxidation of sulfhydryl groups and the flagellum becomes more stable to external forces during epididymal transit, we hypothesized that ADCY10 is involved in a mechanism regulating flagellar stabilization. Although no differences were observed in global sulfhydryl status between caput and cauda epididymal spermatozoa from wild-type or Adcy10-null mice, two-dimensional fluorescence difference gel electrophoresis was performed to identify specific mouse sperm proteins containing sulfhydryl groups that became oxidized during epididymal maturation. A-kinase anchor protein 4, fatty acid-binding protein 9 (FABP9), glutathione S-transferase mu 5 and voltage-dependent anion channel 2 exhibited changes in thiol status between caput and cauda epididymal spermatozoa. The level and thiol status of each of these proteins were quantified in wild-type and Adcy10-null cauda epididymal spermatozoa. No differences in the abundance of any protein were observed; however, FABP9 in Adcy10-null cauda epididymal spermatozoa contained fewer disulfide bonds than wild-type sperm cells. In caput epididymal spermatozoa, FABP9 was detected in the cytoplasmic droplet, principal piece, midpiece, and non-acrosomal area of the head. However, in cauda epididymal spermatozoa, this protein localized to the perforatorium, post-acrosomal region and principal piece. Together, these results suggest that thiol changes during epididymal maturation have a role in the stabilization of the sperm flagellum. PMID:24254994

  15. Hydrophobic Coatings by Thiol-Ene Click Functionalization of Silsesquioxanes with Tunable Architecture.

    Science.gov (United States)

    Dirè, Sandra; Bottone, Davide; Callone, Emanuela; Maniglio, Devid; Génois, Isabelle; Ribot, François

    2017-08-08

    The hydrolysis-condensation of trialkoxysilanes under strictly controlled conditions allows the production of silsesquioxanes (SSQs) with tunable size and architecture ranging from ladder to cage-like structures. These nano-objects can serve as building blocks for the preparation of hybrid organic/inorganic materials with selected properties. The SSQs growth can be tuned by simply controlling the reaction duration in the in situ water production route (ISWP), where the kinetics of the esterification reaction between carboxylic acids and alcohols rules out the extent of organosilane hydrolysis-condensation. Tunable SSQs with thiol functionalities (SH-NBBs) are suitable for further modification by exploiting the simple thiol-ene click reaction, thus allowing for modifying the wettability properties of derived coatings. In this paper, coatings were prepared from SH-NBBs with different architecture onto cotton fabrics and paper, and further functionalized with long alkyl chains by means of initiator-free UV-induced thiol-ene coupling with 1-decene (C10) and 1-tetradecene (C14). The coatings appeared to homogeneously cover the natural fibers and imparted a multi-scale roughness that was not affected by the click functionalization step. The two-step functionalization of cotton and paper warrants a stable highly hydrophobic character to the surface of natural materials that, in perspective, suggests a possible application in filtration devices for oil-water separation. Furthermore, the purification of SH-NBBs from ISWP by-products was possible during the coating process, and this step allowed for the fast, initiator-free, click-coupling of purified NBBs with C10 and C14 in solution with a nearly quantitative yield. Therefore, this approach is an alternative route to get sol-gel-derived, ladder-like, and cage-like SSQs functionalized with long alkyl chains.

  16. Quantification of Polyfunctional Thiols in Wine by HS-SPME-GC-MS Following Extractive Alkylation

    Directory of Open Access Journals (Sweden)

    Lauren E. Musumeci

    2015-07-01

    Full Text Available Analyses of key odorous polyfunctional volatile thiols in wines (3-mercaptohexanol (3-MH, 3-mercaptohexylacetate (3-MHA, and 4-mercapto-4-methyl-2-pentanone (4-MMP are challenging due to their high reactivity and ultra-trace concentrations, especially when using conventional gas-chromatography electron impact mass spectrometry (GC-EI-MS. We describe a method in which thiols are converted to pentafluorobenzyl (PFB derivatives by extractive alkylation and the organic layer is evaporated prior to headspace solid phase microextraction (HS-SPME and GC-EI-MS analysis. Optimal parameters were determined by response surface area modeling. The addition of NaCl solution to the dried SPME vials prior to extraction resulted in up to less than fivefold improvement in detection limits. Using 40 mL wine samples, limits of detection for 4-MMP, 3-MH, and 3-MHA were 0.9 ng/L, 1 ng/L, and 17 ng/L, respectively. Good recovery (90%–109% and precision (5%–11% RSD were achieved in wine matrices. The new method was used to survey polyfunctional thiol concentrations in 61 commercial California and New York State wines produced from V. vinifera (Riesling, Gewürztraminer, Cabernet Sauvignon, Sauvignon blanc and non-varietal rosé wines, V. labruscana (Niagara, and Vitis spp. (Cayuga White. Mean 4-MMP concentrations in New York Niagara (17 ng/L were not significantly different from concentrations in Sauvignon blanc, but were significantly higher than 4-MMP in other varietal wines.

  17. Iron and thiols as two major players in carcinogenesis: friends or foes?

    Science.gov (United States)

    Toyokuni, Shinya

    2014-01-01

    Iron is the most abundant metal in the human body and mainly works as a cofactor for proteins such as hemoglobin and various enzymes. No independent life forms on earth can survive without iron. However, excess iron is intimately associated with carcinogenesis by increasing oxidative stress via its catalytic activity to generate hydroxyl radicals. Biomolecules with redox-active sulfhydryl function(s) (thiol compounds) are necessary for the maintenance of mildly reductive cellular environments to counteract oxidative stress, and for the execution of redox reactions for metabolism and detoxification. Involvement of glutathione S-transferase and thioredoxin has long attracted the attention of cancer researchers. Here, I update recent findings on the involvement of iron and thiol compounds during carcinogenesis and in cancer cells. It is now recognized that the cystine/glutamate transporter (antiporter) is intimately associated with ferroptosis, an iron-dependent, non-apoptotic form of cell death, observed in cancer cells, and also with cancer stem cells; the former with transporter blockage but the latter with its stabilization. Excess iron in the presence of oxygen appears the most common known mutagen. Ironically, the persistent activation of antioxidant systems via genetic alterations in Nrf2 and Keap1 also contributes to carcinogenesis. Therefore, it is difficult to conclude the role of iron and thiol compounds as friends or foes, which depends on the quantity/distribution and induction/flexibility, respectively. Avoiding further mutation would be the most helpful strategy for cancer prevention, and myriad of efforts are being made to sort out the weaknesses of cancer cells.

  18. Protein tyrosine nitration and thiol oxidation by peroxynitrite-strategies to prevent these oxidative modifications.

    Science.gov (United States)

    Daiber, Andreas; Daub, Steffen; Bachschmid, Markus; Schildknecht, Stefan; Oelze, Matthias; Steven, Sebastian; Schmidt, Patrick; Megner, Alexandra; Wada, Masayuki; Tanabe, Tadashi; Münzel, Thomas; Bottari, Serge; Ullrich, Volker

    2013-04-08

    The reaction product of nitric oxide and superoxide, peroxynitrite, is a potent biological oxidant. The most important oxidative protein modifications described for peroxynitrite are cysteine-thiol oxidation and tyrosine nitration. We have previously demonstrated that intrinsic heme-thiolate (P450)-dependent enzymatic catalysis increases the nitration of tyrosine 430 in prostacyclin synthase and results in loss of activity which contributes to endothelial dysfunction. We here report the sensitive peroxynitrite-dependent nitration of an over-expressed and partially purified human prostacyclin synthase (3.3 μM) with an EC50 value of 5 μM. Microsomal thiols in these preparations effectively compete for peroxynitrite and block the nitration of other proteins up to 50 μM peroxynitrite. Purified, recombinant PGIS showed a half-maximal nitration by 10 μM 3-morpholino sydnonimine (Sin-1) which increased in the presence of bicarbonate, and was only marginally induced by freely diffusing NO2-radicals generated by a peroxidase/nitrite/hydrogen peroxide system. Based on these observations, we would like to emphasize that prostacyclin synthase is among the most efficiently and sensitively nitrated proteins investigated by us so far. In the second part of the study, we identified two classes of peroxynitrite scavengers, blocking either peroxynitrite anion-mediated thiol oxidations or phenol/tyrosine nitrations by free radical mechanisms. Dithiopurines and dithiopyrimidines were highly effective in inhibiting both reaction types which could make this class of compounds interesting therapeutic tools. In the present work, we highlighted the impact of experimental conditions on the outcome of peroxynitrite-mediated nitrations. The limitations identified in this work need to be considered in the assessment of experimental data involving peroxynitrite.

  19. Protein Tyrosine Nitration and Thiol Oxidation by Peroxynitrite—Strategies to Prevent These Oxidative Modifications

    Science.gov (United States)

    Daiber, Andreas; Daub, Steffen; Bachschmid, Markus; Schildknecht, Stefan; Oelze, Matthias; Steven, Sebastian; Schmidt, Patrick; Megner, Alexandra; Wada, Masayuki; Tanabe, Tadashi; Münzel, Thomas; Bottari, Serge; Ullrich, Volker

    2013-01-01

    The reaction product of nitric oxide and superoxide, peroxynitrite, is a potent biological oxidant. The most important oxidative protein modifications described for peroxynitrite are cysteine-thiol oxidation and tyrosine nitration. We have previously demonstrated that intrinsic heme-thiolate (P450)-dependent enzymatic catalysis increases the nitration of tyrosine 430 in prostacyclin synthase and results in loss of activity which contributes to endothelial dysfunction. We here report the sensitive peroxynitrite-dependent nitration of an over-expressed and partially purified human prostacyclin synthase (3.3 μM) with an EC50 value of 5 μM. Microsomal thiols in these preparations effectively compete for peroxynitrite and block the nitration of other proteins up to 50 μM peroxynitrite. Purified, recombinant PGIS showed a half-maximal nitration by 10 μM 3-morpholino sydnonimine (Sin-1) which increased in the presence of bicarbonate, and was only marginally induced by freely diffusing NO2-radicals generated by a peroxidase/nitrite/hydrogen peroxide system. Based on these observations, we would like to emphasize that prostacyclin synthase is among the most efficiently and sensitively nitrated proteins investigated by us so far. In the second part of the study, we identified two classes of peroxynitrite scavengers, blocking either peroxynitrite anion-mediated thiol oxidations or phenol/tyrosine nitrations by free radical mechanisms. Dithiopurines and dithiopyrimidines were highly effective in inhibiting both reaction types which could make this class of compounds interesting therapeutic tools. In the present work, we highlighted the impact of experimental conditions on the outcome of peroxynitrite-mediated nitrations. The limitations identified in this work need to be considered in the assessment of experimental data involving peroxynitrite. PMID:23567270

  20. Thiol changes during epididymal maturation: a link to flagellar angulation in mouse spermatozoa?

    Science.gov (United States)

    Ijiri, T W; Vadnais, M L; Huang, A P; Lin, A M; Levin, L R; Buck, J; Gerton, G L

    2014-01-01

    Caput epididymal wild-type spermatozoa and cauda epididymal spermatozoa from mice null for the adenylyl cyclase Adcy10 gene are immotile unless stimulated by a membrane-permeant cyclic AMP analogue. Both types of spermatozoa exhibit flagellar angulation where the head folds back under these conditions. As sperm proteins undergo oxidation of sulfhydryl groups and the flagellum becomes more stable to external forces during epididymal transit, we hypothesized that ADCY10 is involved in a mechanism regulating flagellar stabilization. Although no differences were observed in global sulfhydryl status between caput and cauda epididymal spermatozoa from wild-type or Adcy10-null mice, two-dimensional fluorescence difference gel electrophoresis was performed to identify specific mouse sperm proteins containing sulfhydryl groups that became oxidized during epididymal maturation. A-kinase anchor protein 4, fatty acid-binding protein 9 (FABP9), glutathione S-transferase mu 5 and voltage-dependent anion channel 2 exhibited changes in thiol status between caput and cauda epididymal spermatozoa. The level and thiol status of each of these proteins were quantified in wild-type and Adcy10-null cauda epididymal spermatozoa. No differences in the abundance of any protein were observed; however, FABP9 in Adcy10-null cauda epididymal spermatozoa contained fewer disulfide bonds than wild-type sperm cells. In caput epididymal spermatozoa, FABP9 was detected in the cytoplasmic droplet, principal piece, midpiece, and non-acrosomal area of the head. However, in cauda epididymal spermatozoa, this protein localized to the perforatorium, post-acrosomal region and principal piece. Together, these results suggest that thiol changes during epididymal maturation have a role in the stabilization of the sperm flagellum. © 2013 American Society of Andrology and European Academy of Andrology.

  1. Characterization of thiol-functionalised silica films deposited on electrode surfaces

    Directory of Open Access Journals (Sweden)

    Ivana Cesarino

    2008-12-01

    Full Text Available Thiol-functionalised silica films were deposited on various electrode surfaces (gold, platinum, glassy carbon by spin-coating sol-gel mixtures in the presence of a surfactant template. Film formation occurred by evaporation induced self-assembly (EISA involving the hydrolysis and (cocondensation of silane and organosilane precursors on the electrode surface. The characterization of such material was performed by IR spectroscopy, thermogravimetry (TG, elemental analysis (EA, atomic force microscopy (AFM, scanning electron microscopy (SEM and cyclic voltammetry (CV.

  2. Subcellular Localization of Thiol-Capped CdTe Quantum Dots in Living Cells

    Directory of Open Access Journals (Sweden)

    Chen Ji-Yao

    2009-01-01

    Full Text Available Abstract Internalization and dynamic subcellular distribution of thiol-capped CdTe quantum dots (QDs in living cells were studied by means of laser scanning confocal microscopy. These unfunctionalized QDs were well internalized into human hepatocellular carcinoma and rat basophilic leukemia cells in vitro. Co-localizations of QDs with lysosomes and Golgi complexes were observed, indicating that in addition to the well-known endosome-lysosome endocytosis pathway, the Golgi complex is also a main destination of the endocytosed QDs. The movement of the endocytosed QDs toward the Golgi complex in the perinuclear region of the cell was demonstrated.

  3. “Oxygen sensing” by Na,K-ATPase: these miraculous thiols

    Directory of Open Access Journals (Sweden)

    Anna Bogdanova

    2016-08-01

    Full Text Available Control over the Na,K-ATPase function plays a central role in adaptation of the organisms to hypoxic and anoxic conditions. As the enzyme itself does not possess O2 binding sites its oxygen-sensitivity is mediated by a variety of redox-sensitive modifications including S-glutathionylation, S-nitrosylation and redox-sensitive phosphorylation. This is an overview of the current knowledge on the plethora of molecular mechanisms tuning the activity of the ATP-consuming Na,K-ATPase to the cellular metabolic activity. Recent findings suggest that oxygen-derived free radicals and H2O2, NO, and oxidised glutathione are the signalling messengers that make the Na,K-ATPase oxygen-sensitive. This very ancient signalling pathway targeting thiols of all three subunits of the Na,K-ATPase as well as redox-sensitive kinases sustains the enzyme activity at the optimal level avoiding terminal ATP depletion and maintaining the transmembrane ion gradients in cells of anoxia-tolerant species. We acknowledge the complexity of the underlying processes as we characterise the sources of reactive oxygen and nitrogen species production in hypoxic cells, and identify their targets, the reactive thiol groups which, upon modification, impact the enzyme activity. Structured accordingly, this review presents a summery on (i the sources of free radical production in hypoxic cells, (ii localisation of regulatory thiols within the Na,K-ATPase and the role reversible thiol modifications play in responses of the enzymes to a variety of stimuli (hypoxia, receptors’ activation control of the enzyme activity (iii redox-sensitive regulatory phosphorylation, and (iv the role of fine modulation of the Na,K-ATPase function in survival success under hypoxic conditions. The co-authors attempted to cover all the contradictions and standing hypotheses in the field and propose the possible future developments in this dynamic area of research, the importance of which is hard to overestimate

  4. Enhancing Electrophoretic Display Lifetime: Thiol-Polybutadiene Evaporation Barrier Property Response to Network Microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Cook, Caitlyn Christian [California State Polytechnic State Univ., San Luis Obispo, CA (United States)

    2017-02-27

    An evaporation barrier is required to enhance the lifetime of electrophoretic deposition (EPD) displays. As EPD functions on the basis of reversible deposition and resuspension of colloids suspended in a solvent, evaporation of the solvent ultimately leads to device failure. Incorporation of a thiol-polybutadiene elastomer into EPD displays enabled display lifetime surpassing six months in counting and catalyzed rigid display transition into a flexible package. Final flexible display transition to mass production compels an electronic-ink approach to encapsulate display suspension within an elastomer shell. Final thiol-polybutadiene photosensitive resin network microstructure was idealized to be dense, homogeneous, and expose an elastic response to deformation. Research at hand details an approach to understanding microstructural change within display elastomers. Polybutadiene-based resin properties are modified via polymer chain structure, with and without added aromatic urethane methacrylate difunctionality, and in measuring network response to variation in thiol and initiator concentration. Dynamic mechanical analysis results signify that cross-linked segments within a difunctionalized polybutadiene network were on average eight times more elastically active than that of linked segments within a non-functionalized polybutadiene network. Difunctionalized polybutadiene samples also showed a 2.5 times greater maximum elastic modulus than non-functionalized samples. Hybrid polymer composed of both polybutadiene chains encompassed TE-2000 stiffness and B-1000 elasticity for use in encapsulating display suspension. Later experiments measured kinetic and rheological response due to alteration in dithiol cross-linker chain length via real time Fourier transform infrared spectroscopy and real-time dynamic rheology. Distinct differences were discovered between dithiol resin systems, as maximum thiol conversion achieved in short and long chain length dithiols was 86% and

  5. Coumarin-based thiol chemosensor: synthesis, turn-on mechanism, and its biological application.

    Science.gov (United States)

    Jung, Hyo Sung; Ko, Kyoung Chul; Kim, Gun-Hee; Lee, Ah-Rah; Na, Yun-Cheol; Kang, Chulhun; Lee, Jin Yong; Kim, Jong Seung

    2011-03-18

    A new chemodosimetric probe (1) is reported that selectively detects thiols over other relevant biological species by the turning on of its fluorescence through a Michael type reaction. The fluorogenic process upon its reaction was revealed to be mediated by intramolecular charge transfer, as confirmed by time-dependent density functional theory calculations. The application of probe 1 to cells is also examined by confocal microscopy, and its cysteine preference was observed by an ex vivo LC-MS analysis of the cellular metabolite.

  6. A facile synthesis of new 5-aryl-thiophenes bearing sulfonamide moiety via Pd(0-catalyzed Suzuki–Miyaura cross coupling reactions and 5-bromothiophene-2-acetamide: As potent urease inhibitor, antibacterial agent and hemolytically active compounds

    Directory of Open Access Journals (Sweden)

    Mnaza Noreen

    2017-01-01

    Full Text Available The present study reports a convenient approach for the synthesis of thiophene sulfonamide derivatives (3a–3k via Suzuki cross coupling reaction. This method of synthesis involved the reactions of various aryl boronic acids and esters with 5-bromthiophene-2-sulfonamide (2 under mild and suitable temperature conditions. The compounds synthesized in the present study were subjected to urease inhibition and hemolytic activities. The substitution pattern and the electronic effects of different functional groups (i.e., Cl, CH3, OCH3, F etc. available on the aromatic ring are found to have significant effect on the overall results. The compound 5-Phenylthiophene-2-sulfonamide 3a showed the highest urease inhibition activity with IC50 value ∼ 30.8 μg/mL compared with the thiourea (used as standard having IC50 value ∼ 43 μg/mL. Moreover, almost all of the compounds were examined for the hemolytic activity against triton X-100 with positive results obtained in most of the cases. In addition, the antibacterial activities of the derivatives of 5-arylthiophene-2-sulfonamide and 5-bromothiophene-2-acetamide were also investigated during the course of the study.

  7. Ligand-Controlled Chemoselective C(acyl)–O Bond vs C(aryl)–C Bond Activation of Aromatic Esters in Nickel Catalyzed C(sp2)–C(sp3) Cross-Couplings

    KAUST Repository

    Chatupheeraphat, Adisak

    2018-02-20

    A ligand-controlled and site-selective nickel catalyzed Suzuki-Miyaura cross-coupling reaction with aromatic esters and alkyl organoboron reagents as coupling partners was developed. This methodology provides a facile route for C(sp2)-C(sp3) bond formation in a straightforward fashion by successful suppression of the undesired β-hydride elimination process. By simply switching the phosphorus ligand, the ester substrates are converted into the alkylated arenes and ketone products, respectively. The utility of this newly developed protocol was demonstrated by its wide substrate scope, broad functional group tolerance and application in the synthesis of key intermediates for the synthesis of bioactive compounds. DFT studies on the oxidative addition step helped rationalizing this intriguing reaction chemoselectivity: whereas nickel complexes with bidentate ligands favor the C(aryl)-C bond cleavage in the oxidative addition step leading to the alkylated product via a decarbonylative process, nickel complexes with monodentate phosphorus ligands favor activation of the C(acyl)-O bond, which later generates the ketone product.

  8. Quantifying changes in the cellular thiol-disulfide status during differentiation of B cells into antibody-secreting plasma cells

    DEFF Research Database (Denmark)

    Hansen, Rosa Rebecca Erritzøe; Otsu, Mieko; Braakman, Ineke

    2013-01-01

    Plasma cells produce and secrete massive amounts of disulfide-containing antibodies. To accommodate this load on the secretory machinery, the differentiation of resting B cells into antibody-secreting plasma cells is accompanied by a preferential expansion of the secretory compartments of the cells...... and by an up-regulation of enzymes involved in redox regulation and protein folding. We have quantified the absolute levels of protein thiols, protein disulfides, and glutathionylated proteins in whole cells. The results show that while the global thiol-disulfide state is affected to some extent...... by the differentiation, steady-state levels of glutathionylated protein thiols are less than 0.3% of the total protein cysteines, even in fully differentiated cells, and the overall protein redox state is not affected until late in differentiation, when large-scale IgM production is ongoing. A general expansion...

  9. CdS quantum dots for measurement of the size-dependent optical properties of thiol capping

    Science.gov (United States)

    Liji Sobhana, S. S.; Vimala Devi, M.; Sastry, T. P.; Mandal, Asit Baran

    2011-04-01

    The optical- and size-dependent properties of CdS quantum dots (QDs) were analyzed in the presence and absence of different capping agents in aqueous medium. The QDs have been characterized by UV-Vis, Photoluminescence, Fourier-transform infrared spectroscopy, X-ray diffraction, and Fluorescence lifetime measurements. QDs with the presence of thiol group in cubic phase with small grain size were observed in XRD and decrease in particle size of the same with increase in band gap is deduced through UV-Vis and XRD studies. The FT-IR spectrum confirms the interaction of thiol group with CdS. Fluorescence lifetime of capped QDs was higher compared to uncapped CdS QDs. The surface passivation of thiol group on CdS is shown in photoluminescence studies.

  10. Antioxidative Mechanisms of Sulfite and Protein-Derived Thiols during Early Stages of Metal Induced Oxidative Reactions in Beer.

    Science.gov (United States)

    Lund, Marianne N; Krämer, Anna C; Andersen, Mogens L

    2015-09-23

    The radical-mediated reactions occurring during the early stages of beer storage were studied by following the rate of oxygen consumption, radical formation as detected by electron spin resonance spectroscopy, and concentrations of the antioxidant compounds sulfite and thiols. Addition of either Fe(III) or Fe(II) had similar effects, indicating that a fast redox equilibrium is obtained between the two species in beer. Addition of iron in combination with hydrogen peroxide gave the most pronounced levels of oxidation due to a direct initiation of ethanol oxidation through generation of hydroxyl radicals by the Fenton reaction. The concentration of sulfite decreased more than the thiol concentration, suggesting that thiols play a secondary role as antioxidants by mainly quenching 1-hydroxyethyl radicals that are intermediates in the oxidation of ethanol. Increasing the temperature had a minor effect on the rate of oxygen consumption.

