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Sample records for macrocyclic knotted peptide

  1. Comprehensive computational design of ordered peptide macrocycles

    Energy Technology Data Exchange (ETDEWEB)

    Hosseinzadeh, Parisa; Bhardwaj, Gaurav; Mulligan, Vikram K.; Shortridge, Matthew D.; Craven, Timothy W.; Pardo-Avila, Fatima; Rettie, Stephan A.; Kim, David E.; Silva, Daniel A.; Ibrahim, Yehia M.; Webb, Ian K.; Cort, John R.; Adkins, Joshua N.; Varani, Gabriele; Baker, David

    2017-12-14

    Mixed chirality peptide macrocycles such as cyclosporine are among the most potent therapeutics identified to-date, but there is currently no way to systematically search through the structural space spanned by such compounds for new drug candidates. Natural proteins do not provide a useful guide: peptide macrocycles lack regular secondary structures and hydrophobic cores and have different backbone torsional constraints. Hence the development of new peptide macrocycles has been approached by modifying natural products or using library selection methods; the former is limited by the small number of known structures, and the latter by the limited size and diversity accessible through library-based methods. To overcome these limitations, here we enumerate the stable structures that can be adopted by macrocyclic peptides composed of L and D amino acids. We identify more than 200 designs predicted to fold into single stable structures, many times more than the number of currently available unbound peptide macrocycle structures. We synthesize and characterize by NMR twelve 7-10 residue macrocycles, 9 of which have structures very close to the design models in solution. NMR structures of three 11-14 residue bicyclic designs are also very close to the computational models. Our results provide a nearly complete coverage of the rich space of structures possible for short peptide based macrocycles unparalleled for other molecular systems, and vastly increase the available starting scaffolds for both rational drug design and library selection methods.

  2. Comprehensive computational design of ordered peptide macrocycles

    Science.gov (United States)

    Hosseinzadeh, Parisa; Bhardwaj, Gaurav; Mulligan, Vikram Khipple; Shortridge, Matthew D.; Craven, Timothy W.; Pardo-Avila, Fátima; Rettie, Stephen A.; Kim, David E.; Silva, Daniel-Adriano; Ibrahim, Yehia M.; Webb, Ian K.; Cort, John R.; Adkins, Joshua N.; Varani, Gabriele; Baker, David

    2018-01-01

    Mixed-chirality peptide macrocycles such as cyclosporine are among the most potent therapeutics identified to date, but there is currently no way to systematically search the structural space spanned by such compounds. Natural proteins do not provide a useful guide: Peptide macrocycles lack regular secondary structures and hydrophobic cores, and can contain local structures not accessible with L-amino acids. Here, we enumerate the stable structures that can be adopted by macrocyclic peptides composed of L- and D-amino acids by near-exhaustive backbone sampling followed by sequence design and energy landscape calculations. We identify more than 200 designs predicted to fold into single stable structures, many times more than the number of currently available unbound peptide macrocycle structures. Nuclear magnetic resonance structures of 9 of 12 designed 7- to 10-residue macrocycles, and three 11- to 14-residue bicyclic designs, are close to the computational models. Our results provide a nearly complete coverage of the rich space of structures possible for short peptide macrocycles and vastly increase the available starting scaffolds for both rational drug design and library selection methods. PMID:29242347

  3. Structural basis for precursor protein-directed ribosomal peptide macrocyclization

    Science.gov (United States)

    Li, Kunhua; Condurso, Heather L.; Li, Gengnan; Ding, Yousong; Bruner, Steven D.

    2016-01-01

    Macrocyclization is a common feature of natural product biosynthetic pathways including the diverse family of ribosomal peptides. Microviridins are architecturally complex cyanobacterial ribosomal peptides whose members target proteases with potent reversible inhibition. The product structure is constructed by three macrocyclizations catalyzed sequentially by two members of the ATP-grasp family, a unique strategy for ribosomal peptide macrocyclization. Here, we describe the detailed structural basis for the enzyme-catalyzed macrocyclizations in the microviridin J pathway of Microcystis aeruginosa. The macrocyclases, MdnC and MdnB, interact with a conserved α-helix of the precursor peptide using a novel precursor peptide recognition mechanism. The results provide insight into the unique protein/protein interactions key to the chemistry, suggest an origin of the natural combinatorial synthesis of microviridin peptides and provide a framework for future engineering efforts to generate designed compounds. PMID:27669417

  4. Structural basis for precursor protein-directed ribosomal peptide macrocyclization.

    Science.gov (United States)

    Li, Kunhua; Condurso, Heather L; Li, Gengnan; Ding, Yousong; Bruner, Steven D

    2016-11-01

    Macrocyclization is a common feature of natural product biosynthetic pathways including the diverse family of ribosomal peptides. Microviridins are architecturally complex cyanobacterial ribosomal peptides that target proteases with potent reversible inhibition. The product structure is constructed via three macrocyclizations catalyzed sequentially by two members of the ATP-grasp family, a unique strategy for ribosomal peptide macrocyclization. Here we describe in detail the structural basis for the enzyme-catalyzed macrocyclizations in the microviridin J pathway of Microcystis aeruginosa. The macrocyclases MdnC and MdnB interact with a conserved α-helix of the precursor peptide using a novel precursor-peptide recognition mechanism. The results provide insight into the unique protein-protein interactions that are key to the chemistry, suggest an origin for the natural combinatorial synthesis of microviridin peptides, and provide a framework for future engineering efforts to generate designed compounds.

  5. Structural basis of nonribosomal peptide macrocyclization in fungi.

    Science.gov (United States)

    Zhang, Jinru; Liu, Nicholas; Cacho, Ralph A; Gong, Zhou; Liu, Zhu; Qin, Wenming; Tang, Chun; Tang, Yi; Zhou, Jiahai

    2016-12-01

    Nonribosomal peptide synthetases (NRPSs) in fungi biosynthesize important pharmaceutical compounds, including penicillin, cyclosporine and echinocandin. To understand the fungal strategy of forging the macrocyclic peptide linkage, we determined the crystal structures of the terminal condensation-like (C T ) domain and the holo thiolation (T)-C T complex of Penicillium aethiopicum TqaA. The first, to our knowledge, structural depiction of the terminal module in a fungal NRPS provides a molecular blueprint for generating new macrocyclic peptide natural products.

  6. Acetone-Linked Peptides: A Convergent Approach for Peptide Macrocyclization and Labeling.

    Science.gov (United States)

    Assem, Naila; Ferreira, David J; Wolan, Dennis W; Dawson, Philip E

    2015-07-20

    Macrocyclization is a broadly applied approach for overcoming the intrinsically disordered nature of linear peptides. Herein, it is shown that dichloroacetone (DCA) enhances helical secondary structures when introduced between peptide nucleophiles, such as thiols, to yield an acetone-linked bridge (ACE). Aside from stabilizing helical structures, the ketone moiety embedded in the linker can be modified with diverse molecular tags by oxime ligation. Insights into the structure of the tether were obtained through co-crystallization of a constrained S-peptide in complex with RNAse S. The scope of the acetone-linked peptides was further explored through the generation of N-terminus to side chain macrocycles and a new approach for generating fused macrocycles (bicycles). Together, these studies suggest that acetone linking is generally applicable to peptide macrocycles with a specific utility in the synthesis of stabilized helices that incorporate functional tags. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Selective CO2 gas adsorption in the narrow crystalline cavities of flexible peptide metallo-macrocycles.

    Science.gov (United States)

    Miyake, Ryosuke; Kuwata, Chika; Masumoto, Yui

    2015-02-21

    Crystalline peptide Ni(ii)-macrocycles (BF4(-) salt) exhibited moderate CO2 gas adsorption (ca. 6-7 CO2 molecules per macrocycle) into very narrow cavities (narrowest part gas in preference to CH4 and N2 gases.

  8. Novel Inhibitor Cystine Knot Peptides from Momordica charantia

    Science.gov (United States)

    Clark, Richard J.; Tang, Jun; Zeng, Guang-Zhi; Franco, Octavio L.; Cantacessi, Cinzia; Craik, David J.; Daly, Norelle L.; Tan, Ning-Hua

    2013-01-01

    Two new peptides, MCh-1 and MCh-2, along with three known trypsin inhibitors (MCTI-I, MCTI-II and MCTI-III), were isolated from the seeds of the tropical vine Momordica charantia. The sequences of the peptides were determined using mass spectrometry and NMR spectroscopy. Using a strategy involving partial reduction and stepwise alkylation of the peptides, followed by enzymatic digestion and tandem mass spectrometry sequencing, the disulfide connectivity of MCh-1 was elucidated to be CysI-CysIV, CysII-CysV and CysIII-CysVI. The three-dimensional structures of MCh-1 and MCh-2 were determined using NMR spectroscopy and found to contain the inhibitor cystine knot (ICK) motif. The sequences of the novel peptides differ significantly from peptides previously isolated from this plant. Therefore, this study expands the known peptide diversity in M. charantia and the range of sequences that can be accommodated by the ICK motif. Furthermore, we show that a stable two-disulfide intermediate is involved in the oxidative folding of MCh-1. This disulfide intermediate is structurally homologous to the proposed ancestral fold of ICK peptides, and provides a possible pathway for the evolution of this structural motif, which is highly prevalent in nature. PMID:24116036

  9. Novel inhibitor cystine knot peptides from Momordica charantia.

    Directory of Open Access Journals (Sweden)

    Wen-Jun He

    Full Text Available Two new peptides, MCh-1 and MCh-2, along with three known trypsin inhibitors (MCTI-I, MCTI-II and MCTI-III, were isolated from the seeds of the tropical vine Momordica charantia. The sequences of the peptides were determined using mass spectrometry and NMR spectroscopy. Using a strategy involving partial reduction and stepwise alkylation of the peptides, followed by enzymatic digestion and tandem mass spectrometry sequencing, the disulfide connectivity of MCh-1 was elucidated to be CysI-CysIV, CysII-CysV and CysIII-CysVI. The three-dimensional structures of MCh-1 and MCh-2 were determined using NMR spectroscopy and found to contain the inhibitor cystine knot (ICK motif. The sequences of the novel peptides differ significantly from peptides previously isolated from this plant. Therefore, this study expands the known peptide diversity in M. charantia and the range of sequences that can be accommodated by the ICK motif. Furthermore, we show that a stable two-disulfide intermediate is involved in the oxidative folding of MCh-1. This disulfide intermediate is structurally homologous to the proposed ancestral fold of ICK peptides, and provides a possible pathway for the evolution of this structural motif, which is highly prevalent in nature.

  10. Peptide Macrocycles Featuring a Backbone Secondary Amine: A Convenient Strategy for the Synthesis of Lipidated Cyclic and Bicyclic Peptides on Solid Support

    DEFF Research Database (Denmark)

    Oddo, Alberto; Münzker, Lena; Hansen, Paul Robert

    2015-01-01

    A convenient strategy for the on-resin synthesis of macrocyclic peptides (3- to 13-mers) via intramolecular halide substitution by a diamino acid is described. The method is compatible with standard Fmoc/tBu SPPS and affords a tail-to-side-chain macrocyclic peptide featuring an endocyclic secondary...

  11. Design and synthesis of macrocyclic peptidyl hydroxamates as peptide deformylase inhibitors.

    Science.gov (United States)

    Shen, Gang; Zhu, Jinge; Simpson, Anthony M; Pei, Dehua

    2008-05-15

    Macrocyclic peptidyl hydroxamates were designed, synthesized, and evaluated as peptide deformylase (PDF) inhibitors. The most potent compound exhibited tight, slow-binding inhibition of Escherichia coli PDF (K(I)(*)=4.4 nM) and had potent antibacterial activity against Gram-positive bacterium Bacillus subtilis (MIC=2-4 microg/mL).

  12. Macrocycle peptides delineate locked-open inhibition mechanism for microorganism phosphoglycerate mutases

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Hao; Dranchak, Patricia; Li, Zhiru; MacArthur, Ryan; Munson, Matthew S.; Mehzabeen, Nurjahan; Baird, Nathan J.; Battalie, Kevin P.; Ross, David; Lovell, Scott; Carlow, Clotilde K.S.; Suga, Hiroaki; Inglese, James (U of Tokyo); (NEB); (Kansas); (NIH); (NIST); (HHMI)

    2017-04-03

    Glycolytic interconversion of phosphoglycerate isomers is catalysed in numerous pathogenic microorganisms by a cofactor-independent mutase (iPGM) structurally distinct from the mammalian cofactor-dependent (dPGM) isozyme. The iPGM active site dynamically assembles through substrate-triggered movement of phosphatase and transferase domains creating a solvent inaccessible cavity. Here we identify alternate ligand binding regions using nematode iPGM to select and enrich lariat-like ligands from an mRNA-display macrocyclic peptide library containing >1012 members. Functional analysis of the ligands, named ipglycermides, demonstrates sub-nanomolar inhibition of iPGM with complete selectivity over dPGM. The crystal structure of an iPGM macrocyclic peptide complex illuminated an allosteric, locked-open inhibition mechanism placing the cyclic peptide at the bi-domain interface. This binding mode aligns the pendant lariat cysteine thiolate for coordination with the iPGM transition metal ion cluster. The extended charged, hydrophilic binding surface interaction rationalizes the persistent challenges these enzymes have presented to small-molecule screening efforts highlighting the important roles of macrocyclic peptides in expanding chemical diversity for ligand discovery.

  13. A Macrocyclic Peptide that Serves as a Cocrystallization Ligand and Inhibits the Function of a MATE Family Transporter

    Directory of Open Access Journals (Sweden)

    Hiroaki Suga

    2013-08-01

    Full Text Available The random non-standard peptide integrated discovery (RaPID system has proven to be a powerful approach to discover de novo natural product-like macrocyclic peptides that inhibit protein functions. We have recently reported three macrocyclic peptides that bind to Pyrococcus furiosus multidrug and toxic compound extrusion (PfMATE transporter and inhibit the transport function. Moreover, these macrocyclic peptides were successfully employed as cocrystallization ligands of selenomethionine-labeled PfMATE. In this report, we disclose the details of the RaPID selection strategy that led to the identification of these three macrocyclic peptides as well as a fourth macrocyclic peptide, MaD8, which is exclusively discussed in this article. MaD8 was found to bind within the cleft of PfMATE’s extracellular side and blocked the path of organic small molecules being extruded. The results of an ethidium bromide efflux assay confirmed the efflux inhibitory activity of MaD8, whose behavior was similar to that of previously reported MaD5.

  14. Fast and versatile microwave-assisted intramolecular Heck reaction in peptide macrocyclization using microwave energy.

    Science.gov (United States)

    Byk, Gerardo; Cohen-Ohana, Mirit; Raichman, Daniel

    2006-01-01

    We have revisited the intramolecular Heck reaction and investigated the microwave-assisted macrocyclization on preformed peptides using a model series of ring-varying peptides acryloyl-Gly-[Gly](n)-Phe(4-I)NHR; n = 0-4. The method was applied to both solution and solid supported cyclizations. We demonstrate that the intramolecular Heck reaction can be performed in peptides both in solution and solid support using a modified domestic microwave within 1 to 30 minutes in DMF under reflux with moderate yields ranging from 15 to 25% for a scale between 2-45 mg of linear precursors. The approach was applied to the synthesis of a constrained biologically relevant peptidomimetic bearing an Arg-Gly-Asp (RGD) sequence. These results make the microwave-assisted Heck reaction an attractive renovated approach for peptidomimetics. Copyright 2006 Wiley Periodicals, Inc.

  15. Macrocyclic peptides decrease c-Myc protein levels and reduce prostate cancer cell growth.

    Science.gov (United States)

    Mukhopadhyay, Archana; Hanold, Laura E; Thayele Purayil, Hamsa; Gisemba, Solomon A; Senadheera, Sanjeewa N; Aldrich, Jane V

    2017-08-03

    The oncoprotein c-Myc is often overexpressed in cancer cells, and the stability of this protein has major significance in deciding the fate of a cell. Thus, targeting c-Myc levels is an attractive approach for developing therapeutic agents for cancer treatment. In this study, we report the anti-cancer activity of the macrocyclic peptides [D-Trp]CJ-15,208 (cyclo[Phe-D-Pro-Phe-D-Trp]) and the natural product CJ-15,208 (cyclo[Phe-D-Pro-Phe-Trp]). [D-Trp]CJ-15,208 reduced c-Myc protein levels in prostate cancer cells and decreased cell proliferation with IC 50 values ranging from 2.0 to 16 µM in multiple PC cell lines. [D-Trp]CJ-15,208 induced early and late apoptosis in PC-3 cells following 48 hours treatment, and growth arrest in the G2 cell cycle phase following both 24 and 48 hours treatment. Down regulation of c-Myc in PC-3 cells resulted in loss of sensitivity to [D-Trp]CJ-15,208 treatment, while overexpression of c-Myc in HEK-293 cells imparted sensitivity of these cells to [D-Trp]CJ-15,208 treatment. This macrocyclic tetrapeptide also regulated PP2A by reducing the levels of its phosphorylated form which regulates the stability of cellular c-Myc protein. Thus [D-Trp]CJ-15,208 represents a new lead compound for the potential development of an effective treatment of prostate cancer.

  16. Macrocyclic peptide inhibitors for the protein-protein interaction of Zaire Ebola virus protein 24 and karyopherin alpha 5.

    Science.gov (United States)

    Song, Xiao; Lu, Lu-Yi; Passioura, Toby; Suga, Hiroaki

    2017-06-21

    Ebola virus infection leads to severe hemorrhagic fever in human and non-human primates with an average case fatality rate of 50%. To date, numerous potential therapies are in development, but FDA-approved drugs or vaccines are yet unavailable. Ebola viral protein 24 (VP24) is a multifunctional protein that plays critical roles in the pathogenesis of Ebola virus infection, e.g. innate immune suppression by blocking the interaction between KPNA and PY-STAT1. Here we report macrocyclic peptide inhibitors of the VP24-KPNA5 protein-protein interaction (PPI) by means of the RaPID (Random non-standard Peptides Integrated Discovery) system. These macrocyclic peptides showed remarkably high affinity to recombinant Zaire Ebola virus VP24 (eVP24), with a dissociation constant in the single digit nanomolar range, and could also successfully disrupt the eVP24-KPNA interaction. This work provides for the first time a chemical probe capable of modulating this PPI interaction and is the starting point for the development of unique anti-viral drugs against the Ebola virus.

  17. Macrocyclic Peptoid–Peptide Hybrids as Inhibitors of Class I Histone Deacetylases

    DEFF Research Database (Denmark)

    Olsen, Christian Adam; Montero, Ana; Leman, Luke J.

    2012-01-01

    We report the design, synthesis, and biological evaluation of the first macrocyclic peptoid-containing histone deacetylase (HDAC) inhibitors. The compounds selectively inhibit human class I HDAC isoforms in vitro, with no inhibition of the tubulin deacetylase activity associated with class IIb HDAC...

  18. A general strategy for synthesis of cyclophane-braced peptide macrocycles via palladium-catalysed intramolecular sp3 C-H arylation

    Science.gov (United States)

    Zhang, Xuekai; Lu, Gang; Sun, Meng; Mahankali, Madhu; Ma, Yanfei; Zhang, Mingming; Hua, Wangde; Hu, Yuting; Wang, Qingbing; Chen, Jinghuo; He, Gang; Qi, Xiangbing; Shen, Weijun; Liu, Peng; Chen, Gong

    2018-05-01

    New methods capable of effecting cyclization, and forming novel three-dimensional structures while maintaining favourable physicochemical properties are needed to facilitate the development of cyclic peptide-based drugs that can engage challenging biological targets, such as protein-protein interactions. Here, we report a highly efficient and generally applicable strategy for constructing new types of peptide macrocycles using palladium-catalysed intramolecular C(sp3)-H arylation reactions. Easily accessible linear peptide precursors of simple and versatile design can be selectively cyclized at the side chains of either aromatic or modified non-aromatic amino acid units to form various cyclophane-braced peptide cycles. This strategy provides a powerful tool to address the long-standing challenge of size- and composition-dependence in peptide macrocyclization, and generates novel peptide macrocycles with uniquely buttressed backbones and distinct loop-type three-dimensional structures. Preliminary cell proliferation screening of the pilot library revealed a potent lead compound with selective cytotoxicity toward proliferative Myc-dependent cancer cell lines.

  19. Dual function of a bee (Apis cerana) inhibitor cysteine knot peptide that acts as an antifungal peptide and insecticidal venom toxin.

    Science.gov (United States)

    Park, Hee Geun; Kyung, Seung Su; Lee, Kwang Sik; Kim, Bo Yeon; Choi, Yong Soo; Yoon, Hyung Joo; Kwon, Hyung Wook; Je, Yeon Ho; Jin, Byung Rae

    2014-12-01

    Inhibitor cysteine knot (ICK) peptides exhibit ion channel blocking, insecticidal, and antimicrobial activities, but currently, no functional roles for bee-derived ICK peptides have been identified. In this study, a bee (Apis cerana) ICK peptide (AcICK) that acts as an antifungal peptide and as an insecticidal venom toxin was identified. AcICK contains an ICK fold that is expressed in the epidermis, fat body, or venom gland and is present as a 6.6-kDa peptide in bee venom. Recombinant AcICK peptide (expressed in baculovirus-infected insect cells) bound directly to Beauveria bassiana and Fusarium graminearum, but not to Escherichia coli or Bacillus thuringiensis. Consistent with these findings, AcICK showed antifungal activity, indicating that AcICK acts as an antifungal peptide. Furthermore, AcICK expression is induced in the fat body and epidermis after injection with B. bassiana. These results provide insight into the role of AcICK during the innate immune response following fungal infection. Additionally, we show that AcICK has insecticidal activity. Our results demonstrate a functional role for AcICK in bees: AcICK acts as an antifungal peptide in innate immune reactions in the body and as an insecticidal toxin in venom. The finding that the AcICK peptide functions with different mechanisms of action in the body and in venom highlights the two-pronged strategy that is possible with the bee ICK peptide. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. Handling a tricycle: Orthogonal versus random oxidation of the tricyclic inhibitor cystine knotted peptide gurmarin

    DEFF Research Database (Denmark)

    Eliasen, Rasmus; Andresen, Thomas L.; Conde-Frieboes, Kilian W.

    2012-01-01

    random oxidation strategy. We compared two oxidation procedures to form the three disulfide bridges. In the first, based on random oxidation, reduced gurmarin was synthesized using trityl for cysteine protection, and oxidized for 48h in a Tris–HCl buffer containing cystamine and reduced glutathione...... to facilitate disulfide scrambling. The second was based on step-wise deprotection followed by oxidation in which the cysteine pairs are orthogonally protected with tert-Butylthio, trityl and acetamidomethyl. To verify that the native gurmarin oxidation product was obtained, thermolysin cleavage was used...... UPLC. It was found that the random oxidation procedure leads to native gurmarin in high yield. Thus, the synthetic route was simple and significantly more efficient than previously reported syntheses of gurmarin and other cysteine rich peptides. Importantly, native gurmarin was obtained by random...

  1. The effect of macrocyclic chelators on the targeting properties of the 68Ga-labeled gastrin releasing peptide receptor antagonist PEG2-RM26

    International Nuclear Information System (INIS)

    Varasteh, Zohreh; Mitran, Bogdan; Rosenström, Ulrika; Velikyan, Irina; Rosestedt, Maria; Lindeberg, Gunnar; Sörensen, Jens; Larhed, Mats; Tolmachev, Vladimir; Orlova, Anna

    2015-01-01

    Introduction: Overexpression of gastrin-releasing peptide receptors (GRPR) has been reported in several cancers. Bombesin (BN) analogs are short peptides with a high affinity for GRPR. Different BN analogs were evaluated for radionuclide imaging and therapy of GRPR-expressing tumors. We have previously investigated an antagonistic analog of BN (D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH 2 , RM26) conjugated to NOTA via a PEG 2 spacer (NOTA-PEG 2 -RM26) labeled with 68 Ga, 111 In and Al 18 F. 68 Ga-labeled NOTA-PEG 2 -RM26 showed high tumor-to-organ ratios. Methods: The influence of different macrocyclic chelators (NOTA, NODAGA, DOTA and DOTAGA) on the targeting properties of 68 Ga-labeled PEG 2 -RM26 was studied in vitro and in vivo. Results: All conjugates were labeled with generator-produced 68 Ga with high yields and demonstrated high stability and specific binding to GRPR. The IC 50 values of nat Ga-X-PEG 2 -RM26 (X = NOTA, DOTA, NODAGA, DOTAGA) were 2.3 ± 0.2, 3.0 ± 0.3, 2.9 ± 0.3 and 10.0 ± 0.6 nM, respectively. The internalization of the conjugates by PC-3 cells was low. However, the DOTA-conjugated analog demonstrated a higher internalization rate compared to other analogs. GRPR-specific uptake was found in receptor-positive normal tissues and PC-3 xenografts for all conjugates. The biodistribution of the conjugates was influenced by the choice of the chelator moiety. Although all radiotracers cleared rapidly from the blood, [ 68 Ga]Ga-NOTA-PEG 2 -RM26 showed significantly lower uptake in lung, muscle and bone compared to the other analogs. The uptake in tumors (5.40 ± 1.04 %ID/g at 2 h p.i.) and the tumor-to-organ ratios (25 ± 3, 157 ± 23 and 39 ± 4 for blood, muscle and bone, respectively) were significantly higher for the NOTA-conjugate than the other analogs. Conclusions: Chelators had a clear influence on the biodistribution and targeting properties of 68 Ga-labeled antagonistic BN analogs. Positively charged [ 68 Ga]Ga-NOTA-PEG 2 -RM26 provided

  2. Multicomponent Syntheses of Macrocycles

    Science.gov (United States)

    Masson, Géraldine; Neuville, Luc; Bughin, Carine; Fayol, Aude; Zhu, Jieping

    How to access efficiently the macrocyclic structure remained to be a challenging synthetic topic. Although many elegant approaches/reactions have been developed, construction of diverse collection of macrocycles is still elusive. This chapter summarized the recently emerged research area dealing with multicomponent synthesis of macrocycles, with particular emphasis on the approach named "multiple multicomponent reaction using two bifunctional building blocks".

  3. Design, Properties and Recent Application of Macrocycles in Medicinal Chemistry.

    Science.gov (United States)

    Ermert, Philipp

    2017-10-25

    Macrocyclic compounds have recently received increasing attention in drug discovery as these compounds offer the potential to modulate difficult targets and to access novel chemotypes. Approaches towards libraries of macrocyclic compounds based on modular organic synthesis and applications of these technology platforms to find and improve biologically active compounds are introduced in this minireview. Alternatively, lead compounds may be obtained by truncation and modification of macrocyclic natural products. Selected medicinal chemistry programs are discussed, illustrating a macrocyclization approach toward ligands with improved properties. The design of such ligands is often informed by X-ray crystal structures of protein-ligand complexes. Efforts to understand cellular permeability and oral bioavailability of cyclic peptides and non-peptidic macrocycles are summarized.

  4. A Midsummer Knot's Dream

    Science.gov (United States)

    Henrich, A.; MacNaughton, N.; Narayan, S.; Pechenik, O.; Silversmith, R.; Townsend, J.

    2011-01-01

    We introduce playing games on the shadows of knots and demonstrate two novel games, namely, "To Knot or Not to Knot" and "Much Ado about Knotting." We discuss winning strategies for these games on certain families of knot shadows and go on to suggest variations of these games for further study.

  5. Macrocyclic fragrance materials

    DEFF Research Database (Denmark)

    Salvito, Daniel; Lapczynski, Aurelia; Sachse-Vasquez, Christen

    2011-01-01

    A screening-level aquatic environmental risk assessment for macrocyclic fragrance materials using a “group approach” is presented using data for 30 macrocyclic fragrance ingredients. In this group approach, conservative estimates of environmental exposure and ecotoxicological effects thresholds....../L and for macrocyclic lactones/lactides is 2.7 μg/L. The results of this screening-level aquatic ecological risk assessment indicate that at their current tonnage, often referred to as volumes of use, macrocyclic fragrance materials in Europe and North America, pose a negligible risk to aquatic biota; with no PEC...... for compounds within two subgroups (15 macrocyclic ketones and 15 macrocyclic lactones/lactides) were used to estimate the aquatic ecological risk potential for these subgroups. It is reasonable to separate these fragrance materials into the two subgroups based on the likely metabolic pathway required...

  6. Trapping a Knot into Tight Conformations by Intra-Chain Repulsions

    Directory of Open Access Journals (Sweden)

    Liang Dai

    2017-02-01

    Full Text Available Knots can occur in biopolymers such as DNA and peptides. In our previous study, we systematically investigated the effects of intra-chain interactions on knots and found that long-range repulsions can surprisingly tighten knots. Here, we use this knowledge to trap a knot into tight conformations in Langevin dynamics simulations. By trapping, we mean that the free energy landscape with respect to the knot size exhibits a potential well around a small knot size in the presence of long-range repulsions, and this potential can well lead to long-lived tight knots when its depth is comparable to or larger than thermal energy. We tune the strength of intra-chain repulsion such that a knot is weakly trapped. Driven by thermal fluctuations, the knot can escape from the trap and is then re-trapped. We find that the knot switches between tight and loose conformations—referred to as “knot breathing”. We use a Yukawa potential to model screened electrostatic interactions to explore the relevance of knot trapping and breathing in charged biopolymers. We determine the minimal screened length and the minimal strength of repulsion for knot trapping. We find that Coulomb-induced knot trapping is possible to occur in single-stranded DNA and peptides for normal ionic strengths.

  7. Handbook of knot theory

    CERN Document Server

    Menasco, William

    2005-01-01

    This book is a survey of current topics in the mathematical theory of knots. For a mathematician, a knot is a closed loop in 3-dimensional space: imagine knotting an extension cord and then closing it up by inserting its plug into its outlet. Knot theory is of central importance in pure and applied mathematics, as it stands at a crossroads of topology, combinatorics, algebra, mathematical physics and biochemistry.* Survey of mathematical knot theory* Articles by leading world authorities* Clear exposition, not over-technical* Accessible to readers with undergraduate background in mathematics

  8. Knots with proprety R+

    OpenAIRE

    Clark, Bradd Evans

    1983-01-01

    If we consider the set of manifolds that can be obtained by surgery on a fixed knot K, then we have an associated set of numbers corresponding to the Heegaard genus of these manifolds. It is known that there is an upper bound to this set of numbers. A knot K is said to have Property R+ if longitudinal surgery yields a manifold of highest possible Heegaard genus among those obtainable by surgery on K. In this paper we show that torus knots, 2-bridge knots, and knots which are the connected ...

  9. Knots and links

    CERN Document Server

    Rolfsen, Dale

    2003-01-01

    Rolfsen's beautiful book on knots and links can be read by anyone, from beginner to expert, who wants to learn about knot theory. Beginners with a basic background find an inviting introduction to the elements of topology, emphasizing the tools needed for understanding knots, the fundamental group and van Kampen's theorem, for example, which are then applied to concrete problems, such as computing knot groups. For experts, Rolfsen explains advanced topics, such as the connections between knot theory and surgery and how they are useful to understanding three-manifolds. Besides providing a guide

  10. Knots in Art

    Directory of Open Access Journals (Sweden)

    Radmila Sazdanović

    2012-06-01

    Full Text Available We analyze applications of knots and links in the Ancient art, beginning from Babylonian, Egyptian, Greek, Byzantine and Celtic art. Construction methods used in art are analyzed on the examples of Celtic art and ethnical art of Tchokwe people from Angola or Tamil art, where knots are constructed as mirror-curves. We propose different methods for generating knots and links based on geometric polyhedra, suitable for applications in architecture and sculpture.

  11. Knots in Art

    OpenAIRE

    Jablan, Slavik; Radović, Ljiljana; Sazdanović, Radmila; Zeković, Ana

    2012-01-01

    We analyze applications of knots and links in the Ancient art, beginning from Babylonian, Egyptian, Greek, Byzantine and Celtic art. Construction methods used in art are analyzed on the examples of Celtic art and ethnical art of Tchokwe people from Angola or Tamil art, where knots are constructed as mirror-curves. We propose different methods for generating knots and links based on geometric polyhedra, suitable for applications in architecture and sculpture.

  12. History and science of knots

    CERN Document Server

    Turner, J C

    1996-01-01

    This book brings together twenty essays on diverse topics in the history and science of knots. It is divided into five parts, which deal respectively with knots in prehistory and antiquity, non-European traditions, working knots, the developing science of knots, and decorative and other aspects of knots.Its authors include archaeologists who write on knots found in digs of ancient sites (one describes the knots used by the recently discovered Ice Man); practical knotters who have studied the history and uses of knots at sea, for fishing and for various life support activities; a historian of l

  13. A Stevedore's protein knot.

    Directory of Open Access Journals (Sweden)

    Daniel Bölinger

    2010-04-01

    Full Text Available Protein knots, mostly regarded as intriguing oddities, are gradually being recognized as significant structural motifs. Seven distinctly knotted folds have already been identified. It is by and large unclear how these exceptional structures actually fold, and only recently, experiments and simulations have begun to shed some light on this issue. In checking the new protein structures submitted to the Protein Data Bank, we encountered the most complex and the smallest knots to date: A recently uncovered alpha-haloacid dehalogenase structure contains a knot with six crossings, a so-called Stevedore knot, in a projection onto a plane. The smallest protein knot is present in an as yet unclassified protein fragment that consists of only 92 amino acids. The topological complexity of the Stevedore knot presents a puzzle as to how it could possibly fold. To unravel this enigma, we performed folding simulations with a structure-based coarse-grained model and uncovered a possible mechanism by which the knot forms in a single loop flip.

  14. Knots in polymers

    Indian Academy of Sciences (India)

    Abstract. Knots and topological entanglements play an important role in the statistical mechanics of polymers. While topological entanglement is a global property, it is possible to study the size of a knotted region both numerically and analytically. It can be shown that long-range repulsive interactions, as well as entropy ...

  15. Knot topology in QCD

    International Nuclear Information System (INIS)

    Zou, L.P.; Zhang, P.M.; Pak, D.G.

    2013-01-01

    We consider topological structure of classical vacuum solutions in quantum chromodynamics. Topologically non-equivalent vacuum configurations are classified by non-trivial second and third homotopy groups for coset of the color group SU(N) (N=2,3) under the action of maximal Abelian stability group. Starting with explicit vacuum knot configurations we study possible exact classical solutions. Exact analytic non-static knot solution in a simple CP 1 model in Euclidean space–time has been obtained. We construct an ansatz based on knot and monopole topological vacuum structure for searching new solutions in SU(2) and SU(3) QCD. We show that singular knot-like solutions in QCD in Minkowski space–time can be naturally obtained from knot solitons in integrable CP 1 models. A family of Skyrme type low energy effective theories of QCD admitting exact analytic solutions with non-vanishing Hopf charge is proposed

  16. Colouring and knot polynomials

    International Nuclear Information System (INIS)

    Welsh, D.J.A.