  11. Chitosan scaffold modified with D-(+) raffinose and enriched with thiol-modified gelatin for improved osteoblast adhesion

    International Nuclear Information System (INIS)

    Galli, C; Parisi, L; Smerieri, A; Lumetti, S; Manfredi, E; Macaluso, G M; Elviri, L; Bianchera, A; Bettini, R; Lagonegro, P

    2016-01-01

    The aim of the present study was to investigate whether chitosan-based scaffolds modified with D-(+) raffinose and enriched with thiol-modified gelatin could selectively improve osteoblast adhesion and proliferation. 2, 3 and 4.5% chitosan films were prepared. Chitosan suitability for tissue engineering was confirmed by protein adsorption assay. Scaffolds were incubated with a 2.5 mg ml −1 BSA solution and the decrease of protein content in the supernatants was measured by spectrophotometry. Chitosan films were then enriched with thiol-modified gelatin and their ability to bind BSA was also measured. Then, 2% chitosan discs with or without thiol-modified gelatin were used as culture substrates for MC3T3-E1 cells. After 72 h cells were stained with trypan blue or with calcein AM and propidium iodide for morphology, viability and proliferation assays. Moreover, cell viability was measured at 48, 72, 96 and 168 h to obtain a growth curve. Chitosan films efficiently bound and retained BSA proportionally to the concentration of chitosan discs. The amount of protein retained was higher on chitosan enriched with thiol-modified gelatin. Moreover, chitosan discs allowed the adhesion and the viability of cells, but inhibited their proliferation. The functionalization of chitosan with thiol-modified gelatin enhanced cell spreading and proliferation. Our data confirm that chitosan is a suitable material for tissue engineering. Moreover, our data show that the enrichment of chitosan with thiol-modified gelatin enhances its biological properties. (paper)

  12. Irreversible bonding of polyimide and polydimethylsiloxane (PDMS) based on a thiol-epoxy click reaction

    International Nuclear Information System (INIS)

    Hoang, Michelle V; Chung, Hyun-Joong; Elias, Anastasia L

    2016-01-01

    Polyimide is one of the most popular substrate materials for the microfabrication of flexible electronics, while polydimethylsiloxane (PDMS) is the most widely used stretchable substrate/encapsulant material. These two polymers are essential in fabricating devices for microfluidics, bioelectronics, and the internet of things; bonding these materials together is a crucial challenge. In this work, we employ click chemistry at room temperature to irreversibly bond polyimide and PDMS through thiol-epoxy bonds using two different methods. In the first method, we functionalize the surfaces of the PDMS and polyimide substrates with mercaptosilanes and epoxysilanes, respectively, for the formation of a thiol-epoxy bond in the click reaction. In the second method, we functionalize one or both surfaces with mercaptosilane and introduce an epoxy adhesive layer between the two surfaces. When the surfaces are bonded using the epoxy adhesive without any surface functionalization, an extremely small peel strength (<0.01 N mm −1 ) is measured with a peel test, and adhesive failure occurs at the PDMS surface. With surface functionalization, however, remarkably higher peel strengths of ∼0.2 N mm −1 (method 1) and  >0.3 N mm −1 (method 2) are observed, and failure occurs by tearing of the PDMS layer. We envision that the novel processing route employing click chemistry can be utilized in various cases of stretchable and flexible device fabrication. (paper)

  13. Roll-to-plate fabrication of microfluidic devices with rheology-modified thiol-ene resins

    International Nuclear Information System (INIS)

    Senkbeil, Silja; Aho, Johanna; Rantanen, Jukka; Lafleur, Josiane P; Kutter, Jörg P; Yde, Leif; Lindvold, Lars R; Stensborg, Jan F

    2016-01-01

    In this paper, the replication possibilities of microfluidic channels by UV-roll-to-plate fabrication were investigated and a study of rheology-modified thiol-ene for the application in such a UV-roll-to-plate setup was conducted. The system allows the manufacture of channels with aspect ratios of 2:1 and a maximal channel depth of 90 μ m as well as the sealing of the finished devices with patterning and sealing speeds of up to 19 m min −1 . By adding fumed silica nanoparticles to the uncured resins, it was possible to alter the rheological behavior of the resin system to fabricate shallow microfluidic channels with 40  ×  95 μ m cross-sectional dimensions. Moreover, deeper (90 μ m) channels can be fabricated with highly viscous resins based on thiol-terminated oligomers. As a demonstration, capillary electrophoresis chips were prepared and tested for a simple separation of two fluorescent dyes. (paper)

  14. Role of peroxide in the radioprotective action of thiols in E. coli

    International Nuclear Information System (INIS)

    Naeslund, M.; Fedorcsak, I.; Ehrenberg, L.

    1976-01-01

    The radioprotective action of cysteamine (MEA) and cysteine in E. coli is due partly to autoxidatively generated hydrogen peroxide (H 2 0 2 ). This effect, which predominates at low concentrations of the thiols (1-2 mM in neutral solution), is regularly correlated with a metabolic block, measured as inhibition of RNA synthesis. In experiments with E. coli 15 (autotroph) under exponential growth in complete medium, the role of H 2 0 2 was demonstrated by (a) a decreased radioprotective action if catalase was present in the medium; (b) a radioprotective action if H 2 0 2 added to the medium; (c) a decreased protective action in the absence of catalytically active copper; and (d) oxygen being required for the radioprotective action to develop. At higher concentrations of the thiols, their radioprotective action, and the accompanying metabolic block, are less dependent on H 2 0 2 generation and presumably due to a different mechanism. The radioprotective action of H 2 0 2 is possibly related to the radioprotective action in mammals of catalase inhibitors. (author)

  15. Thiol-Functionalized Gold-Nanoscale Organic Hybrid Materials-Attractive to Soft glasses

    Science.gov (United States)

    Agrawal, Akanksha; Archer, Lynden

    2014-03-01

    We report on the flow properties of self-suspended nanoparticles based on gold nanoparticles densely grafted with polyethylene glycol methyl ether thiol(PEG) chains. We studied the effect of temperature, olume fraction and polymer chain length on the transition from attractive glass to soft glassy flow behavior. Gold nanoparticles densely grafted with short PEG-thiol chains(MW 800,2kDa and 6kDa)are shown to form self-suspended systems over a range of polymer grafting densities and particle volume fractions, φ.Transmission electron and atomic force microscopy measurements reveal that the particles are uniformly dispersed. Oscillatory shear measurements performed on low φ systems show a two-step yielding behavior reflecting bond breaking and cage breaking transitions at the nanoscale; both characteristics of soft glassy materials dominated by attractive forces. With increased temperature a transition to one-step yielding and subsequently back to two-step yielding is observed. At high φ a single yielding transition and soft glassy flow behavior are observed. We employ SAXS, vibration spectroscopy, thermal analysis, and rheology to interrogate the configuration state of the tethered chains and particle-particle interactions in detail. King Abdullah Univeristy of Science and Technology (KAUST), National Science Foundation, Cornell Center for Materials Research (CCMR), Advance Photon Source at Argonne National Lab.

  16. Adsorption characteristics of self-assembled thiol and dithiol layer on gold

    International Nuclear Information System (INIS)

    Tlili, A.; Abdelghani, A.; Aguir, K.; Gillet, M.; Jaffrezic-Renault, N.

    2007-01-01

    Monolayers of functional proteins are important in many fields related to pure and applied biochemistry and biophysics. The formation of extended uniform protein monolayers by single- or multiple-step self-chemisorption depends on the quality of the functionalized gold surface. The optical and the electrical properties of the 1-nonanethiol and 1,9-nonanedithiol deposited on gold with the self-assembled technique were investigated. We use cyclic voltammetry and impedance spectroscopy to characterize the insulating properties of the two layers. The analysis of the impedance spectra in terms of equivalent circuit of the gold/electrolyte and gold/SAM/electrolyte interface allows defining the thickness of the two thiols and the percentage of coverage area. Atomic force microscopy, contact angle measurement and Fourier transform infra-red spectroscopy have been used for homogeneity, hydrophobic properties and molecular structure of the formed thiols layer, respectively. The measured thickness with impedance spectroscopy fit well the results found with atomic force microscopy

  17. Reaction of [3H]-taurine maleimide with platelet surface thiols

    International Nuclear Information System (INIS)

    Karl, D.W.; Mills, D.C.B.

    1986-01-01

    Taurine Maleimide (2-maleimidoethanesulfonate, TM) was synthesized from [2- 3 H]-taurine and methoxycarbonylmaleimide (MCM). The yield of a 1 μmol synthesis approached 100% (based on taurine) when MCM was used in 4-fold excess. The product (TM*) was purified by ion exchange chromatography. TM* reacted irreversibly with thiol groups on the surface of washed human platelets, leading to incorporation of radioactivity into platelet pellets. Incorporation was blocked by cysteine, mercuribenzenesulfonate (MBS), dithiobisnitrobenzoate, and N-ethylmaleimide, but not by taurine or by inhibitors of anion transport. Reaction of TM* with platelets showed the dependence on time and concentration characteristics of a bimolecular reaction. The number of reactive sites ranged from 1 to 5 x 10 5 /platelet, and the apparent rate constant from 1 to 3 x 10 3 /(M x min). TM was less effective than MBS as an inhibitor of platelet aggregation induced by several agents. TM had no effect on the uptake of serotonin, taurine, or phosphate by the platelets, processes which are sensitive to MBS. These differences, considered with the similarity in size and charge of TM and MBS, suggest that classes of thiols defined as exofacial by their accessibility to MBS can differ substantially in their reactivity with other impermeant reagents

  18. Differential Thiol-Based Switches Jump-Start Vibrio cholerae Pathogenesis

    Directory of Open Access Journals (Sweden)

    Zhi Liu

    2016-01-01

    Full Text Available Bacterial pathogens utilize gene expression versatility to adapt to environmental changes. Vibrio cholerae, the causative agent of cholera, encounters redox-potential changes when it transitions from oxygen-rich aquatic reservoirs to the oxygen-limiting human gastrointestinal tract. We previously showed that the virulence regulator AphB uses thiol-based switches to sense the anoxic host environment and transcriptionally activate the key virulence activator tcpP. Here, by performing a high-throughput transposon sequencing screen in vivo, we identified OhrR as another regulator that enables V. cholerae rapid anoxic adaptation. Like AphB, reduced OhrR binds to and regulates the tcpP promoter. OhrR and AphB displayed differential dynamics in response to redox-potential changes: OhrR is reduced more rapidly than AphB. Furthermore, OhrR thiol modification is required for rapid activation of virulence and successful colonization. This reveals a mechanism whereby bacterial pathogens employ posttranslational modifications of multiple transcription factors to sense and adapt to dynamic environmental changes.

  19. Arsenic affects the production of glucosinolate, thiol and phytochemical compounds: A comparison of two Brassica cultivars.

    Science.gov (United States)

    Pandey, Chandana; Augustine, Rehna; Panthri, Medha; Zia, Ismat; Bisht, Naveen C; Gupta, Meetu

    2017-02-01

    Arsenic (As), a non-essential metalloid, severely affects the normal functioning of plants, animals and humans. Plants play a crucial role in metabolic, physiological and numerous detoxification mechanisms to cope up with As induced stress. This study aimed to examine the differential response in two Brassica juncea cultivars, Varuna and Pusa Jagannath (PJn) exposed to different doses of As (50, 150, 300 μM) for 48 h duration. Change in morphological traits, concentration of individual as well as total GSL, sulfur related thiol proteins, sulfur content, and phytochemicals were analyzed in both cultivars. Accumulation pattern of As showed dose dependent accumulation in both the cultivars, being more in PJn. Our finding revealed that both cultivars were tolerant at low concentrations of As, while at higher concentration Varuna excelled over PJn. The increased tolerance of Varuna cultivar exposed to 150 and 300 μM concentration of As, correlated with its increased thiol related proteins, sulfur content and phytochemicals, which serves as defence strategy in the plant against oxidative stress. Differential pattern of total as well as individual GSLs content was observed in both Varuna and PJn cultivars. Varuna cultivar showed higher level of total and aliphatic GSLs, which serves as defence compound with other detoxification machineries to combat As stress. Our findings provide foundation for developing metalloid tolerant crops by analyzing the role of different genes involved in GSL mechanism and signaling pathways in different organs of plant. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  20. Journey of cystatins from being mere thiol protease inhibitors to at heart of many pathological conditions.

    Science.gov (United States)

    Shamsi, Anas; Bano, Bilqees

    2017-09-01

    Cystatins are thiol proteinase inhibitors (TPI), present ubiquitously in animals, plants and micro-organisms. These are not merely inhibitors rather they are at heart of many pathological conditions ranging from diabetes to renal failure. These are essential for maintenance of protein balance of the cell; once this balance gets disturbed, it may lead to cell death. Thus, cystatins cannot be merely regarded as TPI's as these have been found to play a pivotal role in tumorigenesis and neurodegenerative diseases. Many studies have reported the variation in cystatin level in incidences of different types of cancer; highlighting an important role played by these inhibitors in cancer development and progression. Cystatin C is increasingly replacing creatinine as a biomarker of glomerular filtration rate (GFR) thereby highlighting the importance of this important inhibitor. Some recent studies have also reported the interaction pattern of various anti-cancer drugs with cystatins in a bid to find how these drugs affect this important inhibitors and whether these drugs have any side effect on cystatins. Thus, in this growing disease era it can be said that cystatins are no more just inhibitors blocking the activity of thiol proteases rather they play a pivotal role in variety of pathological conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Thermomechanical characterization of thiol-epoxy shape memory thermosets for mechanical actuators design

    Science.gov (United States)

    Belmonte, Alberto; Fernández-Francos, Xavier; De la Flor, Silvia

    2018-02-01

    In this paper, shape-memory "thiol-epoxy" polymers are synthesized and characterized as potential thermomechanical actuators. Their thermomechanical properties are investigated through dynamo mechanical and tensile analyses and related to their network structural properties by using "thiol" and "epoxy" compounds of different functionality and structure. Their mechanical properties (resistance at break, elongation limits and strain energy) are related to their shape-memory response under free-recovery conditions and partially-constrained conditions, thus, establishing the connection between network relaxation (free-recovery) with the work output capabilities (partially-constrained). Results show high mechanical performance, achieving high elongation at break values (up to 100%) and stress at break values (up to 50 MPa). The shape-memory experiments reveal strong dependence of the programming conditions and network structure on the recovery efficiency at free-conditions, whereas under partially-constrained conditions, the controlling factors are the mechanical limits at high temperature. Moreover, some recommendations to achieve the maximum work output efficiency for a given operational design of a thermomechanical actuator are deduced.

  2. Fluorescent sensors for selective detection of thiols: expanding the intramolecular displacement based mechanism to new chromophores.

    Science.gov (United States)

    Niu, Li-Ya; Zheng, Hai-Rong; Chen, Yu-Zhe; Wu, Li-Zhu; Tung, Chen-Ho; Yang, Qing-Zheng

    2014-03-21

    Biological thiols, including cysteine (Cys), homocystein (Hcy) and glutathione (GSH), play crucial roles in maintaining the appropriate redox status of biological systems. An abnormal level of biothiols is associated with different diseases, therefore, the discrimination between them is of great importance. Herein, we present two fluorescent sensors for selective detection of biothiols based on our recently reported intramolecular displacement mechanism. We expanded this mechanism to commercially available chromophores, 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) and heptamethine cyanine dye IR-780. The sensors operate by undergoing displacement of chloride by thiolate. The amino groups of Cys/Hcy further replace the thiolate to form amino-substituted products, which exhibit dramatically different photophysical properties compared to sulfur-substituted products from the reaction with GSH. NBD-Cl is highly selective towards Cys/Hcy and exhibits significant fluorescence enhancement. IR-780 showed a variation in its fluorescence ratio towards Cys over other thiols. Both of the sensors can be used for live-cell imaging of Cys. The wide applicability of the mechanism may provide a powerful tool for developing novel fluorescent sensors for selective detection of biothiols.

  3. Evaluation of Dynamic Disulphide/Thiol Homeostasis in Silica Exposed Workers

    Directory of Open Access Journals (Sweden)

    Meşide Gündüzöz

    2017-04-01

    Full Text Available Background: Oxidative stress is implicated as one of the main molecular mechanism underlying silicosis. Aims: In this study, our aim was to asses the redox status in occupationally silica-exposed workers, by evaluating the dynamic thiol-disulphide homeostasis. Study Design: Case-control study. Methods: Thirty-six male workers occupationally exposed to silica particles and 30 healthy volunteers, working as office workers were included to the study. Posteroanterior chest radiographs and pulmonary function tests of both groups were evaluated. Also serum thiol disulphide levels were measured using the spectrophotometric method described by Erel and Neşelioğlu. Results: Among the 36 workers that underwent pulmonary function tests 6 (17% had obstructive, 7 (19% had restrictive, 6 (17% had obstructive and restrictive signs whereas 17 (47% had no signs. The mean PFTs results of silica-exposed workers were significantly lower than control subjects. The serum disulphide levels of silica-exposed workers were significantly higher than control subjects (23.84±5.89 μmol/L and 21.18±3.44 μmol/L, respectively p=0.02. Conclusion: The serum disulphide levels, a biomarker of oxidative stress, are found to be higher in silica-exposed workers

  4. Photopolymerized cross-linked thiol-ene polyanhydrides: erosion, release, and toxicity studies.

    Science.gov (United States)

    Poetz, Katie L; Mohammed, Halimatu S; Snyder, Brittany L; Liddil, Garrett; Samways, Damien S K; Shipp, Devon A

    2014-07-14

    Several critical aspects of cross-linked polyanhydrides made using thiol-ene polymerization are reported, in particular the erosion, release, and solution properties, along with their cytotoxicity toward fibroblast cells. The monomers used to synthesize these polyanhydrides were 4-pentenoic anhydride and pentaerythritol tetrakis(3-mercaptopropionate). Techniques used to evaluate the erosion mechanism indicate a complex situation in which several phenomena, such as hydrolysis rates, local pH, water diffusion, and solubility, may be influencing the erosion process. The mass loss profile, the release rate of a hydrophilic dye, the rate of hydrolysis of the polyanhydride, the hydrolysis product solubility as a function of pH, average pK(a) and its cytotoxicity toward fibroblast cells were all determined. The solubility of the degradation product is low at pH values less than 6-7, and the average pKa was determined to be ~5.3. The cytotoxicity of the polymer and the degradation product was found to be low, with cell viabilities of >97% for the various samples studied at concentrations of ~1000-1500 ppm. These important parameters help determine the potential of the thiol-ene polyanhydrides in various biomedical applications. These polyanhydrides can be used as a delivery vehicle, and although the release profile qualitatively followed the mass loss profile for a hydrophilic dye, the release rate appears to be by both diffusion and mass loss mechanisms.

  5. Mixing thiols on the surface of silver nanoparticles: preserving antibacterial properties while introducing SERS activity

    Energy Technology Data Exchange (ETDEWEB)

    Taglietti, Angelo, E-mail: angelo.taglietti@unipv.it [Università di Pavia, Dipartimento di Chimica (Italy); Diaz Fernandez, Yuri A. [Chalmers University of Technology, Department of Chemical and Biological Engineering (Sweden); Galinetto, Pietro [Università di Pavia, Dipartimento di Fisica (Italy); Grisoli, Pietro [Università di Pavia, Dipartimento di Scienze del Farmaco (Italy); Milanese, Chiara; Pallavicini, Piersandro [Università di Pavia, Dipartimento di Chimica (Italy)

    2013-11-15

    Controlling the surface composition of self-assembled monolayers is one of the major experimental challenges in nanotechnology. Despite the significant interest of the scientific community and the considerable number of publications related to this topic, the potential in this field is still far from being fully exploited.We present in this study a versatile method to coat silver nanoparticles (AgNPs) having average diameter of 7 nm with mixed monolayers of two thiols, achieving a precise control of surface composition. Different combinations of thiols have been investigated, and the nanomaterials obtained have been characterized by complementary experimental techniques, addressing the composition of the mixed monolayer. The surface-enhanced Raman spectroscopy (SERS) effect on a Raman reporter (7-mercapto-4-methylcoumarine) introduced into the mixed monolayers has also been investigated. The antibacterial activity of the coated AgNPs was investigated, showing that the colloids were active against Escherichia coli and Staphilococcus aureus irrespective of the nature of the mixed monolayer. These materials are good candidates as SERS-tags for biological applications.

  6. Role of an external cell membrane and its thiols in realization of the radioprotective effect of anoxia

    International Nuclear Information System (INIS)

    Konstantinova, M.M.; Dontsova, G.V.; Panaeva, S.V.

    1988-01-01

    In experiments with Ehrlich ascites tumor cells using a specific thiol blocker 6.6-dithiodinicitinic acid that does not penetrate the cell and therefore only binds SH-groups of peripheral areas of an external cell membrane it was demonstrated that (1) the external cell membrane is the site where the radioprotective effect of anoxia (the oxygen effect) is realized (2) thiols of the esternal cell membrane contribute markedly to the oxygen effect and (3) they are needed at both stages of its realization

  7. Thiols make for better catalysts: Au nanoparticles supported on functional SBA-15 for catalysis of Ullmann-type homocouplings

    KAUST Repository

    Chen, Tianyou

    2017-09-21

    A strategy for arraying small gold nanoparticles on a mesoporous support modified with single-component or mixed self-assembled monolayers is described. The use of mixed surface modifiers allows easy access to a range of surface chemistries and modalities of interaction between nanoparticles and supports. A combination of thiol groups and linear semifluorinated chains effectively stabilized the nanoparticles against aggregation, while preserving their catalytic activity. The thiol-fluorous-supported catalyst was found active in Ullmann-type homocoupling of aryl halides and showed exceptional selectivity in this reaction.

  8. Biocompatibility of a polymer based on Off-Stoichiometry Thiol-Enes + Epoxy (OSTE+) for neural implants

    OpenAIRE

    Ejserholm, Fredrik; Stegmayr, John; Bauer, Patrik; Johansson, Fredrik; Wallman, Lars; Bengtsson, Martin; Oredsson, Stina

    2015-01-01

    Background The flexibility of implantable neural probes has increased during the last 10 years, starting with stiff materials such as silicone to more flexible materials like polyimide. We have developed a novel polymer based on Off-Stoichiometry Thiol-Enes + Epoxy (OSTE+, consisting of a thiol, two allyls, an epoxy resin and two initiators), which is up to 100 times more flexible than polyimide. Since a flexible neural probe should be more biocompatible than a stiff probe, an OSTE+ probe sho...

  9. Antimicrobial activity of new 5-(furan-2-yl)-4-amino-1,2,4-triazole-3-thiol derivatives

    OpenAIRE

    D. M. Danilchenko; V. V. Parchenko

    2017-01-01

    The aim of this research was to investigate the antimicrobial activity of some new 5-(furan-2-yl)-4-amino-1,2,4-triazole-3-thiol substituents and in some cases to trace the relationship between activity of compounds and their structure. Research materials and methods. Antimicrobial activity of new 5-(furan-2-yl)-4-amino-1,2,4-triazole-3-thiol derivatives was studied by the method of serial dilutions. The primary antimicrobial activity screening tests of some 5-(furan-2-yl)-4-amino-1,2,4-t...

  10. Sequence of the gamma-subunit of Spirulina platensis : a new principle of thiol modulation of F0F1 ATP synthase?

    NARCIS (Netherlands)

    Steinemann, D.; Lill, H

    1995-01-01

    The gene encoding the gamma subunit of Spirulina platensis F0F1, the relative of the chloroplast F1 subunit responsible for thiol activation, has been cloned and sequenced. As in other cyanobacteria, a specific couple of cysteines like those involved in thiol modulation of the chloroplast enzyme was

  11. Reactive copolymers based on N-vinyl lactams with pyridyl disulfide side groups via RAFT polymerization and postmodification via thiol-disulfide exchange reaction

    NARCIS (Netherlands)

    Peng, Huan; Rübsam, Kristin; Huang, Xiaobin; Jakob, Felix; Karperien, Marcel; Schwaneberg, Ulrich; Pich, Andrij

    2016-01-01

    Herein, we report the synthesis of a series of novel pyridyl disulfide (PDS)-functionalized statistical reactive copolymers that enable facile access to complex polymeric architectures through highly selective thiol-disulfide exchange reaction with thiol-containing ligands or proteins. Functional

  12. Comparison of Hydrazone Heterobifunctional Crosslinking Agents for Reversible Conjugation of Thiol-Containing Chemistry

    Science.gov (United States)

    Christie, R. James; Anderson, Diana J.; Grainger, David W.

    2010-01-01

    Reversible covalent conjugation chemistries that allow site- and condition-specific coupling and uncoupling reactions are attractive components in nanotechnologies, bioconjugation methods, imaging and drug delivery systems. Here, we compare three heterobifunctional crosslinkers, containing both thiol- and amine- reactive chemistry, to form pH-labile hydrazones with hydrazide derivatives of the known and often published water-soluble polymer, poly[N-(2-hydroxypropyl methacrylamide)] (pHPMA), while subsequently coupling thiol-containing molecules to the crosslinker via maleimide addition. Two novel crosslinkers were prepared from the popular heterobifunctional crosslinking agent, succinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate (SMCC), modified to contain either terminal aldehyde groups (i.e., 1-(N-3-propanal)-4-(N-maleimidomethyl) cyclohexane carboxamide, PMCA) or methylketone groups (i.e., 1-(N-3-butanone)-4-(N-maleimidomethyl) cyclohexane carboxamide, BMCA). A third crosslinking agent was the commercially available N-4-acetylphenyl maleimide (APM). PMCA and BMCA exhibited excellent reactivity towards hydrazide-derivatized pHPMA with essentially complete hydrazone conjugation to polymer reactive sites, while APM coupled only ~ 60% of available reactive sites on the polymer despite a 3-fold molar excess relative to polymer hydrazide groups. All polymer hydrazone conjugates bearing these bifunctional agents were then further reacted with thiol-modified tetramethylrhodamine dye, confirming crosslinker maleimide reactivity after initial hydrazone polymer conjugation. Incubation of dye-labeled polymer conjugates in phosphate buffered saline at 37°C showed that hydrazone coupling resulting from APM exhibited the greatest difference in stability between pH 7.4 and 5.0, with hydrolysis and dye release increased at pH 5.0 over a 24hr incubation period. Polymer conjugates bearing hydrazones formed from crosslinker BMCA exhibited intermediate stability with

  13. Comparison of hydrazone heterobifunctional cross-linking agents for reversible conjugation of thiol-containing chemistry.

    Science.gov (United States)

    Christie, R James; Anderson, Diana J; Grainger, David W

    2010-10-20

    Reversible covalent conjugation chemistries that allow site- and condition-specific coupling and uncoupling reactions are attractive components in nanotechnologies, bioconjugation methods, imaging, and drug delivery systems. Here, we compare three heterobifunctional cross-linkers, containing both thiol- and amine-reactive chemistries, to form pH-labile hydrazones with hydrazide derivatives of the known and often published water-soluble polymer, poly[N-(2-hydroxypropyl methacrylamide)] (pHPMA), while subsequently coupling thiol-containing molecules to the cross-linker via maleimide addition. Two novel cross-linkers were prepared from the popular heterobifunctional cross-linking agent, succinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate (SMCC), modified to contain either terminal aldehyde groups (i.e., 1-(N-3-propanal)-4-(N-maleimidomethyl) cyclohexane carboxamide, PMCA) or methylketone groups (i.e., 1-(N-3-butanone)-4-(N-maleimidomethyl) cyclohexane carboxamide, BMCA). A third cross-linking agent was the commercially available N-4-acetylphenyl maleimide (APM). PMCA and BMCA exhibited excellent reactivity toward hydrazide-derivatized pHPMA with essentially complete hydrazone conjugation to polymer reactive sites, while APM coupled only ∼60% of available reactive sites on the polymer despite a 3-fold molar excess relative to polymer hydrazide groups. All polymer hydrazone conjugates bearing these bifunctional agents were then further reacted with thiol-modified tetramethylrhodamine dye, confirming cross-linker maleimide reactivity after initial hydrazone polymer conjugation. Incubation of dye-labeled polymer conjugates in phosphate buffered saline at 37 °C showed that hydrazone coupling resulting from APM exhibited the greatest difference in stability between pH 7.4 and 5.0, with hydrolysis and dye release increased at pH 5.0 over a 24 h incubation period. Polymer conjugates bearing hydrazones formed from cross-linker BMCA exhibited intermediate stability

  14. Functional Characterization of ABCC Proteins from Trypanosoma cruzi and Their Involvement with Thiol Transport

    Directory of Open Access Journals (Sweden)

    Kelli Monteiro da Costa

    2018-02-01

    Full Text Available Chagas disease is a neglected disease caused by the protozoan Trypanosoma cruzi and affects 8 million people worldwide. The main chemotherapy is based on benznidazole. The efficacy in the treatment depends on factors such as the parasite strain, which may present different sensitivity to treatment. In this context, the expression of ABC transporters has been related to chemotherapy failure. ABC transporters share a well-conserved ABC domain, responsible for ATP binding and hydrolysis, whose the energy released is coupled to transport of molecules through membranes. The most known ABC transporters are ABCB1 and ABCC1, involved in the multidrug resistance phenotype in cancer, given their participation in cellular detoxification. In T. cruzi, 27 ABC genes were identified in the genome. Nonetheless, only four ABC genes were characterized: ABCA3, involved in vesicular trafficking; ABCG1, overexpressed in strains naturally resistant to benznidazole, and P-glycoprotein 1 and 2, whose participation in drug resistance is controversial. Considering P-glycoprotein genes are related to ABCC subfamily in T. cruzi according to the demonstration using BLASTP alignment, we evaluated both ABCB1-like and ABCC-like activities in epimastigote and trypomastigote forms of the Y strain. The transport activities were evaluated by the efflux of the fluorescent dyes Rhodamine 123 and Carboxyfluorescein in a flow cytometer. Results indicated that there was no ABCB1-like activity in both T. cruzi forms. Conversely, results demonstrated ABCC-like activity in both epimastigote and trypomastigote forms of T. cruzi. This activity was inhibited by ABCC transport modulators (probenecid, indomethacin, and MK-571, by ATP-depleting agents (sodium azide and iodoacetic acid and by the thiol-depleting agent N-ethylmaleimide. Additionally, the presence of ABCC-like activity was supported by direct inhibition of the thiol-conjugated compound efflux with indomethacin, characteristic of

  15. Glutathione S-Transferase activity and total thiol status in chronic alcohol abusers before and 30 days after alcohol abstinence

    Directory of Open Access Journals (Sweden)

    Manjunatha S Muttigi

    2009-05-01

    Full Text Available Background: Glutathione S Transferase (GST has been involved in detoxification process in the liver and its activity has been shown to be increased in alcohol abusers. In the current work we measured the GST activity, total thiol status, AST, ALT, and direct bilirubin in chronic alcohol abusers before and 30 days after alcohol abstinence and lifestyle modification. Methods: Serum and urine GST activity and total thiol status were determined using spectrophotometric methods and serum transaminases were determined using clinical chemistry analyzer. Results: We found,significant increase in serum and urine GST (p<0.001, AST (p<0.001, ALT (p<0.001, and decrease in total thiol status (p<0.001 in chronic alcohol abusers. GST activity significantly decreased (p<0.001 and total thiol status were improved significantly (p<0.001 30 days after alcohol abstinence and lifestyle modification. Conclusion: This study provides preliminary data to suggest the role of GST as prognostic indicator of alcohol abstinence with possible trend towards an improvement in liver function.

  16. Location of the redox-active thiols of ribonucleotide reductase: sequences similarity between the Escherichia coli and Lactobacillus leichmannii enzymes

    International Nuclear Information System (INIS)

    Lin, A.N.I.; Ashley, G.W.; Stubbe, J.

    1987-01-01

    The redox-active thiols of Escherichia coli ribonucleoside diphosphate reductase and of Lactobacillus leichmannii ribonucleoside triphosphate reductase have been located by a procedure involving (1) prereduction of enzyme with dithiothreitol, (2) specific oxidation of the redox-active thiols by treatment with substrate in the absence of exogenous reductant, (3) alkylation of other thiols with iodoacetamide, and (4) reduction of the disulfides with dithiothreitol and alkylation with [1- 14 C]iodoacetamide. The dithiothreitol-reduce E. coli B1 subunit is able to convert 3 equiv of CDP to dCDP and is labeled with 5.4 equiv of 14 C. Sequencing of tryptic peptides shows that 2.8 equiv of 14 C is on cysteines-752 and -757 at the C-terminus of B1, while 1.0-1.5 equiv of 14 C is on cysteines-222 and -227. It thus appears that two sets of redox-active dithiols are involved in substrate reduction. The L. leichmannii reductase is able to convert 1.1 equiv of CTP to dCTP and is labeled with 2.1 equiv of 14 C. Sequencing of tryptic peptides shows that 1.4 equiv of 14 C is located on the two cysteines of C-E-G-G-A-C-P-I-K. This peptide shows remarkable and unexpected similarity to the thiol-containing region of the C-terminal peptide of E. coli B1, C-E-S-G-A-C-K-I

  17. Improved electronic coupling in hybrid organic-inorganic nanocomposites employing thiol-functionalized P3HT and bismuth sulfide nanocrystals.

    Science.gov (United States)

    Martinez, L; Higuchi, S; MacLachlan, A J; Stavrinadis, A; Miller, N C; Diedenhofen, S L; Bernechea, M; Sweetnam, S; Nelson, J; Haque, S A; Tajima, K; Konstantatos, G

    2014-09-07

    In this study, we employ a thiol-functionalized polymer (P3HT-SH) as a leverage to tailor the nanomorphology and electronic coupling in polymer-nanocrystal composites for hybrid solar cells. The presence of the thiol functional group allows for a highly crystalline semiconducting polymer film at low thiol content and allows for improved nanomorphologies in hybrid organic-inorganic systems when employing non-toxic bismuth sulfide nanocrystals. The exciton dissociation efficiency and carrier dynamics at this hybrid heterojunction are investigated through photoluminescence quenching and transient absorption spectroscopy measurements, revealing a larger degree of polaron formation when P3HT-SH is employed, suggesting an increased electronic interaction between the metal chalcogenide nanocrystals and the thiol-functionalized P3HT. The fabricated photovoltaic devices show 15% higher power conversion efficiencies as a result of the improved nanomorphology and better charge transfer mechanism together with the higher open circuit voltages arising from the deeper energy levels of P3HT-SH.

  18. Ultrasound-Accelerated Synthesis of Asymmetrical Thiosulfonate S-Esters by Base-Promoted Reaction of Sulfonyl Chlorides with Thiols

    DEFF Research Database (Denmark)

    Pham, Hien Thi; Nguyen, Ngoc-Lan Thi; Duus, Fritz

    2015-01-01

    Amberlyst A-26, Mg-Al hydrotalcite, potassium fluoride absorbed on alumina, triethylamine and pyridine have been tested as base catalysts and reagents for the reaction of sulfonyl chlorides with thiols to prepare thiosulfonate S-esters. The reactions were performed under solvent-free conditions...

  19. Influence of Torulaspora delbrueckii in varietal thiol (3-SH and 4-MSP) release in wine sequential fermentations.

    Science.gov (United States)

    Belda, Ignacio; Ruiz, Javier; Beisert, Beata; Navascués, Eva; Marquina, Domingo; Calderón, Fernando; Rauhut, Doris; Benito, Santiago; Santos, Antonio

    2017-09-18

    In last years, non-Saccharomyces yeasts have emerged as innovative tools to improve wine quality, being able to modify the concentration of sensory-impact compounds. Among them, varietal thiols released by yeasts, play a key role in the distinctive aroma of certain white wines. In this context, Torulaspora delbrueckii is in the spotlight because of its positive contribution to several wine quality parameters. This work studies the physiological properties of an industrial T. delbrueckii strain, for the production of wines with increased thiol concentrations. IRC7 gene, previously described in S. cerevisiae, has been identified in T. delbrueckii, establishing the genetics basis of its thiol-releasing capability. Fermentations involving T. delbrueckii showed improvements on several parameters (such as glycerol content, ethanol index, and major volatile compounds composition), but especially on thiols release. These results confirm the potential of T. delbrueckii on wine improvement, describing new metabolic features regarding the release of cysteinylated aroma precursors. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Thiol-modified gold-coated glass as an efficient hydrophobic substrate for drop coating deposition Raman (DCDR) technique

    Czech Academy of Sciences Publication Activity Database

    Kočišová, E.; Procházka, M.; Šípová, Hana

    2016-01-01

    Roč. 47, č. 11 (2016), s. 1394-1396 ISSN 0377-0486 R&D Projects: GA ČR(CZ) GBP205/12/G118 Institutional support: RVO:67985882 Keywords : thiol-modified Au-coated glass * drop coating deposition Raman * liposome Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.969, year: 2016

  1. Removal of lead(II ions from aqueous solutions using cashew nut shell liquid-templated thiol-silica materials

    Directory of Open Access Journals (Sweden)

    J. E. G. Mdoe

    2014-09-01

    Full Text Available A range of thiol-silica composites were prepared using cashew nut shell liquid (CNSL or one of its phenolic constituents, cardanol, as templates. The procedure involved formation of a CNSL or cardanol emulsion in a water-ethanol system into which (3-mercaptopropyl-trimethoxysilane and tetraethyl orthosilicate were simultaneously added at various ratios. The reaction mixture was aged at room temperature for 18 h followed by a Soxhlet extraction of the template and drying. The materials were characterized by diffuse reflectance Fourier transform infrared, nitrogen physisorption, scanning electron microscopy and acid titration. Results indicated that indeed the thiol-silica composites were successfully prepared, with thiol group loadings ranging from 1.6-2.5 mmol/g. The materials were tested for lead(II adsorption, and results showed that they had maximum adsorption capacities up to 66.7 mg/g, depending on the thiol group loading and type of template used in preparing the adsorbent. DOI: http://dx.doi.org/10.4314/bcse.v28i3.5

  2. Effect of thiol reactive reagents and ionizing radiation on the permeability of erythrocyte membrane for non-electrolyte spin labels

    Energy Technology Data Exchange (ETDEWEB)

    Gwozdzinski, K.

    1986-08-01

    The paper presents some results on the effect of PCMB and NEM on the transport of non-electrolyte spin labels: TEMPO and TEMPOL across non-irradiated and irradiated porcine erythrocyte. Irradiated erythrocytes exhibited increased inhibitory effect of thiol reactive compounds in the TEMPO and TEMPOL transport compared to non-irradiated erythrocytes.

  3. Prebiotic Amino Acid Thioester Synthesis: Thiol-Dependent Amino Acid Synthesis from Formose substrates (Formaldehyde and Glycolaldehyde) and Ammonia

    Science.gov (United States)

    Weber, Arthur L.

    1998-01-01

    Formaldehyde and glycolaldehyde (substrates of the formose autocatalytic cycle) were shown to react with ammonia yielding alanine and homoserine under mild aqueous conditions in the presence of thiol catalysts. Since similar reactions carried out without ammonia yielded alpha-hydroxy acid thioesters, the thiol-dependent synthesis of alanine and homoserine is presumed to occur via amino acid thioesters-intermediates capable of forming peptides. A pH 5.2 solution of 20 mM formaldehyde, 20 mM glycolaldehyde, 20 mM ammonium chloride, 23 mM 3-mercaptopropionic acid, and 23 mM acetic acid that reacted for 35 days at 40 C yielded (based on initial formaldehyde) 1.8% alanine and 0.08% homoserine. In the absence of thiol catalyst, the synthesis of alanine and homoserine was negligible. Alanine synthesis required both formaldehyde and glycolaldehyde, but homoserine synthesis required only glycolaldehyde. At 25 days the efficiency of alanine synthesis calculated from the ratio of alanine synthesized to formaldehyde reacted was 2.1%, and the yield (based on initial formaldehyde) of triose and tetrose intermediates involved in alanine and homoserine synthesis was 0.3 and 2.1%, respectively. Alanine synthesis was also seen in similar reactions containing only 10 mM each of aldehyde substrates, ammonia, and thiol. The prebiotic significance of these reactions that use the formose reaction to generate sugar intermediates that are converted to reactive amino acid thioesters is discussed.

  4. Interaction of cultured mammalian cells with WR-2721 and its thiol, WR-1065: implications for mechanisms of radioprotection

    International Nuclear Information System (INIS)

    Purdie, J.W.; Inhaber, E.R.; Schneider, H.; Labelle, J.L.

    1983-01-01

    An isothermal microcalorimeter was used to measure changes in heat flow when radioprotective drugs were added to cultured mammalian cells. The heat produced when WR-2721 was added continued for at least 90 min. WR-2721 was dephosphorylated by the cells to thiol (WR-1065) which oxidizes to disulphide. In the microcalorimeter, thiols give an immediate burst of heat due to this oxidation. A biological oxygen monitor revealed that WR-1065 and cysteamine rapidly consumed all the oxygen in culture medium. (10mM WR-1065 deoxygenated medium in 2 min.). Rapid consumption of oxygen by radioprotective thiols indicates that they will not co-exist with oxygen for long in cells. This has two important implications with respect to mechanisms of radioprotection: (1) oxygen in tissues will be consumed rapidly and could results in local hypoxia; and, (2) at modest doses of protective agents the thiol will be consumed in oxic cells and hence very little will be available for reactions such as hydrogen donation. The results indicate that anoxia is probably the principle mechanism of protection by aminothiols in mammals and aerated cells. (author)

  5. Inorganic-Organic Thiol-ene Coated Mesh for Oil/Water Separation.

    Science.gov (United States)

    Chen, Qiyi; de Leon, Al; Advincula, Rigoberto C

    2015-08-26

    A highly efficient mesh for oil/water separation was fabricated by using a superhydrophobic and superoleophilic coating of thiol-ene hybrid, consisting of pentaerythritol tetra(3-mercaptopropionate) (PETMP), 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (TMTVSi), and hydrophobic fumed silica nanoparticles, via a simple two-step fabrication process. Spray deposition and UV curing photopolymerization were sequentially performed, during which solvent evaporation provides microscale roughness while nanoparticle aggregation forms nanoscale roughness. The hierarchical morphologies were stabilized after UV curing photopolymerization. High contact angle (>150°) and low roll-off angle (<5°) were achieved due to the multiscale roughness structure of the hierarchical morphologies. These coatings also have excellent chemical resistance, as well as temperature and pH stability, after curing.

  6. Surface analysis of gold nanoparticles functionalized with thiol-modified glucose SAMs for biosensor applications.

    Directory of Open Access Journals (Sweden)

    Valentina eSpampinato

    2016-02-01

    Full Text Available In this work, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS, Principal Component Analysis (PCA and X-ray Photoelectron Spectroscopy (XPS have been used to characterize the surface chemistry of gold substrates before and after functionalization with thiol-modified glucose self-assembled monolayers and subsequent biochemical specific recognition of maltose binding protein (MBP.The results indicate that the surface functionalization is achieved both on flat and nanoparticles gold substrates thus showing the potential of the developed system as biodetection platform. Moreover, the method presented here has been found to be a sound and valid approach to characterize the surface chemistry of nanoparticles functionalized with large molecules.Both techniques were proved to be very useful tools for monitoring all the functionalization steps, including the investigation of the biological behaviour of the glucose-modified particles in presence of the maltose binding protein.

  7. Surface analysis of gold nanoparticles functionalized with thiol-modified glucose SAMs for biosensor applications.

    Science.gov (United States)

    Spampinato, Valentina; Parracino, Mariaantonietta; La Spina, Rita; Rossi, Francois; Ceccone, Giacomo

    2016-02-01

    In this work, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS), Principal Component Analysis (PCA) and X-ray Photoelectron Spectroscopy (XPS) have been used to characterize the surface chemistry of gold substrates before and after functionalization with thiol-modified glucose self-assembled monolayers and subsequent biochemical specific recognition of maltose binding protein (MBP). The results indicate that the surface functionalization is achieved both on flat and nanoparticles gold substrates thus showing the potential of the developed system as biodetection platform. Moreover, the method presented here has been found to be a sound and valid approach to characterize the surface chemistry of nanoparticles functionalized with large molecules. Both techniques were proved to be very useful tools for monitoring all the functionalization steps, including the investigation of the biological behaviour of the glucose-modified particles in presence of the maltose binding protein.

  8. The enhanced cytotoxicity of misonidazole in the thiol depleted state - An oxygen dependent mechanism

    International Nuclear Information System (INIS)

    Tuttle, S.W.; Varnes, M.E.; Donahue, L.; Biaglow, J.E.

    1985-01-01

    Incubating A549 cells in the presence of L-buthionine-S, R-sulfoximine and misonidazole under aerobic conditions results in lowered rates of cell growth and greater cytotoxicity than is seen with either drug alone. The authors previously demonstrated the accumulation of hydrogen peroxide from cells treated with misonidazole following the inhibition of GSH-peroxidase with thiol depleting agents. They hypothesize that the enhancement of misonidazole toxicity by L-BSO results from the increased exposure to hydrogen peroxide, and the possible formation of the highly reactive hydroxyl radical in the presence of trace metals via Fenton chemistry. Support for this hypothesis comes from their observations that addition of radical scavengers (such as SOD and catalase) and nutritional antioxidants (vitamin E) to the culture medium will partially inhibit the cytotoxic effects. Further work is being done to measure the products of reaction of toxic oxygen species with cellular macromolecules, i.e. lipids

  9. Development of a thiol-ene based screening platform for enzyme immobilization demonstrated using horseradish peroxidase

    DEFF Research Database (Denmark)

    Hoffmann, Christian; Pinelo, Manuel; Woodley, John

    2017-01-01

    Efficient immobilization of enzymes on support surfaces requires an exact match between the surface chemistry and the specific enzyme. A successful match would normally be identified through time consuming screening of conventional resins in multiple experiments testing individual immobilization...... strategies. In this study we present a versatile strategy that largely expands the number of possible surface functionalities for enzyme immobilization in a single, generic platform. The combination of many individual surface chemistries and thus immobilization methods in one modular system permits faster...... functionalization by thiol-ene chemistry (TEC) resulted in the formation of a functional monolayer in each well, whereas, polymer surface grafts were introduced through surface chain transfer free radical polymerization (SCT-FRP). Enzyme immobilization on the modified surfaces was evaluated by using a rhodamine...

  10. Atomically precise organomimetic cluster nanomolecules assembled via perfluoroaryl-thiol SNAr chemistry

    Science.gov (United States)

    Qian, Elaine A.; Wixtrom, Alex I.; Axtell, Jonathan C.; Saebi, Azin; Jung, Dahee; Rehak, Pavel; Han, Yanxiao; Moully, Elamar Hakim; Mosallaei, Daniel; Chow, Sylvia; Messina, Marco S.; Wang, Jing Yang; Royappa, A. Timothy; Rheingold, Arnold L.; Maynard, Heather D.; Král, Petr; Spokoyny, Alexander M.

    2017-04-01

    The majority of biomolecules are intrinsically atomically precise, an important characteristic that enables rational engineering of their recognition and binding properties. However, imparting a similar precision to hybrid nanoparticles has been challenging because of the inherent limitations of existing chemical methods and building blocks. Here we report a new approach to form atomically precise and highly tunable hybrid nanomolecules with well-defined three-dimensionality. Perfunctionalization of atomically precise clusters with pentafluoroaryl-terminated linkers produces size-tunable rigid cluster nanomolecules. These species are amenable to facile modification with a variety of thiol-containing molecules and macromolecules. Assembly proceeds at room temperature within hours under mild conditions, and the resulting nanomolecules exhibit high stabilities because of their full covalency. We further demonstrate how these nanomolecules grafted with saccharides can exhibit dramatically improved binding affinity towards a protein. Ultimately, the developed strategy allows the rapid generation of precise molecular assemblies to investigate multivalent interactions.

  11. Biological Chemistry and Functionality of Protein Sulfenic Acids and Related Thiol Modifications

    Science.gov (United States)

    Devarie-Baez, Nelmi O.; Silva Lopez, Elsa I.; Furdui, Cristina M.

    2016-01-01

    Selective modification of proteins at cysteine residues by reactive oxygen, nitrogen or sulfur species formed under physiological and pathological states is emerging as a critical regulator of protein activity impacting cellular function. This review focuses primarily on protein sulfenylation (-SOH), a metastable reversible modification connecting reduced cysteine thiols to many products of cysteine oxidation. An overview is first provided on the chemistry principles underlining synthesis, stability and reactivity of sulfenic acids in model compounds and proteins, followed by a brief description of analytical methods currently employed to characterize these oxidative species. The following chapters present a selection of redox-regulated proteins for which the -SOH formation was experimentally confirmed and linked to protein function. These chapters are organized based on the participation of these proteins in the regulation of signaling, metabolism and epigenetics. The last chapter discusses the therapeutic implications of altered redox microenvironment and protein oxidation in disease. PMID:26340608

  12. Controlled UV-C light-induced fusion of thiol-passivated gold nanoparticles.

    Science.gov (United States)

    Pocoví-Martínez, Salvador; Parreño-Romero, Miriam; Agouram, Said; Pérez-Prieto, Julia

    2011-05-03

    Thiol-passivated gold nanoparticles (AuNPs) of a relatively small size, either decorated with chromophoric groups, such as a phthalimide (Au@PH) and benzophenone (Au@BP), or capped with octadecanethiol (Au@ODCN) have been synthesized and characterized by NMR and UV-vis spectroscopy as well as transmission electron microscopy (TEM). These NPs were irradiated in chloroform at different UV-wavelengths using either a nanosecond laser (266 and 355 nm, ca. 12 mJ/pulse, 10 ns pulse) or conventional lamps (300 nm lamp illumination. Remarkably, laser excitation at 266 nm induced a fast (minutes time-scale) increase in the size of the NPs, producing huge spherical nanocrystals, while lamp-irradiation at UV-C wavelengths brought about nanonetworks of partially fused NPs with a larger diameter than the native NPs.

  13. Liquid crystalline polybutadiene diols with chiral thiol side-chain units

    Czech Academy of Sciences Publication Activity Database

    Kašpar, Miroslav; Bubnov, Alexej M.; Sedláková, Zdeňka; Stojanović, M.; Havlíček, J.; Obadović, D.; Ilavský, Michal

    2008-01-01

    Roč. 44, č. 1 (2008), s. 233-243 ISSN 0014-3057 R&D Projects: GA ČR GP202/03/P011; GA ČR GA202/05/0431; GA MŠk OC 175; GA AV ČR IAA100100710; GA AV ČR IAA4112401 Grant - others:MSEP(CS) 141020; ESF-COST(XE) D35 WG13-05 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z40500505 Keywords : chiral thiols * liquid crystal * polybutadiene * diols * side-chain polymer * polarizing optical microscopy * X-ray * dielectric spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.143, year: 2008

  14. Biomimetic surface modification of polypropylene by surface chain transfer reaction based on mussel-inspired adhesion technology and thiol chemistry

    International Nuclear Information System (INIS)

    Niu, Zhijun; Zhao, Yang; Sun, Wei; Shi, Suqing; Gong, Yongkuan

    2016-01-01

    Highlights: • Biomimetic surface modification of PP was successfully conducted by integrating mussel-inspired technology, thiol chemistry and cell outer membranes-like structures. • The resultant biomimetic surface exhibits good interface and surface stability. • The obvious suppression of protein adsorption and platelet adhesion is also achieved. • The residue thoil groups on the surface could be further functionalized. - Abstract: Biomimetic surface modification of polypropylene (PP) is conducted by surface chain transfer reaction based on the mussel-inspired versatile adhesion technology and thiol chemistry, using 2-methacryloyloxyethylphosphorylcholine (MPC) as a hydrophilic monomer mimicking the cell outer membrane structure and 2,2-azobisisobutyronitrile (AIBN) as initiator in ethanol. A layer of polydopamine (PDA) is firstly deposited onto PP surface, which not only offers good interfacial adhesion with PP, but also supplies secondary reaction sites (-NH 2 ) to covalently anchor thiol groups onto PP surface. Then the radical chain transfer to surface-bonded thiol groups and surface re-initiated polymerization of MPC lead to the formation of a thin layer of polymer brush (PMPC) with cell outer membrane mimetic structure on PP surface. X-ray photoelectron spectrophotometer (XPS), atomic force microscopy (AFM) and water contact angle measurements are used to characterize the PP surfaces before and after modification. The protein adsorption and platelet adhesion experiments are also employed to evaluate the interactions of PP surface with biomolecules. The results show that PMPC is successfully grafted onto PP surface. In comparison with bare PP, the resultant PP-PMPC surface exhibits greatly improved protein and platelet resistance performance, which is the contribution of both increased surface hydrophilicity and zwitterionic structure. More importantly, the residue thiol groups on PP-PMPC surface create a new pathway to further functionalize such

  15. Biomimetic surface modification of polypropylene by surface chain transfer reaction based on mussel-inspired adhesion technology and thiol chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Zhijun; Zhao, Yang; Sun, Wei; Shi, Suqing, E-mail: shisq@nwu.edu.cn; Gong, Yongkuan

    2016-11-15

    Highlights: • Biomimetic surface modification of PP was successfully conducted by integrating mussel-inspired technology, thiol chemistry and cell outer membranes-like structures. • The resultant biomimetic surface exhibits good interface and surface stability. • The obvious suppression of protein adsorption and platelet adhesion is also achieved. • The residue thoil groups on the surface could be further functionalized. - Abstract: Biomimetic surface modification of polypropylene (PP) is conducted by surface chain transfer reaction based on the mussel-inspired versatile adhesion technology and thiol chemistry, using 2-methacryloyloxyethylphosphorylcholine (MPC) as a hydrophilic monomer mimicking the cell outer membrane structure and 2,2-azobisisobutyronitrile (AIBN) as initiator in ethanol. A layer of polydopamine (PDA) is firstly deposited onto PP surface, which not only offers good interfacial adhesion with PP, but also supplies secondary reaction sites (-NH{sub 2}) to covalently anchor thiol groups onto PP surface. Then the radical chain transfer to surface-bonded thiol groups and surface re-initiated polymerization of MPC lead to the formation of a thin layer of polymer brush (PMPC) with cell outer membrane mimetic structure on PP surface. X-ray photoelectron spectrophotometer (XPS), atomic force microscopy (AFM) and water contact angle measurements are used to characterize the PP surfaces before and after modification. The protein adsorption and platelet adhesion experiments are also employed to evaluate the interactions of PP surface with biomolecules. The results show that PMPC is successfully grafted onto PP surface. In comparison with bare PP, the resultant PP-PMPC surface exhibits greatly improved protein and platelet resistance performance, which is the contribution of both increased surface hydrophilicity and zwitterionic structure. More importantly, the residue thiol groups on PP-PMPC surface create a new pathway to further functionalize such

  16. Atomistic simulations of thiol-terminated modifiers for hybrid photovoltaic interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Malloci, G. [Istituto Officina dei Materiali (CNR-IOM), Unità di Cagliari, Cittadella Universitaria, I-09042 Monserrato (Italy); Petrozza, A. [Center for Nano Science and Technology @Polimi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, I-20133 Milano (Italy); Mattoni, A., E-mail: mattoni@iom.cnr.it [Istituto Officina dei Materiali (CNR-IOM), Unità di Cagliari, Cittadella Universitaria, I-09042 Monserrato (Italy)

    2014-06-02

    Small aromatic molecules such as benzene or pyridine derivatives are often used as interface modifiers (IMs) at polymer/metal oxide hybrid interfaces. We performed a theoretical investigation on prototypical thiol-terminated IMs aimed at improving the photovoltaic performances of poly(3-hexylthiophene)/TiO{sub 2} devices. By means of first-principles calculations in the framework of the density functional theory we investigate 3-furanthiol (3FT), 4-mercaptobenzoicacid (4MB), and 6-isoquinolinethiol (6QT) molecules. We discuss the role of these molecules as modifiers alternative to 4-mercaptopyridine (4MP) which has recently shown to induce a large improvement in the overall power conversion efficiency of mesoporous films of TiO{sub 2} infiltrated by poly(3-hexylthiophene). The IMs investigated are expected to keep the beneficial features of 4MP giving at the same time the possibility to further tune the interlayer properties (e.g., its thickness, stability, and density). Dense interlayers of 6QT turn out to be slightly unstable since the titania substrate induces a compressive strain in the molecular film. On the contrary, we predict very stable films for both 3FT and 4MB molecules, which makes them interesting candidates for future experimental investigations. - Highlights: • We performed a theoretical investigation on thiol-terminated interface modifiers. • We investigate 3-furanthiol (3FT), 4-mercaptobenzoicacid (4MB), and 6-isoquinolinethiol molecules. • We discuss the role of these molecules as modifiers alternative to 4-mercaptopyridine. • Dense interlayers of 6-isoquinolinethiol turn out to be slightly unstable. • We predict very stable self-assembled thin-films for both 3FT and 4MB molecules.