    1991-01-01

    These lectures will attempt to explain a connection between the recent advances in knot theory using the Jones and related knot polynomials with classical problems in combinatorics and statistical mechanics. The difficulty of some of these problems will be analysed in the context of their computational complexity. In particular we shall discuss colourings and groups valued flows in graphs, knots and the Jones and Kauffman polynomials, the Ising, Potts and percolation problems of statistical physics, computational complexity of the above problems. (author). 20 refs, 9 figs

  17. The Mathematics of Knots

    CERN Document Server

    Banagl, Markus

    2011-01-01

    The present volume grew out of the Heidelberg Knot Theory Semester, organized by the editors in winter 2008/09 at Heidelberg University. The contributed papers bring the reader up to date on the currently most actively pursued areas of mathematical knot theory and its applications in mathematical physics and cell biology. Both original research and survey articles are presented; numerous illustrations support the text. The book will be of great interest to researchers in topology, geometry, and mathematical physics, graduate students specializing in knot theory, and cell biologists interested

  18. The mystery of knots

    CERN Document Server

    Aneziris, Charilaos N

    1999-01-01

    One of the most significant unsolved problems in mathematics is the complete classification of knots. The main purpose of this book is to introduce the reader to the use of computer programming to obtain the table of knots. The author presents this problem as clearly and methodically as possible, starting from the very basics. Mathematical ideas and concepts are extensively discussed, and no advanced background is required.

  19. Third Symposium on Macrocyclic Compounds

    International Nuclear Information System (INIS)

    1979-01-01

    At the Third Symposium on Macrocyclic Compounds there were sessions on facilitated transport, analytical applications, organic synthesis and reactions, phase transfer catalysis, and metal complexation. Abstracts of the individual presentations are included

  20. Fourth symposium on macrocyclic compounds

    International Nuclear Information System (INIS)

    Christensen, J.J.; Izatt, R.M.

    1980-01-01

    Both theoretical and experimental aspects of the properties and behavior of synthetic and naturally occurring macrocyclic compounds are covered in this symposium. This document contains abstracts of the papers

  1. MacroEvoLution: A New Method for the Rapid Generation of Novel Scaffold-Diverse Macrocyclic Libraries.

    Science.gov (United States)

    Saupe, Jörn; Kunz, Oliver; Haustedt, Lars Ole; Jakupovic, Sven; Mang, Christian

    2017-09-04

    Macrocycles are a structural class bearing great promise for future challenges in medicinal chemistry. Nevertheless, there are few flexible approaches for the rapid generation of structurally diverse macrocyclic compound collections. Here, an efficient method for the generation of novel macrocyclic peptide-based scaffolds is reported. The process, named here as "MacroEvoLution", is based on a cyclization screening approach that gives reliable access to novel macrocyclic architectures. Classification of building blocks into specific pools ensures that scaffolds with orthogonally addressable functionalities are generated, which can easily be used for the generation of structurally diverse compound libraries. The method grants rapid access to novel scaffolds with scalable synthesis (multi gram scale) and the introduction of further diversity at a late stage. Despite being developed for peptidic systems, the approach can easily be extended for the synthesis of systems with a decreased peptidic character. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  2. Knotting in stretched polygons

    International Nuclear Information System (INIS)

    Rensburg, E J Janse van; Orlandini, E; Tesi, M C; Whittington, S G

    2008-01-01

    The knotting in a lattice polygon model of ring polymers is examined when a stretching force is applied to the polygon. By examining the incidence of cut-planes in the polygon, we prove a pattern theorem in the stretching regime for large applied forces. This theorem can be used to examine the incidence of entanglements such as knotting and writhing. In particular, we prove that for arbitrarily large positive, but finite, values of the stretching force, the probability that a stretched polygon is knotted approaches 1 as the length of the polygon increases. In the case of writhing, we prove that for stretched polygons of length n, and for every function f(n)=o(√n), the probability that the absolute value of the mean writhe is less than f(n) approaches 0 as n → ∞, for sufficiently large values of the applied stretching force

  3. Knots and Links

    Indian Academy of Sciences (India)

    in a fashion similar to sound waves, whose medium is air. Ether was believed ..... [3] Colin C Adams, The Knot Book, W H Freeman and Company, New. York. ... [5] Kelly S Chichak, Stuart j CantriU, Antony R Pease, Sheng-Hsien. Chiu, Gareth ...

  4. Knot theory in modern chemistry.

    Science.gov (United States)

    Horner, Kate E; Miller, Mark A; Steed, Jonathan W; Sutcliffe, Paul M

    2016-11-21

    Knot theory is a branch of pure mathematics, but it is increasingly being applied in a variety of sciences. Knots appear in chemistry, not only in synthetic molecular design, but also in an array of materials and media, including some not traditionally associated with knots. Mathematics and chemistry can now be used synergistically to identify, characterise and create knots, as well as to understand and predict their physical properties. This tutorial review provides a brief introduction to the mathematics of knots and related topological concepts in the context of the chemical sciences. We then survey the broad range of applications of the theory to contemporary research in the field.

  5. Macrocyclic ligands for uranium complexation

    International Nuclear Information System (INIS)

    Potts, K.T.

    1991-04-01

    A highly preorganized 24-macrocycle containing biuret, thiobiuret and pyridine subunits has been prepared by high dilution ring-closure procedures. Intermediate products to this macrocycle have been utilized to extend this synthetic route to include further representatives where solubility and stability will be influenced by substituent variation. A 1:1 complex has been formed from uranyl acetate and a quinquepyridine derivative, this representing a new type of ligand for the uranyl ion. A very convenient synthetic procedure that will allow the incorporation of these macrocycles into polymeric systems has been developed for the introduction of a vinyl substituent into the 4-position of the pyridine ring. Using triflate, vinyltributyltin and Pd 0 chemistry, this procedure should make a variety of substituted 4-vinylpyridines available for the first time. 3 refs

  6. Proteins analysed as virtual knots

    Science.gov (United States)

    Alexander, Keith; Taylor, Alexander J.; Dennis, Mark R.

    2017-02-01

    Long, flexible physical filaments are naturally tangled and knotted, from macroscopic string down to long-chain molecules. The existence of knotting in a filament naturally affects its configuration and properties, and may be very stable or disappear rapidly under manipulation and interaction. Knotting has been previously identified in protein backbone chains, for which these mechanical constraints are of fundamental importance to their molecular functionality, despite their being open curves in which the knots are not mathematically well defined; knotting can only be identified by closing the termini of the chain somehow. We introduce a new method for resolving knotting in open curves using virtual knots, which are a wider class of topological objects that do not require a classical closure and so naturally capture the topological ambiguity inherent in open curves. We describe the results of analysing proteins in the Protein Data Bank by this new scheme, recovering and extending previous knotting results, and identifying topological interest in some new cases. The statistics of virtual knots in protein chains are compared with those of open random walks and Hamiltonian subchains on cubic lattices, identifying a regime of open curves in which the virtual knotting description is likely to be important.

  7. Chemical Editing of Macrocyclic Natural Products and Kinetic Profiling Reveal Slow, Tight-Binding Histone Deacetylase Inhibitors with Picomolar Affinities

    DEFF Research Database (Denmark)

    Kitir, Betül; Maolanon, Alex R.; Ohm, Ragnhild G.

    2017-01-01

    medicines. Therefore, detailed mechanistic information and precise characterization of the chemical probes used to investigate the effects of HDAC enzymes are vital. We interrogated Nature's arsenal of macrocyclic nonribosomal peptide HDAC inhibitors by chemical synthesis and evaluation of more than 30...... natural products and analogues. This furnished surprising trends in binding affinities for the various macrocycles, which were then exploited for the design of highly potent class I and IIb HDAC inhibitors. Furthermore, thorough kinetic investigation revealed unexpected inhibitory mechanisms of important...

  8. Knotted vs. unknotted proteins: evidence of knot-promoting loops.

    Directory of Open Access Journals (Sweden)

    Raffaello Potestio

    Full Text Available Knotted proteins, because of their ability to fold reversibly in the same topologically entangled conformation, are the object of an increasing number of experimental and theoretical studies. The aim of the present investigation is to assess, on the basis of presently available structural data, the extent to which knotted proteins are isolated instances in sequence or structure space, and to use comparative schemes to understand whether specific protein segments can be associated to the occurrence of a knot in the native state. A significant sequence homology is found among a sizeable group of knotted and unknotted proteins. In this family, knotted members occupy a primary sub-branch of the phylogenetic tree and differ from unknotted ones only by additional loop segments. These "knot-promoting" loops, whose virtual bridging eliminates the knot, are found in various types of knotted proteins. Valuable insight into how knots form, or are encoded, in proteins could be obtained by targeting these regions in future computational studies or excision experiments.

  9. Macrocyclic G-quadruplex ligands

    DEFF Research Database (Denmark)

    Nielsen, M C; Ulven, Trond

    2010-01-01

    are macrocyclic structures which have been modeled after the natural product telomestatin or from porphyrin-based ligands discovered in the late 1990s. These two structural classes of G-quadruplex ligands are reviewed here with special attention to selectivity and structure-activity relationships, and with focus...

  10. Braiding knots with topological strings

    International Nuclear Information System (INIS)

    Gu, Jie

    2015-08-01

    For an arbitrary knot in a three-sphere, the Ooguri-Vafa conjecture associates to it a unique stack of branes in type A topological string on the resolved conifold, and relates the colored HOMFLY invariants of the knot to the free energies on the branes. For torus knots, we use a modified version of the topological recursion developed by Eynard and Orantin to compute the free energies on the branes from the Aganagic-Vafa spectral curves of the branes, and find they are consistent with the known colored HOMFLY knot invariants a la the Ooguri-Vafa conjecture. In addition our modified topological recursion can reproduce the correct closed string free energies, which encode the information of the background geometry. We conjecture the modified topological recursion is applicable for branes associated to hyperbolic knots as well, encouraged by the observation that the modified topological recursion yields the correct planar closed string free energy from the Aganagic-Vafa spectral curves of hyperbolic knots. This has implications for the knot theory concerning distinguishing mutant knots with colored HOMFLY invariants. Furthermore, for hyperbolic knots, we present methods to compute colored HOMFLY invariants in nonsymmetric representations of U(N). The key step in this computation is computing quantum 6j-symbols in the quantum group U q (sl N ).

  11. Computational Elastic Knots

    KAUST Repository

    Zhao, Xin

    2013-05-01

    Elastic rods have been studied intensively since the 18th century. Even now the theory of elastic rods is still developing and enjoying popularity in computer graphics and physical-based simulation. Elastic rods also draw attention from architects. Architectural structures, NODUS, were constructed by elastic rods as a new method of form-finding. We study discrete models of elastic rods and NODUS structures. We also develop computational tools to find the equilibria of elastic rods and the shape of NODUS. Applications of elastic rods in forming torus knot and closing Bishop frame are included in this thesis.

  12. Energy of knots and conformal geometry

    CERN Document Server

    O'Hara, Jun

    2003-01-01

    Energy of knots is a theory that was introduced to create a "canonical configuration" of a knot - a beautiful knot which represents its knot type. This book introduces several kinds of energies, and studies the problem of whether or not there is a "canonical configuration" of a knot in each knot type. It also considers this problems in the context of conformal geometry. The energies presented in the book are defined geometrically. They measure the complexity of embeddings and have applications to physical knotting and unknotting through numerical experiments. Contents: In Search of the "Optima

  13. Torus knots and mirror symmetry

    CERN Document Server

    Brini, Andrea; Marino, Marcos

    2012-01-01

    We propose a spectral curve describing torus knots and links in the B-model. In particular, the application of the topological recursion to this curve generates all their colored HOMFLY invariants. The curve is obtained by exploiting the full Sl(2, Z) symmetry of the spectral curve of the resolved conifold, and should be regarded as the mirror of the topological D-brane associated to torus knots in the large N Gopakumar-Vafa duality. Moreover, we derive the curve as the large N limit of the matrix model computing torus knot invariants.

  14. Intricate knots in proteins: Function and evolution.

    Directory of Open Access Journals (Sweden)

    Peter Virnau

    2006-09-01

    Full Text Available Our investigation of knotted structures in the Protein Data Bank reveals the most complicated knot discovered to date. We suggest that the occurrence of this knot in a human ubiquitin hydrolase might be related to the role of the enzyme in protein degradation. While knots are usually preserved among homologues, we also identify an exception in a transcarbamylase. This allows us to exemplify the function of knots in proteins and to suggest how they may have been created.

  15. Handbook of knotting and splicing

    CERN Document Server

    Hasluck, Paul N

    2005-01-01

    Clearly written and amply illustrated with 208 figures, this classic guide ranges from simple and useful knots to complex varieties. Additional topics include rope splicing, working cordage, hammock making, more.

  16. Recognition algorithms in knot theory

    International Nuclear Information System (INIS)

    Dynnikov, I A

    2003-01-01

    In this paper the problem of constructing algorithms for comparing knots and links is discussed. A survey of existing approaches and basic results in this area is given. In particular, diverse combinatorial methods for representing links are discussed, the Haken algorithm for recognizing a trivial knot (the unknot) and a scheme for constructing a general algorithm (using Haken's ideas) for comparing links are presented, an approach based on representing links by closed braids is described, the known algorithms for solving the word problem and the conjugacy problem for braid groups are described, and the complexity of the algorithms under consideration is discussed. A new method of combinatorial description of knots is given together with a new algorithm (based on this description) for recognizing the unknot by using a procedure for monotone simplification. In the conclusion of the paper several problems are formulated whose solution could help to advance towards the 'algorithmization' of knot theory

  17. Weaving Knotted Vector Fields with Tunable Helicity.

    Science.gov (United States)

    Kedia, Hridesh; Foster, David; Dennis, Mark R; Irvine, William T M

    2016-12-30

    We present a general construction of divergence-free knotted vector fields from complex scalar fields, whose closed field lines encode many kinds of knots and links, including torus knots, their cables, the figure-8 knot, and its generalizations. As finite-energy physical fields, they represent initial states for fields such as the magnetic field in a plasma, or the vorticity field in a fluid. We give a systematic procedure for calculating the vector potential, starting from complex scalar functions with knotted zero filaments, thus enabling an explicit computation of the helicity of these knotted fields. The construction can be used to generate isolated knotted flux tubes, filled by knots encoded in the lines of the vector field. Lastly, we give examples of manifestly knotted vector fields with vanishing helicity. Our results provide building blocks for analytical models and simulations alike.

  18. Biomechanical evaluation of the Nice knot

    OpenAIRE

    Hill, Shannon W.; Chapman, Christopher R.; Adeeb, Samer; Duke, Kajsa; Beaupre, Lauren; Bouliane, Martin J.

    2016-01-01

    Background: The Nice knot is a bulky double-stranded knot. Biomechanical data supporting its use as well as the number of half hitches required to ensure knot security is lacking. Materials and Methods: Nice knots with, one, two, or three half-hitches were compared with the surgeon′s and Tennessee slider knots with three half hitches. Each knot was tied 10 times around a fixed diameter using four different sutures: FiberWire (Arthrex, Naples, FL), Ultrabraid (Smith and Nephew, Andover, MA...

  19. New Macrocyclic Diamide from Rauvolfia Yunnanensis Tsiang

    Institute of Scientific and Technical Information of China (English)

    GENG Chang-an; LIU Xi-kui

    2008-01-01

    A new macrocyclic diamide, 22-membered macrocyclic diamide, named cyciodicaprylamide(2), and five known compounds, bis(2-ethylhexyl) phthalate(1), ethyl 3,4,5-trimethoxybenzoate(3), ethyl 3,4,5-trimethoxycinnamate (4), (+)-syringaresinol(5), loliolide(6), were isolated from the roots of Rauvolfia yunnanensis Tsiang. Their structures were elucidated based on NMR, 2D NMR, and MS spectrum, respectively. They were obtained from it for the first time.

  20. Squaraine rotaxanes with boat conformation macrocycles.

    Science.gov (United States)

    Fu, Na; Baumes, Jeffrey M; Arunkumar, Easwaran; Noll, Bruce C; Smith, Bradley D

    2009-09-04

    Mechanical encapsulation of fluorescent, deep-red bis(anilino)squaraine dyes inside Leigh-type tetralactam macrocycles produces interlocked squaraine rotaxanes. The surrounding macrocycles are flexible and undergo rapid exchange of chair and boat conformations in solution. A series of X-ray crystal structures show how the rotaxane co-conformational exchange process involves simultaneous lateral oscillation of the macrocycle about the center of the encapsulated squaraine thread. Rotaxane macrocycles with 1,4-phenylene sidewalls and 2,6-pyridine dicarboxamide bridging units are more likely to adopt boat conformations in the solid state than analogous squaraine rotaxane systems with isophthalamide-containing macrocycles. A truncated squaraine dye, with a secondary amine attached directly to the central C(4)O(2) core, is less electrophilic than the extended bis(anilino)squaraine analogue, but it is still susceptible to chemical and photochemical bleaching. Its stability is greatly enhanced when it is encapsulated as an interlocked squaraine rotaxane. An X-ray crystal structure of this truncated squaraine rotaxane shows the macrocycle in a boat conformation, and NMR studies indicate that the boat is maintained in solution. Encapsulation as a rotaxane increases the dye's brightness by a factor of 6. The encapsulation process appears to constrain the dye and reduce deformation of the chromophore from planarity. This study shows how mechanical encapsulation as a rotaxane can be used as a rational design parameter to fine-tune the chemical and photochemical properties of squaraine dyes.

  1. Knot invariants derived from quandles and racks

    OpenAIRE

    Kamada, Seiichi

    2002-01-01

    The homology and cohomology of quandles and racks are used in knot theory: given a finite quandle and a cocycle, we can construct a knot invariant. This is a quick introductory survey to the invariants of knots derived from quandles and racks.

  2. Divergent unprotected peptide macrocyclisation by palladium-mediated cysteine arylation.

    Science.gov (United States)

    Rojas, Anthony J; Zhang, Chi; Vinogradova, Ekaterina V; Buchwald, Nathan H; Reilly, John; Pentelute, Bradley L; Buchwald, Stephen L

    2017-06-01

    Macrocyclic peptides are important therapeutic candidates due to their improved physicochemical properties in comparison to their linear counterparts. Here we detail a method for a divergent macrocyclisation of unprotected peptides by crosslinking two cysteine residues with bis-palladium organometallic reagents. These synthetic intermediates are prepared in a single step from commercially available aryl bis-halides. Two bioactive linear peptides with cysteine residues at i , i + 4 and i , i + 7 positions, respectively, were cyclised to introduce a diverse array of aryl and bi-aryl linkers. These two series of macrocyclic peptides displayed similar linker-dependent lipophilicity, phospholipid affinity, and unique volume of distributions. Additionally, one of the bioactive peptides showed target binding affinity that was predominantly affected by the length of the linker. Collectively, this divergent strategy allowed rapid and convenient access to various aryl linkers, enabling the systematic evaluation of the effect of appending unit on the medicinal properties of macrocyclic peptides.

  3. How to Twist a Knot

    DEFF Research Database (Denmark)

    Randrup, Thomas; Røgen, Peter

    1997-01-01

    is an invariant of ambient isotopy measuring the topological twist of the closed strip. We classify closed strips in euclidean 3-space by their knots and their twisting number. We prove that this classification exactly divides closed strips into isotopy classes. Using this classification we point out how some...

  4. Mutual attraction of magnetic knots

    International Nuclear Information System (INIS)

    Parker, E.N.

    1978-01-01

    It is observed that the magnetic knots associated with active regions on the Sun have an attraction for each other during the formative period of the active regions, when new magnetic flux is coming to the surface. The attraction disappears when new flux ceases to rise through the surface. Then the magnetic spots and knots tend to come apart, leading to disintegration of the sunspots previously formed. The dissolution of the fields is to be expected, as a consequence of the magnetic repulsion of knots of like polarity and as a consequence of the hydromagnetic exchange instability.The purpose of this paper is to show that the mutual attraction of knots during the formative stages of a sunspot region may be understood as the mutual hydrodynamic attraction of the rising flux tubes. Two rising tubes attract each other, as a consequence of the wake of the leading tube when one is moving behind the other, and as a consequence of the Bernoulli effect when rising side by side

  5. Phosphorus-containing macrocyclic compounds: synthesis and properties

    International Nuclear Information System (INIS)

    Knyazeva, I R; Burilov, Alexander R; Pudovik, Michael A; Habicher, Wolf D

    2013-01-01

    Main trends in the development of methods for the synthesis of phosphorus-containing macrocyclic compounds in the past 15 years are considered. Emphasis is given to reactions producing macrocyclic structures with the participation of a phosphorus atom and other functional groups involved in organophosphorus molecules and to modifications of macrocycles by phosphorus compounds in different valence states. Possibilities of the practical application of phosphorus-containing macrocyclic compounds in difference areas of science and engineering are discussed. The bibliography includes 205 references.

  6. Constraining cyclic peptides to mimic protein structure motifs

    DEFF Research Database (Denmark)

    Hill, Timothy A.; Shepherd, Nicholas E.; Diness, Frederik

    2014-01-01

    peptides can have protein-like biological activities and potencies, enabling their uses as biological probes and leads to therapeutics, diagnostics and vaccines. This Review highlights examples of cyclic peptides that mimic three-dimensional structures of strand, turn or helical segments of peptides...... and proteins, and identifies some additional restraints incorporated into natural product cyclic peptides and synthetic macrocyclic pepti-domimetics that refine peptide structure and confer biological properties....

  7. Technetium complexation by macrocyclic compounds

    International Nuclear Information System (INIS)

    Li Fan Yu.

    1983-01-01

    Research in nuclear medicine are directed towards the labelling of biological molecules, however, sup(99m)Tc does not show sufficient affinity for these molecules. The aim of this study was to evaluate the ability of macrocyclic compounds to bind strongly technetium in order to be used as complexation intermediate. The reducing agents used were a stannous complex and sodium dithionite. Cryptates and polyesters are not good complexing agents. They form two complexes: a 2:1 sandwich complex or 3:2 and a 1:1 complex. Cyclams are good complexing agents for technetium their complexations strength was determined by competition with pyrophosphate, gluconate and DTPA. Using the method of ligand exchange, the oxidation state of technetium in the Tc-cyclam complex was IV or V. They are 1:1 cationic complexes, the complex charge is +1. The biodistribution in rats of labelling solutions containing (cyclam 14 ane N 4 ) C 12 H 25 shows a good urinary excretion without intoxication risks [fr

  8. Creating molecular macrocycles for anion recognition

    Directory of Open Access Journals (Sweden)

    Amar H. Flood

    2016-03-01

    Full Text Available The creation and functionality of new classes of macrocycles that are shape persistent and can bind anions is described. The genesis of triazolophane macrocycles emerges out of activity surrounding 1,2,3-triazoles made using click chemistry; and the same triazoles are responsible for anion capture. Mistakes made and lessons learnt in anion recognition provide deeper understanding that, together with theory, now provides for computer-aided receptor design. The lessons are acted upon in the creation of two new macrocycles. First, cyanostars are larger and like to capture large anions. Second is tricarb, which also favors large anions but shows a propensity to self-assemble in an orderly and stable manner, laying a foundation for future designs of hierarchical nanostructures.

  9. DNA Knots: Theory and Experiments

    Science.gov (United States)

    Sumners, D. W.

    Cellular DNA is a long, thread-like molecule with remarkably complex topology. Enzymes that manipulate the geometry and topology of cellular DNA perform many vital cellular processes (including segregation of daughter chromosomes, gene regulation, DNA repair, and generation of antibody diversity). Some enzymes pass DNA through itself via enzyme-bridged transient breaks in the DNA; other enzymes break the DNA apart and reconnect it to different ends. In the topological approach to enzymology, circular DNA is incubated with an enzyme, producing an enzyme signature in the form of DNA knots and links. By observing the changes in DNA geometry (supercoiling) and topology (knotting and linking) due to enzyme action, the enzyme binding and mechanism can often be characterized. This paper will discuss some personal research history, and the tangle model for the analysis of site-specific recombination experiments on circular DNA.

  10. Characteristic length of the knotting probability revisited

    International Nuclear Information System (INIS)

    Uehara, Erica; Deguchi, Tetsuo

    2015-01-01

    We present a self-avoiding polygon (SAP) model for circular DNA in which the radius of impermeable cylindrical segments corresponds to the screening length of double-stranded DNA surrounded by counter ions. For the model we evaluate the probability for a generated SAP with N segments having a given knot K through simulation. We call it the knotting probability of a knot K with N segments for the SAP model. We show that when N is large the most significant factor in the knotting probability is given by the exponentially decaying part exp(−N/N K ), where the estimates of parameter N K are consistent with the same value for all the different knots we investigated. We thus call it the characteristic length of the knotting probability. We give formulae expressing the characteristic length as a function of the cylindrical radius r ex , i.e. the screening length of double-stranded DNA. (paper)

  11. The mathematics and physics of knots

    Energy Technology Data Exchange (ETDEWEB)

    Kauffman, Louis H [Department of Mathematics, Statistics and Computer Science, University of Illinois at Chicago, 851 South Morgan Street, Chicago, IL 60607-7045 (United States)

    2005-12-01

    This paper is an introduction to relationships between knot theory and theoretical physics. We give an exposition of the theory of polynomial invariants of knots and links, the Witten functional integral formulation of knot and link invariants, and the beginnings of topological quantum field theory, and show how the theory of knots is related to a number of key issues in mathematical physics, including loop quantum gravity and quantum information theory. Along with the references cited in the text below, we also recommend the following as sources of background information.

  12. Statics and dynamics of DNA knotting

    Science.gov (United States)

    Orlandini, Enzo

    2018-02-01

    Knots and entanglement in polymers and biopolymers such as DNA and proteins constitute a timely topic that spans various scientific disciplines ranging from physics to chemistry, biology and mathematics. Although in the past many advancements have been made in understanding the equilibrium knotting probability and knot complexity of long polymer chains in solutions, many questions have been addressed in recent years by both experimental and theoretical means—for instance, how the knotting probability depends on the quality of the solvent, the elastic properties of the molecule and its degree of confinement. How knots form, evolve and eventually disappear in a fluctuating chain. Are the equilibrium and non-equilibrium properties of knotted molecules affected by the knot swelling/shrinking dynamics? Moreover, thanks to the great advance in nanotechnology and micromanipulation techniques, nowadays knots can be ‘manually’ tied in a single DNA molecule, followed during their motion along the chains, forced to pass through nanopores, or stretched by external forces or elongational flows. All these experimental approaches allow access to new information on the interplay of topology and polymer physics, and this has opened new perspectives in the field. Here, we provide an overview of the current knowledge of this topic, stressing the main results obtained, including the recent developments in experimental and computational approaches. Since almost all experiments on knotting involve DNA, the review will be mainly focused on the topological properties of this fascinating and biologically relevant molecule.

  13. The entropic cost to tie a knot

    International Nuclear Information System (INIS)

    Baiesi, M; Orlandini, E; Stella, A L

    2010-01-01

    We estimate by Monte Carlo simulations the configurational entropy of N-step polygons in the cubic lattice with fixed knot type. By collecting rich statistics of configurations with very large values of N we are able to analyse the asymptotic behaviour of the partition function of the problem for different knot types. Our results confirm that, in the large N limit, each prime knot is localized in a small region of the polygon, regardless of the possible presence of other knots. Each prime knot component may slide along the unknotted region contributing to the overall configurational entropy with a term proportional to lnN. Furthermore, we discover that the mere existence of a knot requires a well defined entropic cost that scales exponentially with its minimal length. In the case of polygons with composite knots it turns out that the partition function can be simply factorized in terms that depend only on prime components, with an additional combinatorial factor that takes into account the statistical property that by interchanging two identical prime knot components in the polygon the corresponding set of overall configurations remains unaltered. Finally, the above results allow one to conjecture a sequence of inequalities for the connective constants of polygons whose topology varies within a given family of composite knot types

  14. Rapid synthesis of macrocycles from diol precursors

    DEFF Research Database (Denmark)

    Wingstrand, Magnus; Madsen, Charlotte Marie; Clausen, Mads Hartvig

    2009-01-01

    A method for the formation of synthetic macrocycles with different ring sizes from diols is presented. Reacting a simple diol precursor with electrophilic reagents leads to a cyclic carbonate, sulfite or phosphate in a single step in 25-60% yield. Converting the cyclization precursor to a bis-ele...

  15. Concise Synthesis of Macrocycles by Multicomponent Reactions

    NARCIS (Netherlands)

    Abdelraheem, Eman M. M.; Khaksar, Samad; Dömling, Alexander

    2018-01-01

    A short reaction pathway was devised to synthesize a library of artificial 18-27-membered macrocycles. The five-step reaction sequence involves ring opening of a cyclic anhydride with a diamine, esterification, coupling with an amino acid isocyanide, saponification, and, finally, macro-ring closure

  16. Macrocyclic complexes of radionuclides in nuclear medicine

    International Nuclear Information System (INIS)

    Majkowska, A.; Bilewicz, A.

    2008-01-01

    The use of radiometal-labeled small complexes and biomolecules as diagnostic and therapeutic agents is a relatively new area of medical research. Radiopharmaceuticals are radiolabeled molecules designed to deliver ionizing radiation doses to specific disease sites. Between the targeting biomolecule and a radionuclide a bifunctional ligand is inserted, one end of which is covalently attached to the targeting molecule either directly or through a linker whereas the other strongly coordinates a metallic radionuclide. Selection of a bifunctional ligand is largely determined by the nature and oxidation state of a metal ion. The metal chelate can significantly affect the tumor uptake and biodistribution of radiopharmaceuticals based on small biomolecules. This is because in many cases the metal chelate contributes greatly to the overall size and lipophilicity of the radiopharmaceutical. Therefore, the design and selection of the ligand is very important for the development of a clinically useful therapeutic agent. The requirement for high thermodynamic and kinetic stability of the metal complex is often achieved through the use of macrocyclic ligands with a functionalized arm for covalent bonding to the biomolecule. In this review synthesis of bifunctional macrocyclic ligands and properties of radionuclide macrocyclic complexes used in nuclear medicine are presented. We describe results in two areas: substituted macrocyclic aza ligands for chelation of hard metal cations, and macrocycles containing sulphur for complexation of soft metal cations. Special attention was paid to stability of the complexes as well as to their lipophilicity, which affect biological properties of the formed radiopharmaceuticals. We also include a forecast of the near-term opportunities that are likely to determine practice in the next few years. (authors)

  17. Integral Suture-Handling Techniques for Arthroscopic Sliding Knots

    OpenAIRE

    Kanchanatawan, Wichan; Kongtharvonskul, Jatupon; Dorjiee, Gem; Suppauksorn, Sunikom; Pornvoranunt, Umpire; Karchana, Pongsakorn

    2016-01-01

    In arthroscopic tissue repair, the final step is achieving adequate tissue approximation with a secure knot. The sliding knot is widely preferred over the nonsliding knot, with numerous publications describing knot configurations. However, in the literature there are few published descriptions of suture-handling techniques, even though they are fundamental to arthroscopic knot tying. We describe integral suture-handling techniques for arthroscopic sliding knots to improve the surgeon's perfor...

  18. Differential and symplectic topology of knots and curves

    CERN Document Server

    Tabachnikov, S

    1999-01-01

    This book presents a collection of papers on two related topics: topology of knots and knot-like objects (such as curves on surfaces) and topology of Legendrian knots and links in 3-dimensional contact manifolds. Featured is the work of international experts in knot theory (""quantum"" knot invariants, knot invariants of finite type), in symplectic and contact topology, and in singularity theory. The interplay of diverse methods from these fields makes this volume unique in the study of Legendrian knots and knot-like objects such as wave fronts. A particularly enticing feature of the volume is

  19. Ileosigmoid knot: A case report

    International Nuclear Information System (INIS)

    Baheti, Akshay D; Patel, Darshana; Hira, Priya; Babu, Donald

    2011-01-01

    The ileosigmoid knot is an uncommon but life-threatening cause of closed loop intestinal obstruction. Its treatment is different from a simple volvulus in that it has to be operated upon immediately. Preoperative CT scan diagnosis and prompt treatment can lead to a good outcome. Findings of simultaneous ileal and sigmoid ischemia with non-ischemic colon interposed in between should, in an appropriate clinical setting, indicate this condition. The presence of the whirl sign, medially deviated distal descending colon and cecum, and mesenteric vascular structures from the superior mesenteric vessels that converge toward the sigmoid colon on CT scan help clinch the diagnosis

  20. Spectrophotometric method for determination of bifunctional macrocyclic ligands in macrocyclic ligand-protein conjugates

    International Nuclear Information System (INIS)

    Dadachova, E.; Chappell, L.L.; Brechbiel, M.W.

    1999-01-01

    A simple spectrophotometric assay for determination of bifunctional polyazacarboxylate-macrocyclic ligands of different sizes that are conjugated to proteins has been developed for: 12-membered macrocycle DOTA (2-[4-nitrobenzyl]-1, 4, 7, 10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid) and analogs, the 15-membered PEPA macrocycle (2-[4-nitrobenzyl]-1,4,7,10,13-pentaazacyclopentadecane-N,N',N'',N''',N'''' -pentaacetic acid), and the large 18-membered macrocycle HEHA (1,4,7,10,13,16-hexaazacyclooctadecane-N,N',N'',N''',N''''-hexaacetic acid). The method is based on titration of the blue-colored 1:1 Pb(II)-Arsenazo III (AAIII) complex with the polyazacarboxylate macrocyclic ligand in the concentration range of 0-2.5 μM, wherein color change occurring upon transchelation of the Pb(II) from the AAIII to the polyazamacrocyclic ligand is monitored at 656 nm. The assay is performed at ambient temperature within 20 min without any interfering interaction between the protein and Pb(II)-AA(III) complex. Thus, this method also provides a ligand-to-protein ratio (L/P ratio) that reflects the effective number of ligands per protein molecule available to radiolabeling. The method is not suitable for 14-membered TETA macrocycle (2-[4-nitrobenzyl]-1, 4, 8, 11-tetraazacyclotetradecane N,N',N'',N'''-tetraacetic acid) because of low stability constant of Pb(II)-TETA complex. The method is rapid, simple and may be customized for other polyazacarboxylate macrocyclic ligands

  1. On two-generator satellite knots

    OpenAIRE

    Bleiler, Steven A.; Jones, Amelia C.

    1997-01-01

    Techniques are introduced which determine the geometric structure of non-simple two-generator $3$-manifolds from purely algebraic data. As an application, the satellite knots in the $3$-sphere with a two-generator presentation in which at least one generator is represented by a meridian for the knot are classified.

  2. Kinetic investigation of uranyl-uranophile complexation. 1. Macrocyclic kinetic effect and macrocyclic protection effect

    International Nuclear Information System (INIS)

    Tabushi, I.; Yoshizawa, A.