  17. Understanding human thiol dioxygenase enzymes: structure to function, and biology to pathology.

    Science.gov (United States)

    Sarkar, Bibekananda; Kulharia, Mahesh; Mantha, Anil K

    2017-04-01

    Amino acid metabolism is a significant metabolic activity in humans, especially of sulphur-containing amino acids, methionine and cysteine (Cys). Cys is cytotoxic and neurotoxic in nature; hence, mammalian cells maintain a constant intracellular level of Cys. Metabolism of Cys is mainly regulated by two thiol dioxygenases: cysteine dioxygenase (CDO) and 2-aminoethanethiol dioxygenase (ADO). CDO and ADO are the only human thiol dioxygenases reported with a role in Cys metabolism and localized to mitochondria. This metabolic pathway is important in various human disorders, as it is responsible for the synthesis of antioxidant glutathione and is also for the synthesis of hypotaurine and taurine. CDO is the most extensively studied protein, whose high-resolution crystallographic structures have been solved. As compared to CDO, ADO is less studied, even though it has a key role in cysteamine metabolism. To further understand ADO's structure and function, the three-dimensional structures have been predicted from I-TASSER and SWISS-MODEL servers and validated with PROCHECK software. Structural superimposition approach using iPBA web server further confirmed near-identical structures (including active sites) for the predicted protein models of ADO as compared to CDO. In addition, protein-protein interaction and their association in patho-physiology are crucial in understanding protein functions. Both ADO and CDO interacting partner profiles have been presented using STRING database. In this study, we have predicted a 3D model structure for ADO and summarized the biological roles and the pathological consequences which are associated with the altered expression and functioning of ADO and CDO in case of cancer, neurodegenerative disorders and other human diseases. © 2017 The Authors. International Journal of Experimental Pathology © 2017 International Journal of Experimental Pathology.

  18. Hydrophobic thiol-ene surfaces fabricated via plasma activation and photo polymerization

    Science.gov (United States)

    Champathet, P.; Ervithayasuporn, V.; Osotchan, T.; Dangtip, S.

    2017-09-01

    Alumina, such as glazed alumina for electrical insulator, operated in an open field subjects to a very harsh condition; resulting in lifetime shortening. Coating hydrophobic layer on alumina surface can help prolonging its lifetime. In this study, 25 ×25 mm alumina sheets were used as substrates. The hydrophobic composite polymers were prepared from (3-mercaptopropyl)trimethoxysilane(MPTMS), 2,4,6,8-tetramethyl-2,4,6,8tetravinylcyclotetra siloxane(TMTVSi), pentaerythritoltetra(3-mercaptopropionate)(PETMP), 2,2-dimethoxy-2-phe nylaceto phenone(photoinitiator) and heptadecafluorodecylmethacrylate(HEFDMA) via the thiol-ene reaction. The alumina sheets were first activated by dielectric-barrier discharge plasma to improve its adhesion. All the polymers were found to optimize at the ratio of (MPTMS:TMTVSi:PETMP:HDFDMA) to 4:2:1:2 for coating on the alumina substrate. To enhance polymerization, 2,2-dimethoxy-2-phenylaceto phenome was also used as a photoinitiator A proper mixing sequence in the thiol-ene reaction results in film with excellent surface retention after prolong soaking in solvent such as acetone. FTIR shows that S-H and C=C functional groups have significantly changed after photopolymerization and thermally cured. The static contact angle increase from mere 53.0°±1.5° of the uncoated substrate to 120.0°±1.2° after coating. SEM shows the film with clear appearance of a few-micron thick. Under AFM, the coated surface roughness was about 9.3 nm with evenly distributed spikes of a few nanometer in height. The cross-cut test also confirmed the film was very smooth and none of the square of the films detached.

  19. Enzymatic improvement of mitochondrial thiol oxidase Erv1 for oxidized glutathione fermentation by Saccharomyces cerevisiae.

    Science.gov (United States)

    Kobayashi, Jyumpei; Sasaki, Daisuke; Hara, Kiyotaka Y; Hasunuma, Tomohisa; Kondo, Akihiko

    2017-03-15

    Oxidized glutathione (GSSG) is the preferred form for industrial mass production of glutathione due to its high stability compared with reduced glutathione (GSH). In our previous study, over-expression of the mitochondrial thiol oxidase ERV1 gene was the most effective for high GSSG production in Saccharomyces cerevisiae cells among three types of different thiol oxidase genes. We improved Erv1 enzyme activity for oxidation of GSH and revealed that S32 and N34 residues are critical for the oxidation. Five engineered Erv1 variant proteins containing S32 and/or N34 replacements exhibited 1.7- to 2.4-fold higher in vitro GSH oxidation activity than that of parental Erv1, whereas the oxidation activities of these variants for γ-glutamylcysteine were comparable. According to three-dimensional structures of Erv1 and protein stability assays, S32 and N34 residues interact with nearby residues through hydrogen bonding and greatly contribute to protein stability. These results suggest that increased flexibility by amino acid replacements around the active center decrease inhibitory effects on GSH oxidation. Over-expressions of mutant genes coding these Erv1 variants also increased GSSG and consequently total glutathione production in S. cerevisiae cells. Over-expression of the ERV1 S32A gene was the most effective for GSSG production in S. cerevisiae cells among the parent and other mutant genes, and it increased GSSG production about 1.5-fold compared to that of the parental ERV1 gene. This is the first study demonstrating the pivotal effects of S32 and N34 residues to high GSH oxidation activity of Erv1. Furthermore, in vivo validity of Erv1 variants containing these S32 and N34 replacements were also demonstrated. This study indicates potentials of Erv1 for high GSSG production.

  20. Modification of nanoelectrode ensembles by thiols and disulfides to prevent non specific adsorption of proteins

    International Nuclear Information System (INIS)

    Silvestrini, M.; Schiavuta, P.; Scopece, P.; Pecchielan, G.; Moretto, L.M.; Ugo, P.

    2011-01-01

    Highlights: → Complex nanostructures are built on the gold surface of ensembles of nanoelectrodes. → Gold surface of nanoelectrodes was functionalized with SAM of organic sulphurs. → The polycarbonate surrounding nanoelectrodes was functionalized with proteins. → SAMs protect the nanoelectrodes from undesired proteins adsorption. - Abstract: The possibility to functionalize selectively with thiols or disulfides the surface of the gold nanoelectrodes of polycarbonate templated nanoelectrode ensembles (NEEs) is studied. It is shown that the Au nanoelectrodes can be coated by a self assembled monolayer (SAM) of thioctic acid (TA) or 2-mercaptoethanesulfonic (MES) acid. The study of the electrochemical behavior of SAM-modified NEEs by cyclic voltammetry (CV) at different solution pH, using ferrocenecarboxylate as an anionic redox probe (FcCOO - ) and (ferrocenylmethyl)trimethylammonium (FA + ) as a cationic redox probe, demonstrate that the SAM-modified nanoelectrodes are permselective, in that only cationic or neutral probes can access the SAM-coated nanoelectrode surface. CV, AFM and FTIR-ATR data indicate that proteins such as casein or bovine serum albumin, which are polyanionic at pH 7, adsorb on the surface of NEEs untreated with thiols, tending to block the electron transfer of the ferrocenyl redox probes. On the contrary, the pre-treatment of the NEE with an anionic SAM protects the nanoelectrodes from protein fouling, allowing the detection of well shaped voltammetric patterns for the redox probe. Experimental results indicate that, in the case of MES treated NEEs, the protein is bound only onto the polycarbonate surface which surrounds the nanoelectrodes, while the tips of the gold nanoelectrodes remain protein free.

  1. Thiol-based redox signaling in the nitrogen-fixing symbiosis

    Directory of Open Access Journals (Sweden)

    Pierre eFrendo

    2013-09-01

    Full Text Available In nitrogen poor soils legumes establish a symbiotic interaction with rhizobia that results in the formation of root nodules. These are unique plant organs where bacteria differentiate into bacteroids, which express the nitrogenase enzyme complex that reduces atmospheric N2 to ammonia. Nodule metabolism requires a tight control of the concentrations of reactive oxygen and nitrogen species (RONS so that they can perform useful signaling roles while avoiding nitro-oxidative damage. In nodules a thiol-dependent regulatory network that senses, transmits and responds to redox changes is starting to be elucidated. A combination of enzymatic, immunological, pharmacological and molecular analyses has allowed to conclude that glutathione and its legume-specific homolog, homoglutathione, are abundant in meristematic and infected cells, their spatio-temporally distribution is correlated with the corresponding (homoglutathione synthetase activities, and are crucial for nodule development and function. Glutathione is at high concentrations in the bacteroids and at moderate amounts in the mitochondria, cytosol and nuclei. Less information is available on other components of the network. The expression of multiple isoforms of glutathione peroxidases, peroxiredoxins, thioredoxins, glutaredoxins and NADPH-thioredoxin reductases has been detected in nodule cells using antibodies and proteomics. Peroxiredoxins and thioredoxins are essential to regulate and in some cases to detoxify RONS in nodules. Further research is necessary to clarify the regulation of the expression and activity of thiol redox-active proteins in response to abiotic, biotic and developmental cues, their interactions with downstream targets by disulfide-exchange reactions, and their participation in signaling cascades. The availability of mutants and transgenic lines will be crucial to facilitate systematic investigations into the function of the various proteins in the legume

  2. Potentiometric determination of trace amounts of volatile thiols in natural gas

    International Nuclear Information System (INIS)

    Farroha, S.M.; Habboush, A.E.; Kurthab, S.Y.

    1986-01-01

    A potentiometric titration method was developed for the determination of volatile thiols in natural gas. An apparatus was devised for the quantitative absorption of volatile thiols. The measurements were performed in an ethanolic ammonium buffer solution containing a known amount of silver nitrate as supporting electrolyte. The excess silver was precipitated by a known amount of potassium iodide. The excess of iodide was back titrated potentiometrically with a standard solution of silver nitrate. The direct titration of the excess silver ions with a standard solution of potassium iodide gave a poor accuracy compared with the back titration method. Iodide selective electrode was employed as an indicator electrode and a silver-silver chloride electrode as reference electrode. The accuracy and reproducibility of the method were established by preparing several synthetic samples in which ethanthiol containing from 346.61 to 12.11 μUg mercaptan sulfur was taken as standard nitrogen as carrier gas with an optimum flow rate of 31.5 L/hr. The results obtained expressed in the form of Grans plot showed an error ranging from 0.16 to 2.39% by weight and the relative standard deviation did not exceed 2.20%. The amount of mercaptan sulfur determined in Iraqi natural gas taken directly in a cylinder from Dora refinery, Baghdad, Iraq, and after six months of storage we 23.15 Ug/L and 21.25 Ug/L respectively with a relative standard deviation not exceeded 1%. The interferences of hydrogen sulfide could be eliminated by absorption in cadimium acetate containing solution. Other sulfur containing compounds e.g. disulfides, sulfoxides which may be present in natural gas do not interfere with the analysis

  3. Thiol-based redox regulation in sexual plant reproduction: new insights and perspectives

    Directory of Open Access Journals (Sweden)

    Jose A Traverso

    2013-11-01

    Full Text Available The success of sexual reproduction in plants involves (i the proper formation of the plant gametophytes (pollen and embryo sac containing the gametes, (ii the accomplishment of specific interactions between pollen grains and the stigma, which subsequently lead to (iii the fusion of the gametes and eventually to (iv the seed setting. Owing to the lack of mobility, plants have developed specific regulatory mechanisms to control all developmental events underlying the sexual plant reproduction according to environmental challenges. Over the last decade, redox regulation and signaling have come into sight as crucial mechanisms able to manage critical stages during sexual plant reproduction. This regulation involves a complex redox network which includes reactive oxygen species (ROS, reactive nitrogen species (RNS, glutathione and other classic buffer molecules or antioxidant proteins, and some thiol/disulphide-containing proteins belonging to the thioredoxin superfamily, like glutaredoxins (GRXs or thioredoxins (TRXs. These proteins participate as critical elements not only in the switch between the mitotic to the meiotic cycle but also at further developmental stages of microsporogenesis. They are also implicated in the regulation of pollen rejection as the result of self incompatibility. In addition, they display precise space-temporal patterns of expression and are present in specific localizations like the stigmatic papillae or the mature pollen, although their functions and subcellular localizations are not clear yet. In this review we summarize insights and perspectives about the presence of thiol/disulphide-containing proteins in plant reproduction, taking into account the general context of the cell redox network.

  4. Differential regulation of tissue thiol-disulfide redox status in a murine model of peritonitis

    Directory of Open Access Journals (Sweden)

    Benton Shana M

    2012-10-01

    Full Text Available Abstract Background Glutathione (GSH/glutathione disulfide (GSSG and cysteine (Cys/cystine (CySS are major redox pools with important roles in cytoprotection. We determined the impact of septic peritonitis on thiol-disulfide redox status in mice. Methods FVB/N mice (6–12 week old; 8/group underwent laparotomy with cecal ligation and puncture (CLP or laparotomy alone (control. Sections of ileum, colon, lung and liver were obtained and GSH, GSSG, Cys and CySS concentrations determined by HPLC 24 h after laparotomy. Redox potential [Eh in millivolts (mV] of the GSH/GSSG and Cys/CySS pools was calculated using the Nernst equation. Data were analyzed by ANOVA (mean ± SE. Results GSH/GSSG Eh in ileum, colon, and liver was significantly oxidized in septic mice versus control mice (ileum: septic −202±4 versus control −228±2 mV; colon: -195±8 versus −214±1 mV; and liver: -194±3 vs. -210±1 mV, all Ph was unchanged with CLP, while liver and lung Cys/CySS Eh became significantly more reducing (liver: septic = −103±3 versus control −90±2 mV; lung: -101±5 versus −81±1 mV, each P Conclusions Septic peritonitis induced by CLP oxidizes ileal and colonic GSH/GSSG redox but Cys/CySS Eh remains unchanged in these intestinal tissues. In liver, CLP oxidizes the GSH/GSSG redox pool and CyS/CySS Eh becomes more reducing; in lung, CLP does not alter GSH/GSSG Eh, and Cys/CySS Eh is less oxidized. CLP-induced infection/inflammation differentially regulates major thiol-disulfide redox pools in this murine model.

  5. Amino acid-incorporated polymer network by thiol-ene polymerization

    Directory of Open Access Journals (Sweden)

    R. Yokose

    2015-08-01

    Full Text Available Triallyl L-alanine (A3A and triallyl L-phenylalanine (A3F were synthesized by reactions of L-alanine and L-phenylalanine with allyl bromide in the presence of sodium hydroxide, respectively. Thiol-ene thermal polymerization of A3A or A3F with pentaerythritol-based primary tetrathiol (pS4P or pentaerythritol-based secondary tetrathiol (S4P at allyl/SH 1/1 in the presence of 2,2'-azobis(isobutyronitrile produced an amino acid-incorporated polymer network (A3ApS4P, A3A-S4P or A3F-S4P. Although the thermally cured resins were homogeneous and flat films, the corresponding thiol-ene photopolymerization did not give a successful result. Degree of swelling for each thermally cured film in N,Ndimethylformamide was much higher than that in water. The glass transition and 5% weight loss temperatures (Tg and T5 of A3F-pS4P and A3F-S4P were higher than those of A3A-pS4P and A3A-S4P, respectively. Also, A3F-pS4P and A3F-S4P exhibited much higher tensile strengths and moduli than A3A-pS4P and A3A-S4P did, respectively. Consequently, A3FpS4P displayed the highest Tg (38.7°C, T5 (282.0°C, tensile strength (9.5 MPa and modulus (406 MPa among all the thermally cured resins.

  6. Modification of nanoelectrode ensembles by thiols and disulfides to prevent non specific adsorption of proteins

    Energy Technology Data Exchange (ETDEWEB)

    Silvestrini, M. [Department of Molecular Sciences and Nanosystems, University Ca' Foscari of Venice, Santa Marta 2137, 30123 Venice (Italy); Schiavuta, P.; Scopece, P. [Associazione CIVEN, via delle Industrie 5, 30175 Marghera - Venice (Italy); Pecchielan, G.; Moretto, L.M. [Department of Molecular Sciences and Nanosystems, University Ca' Foscari of Venice, Santa Marta 2137, 30123 Venice (Italy); Ugo, P., E-mail: ugo@unive.it [Department of Molecular Sciences and Nanosystems, University Ca' Foscari of Venice, Santa Marta 2137, 30123 Venice (Italy)

    2011-09-01

    Highlights: > Complex nanostructures are built on the gold surface of ensembles of nanoelectrodes. > Gold surface of nanoelectrodes was functionalized with SAM of organic sulphurs. > The polycarbonate surrounding nanoelectrodes was functionalized with proteins. > SAMs protect the nanoelectrodes from undesired proteins adsorption. - Abstract: The possibility to functionalize selectively with thiols or disulfides the surface of the gold nanoelectrodes of polycarbonate templated nanoelectrode ensembles (NEEs) is studied. It is shown that the Au nanoelectrodes can be coated by a self assembled monolayer (SAM) of thioctic acid (TA) or 2-mercaptoethanesulfonic (MES) acid. The study of the electrochemical behavior of SAM-modified NEEs by cyclic voltammetry (CV) at different solution pH, using ferrocenecarboxylate as an anionic redox probe (FcCOO{sup -}) and (ferrocenylmethyl)trimethylammonium (FA{sup +}) as a cationic redox probe, demonstrate that the SAM-modified nanoelectrodes are permselective, in that only cationic or neutral probes can access the SAM-coated nanoelectrode surface. CV, AFM and FTIR-ATR data indicate that proteins such as casein or bovine serum albumin, which are polyanionic at pH 7, adsorb on the surface of NEEs untreated with thiols, tending to block the electron transfer of the ferrocenyl redox probes. On the contrary, the pre-treatment of the NEE with an anionic SAM protects the nanoelectrodes from protein fouling, allowing the detection of well shaped voltammetric patterns for the redox probe. Experimental results indicate that, in the case of MES treated NEEs, the protein is bound only onto the polycarbonate surface which surrounds the nanoelectrodes, while the tips of the gold nanoelectrodes remain protein free.

  7. A neutral polyacrylate copolymer coating for surface modification of thiol-ene microchannels for improved performance of protein separation by microchip electrophoresis

    DEFF Research Database (Denmark)

    Mesbah, Kiarach; Mai, T.D.; Jensen, Thomas Glasdam

    2016-01-01

    We have investigated the behavior of thiol-ene substrates that is a class of promising materials for lab-on-a-chip electrophoresis applications. Two polymeric materials were prepared by copolymerization of N, N-dimethylacrylamide (DMA), (3-(methacryloyl-oxy)propyl)trimethoxysilane (PMA) and 3......-(DMA-PMAMAPS) copolymer were evaluated in terms of surface hydrophilicity, suppression and stability of electro-osmotic flow and prevention of protein adsorption. Surface modification of thiol-ene containing a 20 % excess of thiols with the terpolymer p-(DMA-PMA-MAPS) was found to offer the most stable coating and most...

  8. Potentiometric study of rhenium (V) complex formation with 4-methyl-1.2.4-triazol thiol-5 in the medium of 7 mol/l HBr

    International Nuclear Information System (INIS)

    Amindzhanov, A.A.; Safarmamadov, S.M.

    1992-01-01

    Present article is devoted to potentiometric study of rhenium (V) complex formation with 4-methyl-1.2.4-triazol thiol-5 in the medium of 7 mol/l HBr. The function of formation of oxo bromine-4-methyl-1.2.4-triazol thiol complexes of rhenium (V) in the medium of 5 mol/l HBr at 273 K temperature was determined. The function of formation of oxo bromine-4-methyl-1.2.4-triazol thiol complexes of rhenium (V) in the medium of 5 mol/l HBr at 298 K temperature was determined as well.

  9. Antibiofouling hybrid dendritic Boltorn/star PEG thiol-ene cross-linked networks.

    Science.gov (United States)

    Bartels, Jeremy W; Imbesi, Philip M; Finlay, John A; Fidge, Christopher; Ma, Jun; Seppala, Jonathan E; Nystrom, Andreas M; Mackay, Michael E; Callow, James A; Callow, Maureen E; Wooley, Karen L

    2011-06-01

    A series of thiol-ene generated amphiphilic cross-linked networks was prepared by reaction of alkene-modified Boltorn polyesters (Boltorn-ene) with varying weight percent of 4-armed poly(ethylene glycol) (PEG) tetrathiol (0-25 wt%) and varying equivalents of pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) (0-64 wt%). These materials were designed to present complex surface topographies and morphologies, with heterogeneity of surface composition and properties and robust mechanical properties, to serve as nontoxic antibiofouling coatings that are amenable to large-scale production for application in the marine environment. Therefore, a two-dimensional matrix of materials compositions was prepared to study the physical and mechanical properties, over which the compositions spanned from 0 to 25 wt% PEG tetrathiol and 0-64 wt% PETMP (the overall thiol/alkene (SH/ene) ratios ranged from 0.00 to 1.00 equiv), with both cross-linker weight percentages calculated with respect to the weight of Boltorn-ene. The Boltorn-ene components were prepared through the esterification of commercially available Boltorn H30 with 3-butenoic acid. The subsequent cross-linking of the Boltorn-PEG-PETMP films was monitored using IR spectroscopy, where it was found that near-complete consumption of both thiol and alkene groups occurred when the stoichiometry was ca. 48 wt% PETMP (0.75 equiv SH/ene, independent of PEG amount). The thermal properties of the films showed an increase in T(g) with an increase in 4-armed PEG-tetrathiol wt%, regardless of the PETMP concentration. Investigation of the bulk mechanical properties in dry and wet states found that the Young's modulus was the greatest at 48 wt% PETMP (0.75 equiv of SH/ene). The ultimate tensile strength increased when PETMP was constant and the PEG concentration was increased. The Young's modulus was slightly lower for wet films at constant PEG or constant PETMP amounts, than for the dry samples. The nanoscopic surface features were

  10. On the effect of oxygen or copper(II) in radiation-induced degradation of DNA in the presence of thiols

    International Nuclear Information System (INIS)

    Pruetz, W.A.; Moenig, Hans

    1987-01-01

    Degradiation of DNA when γ-irradiated in aqueous solutions containing cysteine can be efficiently enhanced not only with oxygen, but to the same extent also with Cu 2+ ions under hypoxic conditions. The result can be explained by 'self-repair' in this sytem due to recombination of DNA radical with RSS radical - R intermediates, and repair inhibition by oxygen or copper involving RSS radical - R scavenging. It is emphasized that oxygen enhancement in DNA-thiol systems may occur not only by peroxidation, via defect fixation (DNA-O radical 2 ) or thiol activation (RS-O radical 2 ), but also by the well-established inactivation of RSS radical - R by oxygen. There is evidence also from literature data for a correlation between oxygen enhancement and RSS radical - R stability, which varies with thiol concentration, pH and thiol structure. (author)

  11. An Auto-Inductive Cascade for the Optical Sensing of Thiols in Aqueous Media: Application in the Detection of a VX Nerve Agent Mimic.

    Science.gov (United States)

    Sun, Xiaolong; Anslyn, Eric V

    2017-08-01

    A new auto-inductive protocol employs a Meldrum's-acid-based conjugate acceptor (1) as a latent source of thiol for signal amplification, as well as optical detection of thiols. The auto-induction is initiated by a thiol-disulfide exchange that leads to the generation of β-mercaptoethanol, which in turn decouples the conjugate acceptor to release more thiols, resulting in a self-propagating cycle that continues until all the conjugate acceptor is consumed. Using 1 in a two-step integrated protocol yields a rapid, sensitive, and precise diagnostic assay for the ultratrace quantitation of a thiophosphate nerve agent surrogate. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Synchrotron radiation based STXM analysis and micro-XRF mapping of differential expression of extracellular thiol groups by Acidithiobacillus ferrooxidans grown on Fe(2+) and S(0).

    Science.gov (United States)

    Xia, Jin-Lan; Liu, Hong-Chang; Nie, Zhen-Yuan; Peng, An-An; Zhen, Xiang-Jun; Yang, Yun; Zhang, Xiu-Li

    2013-09-01

    The differential expression of extracellular thiol groups by Acidithiobacillus ferrooxidans grown on substrates Fe(2+) and S(0) was investigated by using synchrotron radiation based scanning transmission X-ray microscopy (STXM) imaging and microbeam X-ray fluorescence (μ-XRF) mapping. The extracellular thiol groups (SH) were first alkylated by iodoacetic acid forming Protein-SCH2COOH and then the P-SCH2COOH was marked by calcium ions forming P-SCH2COOCa. The STXM imaging and μ-XRF mapping of SH were based on analysis of SCH2COO-bonded Ca(2+). The results indicated that the thiol group content of A. ferrooxidans grown on S(0) is 3.88 times to that on Fe(2+). Combined with selective labeling of SH by Ca(2+), the STXM imaging and μ-XRF mapping provided an in situ and rapid analysis of differential expression of extracellular thiol groups. © 2013.

  13. Spectroscopic Characterization of Extracellular Polymeric Substances from Escherichia coli and Serratia marcescens: Suppression using Sub-Inhibitory Concentrations of Bismuth Thiols

    Energy Technology Data Exchange (ETDEWEB)

    Badireddy, Appala R.; Korpol, Bhoom Reddy; Chellam, Shankararaman; Gassman, Paul L.; Engelhard, Mark H.; Lea, Alan S.; Rosso, Kevin M.

    2008-10-21

    Free and capsular EPS produced by Escherichia coli and Serratia marcescens were characterized in detail using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES). Total EPS production decreased upon treatment with sub-inhibitory concentrations of lipophilic bismuth thiols (bismuth dimercaptopropanol, BisBAL; bismuth ethanedithiol, BisEDT; and bismuth pyrithione, BisPYR), BisBAL being most effective. Bismuth thiols also influenced acetylation and carboxylation of polysaccharides in EPS from S. marcescens. Extensive homology between EPS samples in the presence and absence of bismuth was observed with proteins, polysaccharides, and nucleic acids varying predominantly only in the total amount expressed. Second derivative analysis of the amide I region of FTIR spectra revealed decreases in protein secondary structures in the presence of bismuth thiols. Hence, anti-fouling properties of bismuth thiols appear to originate in their ability to suppress O-acetylation and protein secondary structures in addition to total EPS secretion.

  14. Custom-designed multidentate aromatic thiols offer organic thin films with enhanced stability

    Science.gov (United States)

    Rittikulsittichai, Supachai

    2011-12-01

    This dissertation reports a comparative study of the film characteristics of self-assembled monolayers (SAMs) on gold generated from the adsorption of custom-designed aromatic thiol adsorbates containing systematically varying alkoxy chain-to-sulfur headgroup ratios. Furthermore, the relative thermal stabilities of the selected monolayers were evaluated by comparing the solution-phase desorption of the SAMs in isooctane at 80°C as a function of time. Characterization of the SAMs derived from the monodentate adsorbates with multiple chained tailgroups varying from 1 to 3, R1ArMT, R2ArMT, and R3ArMT, respectively, revealed that the conformational order of the former monolayer is higher than that of the two latter monolayers. Additionally, the results from PM-IRRAS and XPS studies pointed out the strong influence of branched chains on intramolecular chain-chain interactions, chain packing densities, and chain conformation of the monolayers derived from R2ArMT and R3ArMT. Similarly, the intramolecular interactions between the chains themselves were found to exert a strong influence on the chain conformation of the monolayers derived from the aromatic dithiolates with branched tailgroups, R2ArDT and R3ArDT, while the interchain interactions for the R1ArDT monolayer is less favorable due to the structural mismatch between the molecular counterparts. Furthermore, characterization of the monolayers derived from the multidentate aromatic thiols with single-chain tailgroups showed that the aromatic trithiolate, R1ArTT, generated the most loosely packed monolayer with the least chain conformation when compared to R1ArDT and R1ArMT. Comparison of the monolayer films derived from R1ArDT and R1ArmDT with the specific design of an extended intramolecular space between the chelating sulfur atoms revealed that the monolayer films were structurally similar. The relative thermal stability of the selected SAMs in this present study increases as follows: R1ArmDT > R1ArTT > R3ArDT > R2

  15. Determination of volatile thiols in virgin olive oil by derivatisation and LC-HRMS, and relation with sensory attributes.

    Science.gov (United States)

    Vichi, Stefania; Cortés-Francisco, Nuria; Romero, Agustí; Caixach, Josep

    2014-04-15

    Volatile thiols were determined by derivatisation followed by ESI-LC-HRMS in twenty-five virgin olive oils (VOOs) pertaining to different commercial classes. 4-Methoxy-2-methyl-2-butanethiol (4MMB) was quantified, and 3-methyl-2-butenethiol and methanethiol were identified for the first time in VOO by non-target analysis. In order to evaluate the influence of volatile thiols on VOO aroma, the sensory notes, defects and secondary attributes were determined in samples according to European regulation by an Official VOO Panel. A significant correlation was found between the concentration of 4MMB in VOO samples and the 'fig tree leaf' sensory attribute. To confirm these results, 4MMB odour detection threshold and odour recognition were investigated. Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. Potassium carbonate: a highly efficient catalyst for the acylation of alco-hols, phenols and thiols under mild conditions

    Directory of Open Access Journals (Sweden)

    Mosstafa Kazemi

    2014-02-01

    Full Text Available A general, mild and efficient protocol has been developed for the synthesis of esters and thioesters. The process has been taking place using tetra n-butylammonium iodide (TBAI as a phase-transfer catalyst and in the presence of potassium carbonate (K2CO3. A wide range of esters and thioesters was prepared in high yields and suitable times by the treatment of alcohols, phenols and thiols with acetic anhydride. Acylation reactions of a number of alcohols, phenols and thiols with acetic anhydride demonstrated that potassium carbonate is a convenient and efficient catalyst for the synthesis of esters and thioesters. This is a mild, general and practical procedure for the synthesis of esters and thioesters in high yields and suitable times.

  17. Lithium-Catalyzed Thiol Alkylation with Tertiary and Secondary Alcohols: Synthesis of 3-Sulfanyl-Oxetanes as Bioisosteres.

    Science.gov (United States)

    Croft, Rosemary A; Mousseau, James J; Choi, Chulho; Bull, James A

    2018-01-19

    3-Sulfanyl-oxetanes are presented as promising novel bioisosteric replacements for thioesters or benzyl sulfides. From oxetan-3-ols, a mild and inexpensive Li catalyst enables chemoselective C-OH activation and thiol alkylation. Oxetane sulfides are formed from various thiols providing novel motifs in new chemical space and specifically as bioisosteres for thioesters due to their similar shape and electronic properties. Under the same conditions, various π-activated secondary and tertiary alcohols are also successful. Derivatization of the oxetane sulfide linker provides further novel oxetane classes and building blocks. Comparisons of key physicochemical properties of the oxetane compounds to selected carbonyl and methylene analogues indicate that these motifs are suitable for incorporation into drug discovery efforts. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. X-ray magnetic circular dichroism and small angle neutron scattering studies of thiol capped gold nanoparticles

    International Nuclear Information System (INIS)

    de la Venta, J.; Bouzas, V.; Pucci, A.; Laguna-Marco, M.A.; Haskel, D.; te Velthuis, S.G.E; Hoffmann, A.; Lal, J.; Bleuel, M.; Ruggeri, G.; de Julian Fernandez, C.; Garcia, M.A.

    2009-01-01

    X-ray magnetic circular dichroism (XMCD) and Small Angle Neutron Scattering (SANS) measurements were performed on thiol capped Au nanoparticles (NPs) embedded into polyethylene. An XMCD signal of 0.8 · 10 -4 was found at the Au L 3 edge of thiol capped Au NPs embedded in a polyethylene matrix for which Superconducting Quantum Interference Device (SQUID) magnetometry yielded a saturation magnetization, M s , of 0.06 emu/g Au . SANS measurements showed that the 3.2 nm average-diameter nanoparticles are 28% polydispersed, but no detectable SANS magnetic signal was found with the resolution and sensitivity accessible with the neutron experiment. A comparison with previous experiments carried out on Au NPs and multilayers, yield to different values between XMCD signals and magnetization measured by SQUID magnetometer. We discuss the origin of those differences

  19. X-ray magnetic circular dichroism and small angle neutron scattering studies of thiol capped gold nanoparticles.

    Science.gov (United States)

    de la Venta, J; Bouzas, V; Pucci, A; Laguna-Marco, M A; Haskel, D; te Velthuis, S G E; Hoffmann, A; Lal, J; Bleuel, M; Ruggeri, G; de Julián Fernández, C; García, M A

    2009-11-01

    X-ray magnetic circular dichroism (XMCD) and Small Angle Neutron Scattering (SANS) measurements were performed on thiol capped Au nanoparticles (NPs) embedded into polyethylene. An XMCD signal of 0.8 x 10(-4) was found at the Au L3 edge of thiol capped Au NPs embedded in a polyethylene matrix for which Superconducting Quantum Interference Device (SQUID) magnetometry yielded a saturation magnetization, M(S), of 0.06 emu/g(Au). SANS measurements showed that the 3.2 nm average-diameter nanoparticles are 28% polydispersed, but no detectable SANS magnetic signal was found with the resolution and sensitivity accessible with the neutron experiment. A comparison with previous experiments carried out on Au NPs and multilayers, yield to different values between XMCD signals and magnetization measured by SQUID magnetometer. We discuss the origin of those differences.

  20. Photostability and Performance of Polystyrene Films Containing 1,2,4-Triazole-3-thiol Ring System Schiff Bases

    Directory of Open Access Journals (Sweden)

    Gassan Q. Ali

    2016-12-01

    Full Text Available Series of 4-(4-substituted benzylideneamino-5-(3,4,5-trimethoxyphenyl-4H-1,2,4-triazole-3-thiols were synthesized and their structures were confirmed. The synthesized Schiff bases were used as photostabilizers for polystyrene against photodegradation. Polystyrene polymeric films containing synthesized Schiff bases (0.5% by weight were irradiated (λmax = 365 nm and light intensity = 6.43 × 10−9 ein·dm−3·s−1 at room temperature. The photostabilization effect of 1,2,4-triazole-3-thiols Schiff bases was determined using various methods. All the additives used enhanced the photostability of polystyrene films against irradiation compared with the result obtained in the absence of Schiff base. The Schiff bases can act as photostabilizers for polystyrene through the direct absorption of UV radiation and/or radical scavengers.

  1. X-ray magnetic circular dichroism and small angle neutron scattering studies of thiol capped gold nanoparticles.

    Energy Technology Data Exchange (ETDEWEB)

    de la Venta, J.; Bouzas, V.; Pucci, A.; Laguna-Marco, M. A.; Haskel, D.; te Velthuis, S. G. E; Hoffmann, A.; Lal, J.; Bleuel, M.; Ruggeri, G.; de Julian Fernandez, C.; Garcia, M. A.; Univ.Complutense de Madrid; Inst. de Magnetismo Aplicado; Univ. of Pisa; Lab. di Magnetismo Molecolare

    2009-01-01

    X-ray magnetic circular dichroism (XMCD) and Small Angle Neutron Scattering (SANS) measurements were performed on thiol capped Au nanoparticles (NPs) embedded into polyethylene. An XMCD signal of 0.8 {center_dot} 10{sup -4} was found at the Au L{sub 3} edge of thiol capped Au NPs embedded in a polyethylene matrix for which Superconducting Quantum Interference Device (SQUID) magnetometry yielded a saturation magnetization, M{sub s}, of 0.06 emu/g{sub Au}. SANS measurements showed that the 3.2 nm average-diameter nanoparticles are 28% polydispersed, but no detectable SANS magnetic signal was found with the resolution and sensitivity accessible with the neutron experiment. A comparison with previous experiments carried out on Au NPs and multilayers, yield to different values between XMCD signals and magnetization measured by SQUID magnetometer. We discuss the origin of those differences.

  2. X-ray magnetic circular dichroism and small angle neutron scattering study of thiol capped gold nanoparticles.

    Energy Technology Data Exchange (ETDEWEB)

    de la Venta, J.; Bouzas, V.; Pucci, A.; Laguna-Marco, M. A.; Haskel, D.; Pinel, E. F.; te Velthuis, S. G. E.; Hoffmann, A.; Lal, J.; Bleuel, M.; Ruggeri, G.; de Julian, C.; Garcia, M. A.; Univ. Complutense de Madrid; Inst. de Magnetismo Aplicado UCM; Univ. Pisa; Univ. di Padova

    2009-11-01

    X-ray magnetic circular dichroism (XMCD) and Small Angle Neutron Scattering (SANS) measurements were performed on thiol capped Au nanoparticles (NPs) embedded into polyethylene. An XMCD signal of 0.8 {center_dot} 10{sup -4} was found at the Au L{sub 3} edge of thiol capped Au NPs embedded in a polyethylene matrix for which Superconducting Quantum Interference Device (SQUID) magnetometry yielded a saturation magnetization, M{sub s}, of 0.06 emu/g{sub Au}. SANS measurements showed that the 3.2 nm average-diameter nanoparticles are 28% polydispersed, but no detectable SANS magnetic signal was found with the resolution and sensitivity accessible with the neutron experiment. A comparison with previous experiments carried out on Au NPs and multilayers, yield to different values between XMCD signals and magnetization measured by SQUID magnetometer. We discuss the origin of those differences.

  3. Impairment of blood lipids pattern in gamma irradiated albino mice and prophylactic role of thiols and W R-2721

    International Nuclear Information System (INIS)

    EL-dighidy, E.A.M.; El-Kady, M.H.R.

    1986-01-01

    The present work aims to investigate the effect of shot doses of whole body gamma irradiation at the levels, 6, 7.5, 11, 25 and 15 Gy, on the blood lipids pattern in male swiss albino mice. This has been manifested by the levels of total lipids, triglycerides, phospholipids and cholesterol. The radioprotective capacities of two sulfhydryl compounds: thiols and W R-2721, against impairment in blood lipids pattern, have been evaluated in mice received the higher shot radiation dose-level at 15 Gy. Significant increases in the levels of blood total lipid, phospholipids, triglycerides and cholesterol have been recorded on the third day post exposure under the experiment conditions, the data indicated more efficient protection of blood lipid pattern exerted by W R-2721 than in case of thiols. 2 figs., 2 tabs

  4. Species-Specific Thiol-Disulfide Equilibrium Constant: A Tool To Characterize Redox Transitions of Biological Importance.

    Science.gov (United States)

    Mirzahosseini, Arash; Somlyay, Máté; Noszál, Béla

    2015-08-13

    Microscopic redox equilibrium constants, a new species-specific type of physicochemical parameters, were introduced and determined to quantify thiol-disulfide equilibria of biological significance. The thiol-disulfide redox equilibria of glutathione with cysteamine, cysteine, and homocysteine were approached from both sides, and the equilibrium mixtures were analyzed by quantitative NMR methods to characterize the highly composite, co-dependent acid-base and redox equilibria. The directly obtained, pH-dependent, conditional constants were then decomposed by a new evaluation method, resulting in pH-independent, microscopic redox equilibrium constants for the first time. The 80 different, microscopic redox equilibrium constant values show close correlation with the respective thiolate basicities and provide sound means for the development of potent agents against oxidative stress.

  5. Live-cell imaging of biothiols via thiol/disulfide exchange to trigger the photoinduced electron transfer of gold-nanodot sensor

    International Nuclear Information System (INIS)

    Liu, Ching-Ping; Wu, Te-Haw; Liu, Chia-Yeh; Lin, Shu-Yi

    2014-01-01

    Highlights: • The ultrasmall size, PAMAM dendrimer-entrapped Au 8 -clusters were synthesized. • Thiol/disulfide exchange with biothiols to release 2-PyT resulted in quenching. • The sensing platform can detect both low and high molecular weight thiols. • Capable of imaging biothiols including protein thiols in living cells. - Abstract: Biothiols have been reported to involve in intracellular redox-homeostasis against oxidative stress. In this study, a highly selective and sensitive fluorescent probe for sensing biothiols is explored by using an ultrasmall gold nanodot (AuND), the dendrimer-entrapped Au 8 -cluster. This strategy relies upon a thiol/disulfide exchange to trigger the fluorescence change through a photoinduced electron transfer (PET) process between the Au 8 -cluster (as an electron donor) and 2-pyridinethiol (2-PyT) (as an electron acceptor) for sensing biothiols. When 2-PyT is released via the cleavage of disulfide bonds by biothiols, the PET process from the Au 8 -cluster to 2-PyT is initiated, resulting in fluorescence quenching. The fluorescence intensity was found to decrease linearly with glutathione (GSH) concentration (0–1500 μM) at physiological relevant levels and the limit of detection for GSH was 15.4 μM. Compared to most nanoparticle-based fluorescent probes that are limited to detect low molecular weight thiols (LMWTs; i.e., GSH and cysteine), the ultrasmall Au 8 -cluster-based probe exhibited less steric hindrance and can be directly applied in selectively and sensitively detecting both LMWTs and high molecular weight thiols (HMWTs; i.e., protein thiols). Based on such sensing platform, the surface-functionalized Au 8 -cluster has significant promise for use as an efficient nanoprobe for intracellular fluorescence imaging of biothiols including protein thiols in living cells whereas other nanoparticle-based fluorescent probes cannot

  6. Effectiveness of the antimicrobial removal device, BACTEC 16B medium, and thiol broth in neutralizing antibacterial activities of imipenem, norfloxacin, and related agents.

    OpenAIRE

    Weinberg, E; Shungu, D L; Gadebusch, H H

    1984-01-01

    The Antimicrobial Removal Device (ARD), BACTEC 16B medium, and Thiol broth were evaluated for their effectiveness in reducing the activity of imipenem (IPM), cefoxitin, moxalactam, and ceftazidime in blood samples. In addition, the capability of the ARD and Thiol broth to bind norfloxacin and the ARD to bind oxolinic and nalidixic acids in urine samples was investigated. At the highest concentrations of the drugs tested (32 micrograms/ml for the four beta-lactams and 256 micrograms/ml for the...

  7. Influence of liposome forms of the rhenium compounds and cis-platin on thiol-disulfide coefficient in the rats’ blood

    Directory of Open Access Journals (Sweden)

    I. V. Klenina

    2007-12-01

    Full Text Available Thiol-disulfide coefficient (TDC and its different modifications in model in vivo were studied. Introduction of the liposome forms of cluster rhenium compounds with organic ligands (CROL leads to both TDC increasing and to the constancy of the TDC. Thus, CROLs aren’t toxic agents and some compounds could mobilize organisms’ thiol defence system. Liposome form of cis-platin leads to the TDC decreasing. Important CROL capacities for its future medical treatment practice were shown.

  8. Live-cell imaging of biothiols via thiol/disulfide exchange to trigger the photoinduced electron transfer of gold-nanodot sensor

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ching-Ping; Wu, Te-Haw; Liu, Chia-Yeh; Lin, Shu-Yi, E-mail: shuyi@nhri.org.tw

    2014-11-07

    Highlights: • The ultrasmall size, PAMAM dendrimer-entrapped Au{sub 8}-clusters were synthesized. • Thiol/disulfide exchange with biothiols to release 2-PyT resulted in quenching. • The sensing platform can detect both low and high molecular weight thiols. • Capable of imaging biothiols including protein thiols in living cells. - Abstract: Biothiols have been reported to involve in intracellular redox-homeostasis against oxidative stress. In this study, a highly selective and sensitive fluorescent probe for sensing biothiols is explored by using an ultrasmall gold nanodot (AuND), the dendrimer-entrapped Au{sub 8}-cluster. This strategy relies upon a thiol/disulfide exchange to trigger the fluorescence change through a photoinduced electron transfer (PET) process between the Au{sub 8}-cluster (as an electron donor) and 2-pyridinethiol (2-PyT) (as an electron acceptor) for sensing biothiols. When 2-PyT is released via the cleavage of disulfide bonds by biothiols, the PET process from the Au{sub 8}-cluster to 2-PyT is initiated, resulting in fluorescence quenching. The fluorescence intensity was found to decrease linearly with glutathione (GSH) concentration (0–1500 μM) at physiological relevant levels and the limit of detection for GSH was 15.4 μM. Compared to most nanoparticle-based fluorescent probes that are limited to detect low molecular weight thiols (LMWTs; i.e., GSH and cysteine), the ultrasmall Au{sub 8}-cluster-based probe exhibited less steric hindrance and can be directly applied in selectively and sensitively detecting both LMWTs and high molecular weight thiols (HMWTs; i.e., protein thiols). Based on such sensing platform, the surface-functionalized Au{sub 8}-cluster has significant promise for use as an efficient nanoprobe for intracellular fluorescence imaging of biothiols including protein thiols in living cells whereas other nanoparticle-based fluorescent probes cannot.

  9. Thiol oxidation of hemolymph proteins in oysters Crassostrea brasiliana as markers of oxidative damage induced by urban sewage exposure.

    Science.gov (United States)

    Trevisan, Rafael; Flores-Nunes, Fabrício; Dolores, Euler S; Mattos, Jacó J; Piazza, Clei E; Sasaki, Sílvio T; Taniguchi, Satie; Montone, Rosalinda C; Bícego, Márcia C; Dos Reis, Isis M M; Zacchi, Flávia L; Othero, Bárbara N M; Bastolla, Camila L V; Mello, Danielle F; Fraga, Ana Paula M; Wendt, Nestor; Toledo-Silva, Guilherme; Razzera, Guilherme; Dafre, Alcir L; de Melo, Cláudio M R; Bianchini, Adalto; Marques, Maria R F; Bainy, Afonso C D

    2017-07-01

    Urban sewage is a concerning issue worldwide, threatening both wildlife and human health. The present study investigated protein oxidation in mangrove oysters (Crassostrea brasiliana) exposed to seawater from Balneário Camboriú, an important tourist destination in Brazil that is affected by urban sewage. Oysters were exposed for 24 h to seawater collected close to the Camboriú River (CAM1) or 1 km away (CAM2). Seawater from an aquaculture laboratory was used as a reference. Local sewage input was marked by higher levels of coliforms, nitrogen, and phosphorus in seawater, as well as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), linear alkylbenzenes (LABs), and fecal steroid in sediments at CAM1. Exposure of oysters to CAM1 caused marked bioaccumulation of LABs and decreased PAH and PCB concentrations after exposure to both CAM1 and CAM2. Protein thiol oxidation in gills, digestive gland, and hemolymph was evaluated. Lower levels of reduced protein thiols were detected in hemolymph from CAM1, and actin, segon, and dominin were identified as targets of protein thiol oxidation. Dominin susceptibility to oxidation was confirmed in vitro by exposure to peroxides and hypochlorous acid, and 2 cysteine residues were identified as potential sites of oxidation. Overall, these data indicate that urban sewage contamination in local waters has a toxic potential and that protein thiol oxidation in hemolymph could be a useful biomarker of oxidative stress in bivalves exposed to contaminants. Environ Toxicol Chem 2017;36:1833-1845. © 2016 SETAC. © 2016 SETAC.

  10. Iodine-catalyzed regioselective thiolation of imidazo[1,2-a]pyridines using sulfonyl hydrazides as a thiol surrogate.

    Science.gov (United States)

    Bagdi, Avik Kumar; Mitra, Shubhanjan; Ghosh, Monoranjan; Hajra, Alakananda

    2015-03-21

    Iodine-catalyzed regioselective sulfenylation of imidazo[1,2-a]pyridines via C(sp(2))-H bond functionalization has been achieved using sulfonyl hydrazides as a thiol surrogate. A library of 3-sulfanylimidazopyridines with broad functionalities was synthesized under metal and oxidant-free practical reaction conditions. This methodology is also applicable for the regioselective sulfenylation of imidazo[2,1-b]thiazole and benzo[d]imidazo[2,1-b]thiazole.