    1986-01-01

    Equilibria and rates of ligand-exchange reactions between uranyl tricarbonate and dithiocarbamates and between uranyl tris-(dithiocarbamates) and carbonate were studied under a variety of conditions. The dithiocarbamates used were acyclic diethyl-dithiocarbamate and macrocyclic tris(dithiocarbamate). The acyclic ligand showed a triphasic (successive three-step) equilibrium with three different equilibrium constants while the macrocyclic ligand showed a clear monophasic (one-step) equilibrium with a much larger stability constant for the dithiocarbamate-uranyl complex. The macrocyclic ligand showed the S/sub N/2-type ligand-exchange rate in the forward as well as reverse process, while the first step of the acyclic ligand-exchange reaction proceeded via the S/sub N/1-type mechanism. This kinetic macrocyclic effect on molecularity is interpreted as the result of a unique topological requirement of uranyl complexation. The macrocyclic ligand also exhibited a clear protection effect, leading to the large stability constant. 19 references, 10 figures, 2 tables

  3. Neighbor-directed histidine N(τ) alkylation. A route to imidazolium-containing phosphopeptide macrocycles

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Wen-Jian [National Cancer Inst., Frederick, MD (United States); Park, Jung-Eun [National Cancer Inst., Bethesda, MD (United States); Grant, Robert [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Lai, Christopher C. [National Cancer Inst., Frederick, MD (United States); Kelley, James A. [National Cancer Inst., Frederick, MD (United States); Yaffe, Michael B. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Lee, Kyung S. [National Cancer Inst., Bethesda, MD (United States); Burke, Terrence R. [National Cancer Inst., Frederick, MD (United States)

    2015-07-07

    Our recently discovered, selective, on-resin route to N(τ)-alkylated imidazolium-containing histidine residues affords new strategies for peptide mimetic design. In this, we demonstrate the use of this chemistry to prepare a series of macrocyclic phosphopeptides, in which imidazolium groups serve as ring-forming junctions. These cationic moieties subsequently serve to charge-mask the phosphoamino acid group that directed their formation. Furthermore, neighbor-directed histidine N(τ)-alkylation opens the door to new families of phosphopeptidomimetics for use in a range of chemical biology contexts.

  4. Asymptotic laws for random knot diagrams

    Science.gov (United States)

    Chapman, Harrison

    2017-06-01

    We study random knotting by considering knot and link diagrams as decorated, (rooted) topological maps on spheres and pulling them uniformly from among sets of a given number of vertices n, as first established in recent work with Cantarella and Mastin. The knot diagram model is an exciting new model which captures both the random geometry of space curve models of knotting as well as the ease of computing invariants from diagrams. We prove that unknot diagrams are asymptotically exponentially rare, an analogue of Sumners and Whittington’s landmark result for self-avoiding polygons. Our proof uses the same key idea: we first show that knot diagrams obey a pattern theorem, which describes their fractal structure. We examine how quickly this behavior occurs in practice. As a consequence, almost all diagrams are asymmetric, simplifying sampling from this model. We conclude with experimental data on knotting in this model. This model of random knotting is similar to those studied by Diao et al, and Dunfield et al.

  5. Phase behaviour of polyethylene knotted ring chains

    International Nuclear Information System (INIS)

    Wen Xiao-Hui; Xia A-Gen; Chen Hong-Ping; Zhang Lin-Xi

    2011-01-01

    The phase behaviour of polyethylene knotted ring chains is investigated by using molecular dynamics simulations. In this paper, we focus on the collapse of the polyethylene knotted ring chain, and also present the results of linear and ring chains for comparison. At high temperatures, a fully extensive knot structure is observed. The mean-square radius of gyration per bond (S 2 )/(Nb 2 ) and the shape factor (δ*) depend on not only the chain length but also the knot type. With temperature decreasing, chain collapse is observed, and the collapse temperature decreases with the chain length increasing. The actual collapse transition can be determined by the specific heat capacity C v , and the knotted ring chain undergoes gas—liquid—solid-like transition directly. The phase transition of a knotted ring chain is only one-stage collapse, which is different from the polyethylene linear and ring chains. This investigation can provide some insights into the statistical properties of knotted polymer chains. (condensed matter: structural, mechanical, and thermal properties)

  6. Legendrian and transverse cables of positive torus knots

    DEFF Research Database (Denmark)

    B. Etnyre, John; la Fountain, Douglas James; Tosun, Bulent

    In this paper we classify Legendrian and transverse knots in the knot types obtained from positive torus knots by cabling. This classification allows us to demonstrate several new phenomena. Specifically, we show there are knot types that have non-destabilizable Legendrian representatives whose T...

  7. Open knot-tying skills: residents skills assessed

    NARCIS (Netherlands)

    van Empel, P.J.; Verdam, M.G.E.; Huirne, J.A.; Bonjer, H.J.; Meijerink, W.J.; Scheele, F.

    2013-01-01

    Aim: Open knot-tying and suturing skills are fundamental surgical skills, founding many alternative knot-tying techniques. It is therefore mandatory for residents to possess adequate basic open knot-tying skills. The aim of this study was to compare an objective assessment of open knot-tying skills

  8. Are There Knots in Chromosomes?

    Directory of Open Access Journals (Sweden)

    Jonathan T. Siebert

    2017-08-01

    Full Text Available Recent developments have for the first time allowed the determination of three-dimensional structures of individual chromosomes and genomes in nuclei of single haploid mouse embryonic stem (ES cells based on Hi–C chromosome conformation contact data. Although these first structures have a relatively low resolution, they provide the first experimental data that can be used to study chromosome and intact genome folding. Here we further analyze these structures and provide the first evidence that G1 phase chromosomes are knotted, consistent with the fact that plots of contact probability vs sequence separation show a power law dependence that is intermediate between that of a fractal globule and an equilibrium structure.

  9. Engineering macrocyclic figure–eight motif

    Indian Academy of Sciences (India)

    TECS

    the helical arrangement is held by intramolecular hydrogen bonding or as a backbone requirement, .... knotted topology through disulfide bonds are called .... Reduction of imine double bond ... of A to NaBH4 in THF transformed to B. B can in.

  10. Grid homology for knots and links

    CERN Document Server

    Ozsváth, Peter S; Szabó, Zoltán

    2015-01-01

    Knot theory is a classical area of low-dimensional topology, directly connected with the theory of three-manifolds and smooth four-manifold topology. In recent years, the subject has undergone transformative changes thanks to its connections with a number of other mathematical disciplines, including gauge theory; representation theory and categorification; contact geometry; and the theory of pseudo-holomorphic curves. Starting from the combinatorial point of view on knots using their grid diagrams, this book serves as an introduction to knot theory, specifically as it relates to some of the ab

  11. Molecular knots in biology and chemistry

    International Nuclear Information System (INIS)

    Lim, Nicole C H; Jackson, Sophie E

    2015-01-01

    Knots and entanglements are ubiquitous. Beyond their aesthetic appeal, these fascinating topological entities can be either useful or cumbersome. In recent decades, the importance and prevalence of molecular knots have been increasingly recognised by scientists from different disciplines. In this review, we provide an overview on the various molecular knots found in naturally occurring biological systems (DNA, RNA and proteins), and those created by synthetic chemists. We discuss the current knowledge in these fields, including recent developments in experimental and, in some cases, computational studies which are beginning to shed light into the complex interplay between the structure, formation and properties of these topologically intricate molecules. (paper)

  12. In Search of Functional Advantages of Knots in Proteins.

    Science.gov (United States)

    Dabrowski-Tumanski, Pawel; Stasiak, Andrzej; Sulkowska, Joanna I

    2016-01-01

    We analysed the structure of deeply knotted proteins representing three unrelated families of knotted proteins. We looked at the correlation between positions of knotted cores in these proteins and such local structural characteristics as the number of intra-chain contacts, structural stability and solvent accessibility. We observed that the knotted cores and especially their borders showed strong enrichment in the number of contacts. These regions showed also increased thermal stability, whereas their solvent accessibility was decreased. Interestingly, the active sites within these knotted proteins preferentially located in the regions with increased number of contacts that also have increased thermal stability and decreased solvent accessibility. Our results suggest that knotting of polypeptide chains provides a favourable environment for the active sites observed in knotted proteins. Some knotted proteins have homologues without a knot. Interestingly, these unknotted homologues form local entanglements that retain structural characteristics of the knotted cores.

  13. Studying uniform thickness II: Transversely nonsimple iterated torus knots

    DEFF Research Database (Denmark)

    LaFountain, Douglas

    2011-01-01

    We prove that an iterated torus knot type in the standard contact 3-sphere fails the uniform thickness property (UTP) if and only if it is formed from repeated positive cablings, which is precisely when an iterated torus knot supports the standard contact structure. This is the first complete UTP...... classification for a large class of knots. We also show that all iterated torus knots that fail the UTP support cabling knot types that are transversely non-simple....

  14. Two-Step Macrocycle Synthesis by Classical Ugi Reaction

    NARCIS (Netherlands)

    Abdelraheem, Eman M M; Khaksar, Samad; Kurpiewska, Katarzyna; Kalinowska-Tłuścik, Justyna; Shaabani, Shabnam; Dömling, Alexander

    2018-01-01

    The direct nonpeptidic macrocycle synthesis of α-isocyano-ω-amines via the classical Ugi four-component reaction (U-4CR) is introduced. Herein an efficient and flexible two-step procedure to complex macrocycles is reported. In the first step, the reaction between unprotected diamines and

  15. Lattices gauge theories in terms of knots

    International Nuclear Information System (INIS)

    Vecernyes, P.

    1989-01-01

    Cluster expansion is developed in lattice gauge theories with finite gauge groups in d≥3 dimensions where the clusters are connected (d - 2)-dimensional surfaces which can branch along (d - 3)-cells. The interaction between them has a knot theoretical interpretation. It can be many body linking or knotting self-interaction. For small enough gauge coupling g the authors prove analyticity of the correlation functions in the variable exp(-1/g 2

  16. On the universality of knot probability ratios

    Energy Technology Data Exchange (ETDEWEB)

    Janse van Rensburg, E J [Department of Mathematics and Statistics, York University, Toronto, Ontario M3J 1P3 (Canada); Rechnitzer, A, E-mail: rensburg@yorku.ca, E-mail: andrewr@math.ubc.ca [Department of Mathematics, University of British Columbia, 1984 Mathematics Road, Vancouver, BC V6T 1Z2 (Canada)

    2011-04-22

    Let p{sub n} denote the number of self-avoiding polygons of length n on a regular three-dimensional lattice, and let p{sub n}(K) be the number which have knot type K. The probability that a random polygon of length n has knot type K is p{sub n}(K)/p{sub n} and is known to decay exponentially with length (Sumners and Whittington 1988 J. Phys. A: Math. Gen. 21 1689-94, Pippenger 1989 Discrete Appl. Math. 25 273-8). Little is known rigorously about the asymptotics of p{sub n}(K), but there is substantial numerical evidence. It is believed that the entropic exponent, {alpha}, is universal, while the exponential growth rate is independent of the knot type but varies with the lattice. The amplitude, C{sub K}, depends on both the lattice and the knot type. The above asymptotic form implies that the relative probability of a random polygon of length n having prime knot type K over prime knot type L. In the thermodynamic limit this probability ratio becomes an amplitude ratio; it should be universal and depend only on the knot types K and L. In this communication we examine the universality of these probability ratios for polygons in the simple cubic, face-centred cubic and body-centred cubic lattices. Our results support the hypothesis that these are universal quantities. For example, we estimate that a long random polygon is approximately 28 times more likely to be a trefoil than be a figure-eight, independent of the underlying lattice, giving an estimate of the intrinsic entropy associated with knot types in closed curves. (fast track communication)

  17. Synthesis of New Macrocyclic Polyamides as Antimicrobial Agent Candidates

    Directory of Open Access Journals (Sweden)

    Osama I. Abd El-Salam

    2012-12-01

    Full Text Available A series of macrocyclic imides and Schiff-bases have been prepared via the cyclocondensation of pyridine-2,6-dicarbonyl dichloride (1 with L-ornithine methyl ester to give the corresponding macrocyclic bisester 2. Treatment of 2 with hydrazine hydrate gave macrocyclic bisacid hydrazide 3, which was used as starting material. Condensation of bishydrazide 3 with diacid anhydrides or aromatic aldehydes in refluxing acetic acid or ethanol gave the corresponding macrocyclic bisimides 4, 5a,b and macrocyclic bis- hydrazones 6a–j, respectively. The structure assignments of the new compounds were based on chemical and spectroscopic evidence. The antimicrobial screening showed that many of these newly synthesized compounds have good antimicrobial activities, comparable to ampicillin and ketaconazole used as reference drugs.

  18. Legendrian and transverse cables of positive torus knots

    DEFF Research Database (Denmark)

    Etnyre, John; LaFountain, Douglas; Tosun, Bülent

    2012-01-01

    Thurston-Bennequin invariant is arbitrarily far from maximal. We also exhibit Legendrian knots requiring arbitrarily many stabilizations before they become Legendrian isotopic. Similar new phenomena are observed for transverse knots. To achieve these results we define and study "partially thickenable" tori......In this paper we classify Legendrian and transverse knots in the knot types obtained from positive torus knots by cabling. This classification allows us to demonstrate several new phenomena. Specifically, we show there are knot types that have non-destabilizable Legendrian representatives whose...

  19. Conformational Restriction of Peptides Using Dithiol Bis-Alkylation.

    Science.gov (United States)

    Peraro, L; Siegert, T R; Kritzer, J A

    2016-01-01

    Macrocyclic peptides are highly promising as inhibitors of protein-protein interactions. While many bond-forming reactions can be used to make cyclic peptides, most have limitations that make this chemical space challenging to access. Recently, a variety of cysteine alkylation reactions have been used in rational design and library approaches for cyclic peptide discovery and development. We and others have found that this chemistry is versatile and robust enough to produce a large variety of conformationally constrained cyclic peptides. In this chapter, we describe applications, methods, mechanistic insights, and troubleshooting for dithiol bis-alkylation reactions for the production of cyclic peptides. This method for efficient solution-phase macrocyclization is highly useful for the rapid production and screening of loop-based inhibitors of protein-protein interactions. © 2016 Elsevier Inc. All rights reserved.

  20. Tolerance of a knotted near infrared fluorescent protein to random circular permutation

    Science.gov (United States)

    Pandey, Naresh; Kuypers, Brianna E.; Nassif, Barbara; Thomas, Emily E.; Alnahhas, Razan N.; Segatori, Laura; Silberg, Jonathan J.

    2016-01-01

    Bacteriophytochrome photoreceptors (BphP) are knotted proteins that have been developed as near-infrared fluorescent protein (iRFP) reporters of gene expression. To explore how rearrangements in the peptides that interlace into the knot within the BphP photosensory core affect folding, we subjected iRFP to random circular permutation using an improved transposase mutagenesis strategy and screened for variants that fluoresce. We identified twenty seven circularly permuted iRFP that display biliverdin-dependent fluorescence in Escherichia coli. The variants with the brightest whole cell fluorescence initiated translation at residues near the domain linker and knot tails, although fluorescent variants were discovered that initiated translation within the PAS and GAF domains. Circularly permuted iRFP retained sufficient cofactor affinity to fluoresce in tissue culture without the addition of biliverdin, and one variant displayed enhanced fluorescence when expressed in bacteria and tissue culture. This variant displayed a similar quantum yield as iRFP, but exhibited increased resistance to chemical denaturation, suggesting that the observed signal increase arose from more efficient protein maturation. These results show how the contact order of a knotted BphP can be altered without disrupting chromophore binding and fluorescence, an important step towards the creation of near-infrared biosensors with expanded chemical-sensing functions for in vivo imaging. PMID:27304983

  1. Tolerance of a Knotted Near-Infrared Fluorescent Protein to Random Circular Permutation.

    Science.gov (United States)

    Pandey, Naresh; Kuypers, Brianna E; Nassif, Barbara; Thomas, Emily E; Alnahhas, Razan N; Segatori, Laura; Silberg, Jonathan J

    2016-07-12

    Bacteriophytochrome photoreceptors (BphP) are knotted proteins that have been developed as near-infrared fluorescent protein (iRFP) reporters of gene expression. To explore how rearrangements in the peptides that interlace into the knot within the BphP photosensory core affect folding, we subjected iRFPs to random circular permutation using an improved transposase mutagenesis strategy and screened for variants that fluoresce. We identified 27 circularly permuted iRFPs that display biliverdin-dependent fluorescence in Escherichia coli. The variants with the brightest whole cell fluorescence initiated translation at residues near the domain linker and knot tails, although fluorescent variants that initiated translation within the PAS and GAF domains were discovered. Circularly permuted iRFPs retained sufficient cofactor affinity to fluoresce in tissue culture without the addition of biliverdin, and one variant displayed enhanced fluorescence when expressed in bacteria and tissue culture. This variant displayed a quantum yield similar to that of iRFPs but exhibited increased resistance to chemical denaturation, suggesting that the observed increase in the magnitude of the signal arose from more efficient protein maturation. These results show how the contact order of a knotted BphP can be altered without disrupting chromophore binding and fluorescence, an important step toward the creation of near-infrared biosensors with expanded chemical sensing functions for in vivo imaging.

  2. In Search of Functional Advantages of Knots in Proteins.

    OpenAIRE

    Dabrowski-Tumanski, P.; Stasiak, A.; Sulkowska, J.I.

    2016-01-01

    We analysed the structure of deeply knotted proteins representing three unrelated families of knotted proteins. We looked at the correlation between positions of knotted cores in these proteins and such local structural characteristics as the number of intra-chain contacts, structural stability and solvent accessibility. We observed that the knotted cores and especially their borders showed strong enrichment in the number of contacts. These regions showed also increased thermal stability, whe...

  3. On the concordance genus of topologically slice knots

    OpenAIRE

    Hom, Jennifer

    2012-01-01

    The concordance genus of a knot K is the minimum Seifert genus of all knots smoothly concordant to K. Concordance genus is bounded below by the 4-ball genus and above by the Seifert genus. We give a lower bound for the concordance genus of K coming from the knot Floer complex of K. As an application, we prove that there are topologically slice knots with 4-ball genus equal to one and arbitrarily large concordance genus.

  4. Synthesis of novel symmetrical macrocycle via oxidative homocoupling of bisalkyne

    Energy Technology Data Exchange (ETDEWEB)

    Kamalulazmy, Nurulain; Hassan, Nurul Izzaty [School of Chemical Sciences and Food Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan (Malaysia)

    2014-09-03

    A novel symmetrical macrocycle has been synthesised via oxidative homocoupling of bisalkyne, diprop-2-ynyl pyridine-2,6-dicarboxylate mediated by copper (I) iodide (CuI) and 4-dimethylaminopyridine (DMAP). The precursor compound was synthesised from 2,6-pyridine dicarbonyl dichloride and propargyl alcohol in the presence of triethylamine. The reaction mixture was stirred overnight and further purified via column chromatograpy with 76% yield. Single crystal for X-ray study was obtained by recrystallization from acetone. Subsequently, a symmetrical macrocycle was synthesised from oxidative homocoupling of precursor compound in open atmosphere. The crude product was purified by column chromatography to furnish macrocycle compound with 5% yield. Both compounds were characterised by IR, {sup 1}H and {sup 13}C NMR and mass spectral techniques. The unusual conformation of the bisalkyne and twisted conformation of designed macrocycle has influence the percentage yield. This has been studied thoroughly by X-ray crystallography and electronic structure calculations.

  5. Knotcraft the practical and entertaining art of tying knots

    CERN Document Server

    Macfarlan, Allan and Paulette

    1983-01-01

    Comprehensive reference work explains how to tie hundreds of practical (and decorative) knots in clear illustrations and precisely worded written instructions. Ideal for boaters and campers. Also covers knots in history, knot mystery and magic, and games, stunts and tricks with rope. Introduction. Index. 166 black-and-white illustrations.

  6. Macrocyclic 2,7-Anthrylene Oligomers.

    Science.gov (United States)

    Yamamoto, Yuta; Wakamatsu, Kan; Iwanaga, Tetsuo; Sato, Hiroyasu; Toyota, Shinji

    2016-05-06

    A macrocyclic compound consisting of six 2,7-anthrylene units was successfully synthesized by Ni-mediated coupling of the corresponding dibromo precursor as a novel π-conjugated compound. This compound was sufficiently stable and soluble in organic solvents due to the presence of mesityl groups. X-ray analysis showed that the molecule had a nonplanar and hexagonal wheel-shaped framework of approximately S6 symmetry. The dynamic process between two S6 structures was observed by using the dynamic NMR technique, the barrier being 58 kJ mol(-1) . The spectroscopic properties of the hexamer were compared with those of analogous linear oligomers. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Neighbor-Directed Histidine N (s)–Alkylation: A Route to Imidazolium-Containing Phosphopeptide Macrocycles-Biopolymers | Center for Cancer Research

    Science.gov (United States)

    Our recently discovered, selective, on-resin route to N(s)-alkylated imidazolium-containing histidine residues affords new strategies for peptide mimetic design. In this, we demonstrate the use of this chemistry to prepare a series of macrocyclic phosphopeptides, in which imidazolium groups serve as ring-forming junctions. Interestingly, these cationic moieties subsequently serve to charge-mask the phosphoamino acid group that directed their formation.

  8. Four-manifolds, geometries and knots

    CERN Document Server

    Hillman, Jonathan A

    2007-01-01

    The goal of this book is to characterize algebraically the closed 4-manifolds that fibre nontrivially or admit geometries in the sense of Thurston, or which are obtained by surgery on 2-knots, and to provide a reference for the topology of such manifolds and knots. The first chapter is purely algebraic. The rest of the book may be divided into three parts: general results on homotopy and surgery (Chapters 2-6), geometries and geometric decompositions (Chapters 7-13), and 2-knots (Chapters 14-18). In many cases the Euler characteristic, fundamental group and Stiefel-Whitney classes together form a complete system of invariants for the homotopy type of such manifolds, and the possible values of the invariants can be described explicitly. The strongest results are characterizations of manifolds which fibre homotopically over S^1 or an aspherical surface (up to homotopy equivalence) and infrasolvmanifolds (up to homeomorphism). As a consequence 2-knots whose groups are poly-Z are determined up to Gluck reconstruc...

  9. The Ileosigmoid Knot: A Case Report

    African Journals Online (AJOL)

    because the clinical signs are difficult to define and the ... describe a case of ileosigmoid knotting in a 40 year old male and .... Prompt relief of obstruction by an emergency laparatomy is a ... the bowel leading to perforation, fecal peritonitis and.

  10. Refined large N duality for knots

    DEFF Research Database (Denmark)

    Kameyama, Masaya; Nawata, Satoshi

    We formulate large N duality of U(N) refined Chern-Simons theory with a torus knot/link in S³. By studying refined BPS states in M-theory, we provide the explicit form of low-energy effective actions of Type IIA string theory with D4-branes on the Ω-background. This form enables us to relate...

  11. Minimal knotted polygons in cubic lattices

    International Nuclear Information System (INIS)

    Van Rensburg, E J Janse; Rechnitzer, A

    2011-01-01

    In this paper we examine numerically the properties of minimal length knotted lattice polygons in the simple cubic, face-centered cubic, and body-centered cubic lattices by sieving minimal length polygons from a data stream of a Monte Carlo algorithm, implemented as described in Aragão de Carvalho and Caracciolo (1983 Phys. Rev. B 27 1635), Aragão de Carvalho et al (1983 Nucl. Phys. B 215 209) and Berg and Foester (1981 Phys. Lett. B 106 323). The entropy, mean writhe, and mean curvature of minimal length polygons are computed (in some cases exactly). While the minimal length and mean curvature are found to be lattice dependent, the mean writhe is found to be only weakly dependent on the lattice type. Comparison of our results to numerical results for the writhe obtained elsewhere (see Janse van Rensburg et al 1999 Contributed to Ideal Knots (Series on Knots and Everything vol 19) ed Stasiak, Katritch and Kauffman (Singapore: World Scientific), Portillo et al 2011 J. Phys. A: Math. Theor. 44 275004) shows that the mean writhe is also insensitive to the length of a knotted polygon. Thus, while these results for the mean writhe and mean absolute writhe at minimal length are not universal, our results demonstrate that these values are quite close the those of long polygons regardless of the underlying lattice and length

  12. Virtual knotting in proteins and other open curves

    Science.gov (United States)

    Alexander, Keith; Taylor, Alexander; Dennis, Mark

    Long filaments naturally knot, from string to long-chain molecules. Knotting in a filament affects its properties, and may be very stable or disappear under slight manipulation. Knotting has been identified in protein backbones for which these mechanical constraints are of fundamental importance to their function, although they are open curves in which knots are not mathematically well defined; knotting can only be identified by closing the ends of the chain. We introduce a new method for resolving knotting in open curves using virtual knots, a wider class of topological objects that do not use a classical closure, capturing the topological ambiguity of open curves. Having analysed all proteins in the Protein Data Bank by this new scheme, we recover and extend previous knotting results, and identify topological interest in some new cases. The statistics of virtual knots in proteins are compared with those of Hamiltonian subchains on cubic lattices, identifying a regime of open curves in which the virtual knotting description is likely to be important. This work was supported by the Leverhulme Trust Programme Grant ``Scientific Properties of Complex Knots'' and the EPSRC.

  13. Biosynthesis of macrocyclic diterpenoids in Euphorbia lathyris L

    DEFF Research Database (Denmark)

    Luo, Dan

    documents the investigation of the biosynthetic pathways of macrocyclic diterpenoids known as Euphorbia factors in Euphorbia lathyris L. (caper spurge). These macrocyclic diterpenoids are the current industrial source of ingenol mebutate, which is approved for the treatment of actinic keratosis...

  14. The coordination chemistry of macrocyclic ligands II

    International Nuclear Information System (INIS)

    Klimes, J.; Knoechel, A.; Rudolph, G.

    1977-01-01

    Compounds of UO 2 (NO 3 ) 2 .6H 2 0 or Th(NO 3 ) 4 .5H 2 0 with five selected crown ethers were prepared according to the method described in Knoeckel et al., Inorg.Nucl.Chem.Lett.; 11:787 (1975). The products were characterized by chemical analysis, NMR, IR and Raman spectroscopy. The results are analyzed and discussed. It is shown that the NO 3 groups remain free after combination, and the H 2 0 groups form the bonds to the polyether. It is concluded that the polyether molecule is attached to two units of UO 2 (NO 3 ) 2 .2H 2 0 (or Th(NO 3 ) 4 .3H 2 0), one each side of the polyether. This would be contrary to the assumption in previous publications, that the U0 2 2+ and Th 4+ ions were coordinated inside the macrocyclic ligand structure. The present hypothesis, however, agrees with a recently published x-ray structure for the uranium compound. In view of the new proposed structure it is suggested that the compounds should be regarded as adducts rather than complexes. (U.K.)

  15. Surface-knots in 4-space an introduction

    CERN Document Server

    Kamada, Seiichi

    2017-01-01

    This introductory volume provides the basics of surface-knots and related topics, not only for researchers in these areas but also for graduate students and researchers who are not familiar with the field. Knot theory is one of the most active research fields in modern mathematics. Knots and links are closed curves (one-dimensional manifolds) in Euclidean 3-space, and they are related to braids and 3-manifolds. These notions are generalized into higher dimensions. Surface-knots or surface-links are closed surfaces (two-dimensional manifolds) in Euclidean 4-space, which are related to two-dimensional braids and 4-manifolds. Surface-knot theory treats not only closed surfaces but also surfaces with boundaries in 4-manifolds. For example, knot concordance and knot cobordism, which are also important objects in knot theory, are surfaces in the product space of the 3-sphere and the interval. Included in this book are basics of surface-knots and the related topics of classical knots, the motion picture method, surf...

  16. Macrocyclic chelator-coupled gastrin-based radiopharmaceuticals for targeting of gastrin receptor-expressing tumours

    International Nuclear Information System (INIS)

    Good, Stephan; Wang, Xuejuan; Maecke, Helmut R.; Walter, Martin A.; Mueller-Brand, Jan; Waser, Beatrice; Reubi, Jean-Claude; Behe, Martin P.

    2008-01-01

    Diethylenetriamine-pentaacetic acid (DTPA)-coupled minigastrins are unsuitable for therapeutic application with the available β-emitting radiometals due to low complex stability. Low tumour-to-kidney ratio of the known radiopharmaceuticals is further limiting their potency. We used macrocyclic chelators for coupling to increase complex stability, modified the peptide sequence to enhance radiolytic stability and studied tumour-to-kidney ratio and metabolic stability using 111 In-labelled derivatives. Gastrin derivatives with decreasing numbers of glutamic acids were synthesised using 111 In as surrogate for therapeutic radiometals for in vitro and in vivo studies. Gastrin receptor affinities of the nat In-metallated compounds were determined by receptor autoradiography using 125 I-CCK as radioligand. Internalisation was evaluated in AR4-2J cells. Enzymatic stability was determined by incubating the 111 In-labelled peptides in human serum. Biodistribution was performed in AR4-2J-bearing Lewis rats. IC 50 values of the nat In-metallated gastrin derivatives vary between 1.2 and 4.8 nmol/L for all methionine-containing derivatives. Replacement of methionine by norleucine, isoleucine, methionine-sulfoxide and methionine-sulfone resulted in significant decrease of receptor affinity (IC 50 between 9.9 and 1,195 nmol/L). All cholecystokinin receptor affinities were >100 nmol/L. All 111 In-labelled radiopeptides showed receptor-specific internalisation. Serum mean-life times varied between 2.0 and 72.6 h, positively correlating with the number of Glu residues. All 111 In-labelled macrocyclic chelator conjugates showed higher tumour-to-kidney ratios after 24 h (0.37-0.99) compared to 111 In-DTPA-minigastrin 0(0.05). Tumour wash out between 4 and 24 h was low. Imaging studies confirmed receptor-specific blocking of the tumour uptake. Reducing the number of glutamates increased tumour-to-kidney ratio but resulted in lower metabolic stability. The properties of the macrocyclic

  17. Macrocyclic chelator-coupled gastrin-based radiopharmaceuticals for targeting of gastrin receptor-expressing tumours

    Energy Technology Data Exchange (ETDEWEB)

    Good, Stephan; Wang, Xuejuan; Maecke, Helmut R. [University Hospital Basel, Division of Radiological Chemistry, Basel (Switzerland); Walter, Martin A.; Mueller-Brand, Jan [University Hospital, Institute of Nuclear Medicine, Basel (Switzerland); Waser, Beatrice; Reubi, Jean-Claude [University of Berne, Department of Pathology, Bern (Switzerland); Behe, Martin P. [Philipps-University of Marburg, Department of Nuclear Medicine, Marburg (Germany)

    2008-10-15

    Diethylenetriamine-pentaacetic acid (DTPA)-coupled minigastrins are unsuitable for therapeutic application with the available {beta}-emitting radiometals due to low complex stability. Low tumour-to-kidney ratio of the known radiopharmaceuticals is further limiting their potency. We used macrocyclic chelators for coupling to increase complex stability, modified the peptide sequence to enhance radiolytic stability and studied tumour-to-kidney ratio and metabolic stability using {sup 111}In-labelled derivatives. Gastrin derivatives with decreasing numbers of glutamic acids were synthesised using {sup 111}In as surrogate for therapeutic radiometals for in vitro and in vivo studies. Gastrin receptor affinities of the {sup nat}In-metallated compounds were determined by receptor autoradiography using {sup 125}I-CCK as radioligand. Internalisation was evaluated in AR4-2J cells. Enzymatic stability was determined by incubating the {sup 111}In-labelled peptides in human serum. Biodistribution was performed in AR4-2J-bearing Lewis rats. IC{sub 50} values of the {sup nat}In-metallated gastrin derivatives vary between 1.2 and 4.8 nmol/L for all methionine-containing derivatives. Replacement of methionine by norleucine, isoleucine, methionine-sulfoxide and methionine-sulfone resulted in significant decrease of receptor affinity (IC{sub 50} between 9.9 and 1,195 nmol/L). All cholecystokinin receptor affinities were >100 nmol/L. All {sup 111}In-labelled radiopeptides showed receptor-specific internalisation. Serum mean-life times varied between 2.0 and 72.6 h, positively correlating with the number of Glu residues. All {sup 111}In-labelled macrocyclic chelator conjugates showed higher tumour-to-kidney ratios after 24 h (0.37-0.99) compared to {sup 111}In-DTPA-minigastrin 0(0.05). Tumour wash out between 4 and 24 h was low. Imaging studies confirmed receptor-specific blocking of the tumour uptake. Reducing the number of glutamates increased tumour-to-kidney ratio but resulted in

  18. Biologically Active Macrocyclic Compounds – from Natural Products to Diversity‐Oriented Synthesis

    DEFF Research Database (Denmark)

    Madsen, Charlotte Marie; Clausen, Mads Hartvig

    2011-01-01

    Macrocyclic compounds are attractive targets when searching for molecules with biological activity. The interest in this compound class is increasing, which has led to a variety of methods for tackling the difficult macrocyclization step in their synthesis. This microreview highlights some recent...... developments in the synthesis of macrocycles, with an emphasis on chemistry developed to generate libraries of putative biologically active compounds....

  19. Knot invariants and higher representation theory

    CERN Document Server

    Webster, Ben

    2018-01-01

    The author constructs knot invariants categorifying the quantum knot variants for all representations of quantum groups. He shows that these invariants coincide with previous invariants defined by Khovanov for \\mathfrak{sl}_2 and \\mathfrak{sl}_3 and by Mazorchuk-Stroppel and Sussan for \\mathfrak{sl}_n. The author's technique is to study 2-representations of 2-quantum groups (in the sense of Rouquier and Khovanov-Lauda) categorifying tensor products of irreducible representations. These are the representation categories of certain finite dimensional algebras with an explicit diagrammatic presentation, generalizing the cyclotomic quotient of the KLR algebra. When the Lie algebra under consideration is \\mathfrak{sl}_n, the author shows that these categories agree with certain subcategories of parabolic category \\mathcal{O} for \\mathfrak{gl}_k.

  20. Towards effective topological field theory for knots

    Directory of Open Access Journals (Sweden)

    A. Mironov

    2015-10-01

    Full Text Available Construction of (colored knot polynomials for double-fat graphs is further generalized to the case when “fingers” and “propagators” are substituting R-matrices in arbitrary closed braids with m-strands. Original version of [25] corresponds to the case m=2, and our generalization sheds additional light on the structure of those mysterious formulas. Explicit expressions are now combined from Racah matrices of the type R⊗R⊗R¯⟶R¯ and mixing matrices in the sectors R⊗3⟶Q. Further extension is provided by composition rules, allowing to glue two blocks, connected by an m-strand braid (they generalize the product formula for ordinary composite knots with m=1.

  1. A state enumeration of the foil knot

    OpenAIRE

    Ramaharo, Franck; Rakotondrajao, Fanja

    2017-01-01

    We split the crossings of the foil knot and enumerate the resulting states with a generating polynomial. Unexpectedly, the number of such states which consist of two components are given by the lazy caterer's sequence. This sequence describes the maximum number of planar regions that is obtained with a given number of straight lines. We then establish a bijection between this partition of the plane and the concerned foil splits sequence.

  2. Computation of Hyperbolic Structures in Knot Theory

    OpenAIRE

    Weeks, Jeffrey R.

    2003-01-01

    This chapter from the upcoming Handbook of Knot Theory (eds. Menasco and Thistlethwaite) shows how to construct hyperbolic structures on link complements and perform hyperbolic Dehn filling. Along with a new elementary exposition of the standard ideas from Thurston's work, the article includes never-before-published explanations of SnapPea's algorithms for triangulating a link complement efficiently and for converging quickly to the hyperbolic structure while avoiding singularities in the par...

  3. Induction effects of torus knots and unknots

    Science.gov (United States)

    Oberti, Chiara; Ricca, Renzo L.

    2017-09-01

    Geometric and topological aspects associated with induction effects of field lines in the shape of torus knots/unknots are examined and discussed in detail. Knots are assumed to lie on a mathematical torus of circular cross-section and are parametrized by standard equations. The induced field is computed by direct integration of the Biot-Savart law. Field line patterns of the induced field are obtained and several properties are examined for a large family of knots/unknots up to 51 crossings. The intensity of the induced field at the origin of the reference system (center of the torus) is found to depend linearly on the number of toroidal coils and reaches maximum values near the boundary of the mathematical torus. New analytical estimates and bounds on energy and helicity are established in terms of winding number and minimum crossing number. These results find useful applications in several contexts when the source field is either vorticity, electric current or magnetic field, from vortex dynamics to astrophysics and plasma physics, where highly braided magnetic fields and currents are present.

  4. Derivatized Pentadentate Macrocyclic Ligands and Their Transition Metal Complexes

    Directory of Open Access Journals (Sweden)

    Muhammad S. Khan

    2002-06-01

    Full Text Available The reaction of the pendant hydroxyethyl group in the planar pentadentate macrocyclic ligand,1,11-bis(2’-hydroxyethyl-4,8;12,16;17,21-trinitrilo-1,2,10,11-tetraazacyclohenicosa- 2,4,6,9,12,14,18,20-octaene (L2, derived from the condensation of 2,6-pyridinedialdehyde with 6,6’-bis(2’ hydroxyethylhydrazino -2,2’-bipyridine (L1, has been investigated. Esterification reactions are facile, and the reaction of the hydroxyethyl-substituted macrocycle with thionyl chloride yields a chloroethyl derivative. Metal complexes of the new derivatized macrocyclic ligands L3-6having general formula ML3-6X2.nH2O (M = Mn, Fe, Co, Ni, Cu, Zn are readily prepared.

  5. Motion of Knots in DNA Stretched by Elongational Fields

    Science.gov (United States)

    Klotz, Alexander R.; Soh, Beatrice W.; Doyle, Patrick S.

    2018-05-01

    Knots in DNA occur in biological systems, serve as a model system for polymer entanglement, and affect the efficacy of modern genomics technologies. We study the motion of complex knots in DNA by stretching molecules with a divergent electric field that provides an elongational force. We demonstrate that the motion of knots is nonisotropic and driven towards the closest end of the molecule. We show for the first time experimentally that knots can go from a mobile to a jammed state by varying an applied strain rate, and that this jamming is reversible. We measure the mobility of knots as a function of strain rate, demonstrating the conditions under which knots can be driven towards the ends of the molecule and untied.

  6. Modeling the Effects of Knots in Structural Timber

    DEFF Research Database (Denmark)

    Foley, Christina

    The main purpose of the pursued research presented in this thesis is to increase knowledge of the effects of knots in structural timber so that characteristics of weaker timber may be determined and applied to improve current grading techniques. In the process, a three-dimensional fiber paradigm...... are given to Shigo's knot formation theory, and thus predicts two separate patterns of fiber direction within annual growth layers related to live knots. In order to determine the possibility to practically and non destructively predict local material directions in structural timber with the three...... was established, which describes variations of radial growth direction and fiber orientation related to knots in timber. The adaptability of the paradigm allows practically any softwood knot and its effect on surrounding wood material to be modeled with an accuracy that is limited only by input data. The knot...

  7. Design and synthesis of chalcone-based macrocyclic polyethers

    Directory of Open Access Journals (Sweden)

    Subrata Jana

    2015-12-01

    Full Text Available A series of chalcone-based macrocyclic ethers have been synthesized. These macrocyclic ethers contain polyether as well as extended conjugation to the benzene ring to function as fluorescent sensor for cations. The modeling studies show that the chalcone part of the receptors remains partially out of plane from the polyether part and the keto moiety of the receptors always directed outwardly in the receptor itself. This may be changed during the recognition of metal ions. The tendency of the fluorophore, to be out of plane, increases with increasing the ring size.

  8. Dysprosium complexes with the tetraphenylporphyrin macrocyclic ligand

    International Nuclear Information System (INIS)

    Martinez M, V.; Padilla, J.; Ramirez, F.M.

    1992-04-01

    In this report, the results obtained on the synthesis, characterization and study of the chemical behavior of dysprosium complex with the acetylacetone chelating agent (Hacac) and the tetraphenylporphyrin macrocyclic ligand (H 2 TFP) are given. Based on the literature but according to our necessities and interest, the appropriate methodology settled down from the synthesis of prime matters until the obtaining and characterization of the products. The acetyl acetonate complex was obtained of mono hydrated dysprosium [Dy(acac) 3 . H 2 0] and trihydrated [Dy(acac) 3 .3 H 2 0], the mono tetra phenyl porphyrinate [Dy(TFP)(acac). 2 ac] the double sandwich of the dysprosium porphyrinate [Dy(TFP) 2 ] and the triple sandwich of the dysprosium porphyrinate [Dy(TFP) 3 . 2 TCB] (TCB = trichlorobenzene). Its were characterized by their melting points, solubility, IR, UV, TGA and DTA both first and besides the techniques already mentioned for NMR'H, RPE and Magnetic susceptibility the three last complexes. From the spectroscopic point of view, IR and RPE its suggested the existence of a complex of inverse mixed valence [Dy(TFP) 2- (TFP) 1- ] for the Dy(TFP) 2 as a result of the existence of the free radical (TFP' 1- and that it was not in none of the other porphyrin compounds. In the NMR'H spectra of the compounds were not observed signals in the region from 0 to 10 ppm that which shows that the dysprosium complexes in special those of the porphyrin type are highly paramagnetic and its could be used as displacement reagents, creators of images and contrast agents of great utility in these days in studies of NMR, technique today by today used in medical diagnoses. (Author)

  9. Sampling large random knots in a confined space

    International Nuclear Information System (INIS)

    Arsuaga, J; Blackstone, T; Diao, Y; Hinson, K; Karadayi, E; Saito, M

    2007-01-01

    DNA knots formed under extreme conditions of condensation, as in bacteriophage P4, are difficult to analyze experimentally and theoretically. In this paper, we propose to use the uniform random polygon model as a supplementary method to the existing methods for generating random knots in confinement. The uniform random polygon model allows us to sample knots with large crossing numbers and also to generate large diagrammatically prime knot diagrams. We show numerically that uniform random polygons sample knots with large minimum crossing numbers and certain complicated knot invariants (as those observed experimentally). We do this in terms of the knot determinants or colorings. Our numerical results suggest that the average determinant of a uniform random polygon of n vertices grows faster than O(e n 2 )). We also investigate the complexity of prime knot diagrams. We show rigorously that the probability that a randomly selected 2D uniform random polygon of n vertices is almost diagrammatically prime goes to 1 as n goes to infinity. Furthermore, the average number of crossings in such a diagram is at the order of O(n 2 ). Therefore, the two-dimensional uniform random polygons offer an effective way in sampling large (prime) knots, which can be useful in various applications

  10. Sampling large random knots in a confined space

    Science.gov (United States)

    Arsuaga, J.; Blackstone, T.; Diao, Y.; Hinson, K.; Karadayi, E.; Saito, M.

    2007-09-01

    DNA knots formed under extreme conditions of condensation, as in bacteriophage P4, are difficult to analyze experimentally and theoretically. In this paper, we propose to use the uniform random polygon model as a supplementary method to the existing methods for generating random knots in confinement. The uniform random polygon model allows us to sample knots with large crossing numbers and also to generate large diagrammatically prime knot diagrams. We show numerically that uniform random polygons sample knots with large minimum crossing numbers and certain complicated knot invariants (as those observed experimentally). We do this in terms of the knot determinants or colorings. Our numerical results suggest that the average determinant of a uniform random polygon of n vertices grows faster than O(e^{n^2}) . We also investigate the complexity of prime knot diagrams. We show rigorously that the probability that a randomly selected 2D uniform random polygon of n vertices is almost diagrammatically prime goes to 1 as n goes to infinity. Furthermore, the average number of crossings in such a diagram is at the order of O(n2). Therefore, the two-dimensional uniform random polygons offer an effective way in sampling large (prime) knots, which can be useful in various applications.

  11. Sampling large random knots in a confined space

    Energy Technology Data Exchange (ETDEWEB)

    Arsuaga, J [Department of Mathematics, San Francisco State University, 1600 Holloway Ave, San Francisco, CA 94132 (United States); Blackstone, T [Department of Computer Science, San Francisco State University, 1600 Holloway Ave., San Francisco, CA 94132 (United States); Diao, Y [Department of Mathematics and Statistics, University of North Carolina at Charlotte, Charlotte, NC 28223 (United States); Hinson, K [Department of Mathematics and Statistics, University of North Carolina at Charlotte, Charlotte, NC 28223 (United States); Karadayi, E [Department of Mathematics, University of South Florida, 4202 E Fowler Avenue, Tampa, FL 33620 (United States); Saito, M [Department of Mathematics, University of South Florida, 4202 E Fowler Avenue, Tampa, FL 33620 (United States)

    2007-09-28

    DNA knots formed under extreme conditions of condensation, as in bacteriophage P4, are difficult to analyze experimentally and theoretically. In this paper, we propose to use the uniform random polygon model as a supplementary method to the existing methods for generating random knots in confinement. The uniform random polygon model allows us to sample knots with large crossing numbers and also to generate large diagrammatically prime knot diagrams. We show numerically that uniform random polygons sample knots with large minimum crossing numbers and certain complicated knot invariants (as those observed experimentally). We do this in terms of the knot determinants or colorings. Our numerical results suggest that the average determinant of a uniform random polygon of n vertices grows faster than O(e{sup n{sup 2}}). We also investigate the complexity of prime knot diagrams. We show rigorously that the probability that a randomly selected 2D uniform random polygon of n vertices is almost diagrammatically prime goes to 1 as n goes to infinity. Furthermore, the average number of crossings in such a diagram is at the order of O(n{sup 2}). Therefore, the two-dimensional uniform random polygons offer an effective way in sampling large (prime) knots, which can be useful in various applications.

  12. Virtual screening using combinatorial cyclic peptide libraries reveals protein interfaces readily targetable by cyclic peptides.

    Science.gov (United States)

    Duffy, Fergal J; O'Donovan, Darragh; Devocelle, Marc; Moran, Niamh; O'Connell, David J; Shields, Denis C

    2015-03-23

    Protein-protein and protein-peptide interactions are responsible for the vast majority of biological functions in vivo, but targeting these interactions with small molecules has historically been difficult. What is required are efficient combined computational and experimental screening methods to choose among a number of potential protein interfaces worthy of targeting lead macrocyclic compounds for further investigation. To achieve this, we have generated combinatorial 3D virtual libraries of short disulfide-bonded peptides and compared them to pharmacophore models of important protein-protein and protein-peptide structures, including short linear motifs (SLiMs), protein-binding peptides, and turn structures at protein-protein interfaces, built from 3D models available in the Protein Data Bank. We prepared a total of 372 reference pharmacophores, which were matched against 108,659 multiconformer cyclic peptides. After normalization to exclude nonspecific cyclic peptides, the top hits notably are enriched for mimetics of turn structures, including a turn at the interaction surface of human α thrombin, and also feature several protein-binding peptides. The top cyclic peptide hits also cover the critical "hot spot" interaction sites predicted from the interaction crystal structure. We have validated our method by testing cyclic peptides predicted to inhibit thrombin, a key protein in the blood coagulation pathway of important therapeutic interest, identifying a cyclic peptide inhibitor with lead-like activity. We conclude that protein interfaces most readily targetable by cyclic peptides and related macrocyclic drugs may be identified computationally among a set of candidate interfaces, accelerating the choice of interfaces against which lead compounds may be screened.

  13. Optical knots and contact geometry II. From Ranada dyons to transverse and cosmetic knots

    Energy Technology Data Exchange (ETDEWEB)

    Kholodenko, Arkady L., E-mail: string@clemson.edu

    2016-08-15

    Some time ago Ranada (1989) obtained new nontrivial solutions of the Maxwellian gauge fields without sources. These were reinterpreted in Kholodenko (2015) [10] (part I) as particle-like (monopoles, dyons, etc.). They were obtained by the method of Abelian reduction of the non-Abelian Yang–Mills functional. The developed method uses instanton-type calculations normally employed for the non-Abelian gauge fields. By invoking the electric–magnetic duality it then becomes possible to replace all known charges/masses by the particle-like solutions of the source-free Abelian gauge fields. To employ these results in high energy physics, it is essential to extend Ranada’s results by carefully analyzing and classifying all dynamically generated knotted/linked structures in gauge fields, including those discovered by Ranada. This task is completed in this work. The study is facilitated by the recent progress made in solving the Moffatt conjecture. Its essence is stated as follows: in steady incompressible Euler-type fluids the streamlines could have knots/links of all types. By employing the correspondence between the ideal hydrodynamics and electrodynamics discussed in part I and by superimposing it with the already mentioned method of Abelian reduction, it is demonstrated that in the absence of boundaries only the iterated torus knots and links could be dynamically generated. Obtained results allow to develop further particle-knot/link correspondence studied in Kholodenko (2015) [13].

  14. Schiff base oligopyrrolic macrocycles as ligands for lanthanides and actinides

    International Nuclear Information System (INIS)

    Sessler, Jonathan L.; Melfi, Patricia J.; Tomat, Elisa; Callaway, Wyeth; Huggins, Michael T.; Gordon, Pamela L.; Webster Keogh, D.; Date, Richard W.; Bruce, Duncan W.; Donnio, Bertrand

    2006-01-01

    The coordination of f-block cations with Schiff base oligopyrrolic macrocycles is discussed. Analysis of the mesophase of a uranyl 2,5-diformylpyrrole-derived expanded porphyrin complex through temperature-dependent X-ray diffraction (XRD) methods has provided evidence for liquid-crystalline properties, and for molecular stacking into columns, arranged in a 2D hexagonal lattice. In separate studies, UV-vis spectral analysis has indicated the formation of three new f-block oligopyrrolic complexes. Addition of neptunyl ([NpO 2 ] 2+ ) or plutonyl ([PuO 2 ] 2+ ) chloride salts to the free base of a dipyrromethane-derived Schiff base macrocycle induces an immediate spectral change, namely the growth of a Q-like band at 630 nm. Such changes in the absorption spectra cause a dramatic color change from pale yellow to blue. It is postulated that oxidation of this macrocycle, stimulated by reduction of the metal center, leads to the observed spectral changes. An immediate visible and spectral change is also observed with the reaction of lutetium silylamide (Lu[N(Si(CH 3 ) 3 ) 2 ] 3 ), with a different, tetrapyrrole-containing Schiff base macrocycle. In this case, the formation of a complex with 1:1 metal-to-ligand binding stoichiometry is further supported by MALDI-TOF mass spectrometry

  15. Characterization and crystal structures of new Schiff base macrocyclic compounds

    Czech Academy of Sciences Publication Activity Database

    Khalaji, A.D.; Ghoran, S.H.; Pojarová, Michaela; Dušek, Michal

    2015-01-01

    Roč. 56, č. 7 (2015), s. 1410-1414 ISSN 0022-4766 R&D Projects: GA ČR(CZ) GA14-03276S Institutional support: RVO:68378271 Keywords : synthesis * macrocyclic Schiff base * single crystal structure analysis * spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.536, year: 2015

  16. Kinetics of oxidation of nickel(II) aza macrocycles by ...

    Indian Academy of Sciences (India)

    The kinetics of the oxidation of nickel (II) hexaaza and nickel (II) pentaaza macrocycles by the peroxydisulphate anion, S2O8 2-, were studied in aqueous media. Effect of H on reaction rate was also studied. The rate increases with increase of S2OO8 2- concentration. Rates are almost independent of acid between H 4 ...

  17. On-Surface Synthesis and Characterization of Honeycombene Oligophenylene Macrocycles.

    Science.gov (United States)

    Chen, Min; Shang, Jian; Wang, Yongfeng; Wu, Kai; Kuttner, Julian; Hilt, Gerhard; Hieringer, Wolfgang; Gottfried, J Michael

    2017-01-24

    We report the on-surface formation and characterization of [30]-honeycombene, a cyclotriacontaphenylene, which consists of 30 phenyl rings (C 180 H 120 ) and has a diameter of 4.0 nm. This shape-persistent, conjugated, and unsubstituted hexagonal hydrocarbon macrocycle was obtained by solvent-free synthesis on a silver (111) single-crystal surface, making solubility-enhancing alkyl side groups unnecessary. Side products include strained macrocycles with square, pentagonal, and heptagonal shape. The molecules were characterized by scanning tunneling microscopy and density functional theory (DFT) calculations. On the Ag(111) surface, the macrocycles act as molecular quantum corrals and lead to the confinement of surface-state electrons inside the central cavity. The energy of the confined surface state correlates with the size of the macrocycle and is well described by a particle-in-the-box model. Tunneling spectroscopy suggests conjugation within the planar rings and reveals influences of self-assembly on the electronic structure. While the adsorbed molecules appear to be approximately planar, the free molecules have nonplanar conformation, according to DFT.

  18. A macrocyclic ellagitannin trimer, oenotherin T(1), from Oenothera species.

    Science.gov (United States)

    Taniguchi, Shoko; Imayoshi, Yoko; Yabu-uchi, Ryoko; Ito, Hideyuki; Hatano, Tsutomu; Yoshida, Takashi

    2002-01-01

    Oenotherin T(1) was isolated from leaves of Oenothera tetraptera as a major ellagitannin. Its structure, that of a macrocyclic trimer with a new acyl group, an isodehydrovaloneoyl group, was established. This compound was also produced by callus tissues induced from O. laciniata leaves.

  19. Schiff base oligopyrrolic macrocycles as ligands for lanthanides and actinides

    Energy Technology Data Exchange (ETDEWEB)

    Sessler, Jonathan L. [Department of Chemistry and Biochemistry, Institute for Cellular and Molecular Biology, 1 University Station A5300, University of Texas at Austin, Austin, TX 78712-0165 (United States)]. E-mail: sessler@mail.utexas.edu; Melfi, Patricia J. [Department of Chemistry and Biochemistry, Institute for Cellular and Molecular Biology, 1 University Station A5300, University of Texas at Austin, Austin, TX 78712-0165 (United States); Tomat, Elisa [Department of Chemistry and Biochemistry, Institute for Cellular and Molecular Biology, 1 University Station A5300, University of Texas at Austin, Austin, TX 78712-0165 (United States); Callaway, Wyeth [Department of Chemistry and Biochemistry, Institute for Cellular and Molecular Biology, 1 University Station A5300, University of Texas at Austin, Austin, TX 78712-0165 (United States); Huggins, Michael T. [Department of Chemistry and Biochemistry, Institute for Cellular and Molecular Biology, 1 University Station A5300, University of Texas at Austin, Austin, TX 78712-0165 (United States); Gordon, Pamela L. [C-Chemistry and NMT-Nuclear Materials Technology Divisions, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Webster Keogh, D. [C-Chemistry and NMT-Nuclear Materials Technology Divisions, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Date, Richard W. [Department of Chemistry, University of Exeter, Stocker Road, Exeter EX4 4QD (United Kingdom); Bruce, Duncan W. [Department of Chemistry, University of Exeter, Stocker Road, Exeter EX4 4QD (United Kingdom); Department of Chemistry, University of York, Heslington, YORK YO10 5DD (United Kingdom); Donnio, Bertrand [Institut de Physique et Chimie des Materiaux de Strasbourg (IPCMS), Groupe des Materiaux Organiques (GMO), CNRS-ULP - UMR 7504, 23 rue du Loess BP 43, F-67034 Strasbourg Cedex 2 (France)

    2006-07-20

    The coordination of f-block cations with Schiff base oligopyrrolic macrocycles is discussed. Analysis of the mesophase of a uranyl 2,5-diformylpyrrole-derived expanded porphyrin complex through temperature-dependent X-ray diffraction (XRD) methods has provided evidence for liquid-crystalline properties, and for molecular stacking into columns, arranged in a 2D hexagonal lattice. In separate studies, UV-vis spectral analysis has indicated the formation of three new f-block oligopyrrolic complexes. Addition of neptunyl ([NpO{sub 2}]{sup 2+}) or plutonyl ([PuO{sub 2}]{sup 2+}) chloride salts to the free base of a dipyrromethane-derived Schiff base macrocycle induces an immediate spectral change, namely the growth of a Q-like band at 630 nm. Such changes in the absorption spectra cause a dramatic color change from pale yellow to blue. It is postulated that oxidation of this macrocycle, stimulated by reduction of the metal center, leads to the observed spectral changes. An immediate visible and spectral change is also observed with the reaction of lutetium silylamide (Lu[N(Si(CH{sub 3}){sub 3}){sub 2}]{sub 3}), with a different, tetrapyrrole-containing Schiff base macrocycle. In this case, the formation of a complex with 1:1 metal-to-ligand binding stoichiometry is further supported by MALDI-TOF mass spectrometry.

  20. Analysis of the tractive force pattern on a knot by force measurement during laparoscopic knot tying.

    Science.gov (United States)

    Takayasu, Kenta; Yoshida, Kenji; Kinoshita, Hidefumi; Yoshimoto, Syunsuke; Oshiro, Osamu; Matsuda, Tadashi

    2017-07-19

    Quantifying surgical skills assists novice surgeons when learning operative techniques. We measured the interaction force at a ligation point and clarified the features of the force pattern among surgeons with different skill levels during laparoscopic knot tying. Forty-four surgeons were divided into three groups based on experience: 13 novice (0-5 years), 16 intermediate (6-15 years), and 15 expert (16-30 years). To assess the tractive force direction and volume during knot tying, we used a sensor that measures six force-torque values (x-axis: Fx, y-axis: Fy, z-axis: Fz, and xy-axis: Fxy) attached to a slit Penrose drain. All participants completed one double knot and five single knot sequences. We recorded completion time, force volume (FV), maximum force (MF), time over 1.5 N, duration of non-zero force, and percentage time when vertical force exceeded horizontal force (PTz). There was a significant difference between groups for completion time (p = 0.007); FV (total: p = 0.002; Fx: p = 0.004, Fy: p = 0.007, Fxy: p = 0.004, Fz: p force (p = 0.029); and PTz (p force pattern at the ligation point during suturing by surgeons with three levels of experience using a force measurement system. We revealed that both force volume and force direction differed depending on surgeons' skill level during knot tying. Copyright © 2017. Published by Elsevier Inc.

  1. Great Knot Calidris tenuirostris at Lutembe Bay, Uganda

    African Journals Online (AJOL)

    Unfortunately it became nervous and flew to another island and we were unable to pursue it before darkness fell. I was, however, able to take some record shots. I circulated the best of four poor photographs to a few birding colleagues for their opinion, and the general consensus favoured Red Knot rather than Great Knot.

  2. Ileosigmoid knotting in pregnancy: A case report from Zimbabwe ...

    African Journals Online (AJOL)

    Ileosigmoid knotting (ISK), also known as compound volvulus, is a rare cause of intestinal obstruction wherein the ileum wraps around the base of the sigmoid colon and forms a knot with rapid progression to gangrene. The worldwide incidence of ISK ranges from 1 in 1500 to 1 in 66,431. ISK is particularly rare in pregnancy ...

  3. Relative symplectic caps, 4-genus and fibered knots

    Indian Academy of Sciences (India)

    We prove relative versions of the symplectic capping theorem and sufficiency of Giroux's criterion for Stein fillability and use these to study the 4-genus of knots. More precisely, suppose we have a symplectic 4-manifold with convex boundary and a symplectic surface in such that is a transverse knot in .

  4. Factorization of differential expansion for antiparallel double-braid knots

    Science.gov (United States)

    Morozov, A.

    2016-09-01

    Continuing the quest for exclusive Racah matrices, which are needed for evaluation of colored arborescent-knot polynomials in Chern-Simons theory, we suggest to extract them from a new kind of a double-evolution — that of the antiparallel double-braids, which is a simple two-parametric family of two-bridge knots, generalizing the one-parametric family of twist knots. In the case of rectangular representations R = [ r s ] we found an evidence that the corresponding differential expansion miraculously factorizes and can be obtained from that for the twist knots. This reduces the problem of rectangular exclusive Racah to constructing the answers for just a few twist knots. We develop a recent conjecture on the structure of differential expansion for the simplest members of this family (the trefoil and the figure-eight knot) and provide the exhaustive answer for the first unknown case of R = [33]. The answer includes HOMFLY of arbitrary twist and double-braid knots and Racah matrices overline{S} and S — what allows to calculate [33]-colored polynomials for arbitrary arborescent (double-fat) knots. For generic rectangular representations fully described are only the contributions of the single-floor pyramids. One step still remains to be done.

  5. True Umbilical Cord Knot Leading to Fetal Demise | Ikechebelu ...

    African Journals Online (AJOL)

    The incidence of true knot of the umbilical cord is not only very low but it is often undiagnosed antenatally when present despite the availability of prenatal ultrasonography. When the true knot remains tight, it may impede the circulation of the fetus and may result to fetal death in utero especially in labor. We report a very ...

  6. Borromean Triangles and Prime Knots in an Ancient Temple

    Indian Academy of Sciences (India)

    a computer mouse with cable which forms the logo of the Topo- logical Quantum .... theory of knots stayed on and was developed into a beautiful. Figure 3. A prime knot ... ematics to build bridges with the inner worlds that these temples seek to ...

  7. Atmospheres of polygons and knotted polygons

    International Nuclear Information System (INIS)

    Janse Rensburg, E J Janse; Rechnitzer, A

    2008-01-01

    In this paper we define two statistics a + (ω) and a - (ω), the positive and negative atmospheres of a lattice polygon ω of fixed length n. These statistics have the property that (a + (ω))/(a - (ω)) = p n+2 /p n , where p n is the number of polygons of length n, counted modulo translations. We use the pivot algorithm to sample polygons and to compute the corresponding average atmospheres. Using these data, we directly estimate the growth constants of polygons in two and three dimensions. We find that μ=2.63805±0.00012 in two dimensions and μ=4.683980±0.000042±0.000067 in three dimensions, where the error bars are 67% confidence intervals, and the second error bar in the three-dimensional estimate of μ is an estimated systematic error. We also compute atmospheres of polygons of fixed knot type K sampled by the BFACF algorithm. We discuss the implications of our results and show that different knot types have atmospheres which behave dramatically differently at small values of n

  8. The mean squared writhe of alternating random knot diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Diao, Y; Hinson, K [Department of Mathematics and Statistics University of North Carolina at Charlotte, NC 28223 (United States); Ernst, C; Ziegler, U, E-mail: ydiao@uncc.ed [Department of Mathematics and Computer Science, Western Kentucky University, Bowling Green, KY 42101 (United States)

    2010-12-10

    The writhe of a knot diagram is a simple geometric measure of the complexity of the knot diagram. It plays an important role not only in knot theory itself, but also in various applications of knot theory to fields such as molecular biology and polymer physics. The mean squared writhe of any sample of knot diagrams with n crossings is n when for each diagram at each crossing one of the two strands is chosen as the overpass at random with probability one-half. However, such a diagram is usually not minimal. If we restrict ourselves to a minimal knot diagram, then the choice of which strand is the over- or under-strand at each crossing is no longer independent of the neighboring crossings and a larger mean squared writhe is expected for minimal diagrams. This paper explores the effect on the correlation between the mean squared writhe and the diagrams imposed by the condition that diagrams are minimal by studying the writhe of classes of reduced, alternating knot diagrams. We demonstrate that the behavior of the mean squared writhe heavily depends on the underlying space of diagram templates. In particular this is true when the sample space contains only diagrams of a special structure. When the sample space is large enough to contain not only diagrams of a special type, then the mean squared writhe for n crossing diagrams tends to grow linearly with n, but at a faster rate than n, indicating an intrinsic property of alternating knot diagrams. Studying the mean squared writhe of alternating random knot diagrams also provides some insight into the properties of the diagram generating methods used, which is an important area of study in the applications of random knot theory.

  9. Multimedia article. The keys to the new laparoscopic world Thumbs up! knot and Tornado knot.

    Science.gov (United States)

    Uchida, K; Haruta, N; Okajima, M; Matsuda, M; Yamamoto, M

    2005-06-01

    Most laparoscopic surgeons feel some anxiety when performing intracorporeal knotting with conventional techniques [1, 2]. Two factors contribute to this anxiety. The first is the necessity of recognizing three dimensions on a two-dimensional monitor. The conventional intracorporeal knotting techniques make loops by twisting the thread with a second pair of forceps. This necessitates cooperative movement of both hands, with the added difficulties of depth perception. Regular touch confirmations reduce problems with depth perception. However, touch confirmation is more complicated in laparoscopic surgery than in laparotomy. The second problem is that tied loops can come loose and escape the instruments, especially with hard thread. This is not only stressful but also increases operation time.

  10. On the groundstate energy spectrum of magnetic knots and links

    International Nuclear Information System (INIS)

    Ricca, Renzo L; Maggioni, Francesca

    2014-01-01

    By using analytical results for the constrained minimum energy of magnetic knots we determine the influence of internal twist on the minimum magnetic energy levels of knots and links, and by using ropelength data from the RIDGERUNNER tightening algorithm (Ashton et al 2011 Exp. Math. 20 57–90) we obtain the groundstate energy spectra of the first 250 prime knots and 130 prime links. The two spectra are found to follow an almost identical logarithmic law. By assuming that the number of knot types grows exponentially with the topological crossing number, we show that this generic behavior can be justified by a general relationship between ropelength and crossing number, which is in good agreement with former analytical estimates (Buck and Simon 1999 Topol. Appl. 91 245–57, Diao 2003 J. Knot Theory Ramifications 12 1–16). Moreover, by considering the ropelength averaged over a given knot family, we establish a new connection between the averaged ropelength and the topological crossing number of magnetic knots. (paper)

  11. Knotting probability of self-avoiding polygons under a topological constraint

    Science.gov (United States)

    Uehara, Erica; Deguchi, Tetsuo

    2017-09-01

    We define the knotting probability of a knot K by the probability for a random polygon or self-avoiding polygon (SAP) of N segments having the knot type K. We show fundamental and generic properties of the knotting probability particularly its dependence on the excluded volume. We investigate them for the SAP consisting of hard cylindrical segments of unit length and radius rex. For various prime and composite knots, we numerically show that a compact formula describes the knotting probabilities for the cylindrical SAP as a function of segment number N and radius rex. It connects the small-N to the large-N behavior and even to lattice knots in the case of large values of radius. As the excluded volume increases, the maximum of the knotting probability decreases for prime knots except for the trefoil knot. If it is large, the trefoil knot and its descendants are dominant among the nontrivial knots in the SAP. From the factorization property of the knotting probability, we derive a sum rule among the estimates of a fitting parameter for all prime knots, which suggests the local knot picture and the dominance of the trefoil knot in the case of large excluded volumes. Here we remark that the cylindrical SAP gives a model of circular DNA which is negatively charged and semiflexible, where radius rex corresponds to the screening length.

  12. Knotting probability of self-avoiding polygons under a topological constraint.

    Science.gov (United States)

    Uehara, Erica; Deguchi, Tetsuo

    2017-09-07

    We define the knotting probability of a knot K by the probability for a random polygon or self-avoiding polygon (SAP) of N segments having the knot type K. We show fundamental and generic properties of the knotting probability particularly its dependence on the excluded volume. We investigate them for the SAP consisting of hard cylindrical segments of unit length and radius r ex . For various prime and composite knots, we numerically show that a compact formula describes the knotting probabilities for the cylindrical SAP as a function of segment number N and radius r ex . It connects the small-N to the large-N behavior and even to lattice knots in the case of large values of radius. As the excluded volume increases, the maximum of the knotting probability decreases for prime knots except for the trefoil knot. If it is large, the trefoil knot and its descendants are dominant among the nontrivial knots in the SAP. From the factorization property of the knotting probability, we derive a sum rule among the estimates of a fitting parameter for all prime knots, which suggests the local knot picture and the dominance of the trefoil knot in the case of large excluded volumes. Here we remark that the cylindrical SAP gives a model of circular DNA which is negatively charged and semiflexible, where radius r ex corresponds to the screening length.

  13. Intracorporeal knotting of a femoral nerve catheter

    Directory of Open Access Journals (Sweden)

    Ghanem, Mohamed

    2015-01-01

    Full Text Available Peripheral nerve catheters are effective and well-established tools to provide postoperative analgesia to patients undergoing orthopedic surgery. The performance of these techniques is usually considered safe. However, placement of nerve catheters may be associated with a considerable number of side effects and major complications have repeatedly been published. In this work, we report on a patient who underwent total knee replacement with spinal anesthesia and preoperative insertion of femoral and sciatic nerve catheters for postoperative analgesia. During insertion of the femoral catheter, significant resistance was encountered upon retracting the catheter. This occurred due to knotting of the catheter. The catheter had to be removed by operative intervention which has to be considered a major complication. The postoperative course was uneventful. The principles for removal of entrapped peripheral catheters are not well established, may differ from those for neuroaxial catheters, and range from cautious manipulation up to surgical intervention.

  14. Stability complexes of lanthanide ions with some macrocyclic polyethers

    International Nuclear Information System (INIS)

    Poluehktov, N.S.; Malinka, E.V.; Meshkova, S.B.; Bel'tyukova, S.V.; Danilkovich, M.M.