  11. In vivo oxidative stress alters thiol redox status of peroxiredoxin 1 and 6 and impairs rat sperm quality

    Science.gov (United States)

    Liu, Yannan; O’Flaherty, Cristian

    2017-01-01

    Oxidative stress, the imbalance between the production of reactive oxygen species (ROS) and antioxidant activity is a major culprit of male infertility. Peroxiredoxins (PRDXs) are major antioxidant enzymes of mammalian spermatozoa and are thiol oxidized and inactivated by ROS in a dose-dependent manner. Their deficiency and/or inactivation have been associated with men infertility. The aim of this study was to elucidate the impact of oxidative stress, generated by the in vivo tert-butyl hydroperoxide (tert-BHP) treatment on rat epididymal spermatozoa during their maturation process. Adult Sprague-Dawley males were treated with μmoles tert-BHP/kg or saline (control) per day intraperitoneal for 15 days. Lipid peroxidation (2-thibarbituric acid reactive substances assay), total amount and thiol oxidation of PRDXs along with the total amount of superoxide dismutase (SOD), motility and DNA oxidation (8-hydroxy-deoxyguanosine) were determined in epididymal spermatozoa. Total amount of PRDXs and catalase and thiol oxidation of PRDXs were determined in caput and cauda epididymis. While animals were not affected by treatment, their epididymal spermatozoa have decreased motility, increased levels of DNA oxidation and lipid peroxidation along with increased PRDXs (and not SOD) amounts. Moreover, sperm PRDXs were highly thiol oxidized. There was a differential regulation in the expression of PRDX1 and PRDX6 in the epididymis that suggests a segment-specific role for PRDXs. In conclusion, PRDXs are increased in epididymal spermatozoa in an attempt to fight against the oxidative stress generated by tert-BHP in the epididymis. These findings highlight the role of PRDXs in the protection of sperm function and DNA integrity during epididymal maturation. PMID:26823067

  12. Thiol Oxidation by Diamide Leads to Dopaminergic Degeneration and Parkinsonism Phenotype in Mice: A Model for Parkinson's Disease.

    Science.gov (United States)

    Ray, Ajit; Kambali, Maltesh; Ravindranath, Vijayalakshmi

    2016-08-10

    This study investigates the role of thiol homeostasis disruption in Parkinson's disease (PD) pathogenesis using a novel animal model. A single unilateral administration of the thiol oxidant, diamide (1.45 μmol) into substantia nigra (SN) of mice leads to locomotor deficits and degeneration of dopaminergic (DA) neurons in SN pars compacta (SNpc). Diamide-injected mice showed hemiparkinsonian behavior, measured as spontaneous contralateral body rotations, poor grip strength, and impaired locomotion on a rotarod. We observed a significant loss of DA neurons in ipsilateral but not contralateral SNpc and their striatal fibers. This was accompanied by increased Fluoro-Jade C-positive cells and a loss of NeuN-positive neurons, indicative of neurodegeneration. Importantly, diamide injection led to α-synuclein aggregation in ipsilateral SNpc, a hallmark of PD pathology not often seen in animal models of PD. On investigating putative mechanism(s) involved, we observed a loss of glutathione, which is essential for maintaining protein thiol homeostasis (PTH). Concomitantly, the redox-sensitive ASK1-p38 mitogen-activated protein kinase (MAPK) death signaling pathway was activated in the ipsilateral but not contralateral ventral midbrain through dissociation of ASK1-Trx1 complex. In Neuro-2a cells, diamide activated ASK1-p38 cascade through Trx1 oxidation, leading to cell death, which was abolished by ASK1 knockdown. Since diamide selectively disrupts PTH, DA neurons appear to be vulnerable to such perturbations and even a single insult with a thiol oxidant can result in long-lasting degeneration. Identification of the role of PTH dysregulation in neurodegeneration, especially in early PD, not only facilitates an understanding of novel regulatory features of molecular signaling cascades but also may aid in developing disease-modifying strategies for PD. Antioxid. Redox Signal. 25, 252-267.

  13. One-step fabrication of PEGylated fluorescent nanodiamonds through the thiol-ene click reaction and their potential for biological imaging

    Science.gov (United States)

    Huang, Hongye; Liu, Meiying; Tuo, Xun; Chen, Junyu; Mao, Liucheng; Wen, Yuanqing; Tian, Jianwen; Zhou, Naigen; Zhang, Xiaoyong; Wei, Yen

    2018-05-01

    Over the past years, fluorescent carbon nanoparticles have got growing interest for biological imaging. Fluorescent nanodiamonds (FNDs) are novel fluorescent carbon nanoparticles with multitudinous useful properties, including remarkable fluorescence properties, extremely low toxicity and high refractive index. However, facile preparation of FNDs with designable properties and functions from non-fluorescent detonation nanodiamonds (DNDs) has demonstrated to be challengeable. In this work, we reported for the first time that preparation of Polyethylene glycol (PEG) functionalized FNDs through a one-step thiol-ene click reaction using thiol containing PEG (PEG-SH) as the coating agent. Based on the characterization results, we demonstrated that PEG-SH could be efficiently introduced on DNDs to obtain FNDs through the thiol-ene click chemistry. The resultant FND-PEG composites showed high water dispersibility, strong fluorescence and low cytotoxicity. Moreover, FND-PEG composites could be internalized by cells and displayed good cell dyeing performance. All of these features implied that FND-PEG composites are of great potential for biological imaging. Taken together, a facile one-step strategy based on the one-step thiol-ene click reaction has been developed for efficient preparation of FND-PEG composites from non-fluorescent DNDs. The strategy should be also useful for fabrication of many other functional FNDs via using different thiol containing compounds for the universality of thiol-ene click reaction.

  14. Influence of oxygen on the repair of direct radiation damage to DNA by thiols in model systems

    International Nuclear Information System (INIS)

    Becker, D.; Summerfield, S.; Gillich, S.; Sevilla, M.D.

    1994-01-01

    Here the reactions of thiols with DNA primary radical intermediates formed after γ-irradiation of frozen (77K) anoxic and oxic solutions of DNA/thiol mixtures are investigated. Through analysis of the experimental composite spectra at each annealing temperature, the relative concentrations of individual radicals present are estimated and reaction sequences inferred. In all samples the primary DNA radical anions and cations (DNA · + and DNA · - ) are suggested to be the predominant radicals at low temperatures. In anoxic samples, TH · (5,6-dihydrothym-5-yl radical), RSSR · - and, in glutathione samples, · GSH [γ-glu-NHC(CH 2 SH) CO-gly] radicals are observed as the temperature is increased. The presence of oxygen efficiently suppresses the formation of RSSR · - and · GSH; instead, in oxic samples, O 2 · - , DNAOO · , RSOO · and RSO · are observed at higher temperatures. The photolytic conversion of RSOO · to RSO 2 · is used to verify the presence of RSOO · in γ-irradiated DNA/thiol systems and confirm that the computer analysis employed yields reasonable estimates of the relative DNAOO · and RSOO · concentrations. (Author)

  15. Changes of muscle-derived cytokines in relation to thiol redox status and reactive oxygen and nitrogen species.

    Science.gov (United States)

    Zembron-Lacny, A; Naczk, M; Gajewski, M; Ostapiuk-Karolczuk, J; Dziewiecka, H; Kasperska, A; Szyszka, K

    2010-01-01

    The aim of this study was to compare the levels of the plasma muscle-derived cytokines (myokines) and reactive oxygen and nitrogen species (RONS) after muscle damage triggered by different exercises, and to demonstrate the relationships between RONS, thiol redox status and myokines. Sixteen young men participated in a 90-min run at 65% VO2max (Ex.1) or 90-min run at 65% VO2max finished with a 15-min eccentric phase (Ex.2, downhill running). Plasma samples were collected before and at 20 min, 24 h and 48 h after exercise. The exercise trials significantly elevated the concentrations of plasma hydrogen peroxide (H2O2) and 8-isoprostane at 20 min rest. Myokines IL-6 and IL-10 increased at 20 min rest while IL-1β and TNFα increased at 24 h rest following both running. Ex.2 caused a significant increase in nitric oxide (NO), IL-6, IL-10 and oxidized glutathione (GSSG) levels. Thiol redox status (GSH(total)-2GSSG/GSSG) decreased by about 30% after Ex.2 as compared to Ex.1. H2O2) and NO directly correlated with IL-6, IL-10, IL-1β, TNFα and glutathione. These results show that eccentric work is an important factor that enhances the production of RONS and muscle-derived cytokines, and that there is a possible participation of thiol redox status in the release of myokines to blood.

  16. Facile synthesis of thiol-polyethylene glycol functionalized magnetic titania nanomaterials for highly efficient enrichment of N-linked glycopeptides.

    Science.gov (United States)

    Wang, Jiawen; Yao, Jizong; Sun, Nianrong; Deng, Chunhui

    2017-08-25

    As protein N-glycosylation involved in generation and development of various cancers and diseases, it is vital to capture glycopeptides from complex biological samples for biomarker discovery. In this work, by taking advantages of the interaction between titania and thiol groups, thiol-polyethylene glycol functionalized magnetic titania nanomaterials (denoted as Fe 3 O 4 @TiO 2 @PEG) were firstly fabricated as an excellent hydrophilic adsorbent of N-linked glycopeptides. On one hand, the special interaction of titanium-thiol makes the synthetic manipulation simple and provides a new idea for design and synthesis of novel nanomaterials; on the other hand, strong magnetic response could realize rapid separation and the outstanding hydrophilicity of polyethylene glycol makes Fe 3 O 4 @TiO 2 @PEG nanomaterials show superior performance for glycopeptides enrichment with ultralow limit of detection (0.1mol/μL) and high selectivity (1:100). As a result, 24 and 33 glycopeptides enriched from HRP and IgG digests were identified respectively by MALDI-TOF MS, and 300 glycopeptides corresponding to 106 glycoproteins were recognized from merely 2μL human serum, indicating a great potential of Fe 3 O 4 @TiO 2 @PEG nanomaterials for glycoproteomic research. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Influence of indium-tin oxide surface structure on the ordering and coverage of carboxylic acid and thiol monolayers

    International Nuclear Information System (INIS)

    Cerruti, Marta; Rhodes, Crissy; Losego, Mark; Efremenko, Alina; Maria, Jon-Paul; Fischer, Daniel; Franzen, Stefan; Genzer, Jan

    2007-01-01

    This paper analyses the variability of self-assembled monolayers (SAMs) formation on ITO depending on the substrate surface features. In particular, we report on the formation of carboxylic acid- and thiol-based SAMs on two lots of commercially prepared indium-tin oxide (ITO) thin films. Contact angle measurements, electrochemical experiments, and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy showed that the quality of monolayers formed differed substantially between the two ITO batches. Only one of the two ITO substrates was capable of forming well-organized thiol- and carboxylic acid-based SAMs. In order to rationalize these observations, atomic force microscopy and x-ray diffraction analyses were carried out, and SAMs were prepared on ITO substrates fabricated by sputtering in our laboratories. An attempt was made to influence the film microstructure and surface morphology by varying substrate temperatures during ITO deposition. Good-quality thiol and carboxylic acid SAMs were obtained on one of the ITO substrates prepared in-house. While our characterization could not single out conclusively one specific parameter in ITO surface structure that could be responsible for good SAMs formation, we could point out homogeneous surface morphology as a relevant factor for the quality of the SAMs. Evidence was also found for ITO crystallographic orientation to be a parameter influencing SAMs organization

  18. Genomics and X-ray microanalysis indicate that Ca2+ and thiols mediate the aggregation and adhesion of Xylella fastidiosa

    Directory of Open Access Journals (Sweden)

    Leite B.

    2002-01-01

    Full Text Available The availability of the genome sequence of the bacterial plant pathogen Xylella fastidiosa, the causal agent of citrus variegated chlorosis, is accelerating important investigations concerning its pathogenicity. Plant vessel occlusion is critical for symptom development. The objective of the present study was to search for information that would help to explain the adhesion of X. fastidiosa cells to the xylem. Scanning electron microscopy revealed that adhesion may occur without the fastidium gum, an exopolysaccharide produced by X. fastidiosa, and X-ray microanalysis demonstrated the presence of elemental sulfur both in cells grown in vitro and in cells found inside plant vessels, indicating that the sulfur signal is generated by the pathogen surface. Calcium and magnesium peaks were detected in association with sulfur in occluded vessels. We propose an explanation for the adhesion and aggregation process. Thiol groups, maintained by the enzyme peptide methionine sulfoxide reductase, could be active on the surface of the bacteria and appear to promote cell-cell aggregation by forming disulfide bonds with thiol groups on the surface of adjacent cells. The enzyme methionine sulfoxide reductase has been shown to be an auxiliary component in the adhesiveness of some human pathogens. The negative charge conferred by the ionized thiol group could of itself constitute a mechanism of adhesion by allowing the formation of divalent cation bridges between the negatively charged bacteria and predominantly negatively charged xylem walls.

  19. Preparation of thiol-functionalized activated carbon from sewage sludge with coal blending for heavy metal removal from contaminated water.

    Science.gov (United States)

    Li, Juan; Xing, Xing; Li, Jiao; Shi, Mei; Lin, Aijun; Xu, Congbin; Zheng, Jianzhong; Li, Ronghua

    2018-03-01

    Sewage sludge produced from wastewater treatment is a pressing environmental issue. Mismanagement of the massive amount of sewage sludge would threat our valuble surface and shallow ground water resources. Use of activated carbon prepared from carbonization of these sludges for heavy metal removal can not only minimize and stabilize these hazardous materials but also realize resources reuse. In this study, thiol-functionalized activated carbon was synthesized from coal-blended sewage sludge, and its capacity was examined for removing Cu(II), Pb(II), Cd(II) and Ni(II) from water. Pyrolysis conditions to prepare activated carbons from the sludge and coal mixture were examined, and the synthesized material was found to achieve the highest BET surface area of 1094 m 2 /g under 500 °C and 30 min. Batch equilibrium tests indicated that the thiol-functionalized activated carbon had a maximum sorption capacity of 238.1, 96.2, 87.7 and 52.4 mg/g for Pb(II), Cd(II), Cu(II) and Ni(II) removal from water, respectively. Findings of this study suggest that thiol-functionalized activated carbon prepared from coal-blended sewage sludge would be a promising sorbent material for heavy metal removal from waters contaminated with Cu(II), Pb(II), Cd(II) and Ni(II). Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Magneto-elastic biosensors: Influence of different thiols on pathogen capture efficiency.

    Science.gov (United States)

    Dalla Pozza, Márcia; Possan, André L; Roesch-Ely, Mariana; Missell, Frank P

    2017-06-01

    Magneto-elastic biosensors have mass sensitivity to biological species, offering reliability and reproducibility in the detection of pathogens such as Escherichia coli. In this work, amorphous ribbons of Metglas 2826MB3 were coated with layers of Cr and Au by DC magnetron sputtering and cut to 5mm×1mm. The influence of different thiols on captured pathogens was studied. The compounds cystamine (CYS), cysteamine (CYSTE) and mercaptopropionic acid (MPA) were deposited on Au-covered surfaces, followed by antibodies. The roughness parameters Ra and Rq were determined using atomic force microscopy (AFM) and micrographs from scanning electron microscopy with a field emission gun (FESEM) were also utilized. Biosensors formed with MPA showed an increased efficiency for attracting E. coli compared to biosensors with CYS and CYSTE, but large standard deviations were observed, making reproducibility and reliability difficult for that biosensor. Sensors tested with CYSTE showed greater efficiency and a lower detection limit than sensors with CYS. The results indicated that the size of the carbon chain and the terminal grouping influence the effectiveness of immobilization on magneto-elastic biosensors. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Epoxy-Thiol Systems Filled with Boron Nitride for High Thermal Conductivity Applications

    Directory of Open Access Journals (Sweden)

    John M. Hutchinson

    2018-03-01

    Full Text Available An epoxy-thiol system filled with boron nitride (BN, in the form of 80 µm agglomerates, has been investigated with a view to achieving enhanced thermal conductivity. The effect of BN content on the cure reaction kinetics has been studied by differential scanning calorimetry (DSC and the thermal conductivity of the cured samples has been measured by the transient hot bridge method. The heat of reaction and the glass transition temperature of the fully cured samples are both independent of the BN content, but the cure reaction kinetics is not: with increasing BN content, the reaction first advances and is then delayed, this behaviour being more pronounced than for the same system with 6 µm BN particles, investigated previously. This dependence on BN content is attributed to the effects of heat transfer, and the DSC results can be correlated with the thermal conductivity of the cured systems, which is found to increase with both BN content and BN particle size. For a given BN content, the values of thermal conductivity obtained are significantly higher than many others reported in the literature, and achieve a value of over 4.0 W/mK for a BN content of about 40 vol %.

  2. Thermoconductive Thermosetting Composites Based on Boron Nitride Fillers and Thiol-Epoxy Matrices

    Directory of Open Access Journals (Sweden)

    Isaac Isarn

    2018-03-01

    Full Text Available In this work, the effect of the addition of boron nitride (BN fillers in a thiol-cycloaliphatic epoxy formulation has been investigated. Calorimetric studies put into evidence that the kinetics of the curing has been scarcely affected and that the addition of particles does not affect the final structure of the network. Rheologic studies have shown the increase in the viscoelastic properties on adding the filler and allow the percolation threshold to be calculated, which was found to be 35.5%. The use of BN agglomerates of bigger size increases notably the viscosity of the formulation. Glass transition temperatures are not affected by the filler added, but Young’s modulus and hardness have been notably enhanced. Thermal conductivity of the composites prepared shows a linear increase with the proportion of BN particle sheets added, reaching a maximum of 0.97 W/K·m. The addition of 80 μm agglomerates, allowed to increase this value until 1.75 W/K·m.

  3. A new oxidative stress marker for thiol-disulphide homeostasis in seasonal allergic rhinitis.

    Science.gov (United States)

    Ulusoy, Seckin; Ayan, Nilhan Nurlu; Dinc, Mehmet Emre; Is, Abdulhalim; Bicer, Cemile; Erel, Ozcan

    2016-05-01

    Reactive oxygen species has a crucial role in the pathogenesis of many diseases. Reactive oxygen species has been effectively documented in patients with asthma, but very little research has been reported in subjects with allergic rhinitis. To investigate thiol (SH)-disulfide (SS) homeostasis, a new oxidative stress marker present in patients with seasonal allergic rhinitis (SAR). A total of 64 subjects, including 32 patients with SAR and 32 healthy controls, were included in the study. We measured the SH levels as a marker of antioxidant protection and SS as a marker related to oxidant stress. Sera specimens were taken from patients with SAR during exacerbation and during asymptomatic time periods. In addition, sera samples from the control group were also obtained during the pollen season to compare with those from patients with SAR. In patients with SAR, during exacerbation periods, SH, SS, % SS/SH, % SS to total SH (TT), and % SH/TT were significantly different (p 0.05) regarding SH, SS, TT, % SS/SH, % SS/TT, and % SH/TT. SAR is a disorder that elevates systemic oxidative stress and reduces antioxidant enzyme activities. Our results shed light on the etiopathogenesis of the disease and can help develop new therapeutic approaches.

  4. Size-controlled synthesis and characterization of thiol-stabilized gold nanoparticles

    Science.gov (United States)

    Frenkel, A. I.; Nemzer, S.; Pister, I.; Soussan, L.; Harris, T.; Sun, Y.; Rafailovich, M. H.

    2005-11-01

    Size-controlled synthesis of nanoparticles of less than a few nanometers in size is a challenge due to the spatial resolution limit of most scattering and imaging techniques used for their structural characterization. We present the self-consistent analysis of the extended x-ray absorption fine-structure (EXAFS) spectroscopy data of ligand-stabilized metal nanoclusters. Our method employs the coordination number truncation and the surface-tension models in order to measure the average diameter and analyze the structure of the nanoparticles. EXAFS analysis was performed on the two series of dodecanethiol-stabilized gold nanoparticles prepared by one-phase and two-phase syntheses where the only control parameter was the gold/thiol ratio ξ, varied between 6:1 and 1:6. The two-phase synthesis resulted in the smaller particles whose size decreased monotonically and stabilized at 16Å when ξ was lowered below 1:1. This behavior is consistent with the theoretically predicted thermodynamic limit obtained previously in the framework of the spherical drop model of Au nanoparticles.

  5. Removal of heavy metals from aqueous systems with thiol functionalized superparamagnetic nanoparticles.

    Science.gov (United States)

    Yantasee, Wassana; Warner, Cynthia L; Sangvanich, Thanapon; Addleman, R Shane; Carter, Timothy G; Wiacek, Robert J; Fryxell, Glen E; Timchalk, Charles; Warner, Marvin G

    2007-07-15

    We have shown that superparamagnetic iron oxide (Fe3O4) nanoparticles with a surface functionalization of dimercaptosuccinic acid (DMSA) are an effective sorbent material for toxic soft metals such as Hg, Ag, Pb, Cd, and Tl, which effectively bind to the DMSA ligands and for As, which binds to the iron oxide lattices. The nanoparticles are highly dispersible and stable in solutions, have a large surface area (114 m2/g), and have a high functional group content (1.8 mmol thiols/g). They are attracted to a magnetic field and can be separated from solution within a minute with a 1.2 T magnet. The chemical affinity, capacity, kinetics, and stability of the magnetic nanoparticles were compared to those of conventional resin based sorbents (GT-73), activated carbon, and nanoporous silica (SAMMS) of similar surface chemistries in river water, groundwater, seawater, and human blood and plasma. DMSA-Fe3O4 had a capacity of 227 mg of Hg/g, a 30-fold larger value than GT-73. The nanoparticles removed 99 wt% of 1 mg/L Pb within a minute, while it took over 10 and 120 min for Chelex-100 and GT-73 to remove 96% of Pb.

  6. Interaction of different thiol-capped CdTe quantum dots with bovine serum albumin

    International Nuclear Information System (INIS)

    Wang Qisui; Zhang Xiaolei; Zhou Xiaolan; Fang Tingting; Liu Pengfei; Liu Peng; Min Xinmin; Li, Xi

    2012-01-01

    Due to their unique optical properties, quantum dots (QDs) are rapidly revolutionizing many areas of medicine and biology. Despite the remarkable speed of development of nanoscience, relatively little is known about the interaction of nanoscale objects with organism. In this work, interaction of CdTe QDs coated with mercaptopropanoic acid (MPA), L-cysteine (L-cys), and glutathione (GSH) with bovine serum albumin (BSA) was investigated. Fluorescence (FL), UV–vis absorption, and circular dichroism (CD) spectra methods were used. The Stern-Volmer quenching constant (K sv ) at different temperatures, corresponding thermodynamic parameters (ΔH, ΔG and ΔS), and information of the structural features of BSA were gained. We found that QDs can effectively quench the FL of BSA in a ligand-dependent manner, electrostatic interactions play a major role in the binding reaction, and the nature of quenching is static, resulting in forming QDs-BSA complexes. The CD spectra showed that the secondary and tertiary structure of BSA was changed. This study contributes to a better understanding of the ligand effects on QDs-proteins interactions, which is a critical issue for the applications in vivo. - Highlights: ► The interaction between three thiol-capped QDs and BSA by UV–vis, FL, and CD spectra. ► The bio-effect of CdTe QDs on BSA was a ligand-dependent manner. ► The thermodynamic parameters and the structural features of BSA were gained.

  7. Crystal Structure of Mammalian Cysteine dioxygenase: A Novel Mononuclear Iron Center for Cysteine Thiol Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Simmons,C.; Liu, Q.; Huang, Q.; Hao, Q.; Begley, T.; Karplus, P.; Stipanuk, M.

    2006-01-01

    Cysteine dioxygenase is a mononuclear iron-dependent enzyme responsible for the oxidation of cysteine with molecular oxygen to form cysteinesulfinate. This reaction commits cysteine to either catabolism to sulfate and pyruvate or to the taurine biosynthetic pathway. Cysteine dioxygenase is a member of the cupin superfamily of proteins. The crystal structure of recombinant rat cysteine dioxygenase has been determined to 1.5 Angstroms resolution, and these results confirm the canonical cupin {beta}-sandwich fold and the rare cysteinyl-tyrosine intramolecular crosslink (between Cys93 and Tyr157) seen in the recently reported murine cysteine dioxygenase structure. In contrast to the catalytically inactive mononuclear Ni(II) metallocenter present in the murine structure, crystallization of a catalytically competent preparation of rat cysteine dioxygenase revealed a novel tetrahedrally coordinated mononuclear iron center involving three histidines (His86, His88, and His140) and a water molecule. Attempts to acquire a structure with bound ligand using either co-crystallization or soaks with cysteine revealed the formation of a mixed disulfide involving Cys164 near the active site, which may explain previously observed substrate inhibition. This work provides a framework for understanding the molecular mechanisms involved in thiol dioxygenation and sets the stage for exploring the chemistry of both the novel mononuclear iron center and the catalytic role of the cysteinyl-tyrosine linkage.

  8. Impact of SCILL catalysts for the S-S coupling of thiols to disulfides.

    Science.gov (United States)

    Pavel, Octavian D; Podolean, Iunia; Parvulescu, Vasile I; Taylor, S F Rebecca; Manyar, Haresh G; Ralphs, Kathryn; Goodrich, Peter; Hardacre, Christopher

    2018-01-01

    This study reports the behaviour of SCILL based catalysts in the oxidative S-S coupling of aliphatic and aromatic thiols, namely 1-butanethiol and thiophenol, to dibutyl disulfide and diphenyl disulfide. A range of ionic liquids (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide) and metal supported catalysts (5% Pt/SiO 2 ; 5% Ru/SiO 2 ; 5% Ru/C; 5% Pt/OMS-2) were used to prepare the SCILL catalysts and all were found to be active for the reaction following the trend 5% Pt-OMS-2 > 5% Pt/SiO 2 > 5% Ru/C > 5% Ru/SiO 2 . The presence of SCILL catalysts afforded high selectivity to the disulfide, and the activity of the SCILL catalyst was dependent on the ionic liquid used. A significant increase in the stability of all the supported metal catalysts was found in the presence of the ionic liquid, and there was no change in the selectivity towards disulfides. This demonstrated that the ionic liquids protect the active sites of the catalyst against sulfation, thus providing more stable and active catalysts.

  9. A thiol probe for measuring unfolded protein load and proteostasis in cells.

    Science.gov (United States)

    Chen, Moore Z; Moily, Nagaraj S; Bridgford, Jessica L; Wood, Rebecca J; Radwan, Mona; Smith, Trevor A; Song, Zhegang; Tang, Ben Zhong; Tilley, Leann; Xu, Xiaohong; Reid, Gavin E; Pouladi, Mahmoud A; Hong, Yuning; Hatters, Danny M

    2017-09-07

    When proteostasis becomes unbalanced, unfolded proteins can accumulate and aggregate. Here we report that the dye, tetraphenylethene maleimide (TPE-MI) can be used to measure cellular unfolded protein load. TPE-MI fluorescence is activated upon labelling free cysteine thiols, normally buried in the core of globular proteins that are exposed upon unfolding. Crucially TPE-MI does not become fluorescent when conjugated to soluble glutathione. We find that TPE-MI fluorescence is enhanced upon reaction with cellular proteomes under conditions promoting accumulation of unfolded proteins. TPE-MI reactivity can be used to track which proteins expose more cysteine residues under stress through proteomic analysis. We show that TPE-MI can report imbalances in proteostasis in induced pluripotent stem cell models of Huntington disease, as well as cells transfected with mutant Huntington exon 1 before the formation of visible aggregates. TPE-MI also detects protein damage following dihydroartemisinin treatment of the malaria parasites Plasmodium falciparum. TPE-MI therefore holds promise as a tool to probe proteostasis mechanisms in disease.Proteostasis is maintained through a number of molecular mechanisms, some of which function to protect the folded state of proteins. Here the authors demonstrate the use of TPE-MI in a fluorigenic dye assay for the quantitation of unfolded proteins that can be used to assess proteostasis on a cellular or proteome scale.

  10. Solution processing of chalcogenide materials using thiol-amine "alkahest" solvent systems.

    Science.gov (United States)

    McCarthy, Carrie L; Brutchey, Richard L

    2017-05-02

    Macroelectronics is a major focus in electronics research and is driven by large area applications such as flat panel displays and thin film solar cells. Innovations for these technologies, such as flexible substrates and mass production, will require efficient and affordable semiconductor processing. Low-temperature solution processing offers mild deposition methods, inexpensive processing equipment, and the possibility of high-throughput processing. In recent years, the discovery that binary "alkahest" mixtures of ethylenediamine and short chain thiols possess the ability to dissolve bulk inorganic materials to yield molecular inks has lead to the wide study of such systems and the straightforward recovery of phase pure crystalline chalcogenide thin films upon solution processing and mild annealing of the inks. In this review, we recount the work that has been done toward elucidating the scope of this method for the solution processing of inorganic materials for use in applications such as photovoltaic devices, electrocatalysts, photodetectors, thermoelectrics, and nanocrystal ligand exchange. We also take stock of the wide range of bulk materials that can be used as soluble precursors, and discuss the work that has been done to reveal the nature of the dissolved species. This method has provided a vast toolbox of over 65 bulk precursors, which can be utilized to develop new routes to functional chalcogenide materials. Future studies in this area should work toward a better understanding of the mechanisms involved in the dissolution and recovery of bulk materials, as well as broadening the scope of soluble precursors and recoverable functional materials for innovative applications.

  11. Thiol-acrylate nanocomposite foams for critical size bone defect repair: A novel biomaterial.

    Science.gov (United States)

    Garber, Leah; Chen, Cong; Kilchrist, Kameron V; Bounds, Christopher; Pojman, John A; Hayes, Daniel

    2013-12-01

    Bone tissue engineering approaches using polymer/ceramic composites show promise as effective biocompatible, absorbable, and osteoinductive materials. A novel class of in situ polymerizing thiol-acrylate based copolymers synthesized via an amine-catalyzed Michael addition was studied for its potential to be used in bone defect repair. Both pentaerythritol triacrylate-co-trimethylolpropane tris(3-mercaptopropionate) (PETA-co-TMPTMP) and PETA-co-TMPTMP with hydroxyapatite (HA) composites were fabricated in solid cast and foamed forms. These materials were characterized chemically and mechanically followed by an in vitro evaluation of the biocompatibility and chemical stability in conjunction with human adipose-derived mesenchymal pluripotent stem cells (hASC). The solid PETA-co-TMPTMP with and without HA exhibited compressive strength in the range of 7-20 MPa, while the cytotoxicity and biocompatibility results demonstrate higher metabolic activity of hASC on PETA-co-TMPTMP than on a polycaprolactone control. Scanning electron microscope imaging of hASC show expected spindle shaped morphology when adhered to copolymer. Micro-CT analysis indicates open cell interconnected pores. Foamed PETA-co-TMPTMP HA composite shows promise as an alternative to FDA-approved biopolymers for bone tissue engineering applications. Copyright © 2013 Wiley Periodicals, Inc., a Wiley Company.

  12. The thiol compounds glutathione and homoglutathione differentially affect cell development in alfalfa (Medicago sativa L.).

    Science.gov (United States)

    Pasternak, Taras; Asard, Han; Potters, Geert; Jansen, Marcel A K

    2014-01-01

    Glutathione (GSH) is an important scavenger of Reactive Oxygen Species (ROS), precursor of metal chelating phytochelatins, xenobiotic defence compound and regulator of cell proliferation. Homoglutathione (hGSH) is a GSH homologue that is present in several taxa in the family of Fabaceae. It is thought that hGSH performs many of the stress-defence roles typically ascribed to GSH, yet little is known about the potential involvement of hGSH in controlling cell proliferation. Here we show that hGSH/GSH ratios vary across organs and cells and that these changes in hGSH/GSH ratio occur during dedifferentiation and/or cell cycle activation events. The use of a GSH/hGSH biosynthesis inhibitor resulted in impaired cytokinesis in isolated protoplasts, showing the critical importance of these thiol-compounds for cell division. However, exposure of isolated protoplasts to exogenous GSH accelerated cytokinesis, while exogenous hGSH was found to inhibit the same process. We conclude that GSH and hGSH have distinct functional roles in cell cycle regulation in Medicago sativa L. GSH is associated with meristemic cells, and promotes cell cycle activation and induction of somatic embryogenesis, while hGSH is associated with differentiated cells and embryo proliferation. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  13. Analysis of Structural Flexibility of Damaged DNA Using Thiol-Tethered Oligonucleotide Duplexes.

    Directory of Open Access Journals (Sweden)

    Masashi Fujita

    Full Text Available Bent structures are formed in DNA by the binding of small molecules or proteins. We developed a chemical method to detect bent DNA structures. Oligonucleotide duplexes in which two mercaptoalkyl groups were attached to the positions facing each other across the major groove were prepared. When the duplex contained the cisplatin adduct, which was proved to induce static helix bending, interstrand disulfide bond formation under an oxygen atmosphere was detected by HPLC analyses, but not in the non-adducted duplex, when the two thiol-tethered nucleosides were separated by six base pairs. When the insert was five and seven base pairs, the disulfide bond was formed and was not formed, respectively, regardless of the cisplatin adduct formation. The same reaction was observed in the duplexes containing an abasic site analog and the (6–4 photoproduct. Compared with the cisplatin case, the disulfide bond formation was slower in these duplexes, but the reaction rate was nearly independent of the linker length. These results indicate that dynamic structural changes of the abasic site- and (6–4 photoproduct-containing duplexes could be detected by our method. It is strongly suggested that the UV-damaged DNA-binding protein, which specifically binds these duplexes and functions at the first step of global-genome nucleotide excision repair, recognizes the easily bendable nature of damaged DNA.

  14. Effective heavy metal removal from aqueous systems by thiol functionalized magnetic mesoporous silica

    International Nuclear Information System (INIS)

    Li Guoliang; Zhao Zongshan; Liu Jiyan; Jiang Guibin

    2011-01-01

    A thiol-functionalized magnetic mesoporous silica material (called SH-mSi-Fe 3 O 4 ), synthesized by a modified Stoeber method, has been investigated as a convenient and effective adsorbent for heavy metal ions. Structural characterization by powder X-ray diffraction, N 2 adsorption-desorption isotherm, Fourier transform infrared spectroscopy and elemental analyses confirms the mesoporous structure and the organic moiety content of this adsorbent. The high saturation magnetization (38.4 emu/g) make it easier and faster to be separated from water under a moderate magnetic field. Adsorption kinetics was elucidated by pseudo-second-order kinetic equation and exhibited 3-stage intraparticle diffusion mode. Adsorption isotherms of Hg and Pb fitted well with Langmuir model, exhibiting high adsorption capacity of 260 and 91.5 mg of metal/g of adsorbent, respectively. The distribution coefficients of the tested metal ions between SH-mSi-Fe 3 O 4 and different natural water sources (groundwater, lake water, tap water and river water) were above the level of 10 5 mL/g. The material was very stable in different water matrices, even in strong acid and alkaline solutions. Metal-loaded SH-mSi-Fe 3 O 4 was able to regenerate in acid solution under ultrasonication. This novel SH-mSi-Fe 3 O 4 is suitable for repeated use in heavy metal removal from different water matrices.

  15. Investigating thiol-modification on hyaluronan via carbodiimide chemistry using response surface methodology.

    Science.gov (United States)

    Santhanam, Sruthi; Liang, Jue; Baid, Rinku; Ravi, Nathan

    2015-07-01

    Hyaluronan (HA) is a naturally occurring glycosaminoglycan widely researched for its use as a biomaterial in tissue engineering, drug delivery, angiogenesis, and ophthalmic surgeries. The mechanical properties of this biomaterial can be altered to a required extent by chemically modifying the pendant reactive groups. However, derivatizing these polymers to a predetermined extent has been the Achilles heel for this process. In this study, we have investigated the factors controlling the derivatization of the carboxyl moieties of HA with amine containing thiol, cystamine dihydrochloride (Cys), via carbodiimide crosslinking chemistry. We used fractional factorial design to screen and identify the significant factor(s) affecting the reaction, and response surface methodology (RSM) to develop a model equation for predicting the degree of thiolation of HA. Also, we analyzed the reaction mechanism for potential side reactions. We observed that N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) (mole ratio with repeat unit of HA) is the significant factor controlling the degree of amidation. The quadratic equations developed from RSM predict the formulation for a desired degree of amidation of HA and percentage of potential side product. Hence, derivatizing HA to a predetermined extent with minimal side product can be achieved using the statistical design of experiments. © 2014 Wiley Periodicals, Inc.

  16. The grape must non-Saccharomyces microbial community: impact on volatile thiol release.

    Science.gov (United States)

    Zott, Katharina; Thibon, Cécile; Bely, Marina; Lonvaud-Funel, Aline; Dubourdieu, Denis; Masneuf-Pomarede, Isabelle

    2011-12-02

    Several studies have reported the beneficial influence of non-Saccharomyces yeasts and their potential applications in the wine industry, mainly in mixed-culture fermentation with S. cerevisiae. The potential impact of 15 non-Saccharomyces strains from 7 species on 4-methyl-4-sulfanylpentan-2-one (4MSP) and 3-sulfanylhexan-1-ol (3SH) release in model medium and Sauvignon Blanc must was evaluated after partial fermentation. Whereas the impact of non-Saccharomyces on 4MSP release in both media was low, some M. pulcherrima, T. delbrueckii and K. thermotolerans strains had a high capacity to release 3SH, despite their minimal fermentation activity. As previously demonstrated for Saccharomyces yeast, this contribution is strain dependant. Taking into account their dynamic and quantitative presence during the whole process, the real impact of non-Saccharomyces yeast on 4MSP and 3SH release was evaluated using a recreated community simulating the yeast ecosystem. Our results revealed a positive impact on 3SH release in Sauvignon Blanc wines by promoting non-Saccharomyces yeast activity and delaying the growth of S. cerevisiae. Some non-Saccharomyces yeast strains are capable of making a positive contribution to volatile thiol release in wines, essentially during the pre-fermentation stage in winemaking, when this microbiological sub-population is dominant. Copyright © 2011. Published by Elsevier B.V.

  17. Polysiloxane-based luminescent elastomers prepared by thiol-ene "click" chemistry.

    Science.gov (United States)

    Zuo, Yujing; Lu, Haifeng; Xue, Lei; Wang, Xianming; Wu, Lianfeng; Feng, Shengyu

    2014-09-26

    Side-chain vinyl poly(dimethylsiloxane) has been modified with mercaptopropionic acid, methyl 3-mercaptopropionate, and mercaptosuccinic acid. Coordinative bonding of Eu(III) to the functionalized polysiloxanes was then carried out and crosslinked silicone elastomers were prepared by thiol-ene curing reactions of these composites. All these europium complexes could be cast to form transparent, uniform, thin elastomers with good flexibility and thermal stability. The networks were characterized by FTIR, NMR, UV/Vis, and luminescence spectroscopy as well as by scanning electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The europium elastomer luminophores exhibited intense red light at 617 nm under UV excitation at room temperature due to the (5)D0 →(7)F2 transition in Eu(III) ions. The newly synthesized luminescent materials offer many advantages, including the desired mechanical flexibility. They cannot be dissolved or fused, and so they have potential for use in optical and electronic applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. The roles of protein disulphide isomerase family A, member 3 (ERp57) and surface thiol/disulphide exchange in human spermatozoa-zona pellucida binding.

    Science.gov (United States)

    Wong, Chi-Wai; Lam, Kevin K W; Lee, Cheuk-Lun; Yeung, William S B; Zhao, Wei E; Ho, Pak-Chung; Ou, Jian-Ping; Chiu, Philip C N

    2017-04-01

    Are multimeric sperm plasma membrane protein complexes, ERp57 and sperm surface thiol content involved in human spermatozoa-zona pellucida (ZP) interaction? ERp57 is a component of a multimeric spermatozoa-ZP receptor complex involved in regulation of human spermatozoa-ZP binding via up-regulation of sperm surface thiol content. A spermatozoon acquires its fertilization capacity within the female reproductive tract by capacitation. Spermatozoa-ZP receptor is suggested to be a composite structure that is assembled into a functional complex during capacitation. Sperm surface thiol content is elevated during capacitation. ERp57 is a protein disulphide isomerase that modulates the thiol-disulphide status of proteins. The binding ability and components of protein complexes in extracted membrane protein fractions of spermatozoa were studied. The roles of capacitation, thiol-disulphide reagent treatments and ERp57 on sperm functions and sperm surface thiol content were assessed. Spermatozoa were obtained from semen samples from normozoospermic men. Human oocytes were obtained from an assisted reproduction programme. Blue native polyacrylamide gel electrophoresis, western ligand blotting and mass spectrometry were used to identify the components of solubilized ZP/ZP3-binding complexes. The localization and expression of sperm surface thiol and ERp57 were studied by immunostaining and sperm surface protein biotinylation followed by western blotting. Sperm functions were assessed by standard assays. Several ZP-binding complexes were isolated from the cell membrane of capacitated spermatozoa. ERp57 was a component of one of these complexes. Capacitation significantly increased the sperm surface thiol content, acrosomal thiol distribution and ERp57 expression on sperm surface. Sperm surface thiol and ERp57 immunoreactivity were localized to the acrosomal region of spermatozoa, a region responsible for ZP-binding. Up-regulation of the surface thiol content or ERp57 surface

  19. Chemical interactions between odor-active thiols and melanoidins involved in the aroma staling of coffee beverages.

    Science.gov (United States)

    Hofmann, Thomas; Schieberle, Peter

    2002-01-16

    Comparative aroma dilution analyses of the headspaces of aqueous solutions containing either the total volatiles isolated from a fresh coffee brew, or these volatiles remixed with the melanoidins isolated from coffee brew, revealed a drastic decrease in the concentrations of the odorous thiols 2-furfurylthiol, 3-methyl-2-butenthiol, 3-mercapto-3-methylbutyl formate, 2-methyl-3-furanthiol, and methanethiol when melanoidins were present. Among these thiols, 2-furfurylthiol was affected the most: e.g., its concentration decreased by a factor of 16 upon addition of melanoidins. This was accompanied by a decrease in the overall roasty-sulfury aroma. Quantitations performed by means of stable isotope dilution assays confirmed the rapid loss of all thiols with increasing time while keeping the coffee brew warm in a thermos flask. Using [2H2]-2-furfurylthiol as an example, [2H]-NMR and LC/MS spectroscopy gave strong evidence that thiols are covalently bound to the coffee melanoidins via Maillard-derived pyrazinium compounds formed as oxidation products of 1,4-bis-(5-amino-5-carboxy-1-pentyl)pyrazinium radical cations (CROSSPY). Using synthetic 1,4-diethyl diquaternary pyrazinium ions and 2-furfurylthiol, it was shown that 2-(2-furyl)methylthio-1,4-dihydro-pyrazines, bis[2-(2-furyl)methylthio]-1,4-dihydro-pyrazines, and 2-(2-furyl)methylthio-hydroxy-1,4-dihydro-pyrazines were formed as the primary reaction products. Similar results were obtained for models in which either 1,4-diethyl diquaternary pyrazinium ions were substituted by Nalpha-acetyl-L-lysine/glycolaldehyde, or the 2-furfurylthiol by 2-methyl-3-furanthiol and 3-mercapto-3-methylbutyl formate. On the basis of these results it can be concluded that the CROSSPY-derived pyrazinium intermediates are involved in the rapid covalent binding of odorous thiols to melanoidins, and, consequently, are responsible for the decrease in the sulfury-roasty odor quality observed shortly after preparation of the coffee brew.

  20. Cisplatin impairs rat liver mitochondrial functions by inducing changes on membrane ion permeability: Prevention by thiol group protecting agents

    International Nuclear Information System (INIS)

    Custodio, Jose B.A.; Cardoso, Carla M.P.; Santos, Maria S.; Almeida, Leonor M.; Vicente, Joaquim A.F.; Fernandes, Maria A.S.

    2009-01-01

    Cisplatin (CisPt) is the most important platinum anticancer drug widely used in the treatment of head, neck, ovarian and testicular cancers. However, the mechanisms by which CisPt induces cytotoxicity, namely hepatotoxicity, are not completely understood. The goal of this study was to investigate the influence of CisPt on rat liver mitochondrial functions (Ca 2+ -induced mitochondrial permeability transition (MPT), mitochondrial bioenergetics, and mitochondrial oxidative stress) to better understand the mechanism underlying its hepatotoxicity. The effect of thiol group protecting agents and some antioxidants against CisPt-induced mitochondrial damage was also investigated. Treatment of rat liver mitochondria with CisPt (20 nmol/mg protein) induced Ca 2+ -dependent mitochondrial swelling, depolarization of membrane potential (ΔΨ), Ca 2+ release, and NAD(P)H fluorescence intensity decay. These effects were prevented by cyclosporine A (CyA), a potent and specific inhibitor of the MPT. In the concentration range of up to 40 nmol/mg protein, CisPt slightly inhibited state 3 and stimulated state 2 and state 4 respiration rates using succinate as respiratory substrate. The respiratory indexes, respiratory control ratio (RCR) and ADP/O ratios, the ΔΨ, and the ADP phosphorylation rate were also depressed. CisPt induced mitochondrial inner membrane permeabilization to protons (proton leak) but did not induce significant changes on mitochondrial H 2 O 2 generation. All the effects induced by CisPt on rat liver mitochondria were prevented by thiol group protecting agents namely, glutathione (GSH), dithiothreitol (DTT), N-acetyl-L-cysteine (NAC) and cysteine (CYS), whereas superoxide-dismutase (SOD), catalase (CAT) and ascorbate (ASC) were without effect. In conclusion, the anticancer drug CisPt: (1) increases the sensitivity of mitochondria to Ca 2+ -induced MPT; (2) interferes with mitochondrial bioenergetics by increasing mitochondrial inner membrane permeabilization to

  1. Antimicrobial activity of new 5-(furan-2-yl-4-amino-1,2,4-triazole-3-thiol derivatives

    Directory of Open Access Journals (Sweden)

    D. M. Danilchenko

    2017-02-01

    Full Text Available The aim of this research was to investigate the antimicrobial activity of some new 5-(furan-2-yl-4-amino-1,2,4-triazole-3-thiol substituents and in some cases to trace the relationship between activity of compounds and their structure. Research materials and methods. Antimicrobial activity of new 5-(furan-2-yl-4-amino-1,2,4-triazole-3-thiol derivatives was studied by the method of serial dilutions. The primary antimicrobial activity screening tests of some 5-(furan-2-yl-4-amino-1,2,4-triazole-3-thiol derivatives have been conducted on standard test cultures of both gram-positive and gram-negative bacteria that belong to clinically significant group of infectious agents with different morphological properties. Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 were taken as the set of standard test strains. Results and their discussion. The most sensitive strain was a strain of S. aureus ATCC 25923. Extension of alkyl substituents by the Sulfur atom does not lead to gradual changes in activity but the introduction of pentyl radical increases the activity of a molecule in two times. The transition from the S-alkyl derivatives of 5-(furan-2-yl-4-amino-1,2,4-triazole-3-thiol to 2-((5-(furan-2-yl-4-amino-1,2,4-triazole-3-yl-thioacetic acid esters doesn’t lead to radical changes of antimicrobial activity and is not drawn. But the introduction of isopropyl and isobutyl radicals in the ester structure of these molecules leads to a sharp increase in activity towards S. aureus ATCC 25923. Conclusions. We have explored antimicrobial activity of new 5-(furan-2-yl-4-amino-1,2,4-triazole-3-thiol alkyl derivatives and 2-((5-(furan-2-yl-4-amino-1,2,4-triazole-3-ylthioacetic acid esters. It was found that all ten compounds exhibit moderate activity. Some influence of studied substituents on the antimicrobial activity results was also found.

  2. Catalysis in the Service of Green Chemistry: Nobel Prize-Winning Palladium-Catalysed Cross-Couplings, Run in Water at Room Temperature: Heck, Suzuki-Miyaura and Negishi reactions carried out in the absence of organic solvents, enabled by micellar catalysis.

    Science.gov (United States)

    Lipshutz, Bruce H; Taft, Benjamin R; Abela, Alexander R; Ghorai, Subir; Krasovskiy, Arkady; Duplais, Christophe

    2012-04-01

    Palladium-catalysed cross-couplings, in particular Heck, Suzuki-Miyaura and Negishi reactions developed over three decades ago, are routinely carried out in organic solvents. However, alternative media are currently of considerable interest given an increasing emphasis on making organic processes 'greener'; for example, by minimising organic waste in the form of organic solvents. Water is the obvious leading candidate in this regard. Hence, this review focuses on the application of micellar catalysis, in which a 'designer' surfactant enables these award-winning coupling reactions to be run in water at room temperature.

  3. In vitro screening of 50 highly prescribed drugs for thiol adduct formation--comparison of potential for drug-induced toxicity and extent of adduct formation.

    Science.gov (United States)

    Gan, Jinping; Ruan, Qian; He, Bing; Zhu, Mingshe; Shyu, Wen C; Humphreys, W Griffith

    2009-04-01

    Reactive metabolite formation has been associated with drug-induced liver, skin, and hematopoietic toxicity of many drugs that has resulted in serious clinical toxicity, leading to clinical development failure, black box warnings, or, in some cases, withdrawal from the market. In vitro and in vivo screening for reactive metabolite formation has been proposed and widely adopted in the pharmaceutical industry with the aim of minimizing the property and thus the risk of drug-induced toxicity (DIT). One of the most common screening methods is in vitro thiol trapping of reactive metabolites. Although it is well-documented that many hepatotoxins form thiol adducts, there is no literature describing the adduct formation potential of safer drugs that are widely used. The objective of this study was to quantitatively assess the thiol adduct formation potential of 50 drugs (10 associated with DIT and 40 not associated) and document apparent differences in adduct formation between toxic and safer drugs. Dansyl glutathione was used as a trapping agent to aid the quantitation of adducts following in vitro incubation of drugs with human liver microsomes in the presence and absence of NADPH. Metabolic turnover of these drugs was also monitored by LC/UV. Overall, 15 out of the 50 drugs screened formed detectable levels of thiol adducts. There were general trends toward more positive findings in the DIT group vs the non-DIT group. These trends became more marked when the relative amount of thiol adducts was taken into account and improved further when dose and total daily reactive metabolite burdens were considered. In conclusion, there appears to be a general trend between the extent of thiol adduct formation and the potential for DIT, which would support the preclinical measurement and minimization of the property through screening of thiol adduct formation as part of an overall discovery optimization paradigm.