    1984-01-01

    Stability of lanthanide complexes with macrocyclic polyethers has been studied versus the number of f-electrons, spin- and orbital angular momenta of the Lu 3+ ion ground states. The following compounds were used as macrocyclic complexones: 12-crown-4 (12C4), tert-bulylbenzo-15-crown-5(BB15C5), 18-crown-6 (18C6), ditert-butylbenzo-18-crown-6(DBB18C6), dibenzo-30-crown-10 (DB30C10), cryptand [2, 2, 1] (Cr[2, 2, 1]). It is shoWn that the stability constants of the studied lanthanide complexes can be described rather satisfactorily by an expression suggested earlier that relates their values with the number of 4f-electrons and the S and L quantum numbers of the ground states of the lantharide ions

  15. A new spermidine macrocyclic alkaloid isolated from Gymnosporia arenicola leaf.

    Science.gov (United States)

    da Silva, Gustavo; Martinho, Ana; Soengas, Raquel González; Duarte, Ana Paula; Serrano, Rita; Gomes, Elsa Teixeira; Silva, Olga

    2015-10-01

    The isolation and structural elucidation of a macrocyclic alkaloid, characterized by the presence of a 13-membered macrolactam ring containing a spermidine unit N-linked to a benzoyl group is hereby reported. The structure of this previously unknown spermidine alkaloid isolated from Gymnosporia arenicola (Celastraceae) leaves has been elucidated by (1)H and (13)C NMR spectroscopy (including bidimensional analysis) and further characterized by high-resolution mass spectrometry and polarimetry. A route for the biosynthesis of this new bioactive macrocycle is proposed and the cytotoxicity of the compound was evaluated against two ATCC cell lines - one normal-derived (MCF10A) and one cancer-derived cell line (MCF7) - using the MTT assay. The alkaloid revealed to be non-cytotoxic against both cell lines. The IC50 values from the cells were also determined. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. A diversity-oriented synthesis strategy enabling the combinatorial-type variation of macrocyclic peptidomimetic scaffolds.

    Science.gov (United States)

    Isidro-Llobet, Albert; Hadje Georgiou, Kathy; Galloway, Warren R J D; Giacomini, Elisa; Hansen, Mette R; Méndez-Abt, Gabriela; Tan, Yaw Sing; Carro, Laura; Sore, Hannah F; Spring, David R

    2015-04-21

    Macrocyclic peptidomimetics are associated with a broad range of biological activities. However, despite such potentially valuable properties, the macrocyclic peptidomimetic structural class is generally considered as being poorly explored within drug discovery. This has been attributed to the lack of general methods for producing collections of macrocyclic peptidomimetics with high levels of structural, and thus shape, diversity. In particular, there is a lack of scaffold diversity in current macrocyclic peptidomimetic libraries; indeed, the efficient construction of diverse molecular scaffolds presents a formidable general challenge to the synthetic chemist. Herein we describe a new, advanced strategy for the diversity-oriented synthesis (DOS) of macrocyclic peptidomimetics that enables the combinatorial variation of molecular scaffolds (core macrocyclic ring architectures). The generality and robustness of this DOS strategy is demonstrated by the step-efficient synthesis of a structurally diverse library of over 200 macrocyclic peptidomimetic compounds, each based around a distinct molecular scaffold and isolated in milligram quantities, from readily available building-blocks. To the best of our knowledge this represents an unprecedented level of scaffold diversity in a synthetically derived library of macrocyclic peptidomimetics. Cheminformatic analysis indicated that the library compounds access regions of chemical space that are distinct from those addressed by top-selling brand-name drugs and macrocyclic natural products, illustrating the value of our DOS approach to sample regions of chemical space underexploited in current drug discovery efforts. An analysis of three-dimensional molecular shapes illustrated that the DOS library has a relatively high level of shape diversity.

  17. Accurate and Reliable Prediction of the Binding Affinities of Macrocycles to Their Protein Targets.

    Science.gov (United States)

    Yu, Haoyu S; Deng, Yuqing; Wu, Yujie; Sindhikara, Dan; Rask, Amy R; Kimura, Takayuki; Abel, Robert; Wang, Lingle

    2017-12-12

    Macrocycles have been emerging as a very important drug class in the past few decades largely due to their expanded chemical diversity benefiting from advances in synthetic methods. Macrocyclization has been recognized as an effective way to restrict the conformational space of acyclic small molecule inhibitors with the hope of improving potency, selectivity, and metabolic stability. Because of their relatively larger size as compared to typical small molecule drugs and the complexity of the structures, efficient sampling of the accessible macrocycle conformational space and accurate prediction of their binding affinities to their target protein receptors poses a great challenge of central importance in computational macrocycle drug design. In this article, we present a novel method for relative binding free energy calculations between macrocycles with different ring sizes and between the macrocycles and their corresponding acyclic counterparts. We have applied the method to seven pharmaceutically interesting data sets taken from recent drug discovery projects including 33 macrocyclic ligands covering a diverse chemical space. The predicted binding free energies are in good agreement with experimental data with an overall root-mean-square error (RMSE) of 0.94 kcal/mol. This is to our knowledge the first time where the free energy of the macrocyclization of linear molecules has been directly calculated with rigorous physics-based free energy calculation methods, and we anticipate the outstanding accuracy demonstrated here across a broad range of target classes may have significant implications for macrocycle drug discovery.

  18. Macrocyclic ligands for uranium complexation: Progress report, August 15, 1987-present

    International Nuclear Information System (INIS)

    Potts, K.T.

    1988-03-01

    The synthesis of several macrocyclic ligands, designed by a computer modeling approach for the complexation of the uranyl ion, has now been completed and their structures established. Preliminary indicate that these macrocycles successfully complex the uranyl ion. Other synthetic efforts have led to a variety of intermediates suitable for final ring closure to the desired macrocycles, providing appreciable potential for variation of the macrocyclic peripheral atoms. A 1:1-uranyl ion complex of one of these precursor products has been shown to undergo a DMSO-induced rearrangement to a 2:1 uranyl ion to ligand complex, both structures having been established by single crystal x-ray data. 10 refs

  19. Motion of charged particles in a knotted electromagnetic field

    International Nuclear Information System (INIS)

    Arrayas, M; Trueba, J L

    2010-01-01

    In this paper we consider the classical relativistic motion of charged particles in a knotted electromagnetic field. After reviewing how to construct electromagnetic knots from maps between the three-sphere and the two-sphere, we introduce a mean quadratic radius of the energy density distribution in order to study some properties of this field. We study the classical relativistic motion of electrons in the electromagnetic field of the Hopf map, and compute their trajectories. It is observed that these electrons initially at rest are strongly accelerated by the electromagnetic force, becoming ultrarelativistic in a period of time that depends on the knot energy and size.

  20. Motion of charged particles in a knotted electromagnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Arrayas, M; Trueba, J L, E-mail: joseluis.trueba@urjc.e [Area de Electromagnetismo, Universidad Rey Juan Carlos, Camino del Molino s/n, 28943 Fuenlabrada, Madrid (Spain)

    2010-06-11

    In this paper we consider the classical relativistic motion of charged particles in a knotted electromagnetic field. After reviewing how to construct electromagnetic knots from maps between the three-sphere and the two-sphere, we introduce a mean quadratic radius of the energy density distribution in order to study some properties of this field. We study the classical relativistic motion of electrons in the electromagnetic field of the Hopf map, and compute their trajectories. It is observed that these electrons initially at rest are strongly accelerated by the electromagnetic force, becoming ultrarelativistic in a period of time that depends on the knot energy and size.

  1. Pinus pinaster Knot: A Source of Polyphenols against Plasmopara viticola.

    Science.gov (United States)

    Gabaston, Julien; Richard, Tristan; Cluzet, Stéphanie; Palos Pinto, Antonio; Dufour, Marie-Cécile; Corio-Costet, Marie-France; Mérillon, Jean-Michel

    2017-10-11

    Pine knot extract from Pinus pinaster byproducts was characterized by UHPLC-DAD-MS and NMR. Fourteen polyphenols divided into four classes were identified as follows: lignans (nortrachelogenin, pinoresinol, matairesinol, isolariciresinol, secoisolariciresinol), flavonoids (pinocembrin, pinobanksin, dihydrokaempferol, taxifolin), stilbenes (pinosylvin, pinosylvin monomethyl ether, pterostilbene), and phenolic acids (caffeic acid, ferulic acid). The antifungal potential of pine knot extract, as well as the main compounds, was tested in vitro against Plasmopara viticola. The ethanolic extract showed a strong antimildew activity. In addition, pinosylvins and pinocembrin demonstrated significant inhibition of zoospore mobility and mildew development. These findings strongly suggest that pine knot is a potential biomass that could be used as a natural antifungal product.

  2. Teaching and Learning of Knot Theory in School Mathematics

    CERN Document Server

    Kawauchi, Akio

    2012-01-01

    This book is the result of a joint venture between Professor Akio Kawauchi, Osaka City University, well-known for his research in knot theory, and the Osaka study group of mathematics education, founded by Professor Hirokazu Okamori and now chaired by his successor Professor Tomoko Yanagimoto, Osaka Kyoiku University. The seven chapters address the teaching and learning of knot theory from several perspectives. Readers will find an extremely clear and concise introduction to the fundamentals of knot theory, an overview of curricular developments in Japan, and in particular a series of teaching

  3. Quandles an introduction to the algebra of knots

    CERN Document Server

    Elhamdadi, Mohamed

    2015-01-01

    From prehistory to the present, knots have been used for purposes both artistic and practical. The modern science of Knot Theory has ramifications for biochemistry and mathematical physics and is a rich source of research projects for undergraduate and graduate students and professionals alike. Quandles are essentially knots translated into algebra. This book provides an accessible introduction to quandle theory for readers with a background in linear algebra. Important concepts from topology and abstract algebra motivated by quandle theory are introduced along the way. With elementary self-co

  4. Searching for a path towards a helicene-based macrocycle

    Czech Academy of Sciences Publication Activity Database

    Houska, Václav; Stará, Irena G.; Starý, Ivo

    2017-01-01

    Roč. 15, č. 1 (2017), s. 9-10 ISSN 2336-7202. [Mezioborové setkání mladých biologů, biochemiků a chemiků /17./. 30.05.2017-01.06.2017, Milovy] R&D Projects: GA ČR(CZ) GA16-08294S Institutional support: RVO:61388963 Keywords : helicenes * macrocycles Subject RIV: CC - Organic Chemistry

  5. Effects of knot type in the folding of topologically complex lattice proteins

    Science.gov (United States)

    Soler, Miguel A.; Nunes, Ana; Faísca, Patrícia F. N.

    2014-07-01

    The folding properties of a protein whose native structure contains a 52 knot are investigated by means of extensive Monte Carlo simulations of a simple lattice model and compared with those of a 31 knot. A 52 knot embedded in the native structure enhances the kinetic stability of the carrier lattice protein in a way that is clearly more pronounced than in the case of the 31 knot. However, this happens at the expense of a severe loss in folding efficiency, an observation that is consistent with the relative abundance of 31 and 52 knots in the Protein Data Bank. The folding mechanism of the 52 knot shares with that of the 31 knot the occurrence of a threading movement of the chain terminus that lays closer to the knotted core. However, co-concomitant knotting and folding in the 52 knot occurs with negligible probability, in sharp contrast to what is observed for the 31 knot. The study of several single point mutations highlights the importance in the folding of knotted proteins of the so-called structural mutations (i.e., energetic perturbations of native interactions between residues that are critical for knotting but not for folding). On the other hand, the present study predicts that mutations that perturb the folding transition state may significantly enhance the kinetic stability of knotted proteins provided they involve residues located within the knotted core.

  6. evaluation of tomato genotypes for resistance to root-knot

    African Journals Online (AJOL)

    Prof. Adipala Ekwamu

    Tomato production in Ghana is threatened by plant parasitic nematodes, especially the root knot ... to be highly resistant to Meloidogyne spp. and also recorded the lowest reproductive factors of 0.71 and 0.53, respectively. ..... VII International.

  7. Knot theory and a physical state of quantum gravity

    International Nuclear Information System (INIS)

    Liko, Tomas; Kauffman, Louis H

    2006-01-01

    We discuss the theory of knots, and describe how knot invariants arise naturally in gravitational physics. The focus of this review is to delineate the relationship between knot theory and the loop representation of non-perturbative canonical quantum general relativity (loop quantum gravity). This leads naturally to a discussion of the Kodama wavefunction, a state which is conjectured to be the ground state of the gravitational field with positive cosmological constant. This review can serve as a self-contained introduction to loop quantum gravity and related areas. Our intent is to make the paper accessible to a wider audience that may include topologists, knot theorists, and other persons innocent of the physical background to this approach to quantum gravity. (topical review)

  8. Integrated management of root-knot nematode (Meloidogyne ...

    African Journals Online (AJOL)

    Integrated management of root-knot nematode (Meloidogyne incognita) for tomato production and productivity. Bayuh Belay1* ... important food and cash crop of the farmers and is ...... some part of the research budget without any reservation.

  9. Knots, splices and rope-work an illustrated handbook

    CERN Document Server

    Verrill, A Hyatt

    2006-01-01

    This treasury of practical and ornamental knots ranges from easy half-hitches and bow-lines to intricate rope-work projects, such as rope buckles and cask slings. Detailed instructions accompany the 148 drawings.

  10. Khovanov homology for virtual knots with arbitrary coefficients

    International Nuclear Information System (INIS)

    Manturov, Vassily O

    2007-01-01

    The Khovanov homology theory over an arbitrary coefficient ring is extended to the case of virtual knots. We introduce a complex which is well-defined in the virtual case and is homotopy equivalent to the original Khovanov complex in the classical case. Unlike Khovanov's original construction, our definition of the complex does not use any additional prescription of signs to the edges of a cube. Moreover, our method enables us to construct a Khovanov homology theory for 'twisted virtual knots' in the sense of Bourgoin and Viro (including knots in three-dimensional projective space). We generalize a number of results of Khovanov homology theory (the Wehrli complex, minimality problems, Frobenius extensions) to virtual knots with non-orientable atoms

  11. Appendicular knot causing closed-loop obstruction, volvulus and ...

    African Journals Online (AJOL)

    Keywords: appendix, appendicular tie/knot syndrome, intestinal obstruction, volvulus, strangulation .... possible contrast reaction and high cost) and its unavailability in some ... morbidity and mortality rise significantly with delay. In. Fevang's ...

  12. Topological effects on the mechanical properties of polymer knots

    Science.gov (United States)

    Zhao, Yani; Ferrari, Franco

    2017-11-01

    The mechanical properties of knotted polymer rings under stretching in a bad or good solvent are investigated by applying a force F to a point of the knot while keeping another point fixed. The Monte Carlo sampling of the polymer conformations is performed on a simple cubic lattice using the Wang-Landau algorithm. The specific energy, specific heat capacity, gyration radius and the force-elongation curves are computed for several knot topologies with lengths up to 120 lattice units. The common features of the mechanical and thermal behavior of stretched short polymer rings forming knots of a given topological type are analyzed as well as the differences arising due to topology and size effects. It is found that these systems admit three different phases depending on the values of the tensile force F and the temperature T. The transitions from one phase to the other are well characterized by the peaks of the specific heat capacity and by the data of the gyration radius and specific energy. At very low temperatures the force-elongation curves show that the stretching of a knot is a stepwise process, which becomes smooth at higher temperatures. Criteria for distinguishing topological and size effects are provided. It turns out from our study that the behavior of short polymer rings is strongly influenced by topological effects. In particular, the swelling and the swelling rate of knots are severely limited by the topological constraints. Several other properties that are affected by topology, like the decay of the specific energy at high tensile forces, are discussed. The fading out of the influences of topological origin with increasing knot lengths has been verified. Some anomalies detected in the plots of the specific heat capacity of very short and complex knots have been explained by the limitations in the number of accessible energy states due to the topological constraints.

  13. Hybrid Threat Center of Gravity Analysis: Cutting the Gordian Knot

    Science.gov (United States)

    2016-04-04

    19b. TELEPHONE NUMBER (Include area code) 04/04/2016 Master’s Thesis 22-7-2015 to 04-04-2016 HYBRID THREAT CENTER OF GRAVITY ANALYSIS: CUTTING THE...CENTER OF GRAVITY ANALYSIS: CUTTING THE GORDIAN KNOT By Michael D. Reilly LtCol, USMC Intentionally left blank...HYBRID THREAT CENTER OF GRAVITY ANALYSIS: CUTTING THE GORDIAN KNOT By Michael D. Reilly LtCol, USMC A paper submitted to the Faculty of the Joint Advanced

  14. Knack knots you need step-by-step instructions for more than 100 of the best sailing, fishing, climbing, camping and decorative knots

    CERN Document Server

    Tilton, Buck

    2008-01-01

    Untie the mystery of knot-making with this clever and handy guide. This new compendium presents all the knots you need to know, with brightly colored photographs enabling you to easily follow the instructions. In addition, the book includes copious information on using knots in most popular activities. With its clear step-by-step instructions and friendly tone, this is the one volume you can count on to guide you toward quick success in knot-making.

  15. Probe Knots and Hopf Insulators with Ultracold Atoms

    Science.gov (United States)

    Deng, Dong-Ling; Wang, Sheng-Tao; Sun, Kai; Duan, L.-M.

    2018-01-01

    Knots and links are fascinating and intricate topological objects. Their influence spans from DNA and molecular chemistry to vortices in superfluid helium, defects in liquid crystals and cosmic strings in the early universe. Here we find that knotted structures also exist in a peculiar class of three-dimensional topological insulators—the Hopf insulators. In particular, we demonstrate that the momentum-space spin textures of Hopf insulators are twisted in a nontrivial way, which implies the presence of various knot and link structures. We further illustrate that the knots and nontrivial spin textures can be probed via standard time-of-flight images in cold atoms as preimage contours of spin orientations in stereographic coordinates. The extracted Hopf invariants, knots, and links are validated to be robust to typical experimental imperfections. Our work establishes the existence of knotted structures in Hopf insulators, which may have potential applications in spintronics and quantum information processing. D.L.D., S.T.W. and L.M.D. are supported by the ARL, the IARPA LogiQ program, and the AFOSR MURI program, and supported by Tsinghua University for their visits. K.S. acknowledges the support from NSF under Grant No. PHY1402971. D.L.D. is also supported by JQI-NSF-PFC and LPS-MPO-CMTC at the final stage of this paper.

  16. Energy, ropelength, and other physical aspects of equilateral knots

    International Nuclear Information System (INIS)

    Millett, Kenneth C.; Rawdon, Eric J.

    2003-01-01

    Closed macromolecular chains may form physically knotted conformations whose relative occurrence and spatial measurements provide insight into their properties and the mechanisms acting upon them. Under the assumption of a degree of structural homogeneity, equilateral spatial polygons are a productive context within which to create mathematical models of these knots and to study their mathematical and physical properties. The ensembles, or spaces, of these knots are models of the settings within which the knots evolve in ways determined by a physical model. In this paper we describe the mathematical foundation of such models as well as such spatial, geometric, statistical, and physical properties of the configurations as mathematical energies, thickness and ropelength, average crossing number, average writhe, and volumes and surfaces areas of standard bodies enclosing the knots. We present methods with which the energy and ropelength are optimized within the families of spatially equivalent equilateral configurations. Numerical results from our implementation of these methods are shown to illustrate connections between the physical measurements and spatial characteristics of the optimized knot configurations. In addition, these data suggest potentially new connections involving their spatial properties

  17. Knots Untie: Molecular Determinants Involved in Knot Formation Induced by Pseudomonas savastanoi in Woody Hosts

    Directory of Open Access Journals (Sweden)

    Eloy Caballo-Ponce

    2017-06-01

    Full Text Available The study of the molecular basis of tree diseases is lately receiving a renewed attention, especially with the emerging perception that pathogens require specific pathogenicity and virulence factors to successfully colonize woody hosts. Pathosystems involving woody plants are notoriously difficult to study, although the use of model bacterial strains together with genetically homogeneous micropropagated plant material is providing a significant impetus to our understanding of the molecular determinants leading to disease. The gammaproteobacterium Pseudomonas savastanoi belongs to the intensively studied Pseudomonas syringae complex, and includes three pathogenic lineages causing tumorous overgrowths (knots in diverse economically relevant trees and shrubs. As it occurs with many other bacteria, pathogenicity of P. savastanoi is dependent on a type III secretion system, which is accompanied by a core set of at least 20 effector genes shared among strains isolated from olive, oleander, and ash. The induction of knots of wild-type size requires that the pathogen maintains adequate levels of diverse metabolites, including the phytohormones indole-3-acetic acid and cytokinins, as well as cyclic-di-GMP, some of which can also regulate the expression of other pathogenicity and virulence genes and participate in bacterial competitiveness. In a remarkable example of social networking, quorum sensing molecules allow for the communication among P. savastanoi and other members of the knot microbiome, while at the same time are essential for tumor formation. Additionally, a distinguishing feature of bacteria from the P. syringae complex isolated from woody organs is the possession of a 15 kb genomic island (WHOP carrying four operons and three other genes involved in degradation of phenolic compounds. Two of these operons mediate the catabolism of anthranilate and catechol and, together with another operon, are required for the induction of full-size tumors

  18. A strategy for the diversity-oriented synthesis of macrocyclic scaffolds using multidimensional coupling

    DEFF Research Database (Denmark)

    Beckmann, Henning S G; Nie, Feilin; Hagerman, Caroline E

    2013-01-01

    the coupling reaction. We applied this step-efficient approach in a DOS of a library that consisted of 73 macrocyclic compounds based around 59 discrete scaffolds. The macrocycles prepared cover a broad range of different molecular shapes, as illustrated by principal moment-of-inertia analysis...

  19. Role of Bending Energy and Knot Chirality in Knot Distribution and Their Effective Interaction along Stretched Semiflexible Polymers

    Directory of Open Access Journals (Sweden)

    Saeed Najafi

    2016-09-01

    Full Text Available Knots appear frequently in semiflexible (biopolymers, including double-stranded DNA, and their presence can affect the polymer’s physical and functional properties. In particular, it is possible and indeed often the case that multiple knots appear on a single chain, with effects which have only come under scrutiny in the last few years. In this manuscript, we study the interaction of two knots on a stretched semiflexible polymer, expanding some recent results on the topic. Specifically, we consider an idealization of a typical optical tweezers experiment and show how the bending rigidity of the chain—And consequently its persistence length—Influences the distribution of the entanglements; possibly more importantly, we observe and report how the relative chirality of the otherwise identical knots substantially modifies their interaction. We analyze the free energy of the chain and extract the effective interactions between embedded knots, rationalizing some of their pertinent features by means of simple effective models. We believe the salient aspect of the knot–knot interactions emerging from our study will be present in a large number of semiflexible polymers under tension, with important consequences for the characterization and manipulation of these systems—Be they artificial or biologica in origin—And for their technological application.

  20. Knots, topology and quantum field theories

    International Nuclear Information System (INIS)

    Lusanna, L.

    1989-01-01

    The title of the workshop, Knots, Topology and Quantum Field Theory, accurate reflected the topics discussed. There have been important developments in mathematical and quantum field theory in the past few years, which had a large impact on physicist thinking. It is historically unusual and pleasing that these developments are taking place as a result of an intense interaction between mathematical physicists and mathematician. On the one hand, topological concepts and methods are playing an increasingly important lead to novel mathematical concepts: for instance, the study of quantum groups open a new chapter in the deformation theory of Lie algebras. These developments at present will lead to new insights into the theory of elementary particles and their interactions. In essence, the talks dealt with three, broadly defined areas of theoretical physics. One was topological quantum field theories, the other the problem of quantum groups and the third one certain aspects of more traditional field theories, such as, for instance, quantum gravity. These topics, however, are interrelated and the general theme of the workshop defies rigid classification; this was evident from the cross references to be found in almo all the talks

  1. Type IIB Ileosigmoid knotting: a case report

    Directory of Open Access Journals (Sweden)

    Ajak Makor

    2018-02-01

    Full Text Available Ileosigmoid knotting is a rare cause of acute intestinal obstruction. It is more common in Africans and Asians than in white populations and it is more prevalent in males than in females with a ratio of 14:1. It is classified into four types (I, II, III and IV with further extra two subtypes of A and B where type A is the most common presentation. Preoperative diagnosis is a challenge to the frontline doctors in the accidents and emergency departments; especially with limited diagnostic tools. Ultrasonography may be misleading in most of the cases due to the similarity of the disease with other causes of acute abdomen, especially acute appendicitis. Clinical presentation of an unprecedented intestinal obstruction with constant upper to mid-abdominal quadrant pain associated with mild to moderate abdominal distension contrary to the severe abdominal distension in sigmoid volvulus are the hallmarks that can help the surgical team to reach an accurate and early diagnosis preoperatively to avoid the devastating ischemia and gangrene in case of delay.

  2. Toward understanding macrocycle specificity of iron on the dioxygen-binding ability: a theoretical study.

    Science.gov (United States)

    Sun, Yong; Chen, Kexian; Jia, Lu; Li, Haoran

    2011-08-14

    In an effort to examine the interaction between dioxygen and iron-macrocyclic complexes, and to understand how this interaction was affected by those different macrocyclic ligands, dioxygen binding with iron-porphyrin, iron-phthalocyanine, iron-dibenzotetraaza[14]annulene, and iron-salen complexes is investigated by means of quantum chemical calculations utilizing Density Functional Theory (DFT). Based on the analysis of factors influencing the corresponding dioxygen binding process, it showed that different macrocyclic ligands possess different O-O bond distances, and different electronic configurations for the bound O(2) and non-aromatic macrocyclic ligands favor dioxygen activation. Furthermore, the smaller the energy gap between the HOMO of iron-macrocyclic complexes and the LUMO of dioxygen, the more active the bound O(2) becomes, with a longer O-O bond distance and a shorter Fe-O bond length.

  3. STABILIZATION OF UNUSUAL SUBSTRATE COORDINATION MODES IN DINUCLEAR MACROCYCLIC COMPLEXES

    Directory of Open Access Journals (Sweden)

    Vasile Lozan

    2010-06-01

    Full Text Available The steric protection offered by the macrobinucleating hexaazaditiophenolate ligand (L allows for the preparation of the first stable dinuclear nickel(II borohydride bridged complex, which reacts rapidly with elemental sulphur producing a tetranuclear nickel(II complex [{(LNi2}2(μ-S6]2+ bearing a helical μ4-hexa- sulfide ligand. The [(LCoII 2]2+ fragment have been able to trap a monomethyl orthomolybdate in the binding pocket. Unusual coordination modes of substrate in dinuclear macrocyclic compounds was demonstrated.

  4. Macrocyclic extractants for separating Am(III)/Ln(III)

    International Nuclear Information System (INIS)

    Ludwig, R.; Nguyen, T.K.D.; Kunogi, K.; Tachimori, Shoichi

    1999-01-01

    The extraction of trivalent f-elements by calix(n)arene-type macrocyclic ligands increases in the order n=4, 8, 6 corresponding to the balance between cavity size, molecular flexibility, and number of donor atoms. Introduction of mixed functionalities into calix(6)arenes, e.g. carboxylic acid and amide groups, results in better extractability of actinides compared with lanthanides. For calix(4)arenes, such a different extractability could not be observed. Furthermore, the effects of solvent composition with respect to a modifier and of the aqueous phase composition were investigated. (author)

  5. Natural and Synthetic Macrocyclic Inhibitors of the Histone Deacetylase Enzymes

    DEFF Research Database (Denmark)

    Maolanon, Alex; Kristensen, Helle; Leman, Luke

    2017-01-01

    Inhibition of histone deacetylase (HDAC) enzymes has emerged as a target for development of cancer chemotherapy. Four compounds have gained approval for clinical use by the Food and Drug Administration (FDA) in the US, and several are currently in clinical trials. However, none of these compounds...... HDAC enzymes may hold an advantage over traditional hydroxamic acid-containing inhibitors, which rely on chelation to the conserved active site zinc ion. Here, we review the literature on macrocyclic HDAC inhibitors obtained from natural sources and structure-activity relationship studies inspired...

  6. Using Gas-Phase Guest-Host Chemistry to Probe the Structures of b Ions of Peptides

    Science.gov (United States)

    Somogyi, Árpád; Harrison, Alex G.; Paizs, Béla

    2012-12-01

    Middle-sized b n ( n ≥ 5) fragments of protonated peptides undergo selective complex formation with ammonia under experimental conditions typically used to probe hydrogen-deuterium exchange in Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Other usual peptide fragments like y, a, a*, etc., and small b n ( n ≤ 4) fragments do not form stable ammonia adducts. We propose that complex formation of b n ions with ammonia is characteristic to macrocyclic isomers of these fragments. Experiments on a protonated cyclic peptide and N-terminal acetylated peptides fully support this hypothesis; the protonated cyclic peptide does form ammonia adducts while linear b n ions of acetylated peptides do not undergo complexation. Density functional theory (DFT) calculations on the proton-bound dimers of all-Ala b 4 , b 5 , and b 7 ions and ammonia indicate that the ionizing proton initially located on the peptide fragment transfers to ammonia upon adduct formation. The ammonium ion is then solvated by N+-H…O H-bonds; this stabilization is much stronger for macrocyclic b n isomers due to the stable cage-like structure formed and entropy effects. The present study demonstrates that gas-phase guest-host chemistry can be used to selectively probe structural features (i.e., macrocyclic or linear) of fragments of protonated peptides. Stable ammonia adducts of b 9 , b 9 -A, and b 9 -2A of A8YA, and b 13 of A20YVFL are observed indicating that even these large b-type ions form macrocyclic structures.

  7. Macrocyclic ligands and their use in chemical separations

    International Nuclear Information System (INIS)

    Izatt, R.M.; Bradshaw, J.S.; Bruening, R.L.; Krakowiak, K.E.; Tarbet, B.J.

    1993-01-01

    Macrocyclic chemistry has had a phenomenal growth curve during the past three decades (Izatt et al.). Interest in this field was catalyzed by Pedersen's report of the synthesis and partial characterization of a large number of novel cyclic polyethers. The unusual affinity of these new compounds for and selectivity among alkali metal cations was noted (Pedersen) and quantitated (Izatt et al.). A 1987 National Academy of Science publication on separations listed three high priority needs in the separations field (King). These were to develop highly selective reagents capable of discriminating among similar chemical species, reagents capable of concentrating trace amounts of solutes even in the presence of large excesses of matrix solutes, and reagents capable of removing solutes from large quantities of solvent. Certain macrocycles offer the promise of being successful in achieving all three of these goals. This promise arises from their high selectivity for particular cations in various series of closely related cations, their large affinities for particular cations, and the ease with which they can be modified to meet particular needs inherent to chemical separations

  8. Solar Thermal Energy Storage in a Photochromic Macrocycle.

    Science.gov (United States)

    Vlasceanu, Alexandru; Broman, Søren L; Hansen, Anne S; Skov, Anders B; Cacciarini, Martina; Kadziola, Anders; Kjaergaard, Henrik G; Mikkelsen, Kurt V; Nielsen, Mogens Brøndsted

    2016-07-25

    The conversion and efficient storage of solar energy is recognized to hold significant potential with regard to future energy solutions. Molecular solar thermal batteries based on photochromic systems exemplify one possible technology able to harness and apply this potential. Herein is described the synthesis of a macrocycle based on a dimer of the dihydroazulene/vinylheptafulvene (DHA/VHF) photo/thermal couple. By taking advantage of conformational strain, this DHA-DHA macrocycle presents an improved ability to absorb and store incident light energy in chemical bonds (VHF-VHF). A stepwise energy release over two sequential ring-closing reactions (VHF→DHA) combines the advantages of an initially fast discharge, hypothetically addressing immediate energy consumption needs, followed by a slow process for consistent, long-term use. This exemplifies another step forward in the molecular engineering and design of functional organic materials towards solar thermal energy storage and release. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Novel macrocyclic carriers for proton-coupled liquid membrane transport. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Lamb, J.D.; Izatt, R.M.; Bradshaw, J.S.; Shirts, R.B.

    1996-08-24

    The objective of this research program is to elucidate the chemical principles which are responsible for the cation selectivity and permeability of liquid membranes containing macrocyclic carriers. Several new macrocyclic carriers were synthesized during the last three year period. In addition, new, more convenient synthetic routes were achieved for several nitrogen-containing bicyclic and tricyclic macrocycles. The cation binding properties of these macrocycles were investigated by potentiometric titration, calorimetric titration, solvent extraction and NMR techniques. In addition, hydrophobic macrocycles were incorporated into dual hollow fiber and other membrane systems to investigate their membrane performance, especially in the proton-coupled transport mode. A study of the effect of methoxyalkyl macrocycle substituents on metal ion transport was completed. A new calorimeter was constructed which made it possible to study the thermodynamics of macrocycle-cation binding to very high temperatures. Measurements of thermodynamic data for the interaction of crown ethers with alkali and alkaline earth cations were achieved to 473 K. Molecular modeling work was begun for the first time on this project and fundamental principles were identified and developed for the establishment of working models in the future.

  10. Sectional meeting on Numerical Methods, Calculations and Simulations in Knot Theory and its Applications

    CERN Document Server

    Millett, Kenneth C; Rawdon, Eric J; Stasiak, Andrzej; Physical and Numerical Models in Knot theory: including Applications to the Life Sciences; Conference on Knots, Random Walks and Biomolecules

    2005-01-01

    The physical properties of knotted and linked configurations in space have long been of interest to mathematicians. More recently, these properties have become significant to biologists, physicists, and engineers among others. Their depth of importance and breadth of application are now widely appreciated and valuable progress continues to be made each year. This volume presents several contributions from researchers using computers to study problems that would otherwise be intractable. While computations have long been used to analyze problems, formulate conjectures, and search for special structures in knot theory, increased computational power has made them a staple in many facets of the field. The volume also includes contributions concentrating on models researchers use to understand knotting, linking, and entanglement in physical and biological systems. Topics include properties of knot invariants, knot tabulation, studies of hyperbolic structures, knot energies, the exploration of spaces of knots, knot...

  11. Classification of knotted tori in 2-metastable dimension

    KAUST Repository

    Cencelj, Matija

    2012-11-30

    This paper is devoted to the classical Knotting Problem: for a given manifold N and number m describe the set of isotopy classes of embeddings N → Sm. We study the specific case of knotted tori, that is, the embeddings Sp × Sq → Sm. The classification of knotted tori up to isotopy in the metastable dimension range m > p + 3 2 q + 2, p 6 q, was given by Haefliger, Zeeman and A. Skopenkov. We consider the dimensions below the metastable range and give an explicit criterion for the finiteness of this set of isotopy classes in the 2-metastable dimension: Theorem. Assume that p+ 4 3 q +2 < mp+ 3 2 q +2 and m > 2p+q +2. Then the set of isotopy classes of smooth embeddings Sp × Sq → Sm is infinite if and only if either q + 1 or p + q + 1 is divisible by 4. © 2012 RAS(DoM) and LMS.