  4. Thiol antioxidant-functionalized CdSe/ZnS quantum dots: synthesis, characterization, cytotoxicity.

    Science.gov (United States)

    Zheng, Hong; Mortensen, Luke J; DeLouise, Lisa A

    2013-03-01

    Nanotechnology is a growing industry with wide ranging applications in consumer product and technology development. In the biomedical field, nanoparticles are finding increasing use as imaging agents for biomolecular labeling and tumor targeting. The nanoparticle physiochemical properties must be tailored for the specific application. For example, nanoparticle chemical and physical stability in the biological milieu (no oxidation, aggregation, agglomeration or toxicity) are often required. Nanoparticles used for biomolecular fluorescent imaging should also have high quantum yield (QY). The aim of this paper is to examine the QY, stability, and cell toxicity of a series of positive, negative and neutral surface charge quantum dot (QD) nanoparticles. Simple protocols are described to prepare water soluble QDs by modifying the surface with thiol containing antioxidant ligands and polymers keeping the QD core/shell composition constant. The ligands used to produce negatively charged QDs include glutathione (GSH), N-acetyl-L-cysteine (NAC), dihydrolipoic acid (DHLA), tiopronin (TP), bucilliamine (BUC), and mercaptosuccinic acid (MSA). Ligands used to produce positively charged QDs include cysteamine (CYS) and polyethylenimine (PEI). Dithiothreitol (DTT) was used to produce neutral charged QDs. Commercially available nonaqueous octadecylamine (ODA) capped QDs served as the starting material. Our results suggest that QD uptake and cytotoxicity are both dependent on surface ligand coating composition. The negative charged GSH coated QDs show superior performance exhibiting low cytotoxicity, high stability, high QY and therefore are best suited for bioimaging applications. PEI coated QD also show superior performance exhibiting high QY and stability. However, they are considerably more cytotoxic due to their high positive charge which is an advantageous property that can be exploited for gene transfection and/or tumor targeting applications. The synthetic procedures

  5. Cadmium sensitivity, uptake, subcellular distribution and thiol induction in a marine diatom: Recovery from cadmium exposure

    Energy Technology Data Exchange (ETDEWEB)

    Wang Mengjiao [State Key Laboratory in Marine Pollution, Section of Marine Ecology and Biotechnology, Division of Life Science, Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon (Hong Kong); Wang Wenxiong, E-mail: wwang@ust.hk [State Key Laboratory in Marine Pollution, Section of Marine Ecology and Biotechnology, Division of Life Science, Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon (Hong Kong)

    2011-01-25

    Studies in the recovery from metal stress and the tolerance development to metal exposure of aquatic organisms are important for the understanding of epidemic pollution. In this study, the responses of a marine diatom, Thalassiosira nordenskioeldii, following recovery from environmental cadmium (Cd) stress were investigated. The diatoms were exposed to different concentrations of Cd for 7 days, and were then allowed different periods of time to recover. The Cd sensitivity increased after recovery from Cd stress, followed by a gradual restoration. The extent of restoration depended on both the recovery time and the environmental Cd stress during the exposure period. A complete restoration of Cd tolerance proved to be impossible for cells pre-exposed to High-Cd. The Cd cellular burden and subcellular Cd concentration decreased to the control level within the first day of recovery, indicating that the elevated sensitivity may have been due to the accumulation of functional damage caused by Cd exposure instead of a result of physical Cd accumulation. The rapid change in phytochelatins (PC) to both the increase in and the withdrawal of environmental Cd stress made it a good quantitative bioindicator of environmental Cd contamination. However, the relationships between Cd distribution in the metal sensitive fraction (MSF-Cd) or intracellular Cd to thiol ratio (intra-Cd/PC-SH) and the relative change in the median inhibition [Cd{sup 2+}] ([Cd{sup 2+}]-based-IC{sub 50}, i.e., Cd sensitivity) differed for the various exposure and recovery periods tested. Our study suggests that more attention should be given to the recovery of aquatic organisms from episodic metal exposure.

  6. Silane-coated magnetic nanoparticles with surface thiol functions for conjugation with gold nanostars

    KAUST Repository

    Pallavicini, Piersandro

    2015-11-10

    Small (d ∼ 8 nm) magnetite nanoparticles, FeONP, are prepared and coated with mercaptopropyl trimethoxysilane (MPTS) to form FeONP@MPTS. In the coating step controlled MPTS/FeONP molar ratios are used, ranging from 1 to 7.8 × 10. The total quantity of MPTS per FeONP is determined by SEM-EDS analysis and the average number of free, reactive -SH groups per FeONP is calculated by a colorimetric method. At very low molar ratios MPTS forms a submonolayer on the FeONP surface with all -SH free to react, while on increasing the MPTS/FeONP molar ratio the (CHO)Si- groups of MPTS polymerize, forming a progressively thicker shell, in which only a small fraction of the -SH groups, positioned on the shell surface, is available for further reaction. The MPTS shell reduces the magnetic interactions occurring between the magnetite cores, lowering the occurrence and strength of collective magnetic states, with FeONP@MPTS showing the typical behaviour expected for a sample with a mono-modal size distribution of superparamagnetic nanoparticles. Interaction of FeONP@MPTS with gold nanostars (GNS) was tested, using both FeONP@MPTS with a MPTS submonolayer and with increasing shell thickness. Provided that a good balance is used between the number of available -SH and the overall size of FeONP@MPTS, the free thiols of such nanoparticles bind GNS decorating their surface, as shown by UV-Vis spectroscopy and TEM imaging.

  7. Silane-coated magnetic nanoparticles with surface thiol functions for conjugation with gold nanostars.

    Science.gov (United States)

    Pallavicini, Piersandro; Cabrini, Elisa; Casu, Alberto; Dacarro, Giacomo; Diaz-Fernandez, Yuri Antonio; Falqui, Andrea; Milanese, Chiara; Vita, Francesco

    2015-12-28

    Small (d∼ 8 nm) magnetite nanoparticles, Fe3O4NP, are prepared and coated with mercaptopropyl trimethoxysilane (MPTS) to form Fe3O4NP@MPTS. In the coating step controlled MPTS/Fe3O4NP molar ratios are used, ranging from 1 to 7.8 × 10(4). The total quantity of MPTS per Fe3O4NP is determined by SEM-EDS analysis and the average number of free, reactive -SH groups per Fe3O4NP is calculated by a colorimetric method. At very low molar ratios MPTS forms a submonolayer on the Fe3O4NP surface with all -SH free to react, while on increasing the MPTS/Fe3O4NP molar ratio the (CH3O)3Si- groups of MPTS polymerize, forming a progressively thicker shell, in which only a small fraction of the -SH groups, positioned on the shell surface, is available for further reaction. The MPTS shell reduces the magnetic interactions occurring between the magnetite cores, lowering the occurrence and strength of collective magnetic states, with Fe3O4NP@MPTS showing the typical behaviour expected for a sample with a mono-modal size distribution of superparamagnetic nanoparticles. Interaction of Fe3O4NP@MPTS with gold nanostars (GNS) was tested, using both Fe3O4NP@MPTS with a MPTS submonolayer and with increasing shell thickness. Provided that a good balance is used between the number of available -SH and the overall size of Fe3O4NP@MPTS, the free thiols of such nanoparticles bind GNS decorating their surface, as shown by UV-Vis spectroscopy and TEM imaging.

  8. In vitro glutathione peroxidase mimicry of ebselen is linked to its oxidation of critical thiols on key cerebral suphydryl proteins - A novel component of its GPx-mimic antioxidant mechanism emerging from its thiol-modulated toxicology and pharmacology.

    Science.gov (United States)

    Kade, I J; Balogun, B D; Rocha, J B T

    2013-10-25

    The antioxidant mechanism of ebselen in rats brain is largely linked with its glutathione peroxidase (GPx) rather than its peroxiredoxin mimicry ability. However, the precise molecular dynamics between the GPx-mimicry of ebselen and thiol utilization is yet to be fully clarified and thus still open. Herein, we investigated the influence of dithiothreitol (DTT) on the antioxidant action of ebselen against oxidant-induced cerebral lipid peroxidation and deoxyribose degradation. Furthermore, the critical inhibitory concentrations of ebselen on the activities of sulphydryl enzymes such as cerebral sodium pump, δ-aminolevulinic acid dehydratase (δ-ALAD) and lactate dehydrogenase (LDH) were also investigated. We observe that ebselen (at ≥42 μM) markedly inhibited lipid peroxidation in the presence and absence of DTT, whereas it inhibited deoxyribose degradation only in the presence of DTT. Furthermore, under in vitro conditions, ebselen inhibited the thiol containing enzymes; cerebral sodium pump (at ≥40 μM), δ-ALAD (≥10 μM) and LDH (≥1 μM) which were either prevented or reversed by DTT. However, the inhibition of the activities of these sulphydryl proteins in diabetic animals was prevented by ebselen. Summarily, it is apparent that the effective in vitro inhibitory doses of ebselen on the activity of the sulphydryl proteins are far less than its antioxidant doses. In addition, the presence of DTT is evidently a critical requirement for ebselen to effect its antioxidant action against deoxyribose degeradation and not lipid peroxidation. Consequently, we conclude that ebselen possibly utilizes available thiols on sulphydryl proteins to effect its GPx mimicry antioxidant action against lipid peroxidation in rat brain homogenate. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  9. Depletion of Intracellular Thiols and Increased Production of 4-Hydroxynonenal that Occur During Cryopreservation of Stallion Spermatozoa Lead to Caspase Activation, Loss of Motility, and Cell Death.

    Science.gov (United States)

    Martin Muñoz, Patricia; Ortega Ferrusola, Cristina; Vizuete, Guillermo; Plaza Dávila, Maria; Rodriguez Martinez, Heriberto; Peña, Fernando J

    2015-12-01

    Oxidative stress has been linked to sperm death and the accelerated senescence of cryopreserved spermatozoa. However, the molecular mechanisms behind this phenomenon remain poorly understood. Reactive oxygen species (ROS) are considered relevant signaling molecules for sperm function, only becoming detrimental when ROS homeostasis is lost. We hereby hypothesize that a major component of the alteration of ROS homeostasis in cryopreserved spermatozoa is the exhaustion of intrinsic antioxidant defense mechanisms. To test this hypothesis, semen from seven stallions was frozen using a standard technique. The parameters of sperm quality (motility, velocity, and membrane integrity) and markers of sperm senescence (caspase 3, 4-hydroxynonenal, and mitochondrial membrane potential) were assessed before and after cryopreservation. Changes in the intracellular thiol content were also monitored. Cryopreservation caused significant increases in senescence markers as well as dramatic depletion of intracellular thiols to less than half of the initial values (P spermatozoa without active caspase 3 (r = 0.996, P spermatozoa; additionally, 4-hydroxynonenal levels were negatively correlated with thiol levels (r = -0.856). In conclusion, sperm functionality postthaw correlates with the maintenance of adequate levels of intracellular thiols. The accelerated senescence of thawed spermatozoa is related to oxidative and electrophilic stress induced by increased production of 4-hydroxynoneal in thawed samples once intracellular thiols are depleted. © 2015 by the Society for the Study of Reproduction, Inc.

  10. A new ensemble approach based chemosensor for the reversible detection of bio-thiols and its application in live cell imaging

    International Nuclear Information System (INIS)

    Wang, Yue; Zhang, Zhiqiang; Meng, Qingtao; He, Cheng; Zhang, Run; Duan, Chunying

    2016-01-01

    Based on an aldazine-copper chemosensing ensemble (NP-Cu 2+ ), a new fluorescence chemosensor for the detection of biothiols (Cys, Hcy and GSH) was designed and synthesized. In aqueous solution, the ligand NP exhibited high selectivity toward Cu 2+ ions by forming a 2:1 complex, accompanied with a dramatic fluorescence quenching and a notable bathochromic-shift of the absorbance band. Due to the high affinity of thiols and copper, the specific interaction of thiols (Cys, Hcy and GSH) with NP-Cu 2+ ensemble led to the liberation of the NP. As the result, recovery of fluorescence and UV–vis absorbance was observed. The detection limits of NP-Cu 2+ to Cys, Hcy and GSH were estimated to be 1.5 μM, 1.8 μM and 2.2 μM, respectively. The fluorescence “OFF–ON” circle can be repeated to a minimum of 5 times by the alternative addition of thiols and Cu 2+ , implying that NP-Cu 2+ is a recyclable chemosensor for thiols. Results of fluorescence microscopy imaging suggested that NP-Cu 2+ has potential to be used as a powerful tool for the detection of intracellular thiols.

  11. Confirmation of 1-Phenylethane-1-thiol as the Character Impact Aroma Compound in Curry Leaves and Its Behavior during Tissue Disruption, Drying, and Frying.

    Science.gov (United States)

    Steinhaus, Martin

    2017-03-15

    The most odor-active compounds previously identified by application of an aroma extract dilution analysis were quantitated in freshly picked curry leaves, either by stable isotope dilution assays in combination with GC-GC-MS or by GC-FID after simultaneous extraction/fractionation. Odor activity values (OAVs) were calculated as ratios of concentrations to odor threshold values. The topmost OAVs were obtained for (3Z)-hex-3-enal (grassy; OAV 180 000), (1S)-1-phenylethane-1-thiol (sulfury, burnt; OAV 150 000), (1R)-1-phenylethane-1-thiol (sulfury, burnt; OAV 120 000), (3R)-linalool (citrusy; OAV 58 000), and myrcene (geranium leaf-like; OAV 23 000). The high OAVs calculated for its enantiomers confirmed 1-phenylethane-1-thiol as character impact compound of the typical sulfury and burnt aroma of curry leaves. The 1-phenylethane-1-thiol concentration in curry leaves decreased upon tissue disruption and drying, as well as upon frying of fresh leaves. By contrast, frying of dried leaves led to an increase of 1-phenylethane-1-thiol, indicating a yet unknown thermolabile precursor.

  12. A new ensemble approach based chemosensor for the reversible detection of bio-thiols and its application in live cell imaging

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yue; Zhang, Zhiqiang [Key Laboratory for Functional Material, Educational Department of Liaoning Province, University of Science and Technology Liaoning, Anshan 114051 (China); Meng, Qingtao, E-mail: qtmeng@ustl.edu.cn [Key Laboratory for Functional Material, Educational Department of Liaoning Province, University of Science and Technology Liaoning, Anshan 114051 (China); State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Road, Dalian High-Tech Industrial Zone, 116024 (China); He, Cheng [State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Road, Dalian High-Tech Industrial Zone, 116024 (China); Zhang, Run [Key Laboratory for Functional Material, Educational Department of Liaoning Province, University of Science and Technology Liaoning, Anshan 114051 (China); Department of Chemistry and Biomolecular Sciences, Faculty of Science and Engineering, Macquarie University, Sydney, NSW, 2109 (Australia); Duan, Chunying, E-mail: cyduan@dlut.edu.cn [State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Road, Dalian High-Tech Industrial Zone, 116024 (China)

    2016-07-15

    Based on an aldazine-copper chemosensing ensemble (NP-Cu{sup 2+}), a new fluorescence chemosensor for the detection of biothiols (Cys, Hcy and GSH) was designed and synthesized. In aqueous solution, the ligand NP exhibited high selectivity toward Cu{sup 2+} ions by forming a 2:1 complex, accompanied with a dramatic fluorescence quenching and a notable bathochromic-shift of the absorbance band. Due to the high affinity of thiols and copper, the specific interaction of thiols (Cys, Hcy and GSH) with NP-Cu{sup 2+} ensemble led to the liberation of the NP. As the result, recovery of fluorescence and UV–vis absorbance was observed. The detection limits of NP-Cu{sup 2+} to Cys, Hcy and GSH were estimated to be 1.5 μM, 1.8 μM and 2.2 μM, respectively. The fluorescence “OFF–ON” circle can be repeated to a minimum of 5 times by the alternative addition of thiols and Cu{sup 2+}, implying that NP-Cu{sup 2+} is a recyclable chemosensor for thiols. Results of fluorescence microscopy imaging suggested that NP-Cu{sup 2+} has potential to be used as a powerful tool for the detection of intracellular thiols.

  13. Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction.

    Science.gov (United States)

    Saed, Mohand O; Torbati, Amir H; Nair, Devatha P; Yakacki, Christopher M

    2016-01-19

    This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline elastomers (LCEs) with facile control over network structure and programming of an aligned monodomain. Tailored LCE networks were synthesized using routine mixing of commercially available starting materials and pouring monomer solutions into molds to cure. An initial polydomain LCE network is formed via a self-limiting thiol-acrylate Michael-addition reaction. Strain-to-failure and glass transition behavior were investigated as a function of crosslinking monomer, pentaerythritol tetrakis(3-mercaptopropionate) (PETMP). An example non-stoichiometric system of 15 mol% PETMP thiol groups and an excess of 15 mol% acrylate groups was used to demonstrate the robust nature of the material. The LCE formed an aligned and transparent monodomain when stretched, with a maximum failure strain over 600%. Stretched LCE samples were able to demonstrate both stress-driven thermal actuation when held under a constant bias stress or the shape-memory effect when stretched and unloaded. A permanently programmed monodomain was achieved via a second-stage photopolymerization reaction of the excess acrylate groups when the sample was in the stretched state. LCE samples were photo-cured and programmed at 100%, 200%, 300%, and 400% strain, with all samples demonstrating over 90% shape fixity when unloaded. The magnitude of total stress-free actuation increased from 35% to 115% with increased programming strain. Overall, the two-stage TAMAP methodology is presented as a powerful tool to prepare main-chain LCE systems and explore structure-property-performance relationships in these fascinating stimuli-sensitive materials.

  14. Thiol-Disulfide Exchange in Peptides Derived from Human Growth Hormone during Lyophilization and Storage in the Solid State

    Science.gov (United States)

    Chandrasekhar, Saradha; Topp, Elizabeth M.

    2015-01-01

    Lyophilization (freeze-drying) is frequently used to stabilize protein therapeutics. However, covalent modifications such as thiol-disulfide exchange and disulfide scrambling can occur even in the solid state. The effects of lyophilization and storage of lyophilized powders on the mechanism and kinetics of thioldisulfide exchange have not been elucidated and are explored here. Reaction kinetics were monitored in peptides corresponding to tryptic fragments of human growth hormone (T20 + T20-T21 or T20 + cT20-T21) during different stages of lyophilization and during storage of the lyophilized powders at 22 °C and ambient RH. The concentrations of reactants and products were determined using RP-HPLC and product identity confirmed using LC-MS. Loss of native disulfide was observed for the reaction of T20 with both linear (T20-T21) and cyclic (cT20-T21) peptides during the primary drying step, however, the native disulfides were regenerated during secondary drying with no further change till the end of lyophilization. Deviations from Arrhenius parameters predicted from solution studies and the absence of buffer effects during lyophilization suggest that factors such as temperature, initial peptide concentration, buffer type and concentration do not influence thiol-disulfide exchange during lyophilization. Results from a ‘cold finger’ method used to study peptide adsorption to ice indicate that there is no preferential adsorption to the ice surface and that its presence may not influence disulfide reactivity during primary drying. Overall, reaction rates and product distribution differ for the reaction of T20 with T20-T21 or cT20-T21 in the solid state and aqueous solution, while the mechanism of thiol-disulfide remains unchanged. Increased reactivity of the cyclic peptide in the solid state suggests that peptide cyclization does not offer protection against lyophilization and that damage induced by a process stress further affects storage stability at 22 °C and

  15. Thiol-ene synthesis and characterization of lithium bis(malonato)borate single-ion conducting gel polymer electrolytes.

    Science.gov (United States)

    Weber, Ryan L; Mahanthappa, Mahesh K

    2017-10-25

    The development of high capacity anodes and high voltage cathodes for advanced lithium-ion batteries motivates the search for new polymer electrolytes that exhibit superior electrochemical stabilities and high ionic conductivities. We report a convenient, three-step synthesis of lithium bis(non-8-enyl-malonato)borate (LiBNMB) as a α,ω-diene monomer, which undergoes thermally initiated thiol-ene crosslinking polymerizations in propylene carbonate to yield gel polymer electrolytes with high lithium ion concentrations (∼0.9 M). By conducting these crosslinking polymerizations using mixtures of di- and tri-thiols and LiBNMB with [thiol] : [ene] = 1 : 1, we synthesized a series of gel networks with dynamic elastic moduli ranging from G' = 40-79 kPa that increase monotonically with trifunctional crosslinker content. While ionic conductivities for these polymer gels measured by electrochemical impedance spectroscopy at 22 °C are σ = 0.82-2.5 × 10 -6 S cm -1 , we show that the conductivity of propylene carbonate-solvated lithium ions though the bulk of these gel electrolytes is 8.5 × 10 -5 S cm -1 independent of crosslinker density. However, the conductivities of the gel interfaces depend sensitively on crosslinker content, suggesting the importance of segmental rearrangement dynamics at the electrode interface in limiting the rate of ion motion. Thus, the design of highly conductive polymer electrolytes for advanced batteries demands careful design of both the internal and interfacial properties of these new materials.

  16. On sulfur core level binding energies in thiol self-assembly and alternative adsorption sites: An experimental and theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Juanjuan [Institut des Sciences Moléculaires d’Orsay, Université-Paris Sud, 91405 Orsay (France); CNRS, UMR 8214, Institut des Sciences Moléculaires d’Orsay, Orsay ISMO, Bâtiment 351, Université Paris Sud, 91405 Orsay (France); Kara, Abdelkader, E-mail: abdelkader.kara@ucf.edu, E-mail: vladimir.esaulov@u-psud.fr [Department of Physics, University of Central Florida, Orlando, Florida 32816 (United States); Pasquali, Luca [Dipartimento di Ingegneria “E. Ferrari,” Università di Modena e Reggio Emilia, Via Vignolese 905, 41125 Modena (Italy); IOM-CNR, s.s. 14, Km. 163.5 in AREA Science Park, 34149 Basovizza, Trieste (Italy); Department of Physics, University of Johannesburg, P.O. Box 524, Auckland Park 2006 (South Africa); Bendounan, Azzedine; Sirotti, Fausto [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette Cedex (France); Esaulov, Vladimir A., E-mail: abdelkader.kara@ucf.edu, E-mail: vladimir.esaulov@u-psud.fr [Institut des Sciences Moléculaires d’Orsay, Université-Paris Sud, 91405 Orsay (France); CNRS, UMR 8214, Institut des Sciences Moléculaires d’Orsay, Orsay ISMO, Bâtiment 351, Université Paris Sud, 91405 Orsay (France); IOM-CNR, s.s. 14, Km. 163.5 in AREA Science Park, 34149 Basovizza, Trieste (Italy)

    2015-09-14

    Characteristic core level binding energies (CLBEs) are regularly used to infer the modes of molecular adsorption: orientation, organization, and dissociation processes. Here, we focus on a largely debated situation regarding CLBEs in the case of chalcogen atom bearing molecules. For a thiol, this concerns the case when the CLBE of a thiolate sulfur at an adsorption site can be interpreted alternatively as due to atomic adsorption of a S atom, resulting from dissociation. Results of an investigation of the characteristics of thiol self-assembled monolayers (SAMs) obtained by vacuum evaporative adsorption are presented along with core level binding energy calculations. Thiol ended SAMs of 1,4-benzenedimethanethiol (BDMT) obtained by evaporation on Au display an unconventional CLBE structure at about 161.25 eV, which is close to a known CLBE of a S atom on Au. Adsorption and CLBE calculations for sulfur atoms and BDMT molecules are reported and allow delineating trends as a function of chemisorption on hollow, bridge, and atop sites and including the presence of adatoms. These calculations suggest that the 161.25 eV peak is due to an alternative adsorption site, which could be associated to an atop configuration. Therefore, this may be an alternative interpretation, different from the one involving the adsorption of atomic sulfur resulting from the dissociation process of the S–C bond. Calculated differences in S(2p) CLBEs for free BDMT molecules, SH group sulfur on top of the SAM, and disulfide are also reported to clarify possible errors in assignments.

  17. 2-nitroveratryl as a photocleavable thiol-protecting group for directed disulfide bond formation in the chemical synthesis of insulin.

    Science.gov (United States)

    Karas, John A; Scanlon, Denis B; Forbes, Briony E; Vetter, Irina; Lewis, Richard J; Gardiner, James; Separovic, Frances; Wade, John D; Hossain, Mohammed A

    2014-07-28

    Chemical synthesis of peptides can allow the option of sequential formation of multiple cysteines through exploitation of judiciously chosen regioselective thiol-protecting groups. We report the use of 2-nitroveratryl (oNv) as a new orthogonal group that can be cleaved by photolysis under ambient conditions. In combination with complementary S-pyridinesulfenyl activation, disulfide bonds are formed rapidly in situ. The preparation of Fmoc-Cys(oNv)-OH is described together with its use for the solid-phase synthesis of complex cystine-rich peptides, such as insulin. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Sub-10 ohm resistance gold films prepared by removal of ligands from thiol-stabilized 6 nm gold nanoparticles.

    Science.gov (United States)

    Sugden, Mark W; Richardson, Tim H; Leggett, Graham

    2010-03-16

    The optical and electrical properties of dodecanethiol-stabilized nanoparticles (6 nm diameter gold core) have been investigated over a range of film thicknesses and temperatures. The surface plasmon resonance absorbance is found to be dependent on temperature. Heating of the nanoparticle film causes desorption of the thiol from the surface of the gold nanoparticle, resulting in irreversible changes to the absorption spectra of the nanoparticle film. Atomic force microscopy images of the samples before and after heating for different film thicknesses reveal structural changes and increased domain connectivity for thicker films leading to sub-10 ohm resistances measured for the 15-layer film.

  19. The effects of counter-ion condensation and co-ion depletion upon the rates of chemical repair of poly(U) radicals by thiols

    International Nuclear Information System (INIS)

    Fahey, R.C.; Vojnovic, B.; Michael, B.D.

    1991-01-01

    Bimolecular rate constants for reactions of poly(U) radicals with a series of thiols of varying net charge (Z) were measured by pulse radiolysis with conductivity detection at low ionic strength. At pH 7 and 18 o C the values of k 2 (M -1 s -1 ) were: reduced glutathione (Z = -1), 3 ; 2-mercaptoethanol (Z =0), 1.8 x 10 5 ; cysteine (Z=0), 2.0 x 10 5 ; cysteamine (Z = +1), 4.1 x 10 7 . Values determined at pH4 were: 2-mercaptoethanol, 6.1 x 10 5 ; cysteamine 2.2 x 10 8 ; N-(2-mercaptoethyl)-1,3-diaminopropane (WR-1065, Z = +2), 4.6 x 10 8 . The variation in rate with structure could not reasonably be attributed to inherent reactivity differences in the thiols and was ascribed to inhomogeneous distributions of the thiols in solution resulting from electrostatic interactions. (Author)

  20. Self-assembled monolayers (SAMs) of alkoxycyanobiphenyl thiols on gold--a study of electron transfer reaction using cyclic voltammetry and electrochemical impedance spectroscopy.

    Science.gov (United States)

    Ganesh, V; Pal, Santanu Kumar; Kumar, Sandeep; Lakshminarayanan, V

    2006-04-01

    Self-assembled monolayers (SAMs) of liquid crystalline thiol-terminated alkoxycyanobiphenyl molecules with different alkyl chain lengths on Au surface have been studied for the first time using electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The barrier property of the SAM-modified surfaces was evaluated using two different redox probes, namely potassium ferro/ferri cyanide and hexaammineruthenium(III) chloride. It was found that for short-length alkyl chain thiol (C5) the electron transfer reaction of hexaammineruthenium(III) chloride takes place through tunneling mechanism. In contrast, redox reaction of potassium ferro/ferri cyanide is almost completely blocked by the SAM-modified Au surface. From the impedance data, a surface coverage value of >99.9% was calculated for all the thiol molecules.