  12. Classification of knotted tori in 2-metastable dimension

    KAUST Repository

    Cencelj, Matija; Repovš, Dušan; Skopenkov, Mikhail

    2012-01-01

    This paper is devoted to the classical Knotting Problem: for a given manifold N and number m describe the set of isotopy classes of embeddings N → Sm. We study the specific case of knotted tori, that is, the embeddings Sp × Sq → Sm. The classification of knotted tori up to isotopy in the metastable dimension range m > p + 3 2 q + 2, p 6 q, was given by Haefliger, Zeeman and A. Skopenkov. We consider the dimensions below the metastable range and give an explicit criterion for the finiteness of this set of isotopy classes in the 2-metastable dimension: Theorem. Assume that p+ 4 3 q +2 < mp+ 3 2 q +2 and m > 2p+q +2. Then the set of isotopy classes of smooth embeddings Sp × Sq → Sm is infinite if and only if either q + 1 or p + q + 1 is divisible by 4. © 2012 RAS(DoM) and LMS.

  13. Knots and Random Walks in Vibrated Granular Chains

    International Nuclear Information System (INIS)

    Ben-Naim, E.; Daya, Z. A.; Vorobieff, P.; Ecke, R. E.

    2001-01-01

    We study experimentally statistical properties of the opening times of knots in vertically vibrated granular chains. Our measurements are in good qualitative and quantitative agreement with a theoretical model involving three random walks interacting via hard-core exclusion in one spatial dimension. In particular, the knot survival probability follows a universal scaling function which is independent of the chain length, with a corresponding diffusive characteristic time scale. Both the large-exit-time and the small-exit-time tails of the distribution are suppressed exponentially, and the corresponding decay coefficients are in excellent agreement with theoretical values

  14. Successful Treatment of Stent Knot in the Proximal Ureter Using Ureteroscopy and Holmium Laser

    Directory of Open Access Journals (Sweden)

    Masters M. Richards

    2011-01-01

    Full Text Available Knotted ureteral stent is rare yet tedious complication that might represent a treatment challenge to the endourologist. Only twelve cases of knotted stent have been reported. Different management options have been reported, including simple traction, ureteroscopy, percutaneous removal, and open surgery. In this paper, we present the successful untying of the knot using ureteroscopy with holmium laser.

  15. Physical Removal of Anions from Aqueous Media by Means of a Macrocycle-Containing Polymeric Network

    KAUST Repository

    Ji, Xiaofan; Wu, Ren-Tsung; Long, Lingliang; Guo, Chenxing; Khashab, Niveen M.; Huang, Feihe; Sessler, Jonathan L.

    2018-01-01

    Reported here is a hydrogel-forming polymer network that contains a water-soluble tetracationic macrocycle. Upon immersion of this polymer network in aqueous solutions containing various inorganic and organic salts, changes in the physical

  16. Versatile Multicomponent Reaction Macrocycle Synthesis Using α-Isocyano-ω-carboxylic Acids

    NARCIS (Netherlands)

    Liao, George P; Abdelraheem, Eman M M; Neochoritis, Constantinos G; Kurpiewska, Katarzyna; Kalinowska-Tłuścik, Justyna; McGowan, David C; Dömling, Alexander

    2015-01-01

    The direct macrocycle synthesis of α-isocyano-ω-carboxylic acids via an Ugi multicomponent reaction is introduced. This multicomponent reaction (MCR) protocol differs by being especially short, convergent, and versatile, giving access to 12-22 membered rings.

  17. Towards tumour targeting with copper-radiolabelled macrocycle-antibody conjugates

    International Nuclear Information System (INIS)

    Morphy, J.R.; Parker, David; Kataky, Ritu

    1989-01-01

    Tetraaza-macrocycles covalently attached to a monoclonal antibody may be efficiently radiolabelled with 64 Cu or 67 Cu at pH4, minimising non-specific binding to the protein, giving a kinetically stable conjugate in vivo. (author)

  18. Complexation of the strontium cation with a macrocyclic lactam receptor: Experimental and theoretical study

    Czech Academy of Sciences Publication Activity Database

    Makrlík, E.; Záliš, Stanislav; Vaňura, P.

    2016-01-01

    Roč. 214, FEB 2016 (2016), s. 171-174 ISSN 0167-7322 Institutional support: RVO:61388955 Keywords : strontium cation * macrocyclic lactam receptor Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.648, year: 2016

  19. True Umbilical Cord Knot Leading to Fetal Demise

    African Journals Online (AJOL)

    weight was 140 kg, height 1.69 m, blood pressure 120 mmHg. The booking ... The fetal heart tones were monitored using Doppler sonicaid. They remained normal throughout .... true knot, seemingly because the umbilical cord vessels can be compressed ... Therefore, the Wharton's jelly surrounding the fetal vessels has the ...

  20. The multivariable Alexander polynomial and modern knot theory

    International Nuclear Information System (INIS)

    Saleur, H.; Yale Univ., New Haven, CT

    1991-01-01

    This note is a summary of several recent works (by the author and collaborators) that study the Conway Alexander link invariant in the light of quantum groups and topological quantum field theories. Their purpose is to understand connections between ''modern'' knot theory and more classical topological concepts. (author)

  1. The multivariable Alexander polynomial and modern knot theory

    International Nuclear Information System (INIS)

    Saleur, H.

    1992-01-01

    This paper is a summary of several recent works (by the author and collaborators) that study the Conway-Alexander link invariant in the light of quantum groups and topological quantum field theories. Their purpose is to understand connections between modern knot theory and more classical topological concepts

  2. The unique cysteine knot regulates the pleotropic hormone leptin.

    Directory of Open Access Journals (Sweden)

    Ellinor Haglund

    Full Text Available Leptin plays a key role in regulating energy intake/expenditure, metabolism and hypertension. It folds into a four-helix bundle that binds to the extracellular receptor to initiate signaling. Our work on leptin revealed a hidden complexity in the formation of a previously un-described, cysteine-knotted topology in leptin. We hypothesized that this unique topology could offer new mechanisms in regulating the protein activity. A combination of in silico simulation and in vitro experiments was used to probe the role of the knotted topology introduced by the disulphide-bridge on leptin folding and function. Our results surprisingly show that the free energy landscape is conserved between knotted and unknotted protein, however the additional complexity added by the knot formation is structurally important. Native state analyses led to the discovery that the disulphide-bond plays an important role in receptor binding and thus mediate biological activity by local motions on distal receptor-binding sites, far removed from the disulphide-bridge. Thus, the disulphide-bridge appears to function as a point of tension that allows dissipation of stress at a distance in leptin.

  3. Spontaneous knot; a rare cause of ventriculoperitoneal shunt blockage.

    LENUS (Irish Health Repository)

    Mohammed, Wail

    2011-02-01

    A 14-year old X linked congenital hydrocephalus presented with unexplained headaches and vomiting. He had external ventricular drain and intracranial pressure monitoring (ICP). Subsequently, he underwent exploration and removal of previously inserted ventriculoperitoneal (VP) shunts. On retrieval of peritoneal catheters a double knot was noted between his two distal catheters. This case illustrates a rare cause of ventriculoperitoneal shunt malfunction.

  4. Spontaneous knot; a rare cause of ventriculoperitoneal shunt blockage.

    LENUS (Irish Health Repository)

    Mohammed, Wail

    2012-02-01

    A 14-year old X linked congenital hydrocephalus presented with unexplained headaches and vomiting. He had external ventricular drain and intracranial pressure monitoring (ICP). Subsequently, he underwent exploration and removal of previously inserted ventriculoperitoneal (VP) shunts. On retrieval of peritoneal catheters a double knot was noted between his two distal catheters. This case illustrates a rare cause of ventriculoperitoneal shunt malfunction.

  5. Braid group, knot theory and statistical mechanics II

    CERN Document Server

    Yang Chen Ning

    1994-01-01

    The present volume is an updated version of the book edited by C N Yang and M L Ge on the topics of braid groups and knot theory, which are related to statistical mechanics. This book is based on the 1989 volume but has new material included and new contributors.

  6. Prevalence, incidence and molecular identification of root-knot ...

    African Journals Online (AJOL)

    Tomato is a widely grown vegetable in Pakistan. However, its production is severely constrained by root knot nematodes (RKNs). Accurate identification of RKNs is essential for an appropriate control program. The current study evaluated the prevalence, incidence and diversity of RKNs of tomato crops grown in the Khyber ...

  7. Macrocyclic bis(ureas as ligands for anion complexation

    Directory of Open Access Journals (Sweden)

    Claudia Kretschmer

    2014-08-01

    Full Text Available Two macrocyclic bis(ureas 1 and 2, both based on diphenylurea, have been synthesized. Compound 1 represents the smaller ring with two ethynylene groups as linkers and 2 the larger ring with two butadiynylene groups. On thermal treatment to 130 °C molecule 1 splits up into two dihydroindoloquinolinone (3 molecules. Both compounds 1 and 2 form adducts with polar molecules such as dimethyl sulfoxide (DMSO and dimethylformamide (DMF and act as complexing agents towards a series of anions (Cl−, Br−, I−, NO3−, HSO4−. The crystal structures of 3, 2·2DMSO, 2·2DMF, and of the complex NEt4[Br·2] have been determined. Quantitative investigations of the complexation equilibria were performed via 1H NMR titrations. While 1 is a rather weak complexing agent, the large ring of 2 binds anions with association constants up to log K = 7.93 for chloride ions.

  8. Selective Extraction of Perrhenate and Pertechnetate by New Macrocyclic Compounds

    Energy Technology Data Exchange (ETDEWEB)

    Paviet-Hartmann, Patricia; Horkley, Jared; Wolfrom, Earle [Idaho State University/Idaho National Laboratory, 1776 Science Center Drive, Idaho Falls, ID 83402 (United States); Pak, Joshua [Idaho State University, 921 S. 8th Avenue, Pocatello, ID 83209 (United States)

    2008-07-01

    The long half-life of technetium-99 and its ability to form an anionic species makes it a major concern when considering long-term disposal of high-level radioactive waste. Furthermore, as its most stable species in the environment, the pertechnetate ion, TcO{sub 4}{sup -} is highly mobile and is considered as a long-term hazard in nuclear waste disposal. There is a need for the development of new extractant systems, such as systems based on crown ethers that may serve to selectively extract and separate this long lived radionuclide from different streams for potential industrial application. In this paper, we are reporting the design and synthesis of new macrocyclic compounds to selectively extract technetium and rhenium from complex mixtures. Preliminary tests performed for the selective extraction of pertechnetate and perrhenate are presented. (authors)

  9. On solvent extraction of metals by macrocyclic polyethers

    International Nuclear Information System (INIS)

    Ionov, V.P.

    1984-01-01

    The Ksub(γ) parameter characterizing effective ion charges in ionic associates of metal salts is suggested; these charges parallel with other factors determine the metals extraction by macrocyclic polyethers (crown-ethers). The dependence of metal extraction constant on the Ksub(γ) parameter is discussed. It is shown that the less effective cation charge of alkali metal ionic associates, the more probable its entering the crown-ether cavity. The synergetic crown-ethers extraction is bound as well with Ksub(γ) of metal salts. The differences in the cation extraction constants having the same ionic radius are explained with account of different values of Ksub(γ) parameters of these salts

  10. Selective Extraction of Perrhenate and Pertechnetate by New Macrocyclic Compounds

    International Nuclear Information System (INIS)

    Paviet-Hartmann, Patricia; Horkley, Jared; Wolfrom, Earle; Pak, Joshua

    2008-01-01

    The long half-life of technetium-99 and its ability to form an anionic species makes it a major concern when considering long-term disposal of high-level radioactive waste. Furthermore, as its most stable species in the environment, the pertechnetate ion, TcO 4 - is highly mobile and is considered as a long-term hazard in nuclear waste disposal. There is a need for the development of new extractant systems, such as systems based on crown ethers that may serve to selectively extract and separate this long lived radionuclide from different streams for potential industrial application. In this paper, we are reporting the design and synthesis of new macrocyclic compounds to selectively extract technetium and rhenium from complex mixtures. Preliminary tests performed for the selective extraction of pertechnetate and perrhenate are presented. (authors)

  11. Macrocyclic bis-thioureas catalyze stereospecific glycosylation reactions.

    Science.gov (United States)

    Park, Yongho; Harper, Kaid C; Kuhl, Nadine; Kwan, Eugene E; Liu, Richard Y; Jacobsen, Eric N

    2017-01-13

    Carbohydrates are involved in nearly all aspects of biochemistry, but their complex chemical structures present long-standing practical challenges to their synthesis. In particular, stereochemical outcomes in glycosylation reactions are highly dependent on the steric and electronic properties of coupling partners; thus, carbohydrate synthesis is not easily predictable. Here we report the discovery of a macrocyclic bis-thiourea derivative that catalyzes stereospecific invertive substitution pathways of glycosyl chlorides. The utility of the catalyst is demonstrated in the synthesis of trans-1,2-, cis-1,2-, and 2-deoxy-β-glycosides. Mechanistic studies are consistent with a cooperative mechanism in which an electrophile and a nucleophile are simultaneously activated to effect a stereospecific substitution reaction. Copyright © 2017, American Association for the Advancement of Science.

  12. Filtration of the classical knot concordance group and Casson-Gordon invariants

    OpenAIRE

    Kim, Taehee

    2002-01-01

    It is known that if any prime power branched cyclic cover of a knot in the 3-sphere is a homology sphere, then the knot has vanishing Casson-Gordon invariants. We construct infinitely many examples of (topologically) non-slice knots in the 3-sphere whose prime power branched cyclic covers are homology spheres. We show that these knots generate an infinite rank subgroup of F_(1.0)/F_(1.5) for which Casson-Gordon invariants vanish in Cochran-Orr-Teichner's filtration of the classical knot conco...

  13. Supramolecular Organocatalysis in Water Mediated by Macrocyclic Compounds

    Directory of Open Access Journals (Sweden)

    Margherita De Rosa

    2018-04-01

    Full Text Available In the last decades many efforts have been devoted to design supramolecular organocatalysts able to work in water as the reaction medium. The use of water as solvent provides promising benefits with respect to environmental impact. In this context, macrocyclic compounds played a role of primary importance thanks to their ease of synthesis and their molecular recognition abilities toward the reactants. The aim of this review is to give an overview of the recent advances in the field of supramolecular organocatalysis in water, focusing the attention on calixarene and cyclodextrins derivatives. Calixarenes and cyclodextrins, thanks to their hydrophobic cavities, are able to host selectively the substrates isolating they from the reaction environment. In addition, the synthetic versatilities of these macrocycles permits to introduce useful functional groups in close proximity of the hydrophobic binding sites. Regarding the cyclodextrins (CDs, we have here reviewed the their most recent uses as organocatalysts for the synthesis of heterocyclic compounds, in multi-component reactions and in carbon-carbon bond forming reactions. Examples have been reported in which CD catalysts are able to drive the regiochemistry of common organic reactions. In addition, cyclodextrins bearing catalytically active chiral groups, have shown excellent enantioselectivity in the catalysis of organic reactions. Recently reported results have shown that calixarene derivatives are able to accelerate organic reaction under “on-water” conditions with a significant selectivity toward the reactants. Under “on-water conditions” the hydrophobic effect, induced by insoluble calixarene derivatives, forces the reactants and the catalyst to aggregate and thus accelerating the reaction between them thanks to an amplification of weak secondary interactions. Regarding the use of water-soluble calixarene organocatalysts, we have here reviewed their role in the acceleration of

  14. Supramolecular Organocatalysis in Water Mediated by Macrocyclic Compounds

    Science.gov (United States)

    De Rosa, Margherita; La Manna, Pellegrino; Talotta, Carmen; Soriente, Annunziata; Gaeta, Carmine; Neri, Placido

    2018-04-01

    In the last decades many efforts have been devoted to design supramolecular organocatalysts able to work in water as the reaction medium. The use of water as solvent provides promising benefits with respect to environmental impact. In this context, macrocyclic compounds played a role of primary importance thanks to their ease of synthesis and their molecular recognition abilities toward the reactants. The aim of this review is to give an overview of the recent advances in the field of supramolecular organocatalysis in water, focusing the attention on calixarene and cyclodextrins derivatives. Calixarenes and cyclodextrins, thanks to their hydrophobic cavities, are able to host selectively the substrates isolating they from the reaction environment. In addition, the synthetic versatilities of these macrocycles permits to introduce useful functional groups in close proximity of the hydrophobic binding sites. Regarding the cyclodextrins (CDs), we have here reviewed the their most recent uses as organocatalysts for the synthesis of heterocyclic compounds, in multi-component reactions and in carbon-carbon bond forming reactions. Examples have been reported in which CD catalysts are able to drive the regiochemistry of common organic reactions. In addition, cyclodextrins bearing catalytically active chiral groups, have shown excellent enantioselectivity in the catalysis of organic reactions. Recently reported results have shown that calixarene derivatives are able to accelerate organic reaction under "on-water" conditions with a significant selectivity toward the reactants. Under "on-water conditions" the hydrophobic effect, induced by insoluble calixarene derivatives, forces the reactants and the catalyst to aggregate and thus accelerating the reaction between them thanks to an amplification of weak secondary interactions. Regarding the use of water-soluble calixarene organocatalysts, we have here reviewed their role in the acceleration of common organic reactions.

  15. C-84 Selective Porphyrin Macrocycle with an Adaptable Cavity Constructed Through Alkyne Metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, C. X.; Long, H.; Zhang, W.

    2012-06-21

    A bisporphyrin macrocycle was constructed from a porphyrin-based diyne monomer in one step through alkyne metathesis. The fullerene binding studies (C{sub 60}, C{sub 70} and C{sub 84}) showed the highest binding affinity of the macrocycle for C{sub 84}, which is in great contrast to its bisporphyrin four-armed cage analogue that showed the strongest binding with C{sub 70}.

  16. Template Syntheses, Crystal Structures and Supramolecular Assembly of Hexaaza Macrocyclic Copper(II) Complexes

    International Nuclear Information System (INIS)

    Kim, Taehyung; Kim, Ju Chang; Lough, Alan J.

    2013-01-01

    Two new hexaaza macrocyclic copper(II) complexes were prepared by a template method and structurally characterized. In the solid state, they were self-assembled by intermolecular interactions to form the corresponding supramolecules 1 and 2, respectively. In the structure of 1, the copper(II) macrocycles are bridged by a tp ligand to form a macrocyclic copper(II) dimer. The dimer extends its structure by intermolecular forces such as hydrogen bonds and C-H···π interactions, resulting in the formation of a double stranded 1D supramolecule. In 2, the basic structure is a monomeric copper(II) macrocycle with deprotonated imidazole pendants. An undulated 1D hydrogen bonded array is achieved through hydrogen bonds between imidazole pendants and secondary amines, where the imidazole pendants act as a hydrogen bond acceptor. The 1D hydrogen bonded supramolecular chain is supported by C-H···π interactions between the methyl groups of acetonitrile ligands and imidazole pendants of the copper(II) macrocycles. In both complexes, the introduction of imidazoles to the macrocycle as a pendant plays an important role for the formation of supramolecules, where they act as intermolecular hydrogen bond donors and/or acceptors, C-H···π and π-π interactions

  17. Scaling behavior of knotted random polygons and self-avoiding polygons: Topological swelling with enhanced exponent.

    Science.gov (United States)

    Uehara, Erica; Deguchi, Tetsuo

    2017-12-07

    We show that the average size of self-avoiding polygons (SAPs) with a fixed knot is much larger than that of no topological constraint if the excluded volume is small and the number of segments is large. We call it topological swelling. We argue an "enhancement" of the scaling exponent for random polygons with a fixed knot. We study them systematically through SAP consisting of hard cylindrical segments with various different values of the radius of segments. Here we mean by the average size the mean-square radius of gyration. Furthermore, we show numerically that the topological balance length of a composite knot is given by the sum of those of all constituent prime knots. Here we define the topological balance length of a knot by such a number of segments that topological entropic repulsions are balanced with the knot complexity in the average size. The additivity suggests the local knot picture.

  18. StraPep: a structure database of bioactive peptides

    Science.gov (United States)

    Wang, Jian; Yin, Tailang; Xiao, Xuwen; He, Dan; Xue, Zhidong; Jiang, Xinnong; Wang, Yan

    2018-01-01

    Abstract Bioactive peptides, with a variety of biological activities and wide distribution in nature, have attracted great research interest in biological and medical fields, especially in pharmaceutical industry. The structural information of bioactive peptide is important for the development of peptide-based drugs. Many databases have been developed cataloguing bioactive peptides. However, to our knowledge, database dedicated to collect all the bioactive peptides with known structure is not available yet. Thus, we developed StraPep, a structure database of bioactive peptides. StraPep holds 3791 bioactive peptide structures, which belong to 1312 unique bioactive peptide sequences. About 905 out of 1312 (68%) bioactive peptides in StraPep contain disulfide bonds, which is significantly higher than that (21%) of PDB. Interestingly, 150 out of 616 (24%) bioactive peptides with three or more disulfide bonds form a structural motif known as cystine knot, which confers considerable structural stability on proteins and is an attractive scaffold for drug design. Detailed information of each peptide, including the experimental structure, the location of disulfide bonds, secondary structure, classification, post-translational modification and so on, has been provided. A wide range of user-friendly tools, such as browsing, sequence and structure-based searching and so on, has been incorporated into StraPep. We hope that this database will be helpful for the research community. Database URL: http://isyslab.info/StraPep PMID:29688386

  19. Peptide dendrimers

    Czech Academy of Sciences Publication Activity Database

    Niederhafner, Petr; Šebestík, Jaroslav; Ježek, Jan

    2005-01-01

    Roč. 11, - (2005), 757-788 ISSN 1075-2617 R&D Projects: GA ČR(CZ) GA203/03/1362 Institutional research plan: CEZ:AV0Z40550506 Keywords : multiple antigen peptides * peptide dendrimers * synthetic vaccine * multipleantigenic peptides Subject RIV: CC - Organic Chemistry Impact factor: 1.803, year: 2005

  20. High yielding synthesis of 2,2′-bipyridine macrocycles, versatile intermediates in the synthesis of rotaxanes

    OpenAIRE

    Lewis, J. E. M.; Bordoli, R. J.; Denis, M.; Fletcher, C. J.; Galli, M.; Neal, E. A.; Rochette, E. M.; Goldup, S. M.

    2016-01-01

    We present an operationally simple approach to 2,2?-bipyridine macrocycles. Our method uses simple starting materials to produce these previously hard to access rotaxane precursors in remarkable yields (typically >65%) across a range of scales (0.1–5 mmol). All of the macrocycles reported are efficiently converted (>90%) to rotaxanes under AT-CuAAC conditions. With the requisite macrocycles finally available in sufficient quantities, we further demonstrate their long term utility throug...

  1. Total synthesis, structure, and oral absorption of a thiazole cyclic peptide, sanguinamide A

    DEFF Research Database (Denmark)

    Nielsen, Daniel S; Hoang, Huy N; Lohman, Rink-Jan

    2012-01-01

    The first total synthesis and three-dimensional solution structure are reported for sanguinamide A, a thiazole-containing cyclic peptide from the sea slug H. sanguineus. Solution phase fragment synthesis, solid phase fragment assembly, and solution macrocyclization were combined to give (1) in 10......% yield. Spectral properties were identical for the natural product, requiring revision of its structure from (2) to (1). Intramolecular transannular hydrogen bonds help to bury polar atoms, which enables oral absorption from the gut....

  2. Design and performance of the APPLE-Knot undulator

    International Nuclear Information System (INIS)

    Ji, Fuhao; Chang, Rui; Zhou, Qiaogen; Zhang, Wei; Ye, Mao; Sasaki, Shigemi; Qiao, Shan

    2015-01-01

    The design and performance of the Apple-Knot undulator which can generate photons with arbitrary polarization and low on-axis heat load are presented. Along with the development of accelerator technology, synchrotron emittance has continuously decreased. This results in increased brightness, but also causes a heavy heat load on beamline optics. Recently, optical surfaces with 0.1 nm micro-roughness and 0.05 µrad slope error (r.m.s.) have become commercially available and surface distortions due to heat load have become a key factor in determining beamline performance, and heat load has become a serious problem at modern synchrotron radiation facilities. Here, APPLE-Knot undulators which can generate photons with arbitrary polarization, with low on-axis heat load, are reported

  3. Design and performance of the APPLE-Knot undulator

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Fuhao [Department of Physics, State Key Laboratory of Surface Physics, and Laboratory of Advanced Materials, Fudan University, 2005 Songhu Road, Shanghai 200438, People’s Republic of (China); Chang, Rui [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050, People’s Republic of (China); Zhou, Qiaogen; Zhang, Wei [Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, 239 Zhangheng Road, Shanghai 201204, People’s Republic of (China); Ye, Mao [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050, People’s Republic of (China); Sasaki, Shigemi [Hiroshima Synchrotron Radiation Center, Hiroshima University, 2-313 Kagamiyama, Hiroshima 739-0046 (Japan); Qiao, Shan, E-mail: qiaoshan@mail.sim.ac.cn [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050, People’s Republic of (China); School of Physical Science and Technology, ShanghaiTech University, 319 Yueyang Road, Shanghai 200031, People’s Republic of (China)

    2015-06-09

    The design and performance of the Apple-Knot undulator which can generate photons with arbitrary polarization and low on-axis heat load are presented. Along with the development of accelerator technology, synchrotron emittance has continuously decreased. This results in increased brightness, but also causes a heavy heat load on beamline optics. Recently, optical surfaces with 0.1 nm micro-roughness and 0.05 µrad slope error (r.m.s.) have become commercially available and surface distortions due to heat load have become a key factor in determining beamline performance, and heat load has become a serious problem at modern synchrotron radiation facilities. Here, APPLE-Knot undulators which can generate photons with arbitrary polarization, with low on-axis heat load, are reported.

  4. BPS counting for knots and combinatorics on words

    Energy Technology Data Exchange (ETDEWEB)

    Kucharski, Piotr [Faculty of Physics, University of Warsaw,ul. Pasteura 5, 02-093 Warsaw (Poland); Sułkowski, Piotr [Faculty of Physics, University of Warsaw,ul. Pasteura 5, 02-093 Warsaw (Poland); Walter Burke Institute for Theoretical Physics, California Institute of Technology,Pasadena, CA 91125 (United States)

    2016-11-21

    We discuss relations between quantum BPS invariants defined in terms of a product decomposition of certain series, and difference equations (quantum A-polynomials) that annihilate such series. We construct combinatorial models whose structure is encoded in the form of such difference equations, and whose generating functions (Hilbert-Poincaré series) are solutions to those equations and reproduce generating series that encode BPS invariants. Furthermore, BPS invariants in question are expressed in terms of Lyndon words in an appropriate language, thereby relating counting of BPS states to the branch of mathematics referred to as combinatorics on words. We illustrate these results in the framework of colored extremal knot polynomials: among others we determine dual quantum extremal A-polynomials for various knots, present associated combinatorial models, find corresponding BPS invariants (extremal Labastida-Mariño-Ooguri-Vafa invariants) and discuss their integrality.

  5. Gordian Knots of Prevision: The lessons of history

    Science.gov (United States)

    Fleming, J. R.

    2017-12-01

    Atmospheric researchers have long attempted to untie the Gordian Knot of meteorology—that intractable and intertwined tangle of observational imprecision, theoretical uncertainties, and non-linear influences—that, if unraveled, would provide perfect prevision of the weather for ten days, of seasonal conditions for the year, and of climatic conditions for a decade, a century, a millennium, or longer. This presentation, based on Inventing Atmospheric Science (M.I.T. Press, 2016), examines the work of four interconnected generations of scientists (Vilhelm Bjerknes, C.-G. Rossby, Harry Wexler, Ed Lorenz) and the influence of four transformative technologies (radio, nuclear, computation, aerospace) from the dawn of applied fluid dynamics to the emergence of the interdisciplinary atmospheric sciences and the new Gordian Knot of chaos.

  6. Energy and helicity of magnetic torus knots and braids

    Science.gov (United States)

    Oberti, Chiara; Ricca, Renzo L.

    2018-02-01

    By considering steady magnetic fields in the shape of torus knots and unknots in ideal magnetohydrodynamics, we compute some fundamental geometric and physical properties to provide estimates for magnetic energy and helicity. By making use of an appropriate parametrization, we show that knots with dominant toroidal coils that are a good model for solar coronal loops have negligible total torsion contribution to magnetic helicity while writhing number provides a good proxy. Hence, by the algebraic definition of writhe based on crossing numbers, we show that the estimated values of writhe based on image analysis provide reliable information for the exact values of helicity. We also show that magnetic energy is linearly related to helicity, and the effect of the confinement of magnetic field can be expressed in terms of geometric information. These results can find useful application in solar and plasma physics, where braided structures are often present.

  7. BPS counting for knots and combinatorics on words

    Science.gov (United States)

    Kucharski, Piotr; Sułkowski, Piotr

    2016-11-01

    We discuss relations between quantum BPS invariants defined in terms of a product decomposition of certain series, and difference equations (quantum A-polynomials) that annihilate such series. We construct combinatorial models whose structure is encoded in the form of such difference equations, and whose generating functions (Hilbert-Poincaré series) are solutions to those equations and reproduce generating series that encode BPS invariants. Furthermore, BPS invariants in question are expressed in terms of Lyndon words in an appropriate language, thereby relating counting of BPS states to the branch of mathematics referred to as combinatorics on words. We illustrate these results in the framework of colored extremal knot polynomials: among others we determine dual quantum extremal A-polynomials for various knots, present associated combinatorial models, find corresponding BPS invariants (extremal Labastida-Mariño-Ooguri-Vafa invariants) and discuss their integrality.

  8. Polynomial invariants for torus knots and topological strings

    International Nuclear Information System (INIS)

    Labastida, J.M.F.

    2001-01-01

    We make a precision test of a recently proposed conjecture relating Chern-Simons gauge theory to topological string theory on the resolution of the conifold. First, we develop a systematic procedure to extract string amplitudes from vacuum expectation values (vevs) of Wilson loops in Chern-Simons gauge theory, and then we evaluate these vevs in arbitrary irreducible representations of SU(N) for torus knots. We find complete agreement with the predictions derived from the target space interpretation of the string amplitudes. We also show that the structure of the free energy of topological open string theory gives further constraints on the Chern-Simons vevs. Our work provides strong evidence towards an interpretation of knot polynomial invariants as generating functions associated to enumerative problems. (orig.)

  9. Electron transfer reactions of macrocyclic compounds of cobalt

    Energy Technology Data Exchange (ETDEWEB)

    Heckman, R.A.

    1978-08-01

    The kinetics and mechanisms of reduction of H/sub 2/O/sub 2/, Br/sub 2/, and I/sub 2/ by various macrocyclic tetraaza complexes of cobalt(II), including Vitamin B/sub 12r/, were studied. The synthetic macrocycles studied were all 14-membered rings which varied in the degree of unsaturation,substitution of methyl groups on the periphery of the ring, and substitution within the ring itself. Scavenging experiments demonstrated that the reductions of H/sub 2/O/sub 2/ produce free hydroxyl radicals only in the case of Co((14)ane)/sup 2 +/ but with none of the others. In the latter instances apparently H/sub 2/O/sub 2/ simultaneously oxidizes the metal center and the ligand. The reductions of Br/sub 2/ and I/sub 2/ produce an aquohalocobalt(III) product for all reductants (except B/sub 12r/ + Br/sub 2/, which was complicated by bromination of the corrin ring). The mechanism of halogen reduction was found to involve rate-limiting inner-sphere electron transfer from cobalt to halogen to produce a dihalide anion coordinated to the cobalt center. This intermediate subsequently decomposes in rapid reactions to halocobalt(III) and halogen atom species or reacts with another cobalt(II) center to give two molecules of halocobalt(III). The reductions of halomethylcobaloximes and related compounds and diamminecobaloxime by Cr/sup 2 +/ were also studied. The reaction was found to be biphasic in all cases with the reaction products being halomethane (for the halomethylcobaloximes), Co/sup 2 +/ (in less than 100 percent yield), a Cr(III)-dimethylglyoxime species, a small amount of free dmgH/sub 2/, and a highly-charged species containing both cobalt and chromium. The first-stage reaction occurs with a stoichiometry of 1:1 producing an intermediate with an absorption maximum at 460 nm for all starting reagents. The results were interpreted in terms of inner-sphere coordination of the cobaloxime to the Cr(II) and electron transfer through the oxime N-O bond.

  10. [Tl(III)(dota)](-): An Extraordinarily Robust Macrocyclic Complex.

    Science.gov (United States)

    Fodor, Tamás; Bányai, István; Bényei, Attila; Platas-Iglesias, Carlos; Purgel, Mihály; Horváth, Gábor L; Zékány, László; Tircsó, Gyula; Tóth, Imre

    2015-06-01

    The X-ray structure of {C(NH2)3}[Tl(dota)]·H2O shows that the Tl(3+) ion is deeply buried in the macrocyclic cavity of the dota(4-) ligand (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate) with average Tl-N and Tl-O distances of 2.464 and 2.365 Å, respectively. The metal ion is directly coordinated to the eight donor atoms of the ligand, which results in a twisted square antiprismatic (TSAP') coordination around Tl(3+). A multinuclear (1)H, (13)C, and (205)Tl NMR study combined with DFT calculations confirmed the TSAP' structure of the complex in aqueous solution, which exists as the Λ(λλλλ)/Δ(δδδδ) enantiomeric pair. (205)Tl NMR spectroscopy allowed the protonation constant associated with the protonation of the complex according to [Tl(dota)](-) + H(+) ⇆ [Tl(Hdota)] to be determined, which turned out to be pK(H)Tl(dota) = 1.4 ± 0.1. [Tl(dota)](-) does not react with Br(-), even when using an excess of the anion, but it forms a weak mixed complex with cyanide, [Tl(dota)](-) + CN(-) ⇆ [Tl(dota)(CN)](2-), with an equilibrium constant of Kmix = 6.0 ± 0.8. The dissociation of the [Tl(dota)](-) complex was determined by UV-vis spectrophotometry under acidic conditions using a large excess of Br(-), and it was found to follow proton-assisted kinetics and to take place very slowly (∼10 days), even in 1 M HClO4, with the estimated half-life of the process being in the 10(9) h range at neutral pH. The solution dynamics of [Tl(dota)](-) were investigated using (13)C NMR spectroscopy and DFT calculations. The (13)C NMR spectra recorded at low temperature (272 K) point to C4 symmetry of the complex in solution, which averages to C4v as the temperature increases. This dynamic behavior was attributed to the Λ(λλλλ) ↔ Δ(δδδδ) enantiomerization process, which involves both the inversion of the macrocyclic unit and the rotation of the pendant arms. According to our calculations, the arm-rotation process limits the Λ(λλλλ) ↔

  11. New Ways to Cut through Ethical Gordian Knots.

    Science.gov (United States)

    Howe, Edmund G

    2017-01-01

    Clinicians and ethicists routinely encounter complex ethical dilemmas that seem intractable, which have been described as ethical Gordian knots. How can they best assist patients and surrogate decision makers who are entangled in struggles around the capacity to make life-or-death treatment decisions? In this article I describe unconventional and unorthodox approaches to help slice through these dilemmas. Copyright 2017 The Journal of Clinical Ethics. All rights reserved.

  12. Southward migration and fuel deposition of Red Knots Calidris canutus

    OpenAIRE

    Helseth, Anders; Lindström, Åke; Stervander, Martin

    2005-01-01

    We compared the differences between spring and autumn in migration speed, fuelling rates and fuel loads of migrating Red Knots Calidris canutus. As a basis we used ringing data from Ottenby Bird Observatory, southeastern Sweden, collected 1948–2003, with morphometrical data from 1990–2003. Numbers ringed varied between 0 and 301 per year (average 56). Morphometrics, recoveries and recaptures of ringed birds indicated that most birds belonged to the Afro-Siberian subspecies C. c. canutus, poss...

  13. The Knot Spectrum of Confined Random Equilateral Polygons

    Directory of Open Access Journals (Sweden)

    Diao Y.

    2014-01-01

    Full Text Available It is well known that genomic materials (long DNA chains of living organisms are often packed compactly under extreme confining conditions using macromolecular self-assembly processes but the general DNA packing mechanism remains an unsolved problem. It has been proposed that the topology of the packed DNA may be used to study the DNA packing mechanism. For example, in the case of (mutant bacteriophage P4, DNA molecules packed inside the bacteriophage head are considered to be circular since the two sticky ends of the DNA are close to each other. The DNAs extracted from the capsid without separating the two ends can thus preserve the topology of the (circular DNAs. It turns out that the circular DNAs extracted from bacteriophage P4 are non-trivially knotted with very high probability and with a bias toward chiral knots. In order to study this problem using a systematic approach based on mathematical modeling, one needs to introduce a DNA packing model under extreme volume confinement condition and test whether such a model can produce the kind of knot spectrum observed in the experiments. In this paper we introduce and study a model of equilateral random polygons con_ned in a sphere. This model is not meant to generate polygons that model DNA packed in a virus head directly. Instead, the average topological characteristics of this model may serve as benchmark data for totally randomly packed circular DNAs. The difference between the biologically observed topological characteristics and our benchmark data might reveal the bias of DNA packed in the viral capsids and possibly lead to a better understanding of the DNA packing mechanism, at least for the bacteriophage DNA. The purpose of this paper is to provide information about the knot spectrum of equilateral random polygons under such a spherical confinement with length and confinement ratios in a range comparable to circular DNAs packed inside bacteriophage heads.

  14. Knot invariants and M-theory: Proofs and derivations

    Science.gov (United States)

    Errasti Díez, Verónica

    2018-01-01

    We construct two distinct yet related M-theory models that provide suitable frameworks for the study of knot invariants. We then focus on the four-dimensional gauge theory that follows from appropriately compactifying one of these M-theory models. We show that this theory has indeed all required properties to host knots. Our analysis provides a unifying picture of the various recent works that attempt an understanding of knot invariants using techniques of four-dimensional physics. This is a companion paper to K. Dasgupta, V. Errasti Díez, P. Ramadevi, and R. Tatar, Phys. Rev. D 95, 026010 (2017), 10.1103/PhysRevD.95.026010, covering all but Sec. III C. It presents a detailed mathematical derivation of the main results there, as well as additional material. Among the new insights, those related to supersymmetry and the topological twist are highlighted. This paper offers an alternative, complementary formulation of the contents in the first paper, but is self-contained and can be read independently.

  15. Rectangular superpolynomials for the figure-eight knot 41

    Science.gov (United States)

    Kononov, Ya. A.; Morozov, A. Yu.

    2017-11-01

    We rewrite the recently proposed differential expansion formula for HOMFLY polynomials of the knot 41 in an arbitrary rectangular representation R = [rs] as a sum over all Young subdiagrams λ of R with surprisingly simple coefficients of the Z factors. Intriguingly, these coefficients are constructed from the quantum dimensions of symmetric representations of the groups SL(r) and SL(s) and restrict the summation to diagrams with no more than s rows and r columns. Moreover, the β-deformation to Macdonald dimensions yields polynomials with positive integer coefficients, which are plausible candidates for the role of superpolynomials for rectangular representations. Both the polynomiality and the positivity of the coefficients are nonobvious, nevertheless true. This generalizes the previously known formulas for symmetric representations to arbitrary rectangular representations. The differential expansion allows introducing additional gradings. For the trefoil knot 31, to which our results for the knot 41 are immediately extended, we obtain the so-called fourth grading of hyperpolynomials. The property of factorization in roots of unity is preserved even in the five-graded case.

  16. Dissociation kinetics of acyclic and macrocyclic polyaminopolycarboxylate complexes of yttrium

    International Nuclear Information System (INIS)

    Pathak, P.N.; Manchanda, V.K.

    2000-01-01

    Dissociation kinetics of Y III complexes of a linear as well as two macrocyclic polyaminopolycarboxylates, ethylenediamine diacetic acid (EDDA), 1,7-diaza-4,10,13-trioxacyclopentadecane-N,N'-diacetic acid (K21DA) and 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N,N'-diacetic acid (K22DA) have been studied at a constant ionic strength (0.1 M) under varying (H + ) and temperatures. Cu II ion acts as the scavenger of the free ligand. Dissociation rate of Y III -K21DA is insensitive to Cu II and acetate (used as buffer anion) concentrations. Kinetic stability of the three complexes follow the order : Y III -K22DA>Y III -K21DA>Y III -EDDA. Enthalpies of activation for K21DA and K22DA complexes of Y III are also evaluated. Thermodynamic stability constant (log K) for Y III -K22DA complex is 10.81 ± 0.04. (author)

  17. Tightening slip knots in raw and degummed silk to increase toughness without losing strength

    OpenAIRE

    Pantano, Maria; Berardo, Alice; Pugno, Nicola

    2016-01-01

    Knots are fascinating topological elements, which can be found in both natural and artificial systems. While in most of the cases, knots cannot be loosened without breaking the strand where they are tightened, herein, attention is focused on slip or running knots, which on the contrary can be unfastened without compromising the structural integrity of their hosting material. Two different topologies are considered, involving opposite unfastening mechanisms, and their influence on the mechanic...

  18. Knotting dynamics of DNA chains of different length confined in nanochannels

    International Nuclear Information System (INIS)

    Suma, Antonio; Micheletti, Cristian; Orlandini, Enzo

    2015-01-01

    Langevin dynamics simulations are used to characterize the typical mechanisms governing the spontaneous tying, untying and the dynamical evolution of knots in coarse-grained models of DNA chains confined in nanochannels. In particular we focus on how these mechanisms depend on the chain contour length, L c , at a fixed channel width D = 56 nm corresponding to the onset of the Odijk scaling regime where chain backfoldings and hence knots are disfavoured but not suppressed altogether. We find that the lifetime of knots grows significantly with L c , while that of unknots varies to a lesser extent. The underlying kinetic mechanisms are clarified by analysing the evolution of the knot position along the chain. At the considered confinement, in fact, knots are typically tied by local backfoldings of the chain termini where they are eventually untied after a stochastic motion along the chain. Consequently, the lifetime of unknots is mostly controlled by backfoldings events at the chain ends, which is largely independent of L c . The lifetime of knots, instead, increases significantly with L c because knots can, on average, travel farther along the chain before being untied. The observed interplay of knots and unknots lifetimes underpins the growth of the equilibrium knotting probability of longer and longer chains at fixed channel confinement. (paper)

  19. Self-assembled monolayers of shape-persistent macrocycles on graphite: interior design and conformational polymorphism.

    Science.gov (United States)

    Vollmeyer, Joscha; Eberhagen, Friederike; Höger, Sigurd; Jester, Stefan-S

    2014-01-01

    Three shape-persistent naphthylene-phenylene-acetylene macrocycles of identical backbone structures and extraannular substitution patterns but different (empty, apolar, polar) nanopore fillings are self-assembled at the solid/liquid interface of highly oriented pyrolytic graphite and 1,2,4-trichlorobenzene. Submolecularly resolved images of the resulting two-dimensional (2D) crystalline monolayer patterns are obtained by in situ scanning tunneling microscopy. A concentration-dependent conformational polymorphism is found, and open and more dense packing motifs are observed. For all three compounds alike lattice parameters are found, therefore the intermolecular macrocycle distances are mainly determined by their size and symmetry. This is an excellent example that the graphite acts as a template for the macrocycle organization independent from their specific interior.

  20. Self-assembled monolayers of shape-persistent macrocycles on graphite: interior design and conformational polymorphism

    Directory of Open Access Journals (Sweden)

    Joscha Vollmeyer

    2014-11-01

    Full Text Available Three shape-persistent naphthylene–phenylene–acetylene macrocycles of identical backbone structures and extraannular substitution patterns but different (empty, apolar, polar nanopore fillings are self-assembled at the solid/liquid interface of highly oriented pyrolytic graphite and 1,2,4-trichlorobenzene. Submolecularly resolved images of the resulting two-dimensional (2D crystalline monolayer patterns are obtained by in situ scanning tunneling microscopy. A concentration-dependent conformational polymorphism is found, and open and more dense packing motifs are observed. For all three compounds alike lattice parameters are found, therefore the intermolecular macrocycle distances are mainly determined by their size and symmetry. This is an excellent example that the graphite acts as a template for the macrocycle organization independent from their specific interior.

  1. Zn2+ -Ion Sensing by Fluorescent Schiff Base Calix[4]arene Macrocycles.

    Science.gov (United States)

    Ullmann, Steve; Schnorr, René; Handke, Marcel; Laube, Christian; Abel, Bernd; Matysik, Jörg; Findeisen, Matthias; Rüger, Robert; Heine, Thomas; Kersting, Berthold

    2017-03-17

    A macrocyclic ligand (H 2 L) containing two o,o'-bis(iminomethyl)phenol and two calix[4]arene head units has been synthesized and its coordination chemistry towards divalent Ni and Zn investigated. The new macrocycle forms complexes of composition [ML] (M=Zn, M=Ni) and [ZnL(py) 2 ], which were characterized by elemental analysis; IR, UV/Vis, and NMR spectroscopy; electrospray ionization mass spectrometry (ESI-MS); and X-ray crystallography (for [ZnL(py) 2 ] and [NiL]). H 2 L allows the sensitive optical detection of Zn 2+ among a series of biologically relevant metal ions by a dual fluorescence enhancement/quenching effect in solution. The fluorescence intensity of the macrocycle increases by a factor of ten in the presence of Zn 2+ with a detection limit in the lower nanomolar region. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Macrocyclic ligands for uranium complexation. Final report, August 1, 1986--March 31, 1993

    International Nuclear Information System (INIS)

    Potts, K.T.

    1993-01-01

    Macrocycles, designed for complexation of the uranyl ion by computer modeling studies and utilizing six ligating atoms in the equatorial plane of the uranyl ions, have been prepared and their complexation of the uranyl ions evaluated. The ligating atoms, either oxygen or sulfur, were part of acylurea, biuret or thiobiuret subunits with alkane chains or pyridine units completing the macrocyclic periphery. These macrocycles with only partial preorganization formed uranyl complexes in solution but no crystalline complexes were isolated. Refinement of the cavity diameter by variation of the peripheral functional groups is currently studied to achieve an optimized cavity diameter of 4.7--5.2 angstrom. Acyclic ligands containing the same ligating atoms in equivalent functional entities were found to form a crystalline 1:1 uranyl-ligand complex (stability constant log K = 10.7) whose structure was established by X-ray data. This complex underwent a facile, DMSO-induced rearrangement to a 2:1 uranyl-ligand complex whose structure was also established by X-ray data. The intermediates to the macrocycles all behaved as excellent ligands for the complexation of transition metals. Acylthiourea complexes of copper and nickel as well as intermolecular, binuclear copper and nickel complexes of bidentate carbonyl thioureas formed readily and their structures were established in several representative instances by X-ray structural determinations. Tetradentate bis(carbonylthioureas) were found to be very efficient selective reagents for the complexation of copper in the presence of nickel ions. Several preorganized macrocycles were also prepared but in most instances these macrocycles underwent ring-opening under complexation conditions

  3. Exploring the Binding of Barbital to a Synthetic Macrocyclic Receptor; a Charge Density Study

    DEFF Research Database (Denmark)

    Du, Jonathan J.; Hanrahan, Jane Rouse; Solomon, V. Raja

    2018-01-01

    Experimental charge density distribution studies, complemented by quantum mechanical theoretical calculations, of a host-guest system comprised of a macrocycle (1) and barbital (2) in a 1:1 ratio (3) have been carried out via high resolution single crystal X-ray diffraction. The data was modelled...... molecule. Visual comparison of the conformations of the macrocyclic ring shows the rotation by 180° of an amide bond attributed to competitive hydrogen bonding. It was found the intraannular and extraannular molecules inside were orientated to maximise the number of hydrogen bonds present...

  4. Use of a macrocyclic antibiotic as the chiral selector for enantiomeric separations by TLC

    Energy Technology Data Exchange (ETDEWEB)

    Armstrong, D.W.; Zhou, Y. (Univ. of Missouri, Rolla, MO (United States). Dept. of Chemistry)

    1994-01-01

    The macrocyclic antibiotic, vancomycin, was used as a chiral mobile phase additive for the thin layer chromatographic (TLC) resolution of 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) derivatized amino acids, racemic drugs and dansyl-amino acids. Excellent separations were achieved for most of these compounds in the reversed phase mode. Both the nature of the stationary phase and the composition of the mobile phase strongly influenced enantiomeric resolution. The best results were obtained using diphenyl stationary phases. Acetonitrile was the organic modifier that produced the most effective separations with the shortest development times. It is highly likely that macrocyclic antibiotics will play a major role in future enantiomeric separations.

  5. A toxicological and dermatological assessment of macrocyclic lactone and lactide derivatives when used as fragrance ingredients

    DEFF Research Database (Denmark)

    Belsito, D.; Bickers, D.; Bruze, M.

    2011-01-01

    The Macrocyclic Lactone and Lactide derivative (ML) group of fragrance ingredients was critically evaluated for safety following a complete literature search. For high end users, calculated maximum dermal exposures vary from 0.47% to 11.15%; systemic exposures vary from 0.0008 to 0.25 mg/kg/day. ......The Macrocyclic Lactone and Lactide derivative (ML) group of fragrance ingredients was critically evaluated for safety following a complete literature search. For high end users, calculated maximum dermal exposures vary from 0.47% to 11.15%; systemic exposures vary from 0.0008 to 0.25 mg...

  6. The Porphobilinogen Conundrum in Prebiotic Routes to Tetrapyrrole Macrocycles

    Science.gov (United States)

    Taniguchi, Masahiko; Ptaszek, Marcin; Chandrashaker, Vanampally; Lindsey, Jonathan S.

    2017-03-01

    Attempts to develop a credible prebiotic route to tetrapyrroles have relied on enzyme-free recapitulation of the extant biosynthesis, but this process has foundered from the inability to form the pyrrole porphobilinogen ( PBG) in good yield by self-condensation of the precursor δ-aminolevulinic acid ( ALA). PBG undergoes robust oligomerization in aqueous solution to give uroporphyrinogen (4 isomers) in good yield. ALA, PBG, and uroporphyrinogen III are universal precursors to all known tetrapyrrole macrocycles. The enzymic formation of PBG entails carbon-carbon bond formation between the less stable enolate/enamine of one ALA molecule (3-position) and the carbonyl/imine (4-position) of the second ALA molecule; without enzymes, the first ALA reacts at the more stable enolate/enamine (5-position) and gives the pyrrole pseudo-PBG. pseudo-PBG cannot self-condense, yet has one open α-pyrrole position and is proposed to be a terminator of oligopyrromethane chain-growth from PBG. Here, 23 analogues of ALA have been subjected to density functional theoretical (DFT) calculations, but no motif has been identified that directs reaction at the 3-position. Deuteriation experiments suggested 5-(phosphonooxy)levulinic acid would react preferentially at the 3- versus 5-position, but a hybrid condensation with ALA gave no observable uroporphyrin. The results suggest efforts toward a biomimetic, enzyme-free route to tetrapyrroles from ALA should turn away from structure-directed reactions and focus on catalysts that orient the two aminoketones to form PBG in a kinetically controlled process, thereby avoiding formation of pseudo-PBG.

  7. Studies of flerovium and element 115 homologs with macrocyclic extractants

    Science.gov (United States)

    Despotopulos, John Dustin

    Study of the chemistry of the heaviest elements, Z ? 104, poses a unique challenge due to their low production cross-sections and short half-lives. Chemistry also must be studied on the one-atom-at-a-time scale, requiring automated, fast, and very efficient chemical schemes. Recent studies of the chemical behavior of copernicium (Cn, element 112) and flerovium (Fl, element 114) together with the discovery of isotopes of these elements with half-lives suitable for chemical studies have spurred a renewed interest in the development of rapid systems designed to study the chemical properties of elements with Z ≥ 114. This dissertation explores both extraction chromatography and solvent extraction as methods for development of a rapid chemical separation scheme for the homologs of flerovium (Pb, Sn, Hg) and element 115 (Bi, Sb), with the goal of developing a chemical scheme that, in the future, can be applied to on-line chemistry of both Fl and element 115. Macrocyclic extractants, specifically crown ethers and their derivatives, were chosen for these studies. Carrier-free radionuclides, used in these studies, of the homologs of Fl and element 115 were obtained by proton activation of high purity metal foils at the Lawrence Livermore National Laboratory (LLNL) Center for Accelerator Mass Spectrometry (CAMS): natIn(p,n)113Sn, natSn(p,n)124Sb, and Au(p,n)197m,gHg. The carrier-free activity was separated from the foils by novel separation schemes based on ion exchange and extraction chromatography techniques. Carrier-free Pb and Bi isotopes were obtained from development of a novel generator based on cation exchange chromatography using the 232U parent to generate 212Pb and 212Bi. Crown ethers show high selectivity for metal ions based on their size compared to the negatively charged cavity of the ether. Extraction by crown ethers occur based on electrostatic ion-dipole interactions between the negatively charged ring atoms (oxygen, sulfur, etc.) and the positively

  8. A 'FIREWORK' OF H2 KNOTS IN THE PLANETARY NEBULA NGC 7293 (THE HELIX NEBULA)

    International Nuclear Information System (INIS)

    Matsuura, M.; Speck, A. K.; McHunu, B. M.; Tanaka, I.; Wright, N. J.; Viti, S.; Wesson, R.; Smith, M. D.; Zijlstra, A. A.

    2009-01-01

    We present a deep and wide field-of-view (4' x 7') image of the planetary nebula (PN) NGC 7293 (the Helix Nebula) in the 2.12 μm H 2 v = 1 → 0 S(1) line. The excellent seeing (0.''4) at the Subaru Telescope, allows the details of cometary knots to be examined. The knots are found at distances of 2.'2-6.'4 from the central star (CS). At the inner edge and in the inner ring (up to 4.'5 from the CS), the knot often show a 'tadpole' shape, an elliptical head with a bright crescent inside and a long tail opposite to the CS. In detail, there are variations in the tadpole shapes, such as narrowing tails, widening tails, meandering tails, or multipeaks within a tail. In the outer ring (4.'5-6.'4 from the CS), the shapes are more fractured, and the tails do not collimate into a single direction. The transition in knot morphology from the inner edge to the outer ring is clearly seen. The number density of knots governs the H 2 surface brightness in the inner ring: H 2 exists only within the knots. Possible mechanisms which contribute to the shaping of the knots are discussed, including photoionization and streaming motions. A plausible interpretation of our images is that inner knots are being overrun by a faster wind, but that this has not (yet) reached the outer knots. Based on H 2 formation and destruction rates, H 2 gas can survive in knots from formation during the late asymptotic giant branch phase throughout the PN phase. These observations provide new constraints on the formation and evolution of knots, and on the physics of molecular gas embedded within ionized gas.

  9. A "Firework" of H2 Knots in the Planetary Nebula NGC 7293 (The Helix Nebula)

    Science.gov (United States)

    Matsuura, M.; Speck, A. K.; McHunu, B. M.; Tanaka, I.; Wright, N. J.; Smith, M. D.; Zijlstra, A. A.; Viti, S.; Wesson, R.

    2009-08-01

    We present a deep and wide field-of-view (4' × 7') image of the planetary nebula (PN) NGC 7293 (the Helix Nebula) in the 2.12 μm H2 v = 1 → 0 S(1) line. The excellent seeing (0farcs4) at the Subaru Telescope, allows the details of cometary knots to be examined. The knots are found at distances of 2farcm2-6farcm4 from the central star (CS). At the inner edge and in the inner ring (up to 4farcm5 from the CS), the knot often show a "tadpole" shape, an elliptical head with a bright crescent inside and a long tail opposite to the CS. In detail, there are variations in the tadpole shapes, such as narrowing tails, widening tails, meandering tails, or multipeaks within a tail. In the outer ring (4farcm5-6farcm4 from the CS), the shapes are more fractured, and the tails do not collimate into a single direction. The transition in knot morphology from the inner edge to the outer ring is clearly seen. The number density of knots governs the H2 surface brightness in the inner ring: H2 exists only within the knots. Possible mechanisms which contribute to the shaping of the knots are discussed, including photoionization and streaming motions. A plausible interpretation of our images is that inner knots are being overrun by a faster wind, but that this has not (yet) reached the outer knots. Based on H2 formation and destruction rates, H2 gas can survive in knots from formation during the late asymptotic giant branch phase throughout the PN phase. These observations provide new constraints on the formation and evolution of knots, and on the physics of molecular gas embedded within ionized gas. Based on data taken with the Subaru Telescope, National Astronomical Observatory of Japan (proposal ID S07B-054).

  10. Knots and surfaces a guide to discovering mathematics

    CERN Document Server

    Farmer, David W

    1995-01-01

    In most mathematics textbooks, the most exciting part of mathematics-the process of invention and discovery-is completely hidden from the reader. The aim of Knots and Surfaces is to change all that. By means of a series of carefully selected tasks, this book leads readers to discover some real mathematics. There are no formulas to memorize; no procedures to follow. The book is a guide: its job is to start you in the right direction and to bring you back if you stray too far. Discovery is left to you. Suitable for a one-semester course at the beginning undergraduate level, there are no prerequi

  11. Explorations in topology map coloring, surfaces and knots

    CERN Document Server

    Gay, David

    2013-01-01

    Explorations in Topology, Second Edition, provides students a rich experience with low-dimensional topology (map coloring, surfaces, and knots), enhances their geometrical and topological intuition, empowers them with new approaches to solving problems, and provides them with experiences that will help them make sense of future, more formal topology courses. The book's innovative story-line style models the problem-solving process, presents the development of concepts in a natural way, and engages students in meaningful encounters with the material. The updated end-of-chapter investigation

  12. Production of highly knotted DNA by means of cosmid circularization inside phage capsids

    Directory of Open Access Journals (Sweden)

    Trigueros Sonia

    2007-12-01

    Full Text Available Abstract Background The formation of DNA knots is common during biological transactions. Yet, functional implications of knotted DNA are not fully understood. Moreover, potential applications of DNA molecules condensed by means of knotting remain to be explored. A convenient method to produce abundant highly knotted DNA would be highly valuable for these studies. Results We had previously shown that circularization of the 11.2 kb linear DNA of phage P4 inside its viral capsid generates complex knots by the effect of confinement. We demonstrate here that this mechanism is not restricted to the viral genome. We constructed DNA cosmids as small as 5 kb and introduced them inside P4 capsids. Such cosmids were then recovered as a complex mixture of highly knotted DNA circles. Over 250 μg of knotted cosmid were typically obtained from 1 liter of bacterial culture. Conclusion With this biological system, DNA molecules of varying length and sequence can be shaped into very complex and heterogeneous knotted forms. These molecules can be produced in preparative amounts suitable for systematic studies and applications.

  13. A summary of modulus of elasticity and knot size surveys for laminating grades of lumber

    Science.gov (United States)

    R. W. Wolfe; R. C. Moody

    1981-01-01

    A summary of modulus of elasticity (MOE) and knot data is presented for grades of lumber commonly used to manufacture glued-laminated (glulam) timber by the laminating Industry. Tabulated values represent 30 different studies covering a time span of over 16 years. Statistical estimates of average and near-maximum knot sizes as well as mean and coefficient of variation...

  14. The volume conjecture, perturbative knot invariants, and recursion relations for topological strings

    NARCIS (Netherlands)

    Dijkgraaf, R.; Fuji, H.; Manabe, M.

    2011-01-01

    We study the relation between perturbative knot invariants and the free energies defined by topological string theory on the character variety of the knot. Such a correspondence between SL(2;C) Chern-Simons gauge theory and the topological open string theory was proposed earlier on the basis of the

  15. First report of the root-knot nematode Meloidogyne ethiopica on tomato in Slovenia

    NARCIS (Netherlands)

    Sirca, S.; Urek, G.; Karssen, G.

    2004-01-01

    The root-knot nematode Meloidogyne ethiopica Whitehead originally described from Tanzania is also distributed in South Africa, Zimbabwe, and Ethiopia (3). Although this species is a relatively unknown root-knot nematode, M. ethiopica parasitizes several economical important crops, such as tomato,

  16. Use of gadolinium chloride as a contrast agent for imaging spruce knots by magnetic resonance

    Science.gov (United States)

    Thomas L. Eberhardt; Chi-Leung So; Amy H. Herlihy; Po-Wah So

    2006-01-01

    Treatments of knot-containing spruce wood blocks with a paramagnetic salt, gadolinium (III) chloride, in combination with solvent pretreatments, were evaluated as strategies to enhance the visualization of wood features by magnetic resonance imaging (MRI). Initial experiments with clear wood and excised knot samples showed differences in moisture uptake after...

  17. Characterization of the psoRPM1 gene for resistance to root-knot ...

    African Journals Online (AJOL)

    Several root-knot nematode (Meloidogyne spp.) resistance genes have been discovered in different stone fruit crops. However, none of them has yet been cloned and they were only located on the chromosomes. In this study, a candidate root-knot nematode resistance gene (designated as psoRPM1) was isolated from the ...

  18. Knot detection in X-ray images of wood planks using dictionary learning

    DEFF Research Database (Denmark)

    Hansson, Nils Mattias; Enescu, Alexandru; Brandt, Sami Sebastian

    2015-01-01

    This paper considers a novel application of x-ray imaging of planks, for the purpose of detecting knots in high quality furniture wood. X-ray imaging allows the detection of knots invisible from the surface to conventional cameras. Our approach is based on texture analysis, or more specifically, ......, discriminative dictionary learning. Experiments show that the knot detection and segmentation can be accurately performed by our approach. This is a promising result and can be directly applied in industrial processing of furniture wood.......This paper considers a novel application of x-ray imaging of planks, for the purpose of detecting knots in high quality furniture wood. X-ray imaging allows the detection of knots invisible from the surface to conventional cameras. Our approach is based on texture analysis, or more specifically...

  19. Filtration of the classical knot concordance group and Casson-Gordon invariants

    Science.gov (United States)

    Kim, Taehee

    2004-09-01

    It is known that if every prime power branched cyclic cover of a knot in S(3) is a homology sphere, then the knot has vanishing Casson-Gordon invariants. We construct infinitely many examples of (topologically) non-slice knots in S(3) whose prime power branched cyclic covers are homology spheres. We show that these knots generate an infinite rank subgroup of scrf_{(1.0)}/scrf_{(1.5)} for which Casson-Gordon invariants vanish in Cochran-Orr-Teichner's filtration of the classical knot concordance group. As a corollary, it follows that Casson-Gordon invariants are not a complete set of obstructions to a second layer of Whitney disks.

  20. Knots on a Torus: A Model of the Elementary Particles

    Directory of Open Access Journals (Sweden)

    Jack S. Avrin

    2012-02-01

    Full Text Available Two knots; just two rudimentary knots, the unknot and the trefoil. That’s all we need to build a model of the elementary particles of physics, one with fermions and bosons, hadrons and leptons, interactions weak and strong and the attributes of spin, isospin, mass, charge, CPT invariance and more. There are no quarks to provide fractional charge, no gluons to sequester them within nucleons and no “colors” to avoid violating Pauli’s principle. Nor do we require the importation of an enigmatic Higgs boson to confer mass upon the particles of our world. All the requisite attributes emerge simply (and relativistically invariant as a result of particle conformation and occupation in and of spacetime itself, a spacetime endowed with the imprimature of general relativity. Also emerging are some novel tools for systemizing the particle taxonomy as governed by the gauge group SU(2 and the details of particle degeneracy as well as connections to Hopf algebra, Dirac theory, string theory, topological quantum field theory and dark matter. One exception: it is found necessary to invoke the munificent geometry of the icosahedron in order to provide, as per the group “flavor” SU(3, a scaffold upon which to organize the well-known three generations—no more, no less—of the particle family tree.

  1. Total synthesis of complestatin: development of a Pd(0)-mediated indole annulation for macrocyclization.

    Science.gov (United States)

    Shimamura, Hiroyuki; Breazzano, Steven P; Garfunkle, Joie; Kimball, F Scott; Trzupek, John D; Boger, Dale L

    2010-06-09

    Full details of the initial development and continued examination of a powerful intramolecular palladium(0)-mediated indole annulation for macrocyclization closure of the strained 16-membered biaryl ring system found in complestatin (1, chloropeptin II) and the definition of factors impacting its intrinsic atropodiastereoselectivity are described. Its examination and use in an alternative, second-generation total synthesis of complestatin are detailed in which the order of the macrocyclization reactions was reversed from our first-generation total synthesis. In this approach and with the ABCD biaryl ether ring system in place, the key Larock cyclization was conducted with substrate 36 (containing four phenols, five secondary amides, one carbamate, and four labile aryl chlorides) and provided the product 37 (56%) exclusively as a single atropisomer (>20:1, detection limits) possessing the natural (R)-configuration. In this instance, the complexity of the substrate and the reverse macrocyclization order did not diminish the atropodiastereoselectivity; rather, it provided an improvement over the 4:1 selectivity that was observed with the analogous substrate used to provide the isolated DEF ring system in our first-generation approach. Just as significant, the atroposelectivity represents a complete reversal of the diasteroselectivity observed with analogous macrocyclizations conducted using a Suzuki biaryl coupling.

  2. Sceliphrolactam, a polyene macrocyclic lactam from a wasp-associated Streptomyces sp

    DEFF Research Database (Denmark)

    Oh, Dong-Chan; Poulsen, Michael; Currie, Cameron R

    2011-01-01

    A previously unreported 26-membered polyene macrocyclic lactam, sceliphrolactam, was isolated from an actinomycete, Streptomyces sp., associated with the mud dauber, Sceliphron caementarium. Sceliphrolactam's structure was determined by 1D- and 2D-NMR, MS, UV, and IR spectral analysis. Sceliphrol...

  3. Study of behaviour of Ni(III) macrocyclic complexes in acidic ...

    Indian Academy of Sciences (India)

    The Cu(II) ion-catalysed kinetics of oxidation of H2O2 by [NiIIIL] [where L ... The rate of the reaction of both complexes with hydrogen peroxide shows contrasting ... enhanced kinetic and thermodynamic stabilities. The redox chemistry of synthetic poly-aza macrocycles explores the properties of nickel containing enzymes.1.

  4. Reactions of copper macrocycles with antioxidants and HOCl: potential for biological redox sensing.

    Science.gov (United States)

    Sowden, Rebecca J; Trotter, Katherine D; Dunbar, Lynsey; Craig, Gemma; Erdemli, Omer; Spickett, Corinne M; Reglinski, John

    2013-02-01

    A series of simple copper N(2)S(2) macrocycles were examined for their potential as biological redox sensors, following previous characterization of their redox potentials and crystal structures. The divalent species were reduced by glutathione or ascorbate at a biologically relevant pH in aqueous buffer. A less efficient reduction was also achieved by vitamin E in DMSO. Oxidation of the corresponding univalent copper species by sodium hypochlorite resulted in only partial (~65 %) recovery of the divalent form. This was concluded to be due to competition between metal oxidation and ligand oxidation, which is believed to contribute to macrocycle demetallation. Electrospray mass spectrometry confirmed that ligand oxidation had occurred. Moreover, the macrocyclic complexes could be demetallated by incubation with EDTA and bovine serum albumin, demonstrating that they would be inappropriate for use in biological systems. The susceptibility to oxidation and demetallation was hypothesized to be due to oxidation of the secondary amines. Consequently these were modified to incorporate additional oxygen donor atoms. This modification led to greater resistance to demetallation and ligand oxidation, providing a better platform for further development of copper macrocycles as redox sensors for use in biological systems.

  5. Synthesis and extended activity of triazole-containing macrocyclic protease inhibitors

    DEFF Research Database (Denmark)

    Pehere, A.D.; Pietsch, M.; Gütschow, M.

    2013-01-01

    of their activity against a panel of proteases. Acyclic azidoalkyne-based aldehydes are also evaluated for comparison. The macrocyclic peptidomimetics showed considerable activity towards calpain II, cathepsin L and S, and the 20S proteasome chymotrypsin-like activity. Some of the first examples of highly potent...

  6. Photoswitchable Dihydroazulene Macrocycles for Solar Energy Storage: The Effects of Ring Strain.

    Science.gov (United States)

    Vlasceanu, Alexandru; Frandsen, Benjamin N; Skov, Anders B; Hansen, Anne Schou; Rasmussen, Mads Georg; Kjaergaard, Henrik G; Mikkelsen, Kurt V; Nielsen, Mogens Brøndsted

    2017-10-06

    Efficient energy storage and release are two major challenges of solar energy harvesting technologies. The development of molecular solar thermal systems presents one approach to address these issues by tuning the isomerization reactions of photo/thermoswitches. Here we show that the incorporation of photoswitches into macrocyclic structures is a particularly attractive solution for increasing the storage time. We present the synthesis and properties of a series of macrocycles incorporating two dihydroazulene (DHA) photoswitching subunits, bridged by linkers of varying chain length. Independent of ring size, all macrocycles exhibit stepwise, light-induced, ring-opening reactions (DHA-DHA to DHA-VHF to VHF-VHF; VHF = vinylheptafulvene) with the first DHA undergoing isomerization with a similar efficiency as the uncyclized parent system while the second (DHA-VHF to VHF-VHF) is significantly slower. The energy-releasing, VHF-to-DHA, ring closures also occur in a stepwise manner and are systematically found to proceed slower in the more strained (smaller) cycles, but in all cases with a remarkably slow conversion of the second VHF to DHA. We managed to increase the half-life of the second VHF-to-DHA conversion from 65 to 202 h at room temperature by simply decreasing the ring size. A computational study reveals the smallest macrocycle to have the most energetic VHF-VHF state and hence highest energy density.

  7. Towards tumour targeting with copper-radiolabelled macrocycle-antibody conjugates

    Energy Technology Data Exchange (ETDEWEB)

    Morphy, J.R.; Parker, David; Kataky, Ritu; Harrison, Alice; Walker, Carole; Eaton, M.A.W.; Millican, Andrew; Phipps, Alison

    1989-06-15

    Tetraaza-macrocycles covalently attached to a monoclonal antibody may be efficiently radiolabelled with /sup 64/Cu or /sup 67/Cu at pH4, minimising non-specific binding to the protein, giving a kinetically stable conjugate in vivo. (author).

  8. Dimetal Complexes of a Bibrachial 2+2 Thiolate-based Macrocycle

    DEFF Research Database (Denmark)

    Lennartson, Anders; McKee, Vickie; Nelson, Jane

    2012-01-01

    Protocols for accessing the [2+3] and [2+2] tren + thiophenolate-based cryptands and macrocycles, respectively, have been devised; however, a propensity towards incomplete crypt formation is clear: Cd(II)2, Mn(II)2, Ni(II)2 and Pd(II)2 complexes of the [2+2] bibrachial systems in which one arm of...

  9. Convergent Synthesis of Rigid Macrocycles Containing One and Two Tetrathiafulvalene Units

    DEFF Research Database (Denmark)

    Simonsen, Klaus B.; Thorup, Niels; Becher, Jan

    1997-01-01

    The synthesis of rigid tetrathiafulvalenophanes containing one or two tetrathiafulvalene units is presented, together with a stepwise convergent synthesis of macrocyclic bis-tetrathiafulvalenes via several open dimeric tetrathiafulvalenes. These systems were investigated by cyclic voltammetry...... and by X-ray crystallography....

  10. Metacridamides A and B, bioactive macrocycles from conidia of the entomopathogenic fungus Metarhizium acridum

    Science.gov (United States)

    Metarhizium acridum, an entomopathogenic fungus, has been commercialized and used successfully for biocontrol of grasshopper pests in Africa and Australia. Its conidia produce two novel 17-membered macrocycles, metacridamides A (1) and B (2), which consist of a Phe unit condensed with a nonaketide....

  11. Experimental and DFT study on complexation of Eu3+ with a macrocyclic lactam receptor

    Czech Academy of Sciences Publication Activity Database

    Makrlík, E.; Záliš, Stanislav; Vaňura, P.; Sedláková, Zdeňka

    2013-01-01

    Roč. 24, č. 6 (2013), s. 2149-2153 ISSN 1040-0400 Institutional support: RVO:61388955 ; RVO:61389013 Keywords : europium * macrocyclic lactam receptor * complexation Subject RIV: CF - Physical ; Theoretical Chemistry; CD - Macromolecular Chemistry (UMCH-V) Impact factor: 1.900, year: 2013

  12. Complexation of Eu3+ with a macrocyclic lactam receptor: Experimental and theoretical study

    Czech Academy of Sciences Publication Activity Database

    Makrlík, E.; Záliš, Stanislav; Sedláková, Zdeňka; Vaňura, P.

    2013-01-01

    Roč. 1038, APR 2013 (2013), s. 216-219 ISSN 0022-2860 Institutional support: RVO:61388955 ; RVO:61389013 Keywords : europium * macrocyclic lactam receptor * complexation Subject RIV: CF - Physical ; Theoretical Chemistry; CD - Macromolecular Chemistry (UMCH-V) Impact factor: 1.599, year: 2013

  13. Studies of Flerovium and Element 115 Homologs with Macrocyclic Extractants

    Energy Technology Data Exchange (ETDEWEB)

    Despotopulos, John D. [Univ. of Nevada, Las Vegas, NV (United States)

    2015-03-12

    Study of the chemistry of the heaviest elements, Z ≥ 104, poses a unique challenge due to their low production cross-sections and short half-lives. Chemistry also must be studied on the one-atom-at-a-time scale, requiring automated, fast, and very efficient chemical schemes. Recent studies of the chemical behavior of copernicium (Cn, element 112) and flerovium (Fl, element 114) together with the discovery of isotopes of these elements with half-lives suitable for chemical studies have spurred a renewed interest in the development of rapid systems designed to study the chemical properties of elements with Z ≥ 114. This dissertation explores both extraction chromatography and solvent extraction as methods for development of a rapid chemical separation scheme for the homologs of flerovium (Pb, Sn, Hg) and element 115 (Bi, Sb), with the goal of developing a chemical scheme that, in the future, can be applied to on-line chemistry of both Fl and element 115. Carrier-free radionuclides, used in these studies, of the homologs of Fl and element 115 were obtained by proton activation of high-purity metal foils at the Lawrence Livermore National Laboratory (LLNL) Center for Accelerator Mass Spectrometry (CAMS): natIn(p,n)113Sn, natSn(p,n)124Sb, and Au(p,n)197m,gHg. The carrier-free activity was separated from the foils by novel separation schemes based on ion exchange and extraction chromatography techniques. Carrier-free Pb and Bi isotopes were obtained from development of a novel generator based on cation exchange chromatography using the 232U parent to generate 212Pb and 212Bi. Macrocyclic extractants, specifically crown ethers and their derivatives, were chosen for these studies; crown ethers show high selectivity for metal ions. Finally. a potential chemical system for Fl was established based on the Eichrom Pb resin, and insight to an improved system based on thiacrown ethers is

  14. Radiolytic and photochemical reduction of carbon dioxide in solution catalyzed by transition metal complexes with some selected macrocycles

    International Nuclear Information System (INIS)

    Grodkowski, J.

    2004-01-01

    The main goal of the work presented in this report is an explanation of the mechanism of carbon dioxide (CO 2 ) reduction catalyzed by transition metal complexes with some selected macrocycles. The catalytic function of two electron exchange centers in the reduction of CO 2 , an inner metal and a macrocycle ring, was defined. Catalytic effects of rhodium, iron and cobalt porphyrins, cobalt and iron phthalocyanines and corroles as well as cobalt corrins have been investigated. CO 2 reduction by iron ions without presence of macrocycles and also in presence of copper compounds in aqueous solutions have been studied as well

  15. m-Diethynylbenzene macrocycles: syntheses and self-association behavior in solution.

    Science.gov (United States)

    Tobe, Yoshito; Utsumi, Naoto; Kawabata, Kazuya; Nagano, Atsushi; Adachi, Kiyomi; Araki, Shunji; Sonoda, Motohiro; Hirose, Keiji; Naemura, Koichiro

    2002-05-15

    m-Diethynylbenzene macrocycles (DBMs), buta-1,3-diyne-bridged [4(n)]metacyclophanes, have been synthesized and their self-association behaviors in solution were investigated. Cyclic tetramers, hexamers, and octamers of DBMs having exo-annular octyl, hexadecyl, and 3,6,9-trioxadecyl ester groups were prepared by intermolecular oxidative coupling of dimer units or intramolecular cyclization of the corresponding open-chain oligomers. The aggregation properties were investigated by two methods, the (1)H NMR spectra and the vapor pressure osmometry (VPO). Although some discrepancies were observed between the association constants obtained from the two methods, the qualitative view was consistent with each other. The analysis of self-aggregation by VPO revealed unique aggregation behavior of DBMs in acetone and toluene, which was not elucidated by the NMR method. Namely, the association constants for infinite association are several times larger than the dimerization constant, suggesting that the aggregation is enhanced by the formation of dimers (a nucleation mechanism). In polar solvents, DBMs aggregate more strongly than in chloroform due to the solvophobic interactions between the macrocyclic framework and the solvents. Moreover, DBMs self-associate in aromatic solvents such as toluene and o-xylene more readily than in chloroform. In particular, the hexameric DBM having a large macrocyclic cavity exhibits extremely large association constants in aromatic solvents. By comparing the aggregation properties of DBMs with the corresponding acyclic oligomers, the effect of the macrocyclic structure on the aggregation propensity was clarified. Finally, it turned out that DBMs tend to aggregate more readily than the corresponding phenylacetylene macrocycles, acetylene-bridged [2(n)]metacyclophanes, owing to the withdrawal of the electron density from the aromatic rings by the butadiyne linkages which facilitates pi-pi stacking interactions.

  16. Pseudomonas savastanoi pv. savastanoi: some like it knot.

    Science.gov (United States)

    Ramos, Cayo; Matas, Isabel M; Bardaji, Leire; Aragón, Isabel M; Murillo, Jesús

    2012-12-01

    Pseudomonas savastanoi pv. savastanoi is the causal agent of olive (Olea europaea) knot disease and an unorthodox member of the P. syringae complex, causing aerial tumours instead of the foliar necroses and cankers characteristic of most members of this complex. Olive knot is present wherever olive is grown; although losses are difficult to assess, it is assumed that olive knot is one of the most important diseases of the olive crop. The last century witnessed a large number of scientific articles describing the biology, epidemiology and control of this pathogen. However, most P. savastanoi pv. savastanoi strains are highly recalcitrant to genetic manipulation, which has effectively prevented the pathogen from benefitting from the scientific progress in molecular biology that has elevated the foliar pathogens of the P. syringae complex to supermodels. A number of studies in recent years have made significant advances in the biology, ecology and genetics of P. savastanoi pv. savastanoi, paving the way for the molecular dissection of its interaction with other nonpathogenic bacteria and their woody hosts. The selection of a genetically pliable model strain was soon followed by the development of rapid methods for virulence assessment with micropropagated olive plants and the analysis of cellular interactions with the plant host. The generation of a draft genome of strain NCPPB 3335 and the closed sequence of its three native plasmids has allowed for functional and comparative genomic analyses for the identification of its pathogenicity gene complement. This includes 34 putative type III effector genes and genomic regions, shared with other pathogens of woody hosts, which encode metabolic pathways associated with the degradation of lignin-derived compounds. Now, the time is right to explore the molecular basis of the P. savastanoi pv. savastanoi-olive interaction and to obtain insights into why some pathovars like it necrotic and why some like it knot

  17. Antagonistic Activities of Streptomyces against Root Knot Nematode of Kiwifruit

    Directory of Open Access Journals (Sweden)

    S. Bashiri

    2016-02-01

    Full Text Available Introduction: Iran is among the world leading kiwifruit producers with 2.816 ha cultivated and 31.567 tones production. Plant parasitic nematodes cause damages to a variety of agricultural crops throughout the world. Interest in biological control of nematodes has increased because of the need for alternative methods to fumigant and non-fumigant nematicides and overall improvement of IPM programs. Bacterial species with nematicidal activity have also been used with some success for controlling root-knot diseases, including Streptomyces spp., Serratia spp., Bacillus spp. and Pseudomonas spp. The goal of the current study was to isolate, identify and investigate the potential of local Streptomyces bacteria for controlling and reducing root-knot nematode population in the north of Iran. Materials and Methods: In order to evaluate the effect of antagonistic bacteria on control of root-knot nematode of Kiwifruit, 100 isolates of bacteria were collected from Kiwifruit rhizosphere in the north of Iran and screened for pigmented microorganisms especially Streptomyces by applying standard serial dilution plate technique, using starch casein nitrate agar and glycerol asparagine agar. Morphological characterizations were achieved by the microscopic method. The microscopic characterization was done by cover slip culture method. The mycelium structure, color and arrangement of conidiospore and arthrospore on the mycelium were observed through the oil immersion (100X. The observed structure was compared with Bergey’s Manual of Determinative Bacteriology and the organism was identified. Various biochemical tests performed for the identification of the potent isolates are as follows: casein hydrolysis, starch hydrolysis, urea hydrolysis, esculin hydrolysis, acid production from sugar, NaCl resistance, temperature tolerance. Soil samples (100g were collected, and then processed for nematode egg and larvae extraction Hussey method. The suspension was pipetted

  18. An Indwelling Urethral Catheter Knotted Around a Double-J Ureteral Stent: An Unusual Complication after Kidney Transplantation

    Directory of Open Access Journals (Sweden)

    E. G. Warmerdam

    2011-01-01

    Full Text Available Urethral catheterization is a common procedure with a relatively low complication rate. Knotting of an indwelling urethral catheter is a very rare complication, and there are only a few case reports on knotted catheters, most of them concerning children. We report an especially rare case where a urethral catheter formed a knot around a double-J ureteral stent after a kidney transplantation. We will discuss the various risk factors for knotting of a catheter and the methods to untangle a knot.

  19. Synergistic extraction of some divalent metal cations into nitrobenzene by using strontium dicarbollylcobaltate and electroneutral macrocyclic lactam receptor

    Czech Academy of Sciences Publication Activity Database

    Makrlík, E.; Sedláková, Zdeňka; Vaňura, P.; Selucký, P.

    2013-01-01

    Roč. 295, č. 3 (2013), s. 2263-2266 ISSN 0236-5731 Institutional support: RVO:61389013 Keywords : divalent metal cations * macrocyclic lactam receptor * complexation Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.415, year: 2013

  20. Dynamic PET and Optical Imaging and Compartment Modeling using a Dual-labeled Cyclic RGD Peptide Probe

    OpenAIRE

    Zhu, Lei; Guo, Ning; Li, Quanzheng; Ma, Ying; Jacboson, Orit; Lee, Seulki; Choi, Hak Soo; Mansfield, James R.; Niu, Gang; Chen, Xiaoyuan

    2012-01-01

    Purpose: The aim of this study is to determine if dynamic optical imaging could provide comparable kinetic parameters to that of dynamic PET imaging by a near-infrared dye/64Cu dual-labeled cyclic RGD peptide. Methods: The integrin αvβ3 binding RGD peptide was conjugated with a macrocyclic chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) for copper labeling and PET imaging and a near-infrared dye ZW-1 for optical imaging. The in vitro biological activity of RGD-C(DOTA)...

  1. Numerical simulation of the knotted nylon netting panel

    Directory of Open Access Journals (Sweden)

    Li Yuwei

    2016-01-01

    Full Text Available A piece of netting, consists of the 8 8 meshes, fixed on a square frame, was simulated and the tensions and their distribution, the positions of knots and netting shape were calculated by means of MATLAB in computer. The dynamic mathematic model was developed based on lumped mass method, the netting was treated as spring-mass system, the Runge-Kutta fifth-order and sixth-order method was used to solve the differential equations for every step, then the displacement and tension of each mass point were obtained. For verify this model, the tests have been carried out in a flume tank. The results of the numerical simulation fully agreed with the experiments.

  2. Disciplinary Knots and Learning Problems in Waves Physics

    Science.gov (United States)

    Di Renzone, Simone; Frati, Serena; Montalbano, Vera

    An investigation on student understanding of waves is performed during an optional laboratory realized in informal extracurricular way with few, interested and talented pupils. The background and smart intuitions of students rendered the learning path very dynamic and ambitious. The activities started by investigating the basic properties of waves by means of a Shive wave machine. In order to make quantitative observed phenomena, the students used a camcorder and series of measures were obtained from the captured images. By checking the resulting data, it arose some learning difficulties especially in activities related to the laboratory. This experience was the starting point for a further analysis on disciplinary knots and learning problems in the physics of waves in order to elaborate a teaching-learning proposal on this topic.

  3. New knotted solutions of Maxwell's equations

    International Nuclear Information System (INIS)

    Hoyos, Carlos; Sircar, Nilanjan; Sonnenschein, Jacob

    2015-01-01

    In this paper we have further developed the study of topologically non-trivial solutions of vacuum electrodynamics. We have discovered a novel method of generating such solutions by applying conformal transformations with complex parameters on known solutions expressed in terms of Bateman's variables. This has enabled us to obtain a wide class of solutions from the basic configuration, such as constant electromagnetic fields and plane-waves. We have introduced a covariant formulation of Bateman's construction and discussed the conserved charges associated with the conformal group as well as a set of four types of conserved helicities. We have also given a formulation in terms of quaternions. This led to a simple map between the electromagnetic knotted and linked solutions into flat connections of SU(2) gauge theory. We have computed the corresponding Chern–Simons charge in a class of solutions and the charge takes integer values. (paper)

  4. Average size of random polygons with fixed knot topology.

    Science.gov (United States)

    Matsuda, Hiroshi; Yao, Akihisa; Tsukahara, Hiroshi; Deguchi, Tetsuo; Furuta, Ko; Inami, Takeo

    2003-07-01

    We have evaluated by numerical simulation the average size R(K) of random polygons of fixed knot topology K=,3(1),3(1) musical sharp 4(1), and we have confirmed the scaling law R(2)(K) approximately N(2nu(K)) for the number N of polygonal nodes in a wide range; N=100-2200. The best fit gives 2nu(K) approximately 1.11-1.16 with good fitting curves in the whole range of N. The estimate of 2nu(K) is consistent with the exponent of self-avoiding polygons. In a limited range of N (N greater, similar 600), however, we have another fit with 2nu(K) approximately 1.01-1.07, which is close to the exponent of random polygons.

  5. Quantum invariants of knots and 3-manifolds. 2. rev. ed.

    International Nuclear Information System (INIS)

    Turaev, Vladimir G.

    2010-01-01

    Due to the strong appeal and wide use of this monograph, it is now available in its second revised edition. The monograph gives a systematic treatment of 3-dimensional topological quantum field theories (TQFTs) based on the work of the author with N. Reshetikhin and O. Viro. This subject was inspired by the discovery of the Jones polynomial of knots and the Witten-Chern-Simons field theory. On the algebraic side, the study of 3-dimensional TQFTs has been influenced by the theory of braided categories and the theory of quantum groups. The book is divided into three parts. Part I presents a construction of 3-dimensional TQFTs and 2-dimensional modular functors from so-called modular categories. This gives a vast class of knot invariants and 3-manifold invariants as well as a class of linear representations of the mapping class groups of surfaces. In Part II the technique of 6j-symbols is used to define state sum invariants of 3-manifolds. Their relation to the TQFTs constructed in Part I is established via the theory of shadows. Part III provides constructions of modular categories, based on quantum groups and skein modules of tangles in the 3-space. This fundamental contribution to topological quantum field theory is accessible to graduate students in mathematics and physics with knowledge of basic algebra and topology. It is an indispensable source for everyone who wishes to enter the forefront of this fascinating area at the borderline of mathematics and physics. From the contents: - Invariants of graphs in Euclidean 3-space and of closed 3-manifolds - Foundations of topological quantum field theory - Three-dimensional topological quantum field theory - Two-dimensional modular functors - 6j-symbols - Simplicial state sums on 3-manifolds - Shadows of manifolds and state sums on shadows - Constructions of modular categories. (orig.)

  6. HOMFLYPT polynomial is the best quantifier for topological cascades of vortex knots

    Science.gov (United States)

    Ricca, Renzo L.; Liu, Xin

    2018-02-01

    In this paper we derive and compare numerical sequences obtained by adapted polynomials such as HOMFLYPT, Jones and Alexander-Conway for the topological cascade of vortex torus knots and links that progressively untie by a single reconnection event at a time. Two cases are considered: the alternate sequence of knots and co-oriented links (with positive crossings) and the sequence of two-component links with oppositely oriented components (negative crossings). New recurrence equations are derived and sequences of numerical values are computed. In all cases the adapted HOMFLYPT polynomial proves to be the best quantifier for the topological cascade of torus knots and links.

  7. Simple Syntheses of Two New Benzo-Fused Macrocycles Incorporating Chalcone Moiety.

    Science.gov (United States)

    Mondal, Rina; Samanta, Swati; Sarkar, Saheli; Mallik, Asok K

    2014-01-01

    Simple syntheses of the benzo-fused 26-membered macrocyclic bischalcone (19E,43E)-2.11.27.36-tetroxaheptacyclo[44.4.0.0(4,9).0(12,17).0(21,26).0(29,34).0(37,42)]pentaconta-1(46),4(9),5,7,12(17),13,15,19,21,23,25,29,31,33,37,39,41,43,47,49-icosaene-18,45-dione (3) and the benzo-fused 13-membered macrocyclic chalcone (19E)-2.11-dioxatetracyclo[19.4.0.0(4,9).0(12,17)]pentacosa-1(25),4(9),5,7,12(17),13,15,19,21,23-decaen-18-one (5) using very common starting materials and reagents are described. The compounds are new and they have been characterized from their analytical and spectral data.

  8. Synthetic approaches to aromatic belts: building up strain in macrocyclic polyarenes.

    Science.gov (United States)

    Eisenberg, David; Shenhar, Roy; Rabinovitz, Mordecai

    2010-08-01

    This tutorial review discusses synthetic strategies towards aromatic belts, defined here as double-stranded conjugated macrocycles, such as [n]cyclacenes, [n]cyclophenacenes, Schlüter belt, and Vögtle belt. Their appeal stems, firstly, from the unique nature of their conjugation, having p orbitals oriented radially rather than perpendicular to the plane of the macrocycle. Secondly, as aromatic belts are model compounds of carbon nanotubes of different chiralities, a synthetic strategy towards the buildup of structural strain in these compounds could finally open a route towards rational chemical synthesis of carbon nanotubes. The elusiveness of these compounds has stimulated fascinating and ingenious synthetic strategies over the last decades. The various strategies are classified here by their approach to the buildup of structural strain, which is the main obstacle in the preparation of these curved polyarenes.

  9. Synthesis and anion recognition properties of shape-persistent binaphthyl-containing chiral macrocyclic amides

    Directory of Open Access Journals (Sweden)

    Marco Caricato

    2012-06-01

    Full Text Available We report on the synthesis and characterization of novel shape-persistent, optically active arylamide macrocycles, which can be obtained using a one-pot methodology. Resolved, axially chiral binol scaffolds, which incorporate either methoxy or acetoxy functionalities in the 2,2' positions and carboxylic functionalities in the external 3,3' positions, were used as the source of chirality. Two of these binaphthyls are joined through amidation reactions using rigid diaryl amines of differing shapes, to give homochiral tetraamidic macrocycles. The recognition properties of these supramolecular receptors have been analyzed, and the results indicate a modulation of binding affinities towards dicarboxylate anions, with a drastic change of binding mode depending on the steric and electronic features of the functional groups in the 2,2' positions.

  10. Ring strain and total syntheses of modified macrocycles of the isoplagiochin type

    Directory of Open Access Journals (Sweden)

    Andreas Speicher

    2009-12-01

    Full Text Available Macrocycles of the bisbibenzyl-type are natural products that are found exclusively in bryophytes (liverworts. The molecular framework of the subtype “isoplagiochin” is of substantial structural interest because of the chirality of the entire molecule, which arises from two biaryl axes in combination with two helical two-carbon units in a cyclic arrangement. From a structural as well as a synthetic point of view we report on the total synthesis of compounds which possess more rigid two-carbon biaryl bridges like stilbene (E or Z or even tolane moieties which were introduced starting with a Sonogashira protocol. The McMurry method proved to be a powerful tool for the cyclization to these considerably ring-strained macrocycles.

  11. Physical Removal of Anions from Aqueous Media by Means of a Macrocycle-Containing Polymeric Network

    KAUST Repository

    Ji, Xiaofan

    2018-02-13

    Reported here is a hydrogel-forming polymer network that contains a water-soluble tetracationic macrocycle. Upon immersion of this polymer network in aqueous solutions containing various inorganic and organic salts, changes in the physical properties are observed that are consistent with absorption of the constituent anions into the polymer network. This absorption is ascribed to host-guest interactions involving the tetracationic macrocyclic receptor. Removal of the anions may then be achieved by lifting the resulting hydrogels out of the aqueous phase. Treating the anion-containing hydrogels with dilute HCl leads to the protonation-induced release of the bound anions. This allows the hydrogels to be recycled for reuse. The present polymer network thus provides a potentially attractive approach to removing undesired anions from aqueous environments.

  12. The influence of intraannular templates on the liquid crystallinity of shape-persistent macrocycles

    Directory of Open Access Journals (Sweden)

    Joscha Vollmeyer

    2014-04-01

    Full Text Available A series of shape-persistent phenylene–ethynylene–naphthylene–butadiynylene macrocycles with different extraannular alkyl groups and intraannular bridges is synthesized by oxidative Glaser-coupling of the appropriate precursors. The intraannular bridges serve in this case as templates that reduce the oligomerization even when the reaction is not performed under pseudo high-dilution conditions. The extraannular as well as the intraannular substituents have a strong influence on the thermal behavior of the compounds. With branched alkyl chains at the periphery, the macrocycles exhibit liquid crystalline (lc phases when the interior is empty or when the length of the alkyl bridge is just right to cross the ring. With a longer alkyl or an oligoethylene oxide bridge no lc phase is observed, most probably because the mesogene is no longer planar.

  13. Macrocyclic lactones: A versatile source for omega radiohalogenated fatty acid analogs

    International Nuclear Information System (INIS)

    Dougan, A.H.; Lyster, D.M.; Robertson, K.A.; Vincent, J.S.

    1984-01-01

    For each omega halogenated fatty acid there exists a potential omega hydroxy fatty acid and the corresponding macrocyclic lactone. The authors have utilized such lactones as starting materials for omega /sup 123/I fatty acid analogs intended for myocardial imaging. Macrocyclic musk lactones are industrially available; 120 analogs are described in the literature. The preparation requires saponification, tosylation, and radio-iodide substitution. Iodo-fatty acids are readily separated from tosylate fatty acids on TLC. While providing a secure source of 16-iodo-hexadecanoic acid and 17-iodo-heptadecanoic acid, the scheme allows ready access to a large number of untried fatty acid analogs. Examples presented are 16-iodo-hexadecanoic acid, 16-iodo-7-hexadecanoic acid, 16-iodo-12-oxa-hexadecanoic acid, 15-iodo-pentadecanoic acid, and 15-iodo-12-keto-pentadecanoic acid. Metabolic studies are in progress in mice and dogs to assess the utility of these analogs for myocardial imaging

  14. Knot numbers used as labels for identifying subject matter of a khipu

    Directory of Open Access Journals (Sweden)

    Alberto Saez-Rodriguez

    2013-03-01

    Full Text Available This investigation presents a new way to look at the numerical khipu, a knotted-string recording device from Pachacamac (Peru, and the types of information it contains. In addition to celestial coordinates, khipu knots apparently pertain to an early form of double-entry accounting. This study hypothesizes that the khipu sample has the recording capacity needed to register double-entry-like accounts. After the identification of its subject matter, the khipu sample was studied in an attempt to ascertain whether the knot values could represent instructions from the Inca state administration to a local accounting center. The results indicate that the numerical information in the pairing quadrants (determined by the distribution of S- and Z-knots should be read from top to bottom along the full length of the string and can then provide certain complementary details regarding the projected corn stocks of the Inca stat

  15. Explicit Gaussian quadrature rules for C^1 cubic splines with symmetrically stretched knot sequence

    KAUST Repository

    Ait-Haddou, Rachid; Barton, Michael; Calo, Victor M.

    2015-01-01

    We provide explicit expressions for quadrature rules on the space of C^1 cubic splines with non-uniform, symmetrically stretched knot sequences. The quadrature nodes and weights are derived via an explicit recursion that avoids an intervention

  16. Effect of soil solarization using plastic mulch in controlling root-knot ...

    African Journals Online (AJOL)

    PRECIOUS

    2009-12-15

    Dec 15, 2009 ... effect of soil solarization using plastic mulch in controlling root-knot nematode infestation and yield of ... addition to their increased toxic effects in the soil over the .... thereby promoting conducive environment for the utiliza- ...

  17. Knotted solutions for linear and nonlinear theories: Electromagnetism and fluid dynamics

    Directory of Open Access Journals (Sweden)

    Daniel W.F. Alves

    2017-10-01

    Full Text Available We examine knotted solutions, the most simple of which is the “Hopfion”, from the point of view of relations between electromagnetism and ideal fluid dynamics. A map between fluid dynamics and electromagnetism works for initial conditions or for linear perturbations, allowing us to find new knotted fluid solutions. Knotted solutions are also found to be solutions of nonlinear generalizations of electromagnetism, and of quantum-corrected actions for electromagnetism coupled to other modes. For null configurations, electromagnetism can be described as a null pressureless fluid, for which we can find solutions from the knotted solutions of electromagnetism. We also map them to solutions of Euler's equations, obtained from a type of nonrelativistic reduction of the relativistic fluid equations.

  18. PRESENCE OF RED KNOT (CALIDRIS CANUTUS) IN ITE WETLANDS, TACNA, PERU

    OpenAIRE

    Jhonson K. Vizcarra

    2012-01-01

    The presence of Red Knot (Calidris canutus, Linnaeus 1758) in Ite Wetlands, Tacna, Peru is documented. Two individuals were observed in October 2011. This species had only one occurrence without details in this area.

  19. Splitting, linking, knotting, and solitonic escape of topological defects in nematic drops with handles.

    Science.gov (United States)

    Tasinkevych, Mykola; Campbell, Michael G; Smalyukh, Ivan I

    2014-11-18

    Topologically nontrivial field excitations, including solitonic, linked, and knotted structures, play important roles in physical systems ranging from classical fluids and liquid crystals, to electromagnetism, classic, and quantum field theories. These excitations can appear spontaneously during symmetry-breaking phase transitions. For example, in cosmological theories, cosmic strings may have formed knotted configurations influencing the Early Universe development, whereas in liquid crystals transient tangled defect lines were observed during isotropic-nematic transitions, eventually relaxing to defect-free states. Knotted and solitonic fields and defects were also obtained using optical manipulation, complex-shaped colloids, and frustrated cholesterics. Here we use confinement of nematic liquid crystal by closed surfaces with varied genus and perpendicular boundary conditions for a robust control of appearance and stability of such field excitations. Theoretical modeling and experiments reveal structure of defect lines as a function of the surface topology and material and geometric parameters, establishing a robust means of controlling solitonic, knotted, linked, and other field excitations.

  20. Stability and kinetics of uranyl ion complexation by macrocycles in propylene carbonate

    International Nuclear Information System (INIS)

    Fux, P.

    1984-06-01

    A thermodynamic study of uranyl ion complexes formation with different macrocyclic ligands was realized in propylene carbonate as solvent using spectrophotometric and potentiometric techniques. Formation kinetics of two UO 2 complexes: a crown ether (18C6) and a coronand (22) was studied by spectrophotometry in propylene carbonate with addition of tetraethylammonium chlorate 0.1M at 25 0 C. Possible structures of complexes in solution are discussed [fr

  1. Lead Diversification through a Prins-Driven Macrocyclization Strategy: Application to C13-Diversified Bryostatin Analogues.

    Science.gov (United States)

    Wender, Paul A; Billingsley, Kelvin L

    2013-01-01

    The design, synthesis, and biological evaluation of a novel class of C13-diversified bryostatin analogues are described. An innovative and general strategy based on a Prins macrocyclization-nucleophilic trapping cascade was used to achieve late-stage diversification. In vitro analysis of selected library members revealed that modification at the C13 position of the bryostatin scaffold can be used as a diversification handle to regulate biological activity.

  2. A method for the preparation of lipophilic macrocyclic technetium-99m complexes

    International Nuclear Information System (INIS)

    Troutner, D.E.; Volkert, W.A.

    1991-01-01

    A procedure for the preparation of technetium complexes applicable as diagnostic radiopharmaceuticals is suggested and documented with 27 examples. Technetium-99m is reacted with a suitable complexant selected from the class of alkylenamine oximes containing 2 or 3 carbon atoms in the alkylene group. The lipophilic macrocyclic complexes possess an amine, amide, carboxy, carboxy ester, hydroxy or alkoxy group or a suitable electron acceptor group. (M.D.). 7 tabs

  3. Total synthesis of haterumalides NA and NC via a chromium-mediated macrocyclization.

    Science.gov (United States)

    Schomaker, Jennifer M; Borhan, Babak

    2008-09-17

    The syntheses of haterumalides NA and NC were accomplished via the macrocyclization of a chlorovinylidene chromium carbenoid onto a pendant aldehyde to generate the C8-C9 bond with the desired stereoisomer as the major product. Utilizing the latter chemistry enables access to both C9 hydroxylated (haterumalides NC and ND) and C9 deoxygenated forms (haterumalides NA, NB, and NE; via deoxygenation of the C9-hydroxyl).

  4. Synthesis and characterization of two new tetrapyrazolic macrocycles for the selective extraction of cesium cation

    Czech Academy of Sciences Publication Activity Database

    Harit, T.; Malek, F.; El Bali, B.; Dušek, Michal; Kučeráková, Monika

    2016-01-01

    Roč. 72, č. 27-28 (2016), s. 3966-3973 ISSN 0040-4020 R&D Projects: GA MŠk LO1603; GA ČR(CZ) GA14-03276S EU Projects: European Commission(XE) CZ.2.16/3.1.00/24510 Institutional support: RVO:68378271 Keywords : cesium cation * liquid–liquid extraction * macrocycle * pyrazole * crystal structure Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.651, year: 2016

  5. Recognition of thymine in DNA bulges by a Zn(II) macrocyclic complex.

    Science.gov (United States)

    del Mundo, Imee Marie A; Fountain, Matthew A; Morrow, Janet R

    2011-08-14

    A Zn(II) macrocyclic complex with appended quinoline is a bifunctional recognition agent that uses both the Zn(II) center and the pendent aromatic group to bind to thymine in bulges with good selectivity over DNA containing G, C or A bulges. Spectroscopic studies show that the stem containing the bulge stays largely intact in a DNA hairpin with the Zn(II) complex bound to the thymine bulge. This journal is © The Royal Society of Chemistry 2011

  6. Toxin structures as evolutionary tools: Using conserved 3D folds to study the evolution of rapidly evolving peptides.

    Science.gov (United States)

    Undheim, Eivind A B; Mobli, Mehdi; King, Glenn F

    2016-06-01

    Three-dimensional (3D) structures have been used to explore the evolution of proteins for decades, yet they have rarely been utilized to study the molecular evolution of peptides. Here, we highlight areas in which 3D structures can be particularly useful for studying the molecular evolution of peptide toxins. Although we focus our discussion on animal toxins, including one of the most widespread disulfide-rich peptide folds known, the inhibitor cystine knot, our conclusions should be widely applicable to studies of the evolution of disulfide-constrained peptides. We show that conserved 3D folds can be used to identify evolutionary links and test hypotheses regarding the evolutionary origin of peptides with extremely low sequence identity; construct accurate multiple sequence alignments; and better understand the evolutionary forces that drive the molecular evolution of peptides. Also watch the video abstract. © 2016 WILEY Periodicals, Inc.

  7. Potential of Tissue Culture for Breeding Root-Knot Nematode Resistance into Vegetables

    OpenAIRE

    Fassuliotis, G.; Bhatt, D. P.

    1982-01-01

    Plant protoplast technology is being investigated as a means of transferring root-knot nematode resistance factors from Solanum sisymbriifolium into the susceptible S. melongena. Solanum sisymbriifolium plants regenerated from callus lost resistance to Meloidogyne javanica but retained resistance to M. incognita. Tomato plants cloned from leaf discs of the root-knot nematode resistant 'Patriot' were completely susceptible to M. incognita, while sections of stems and leaves rooted in sand in t...

  8. Control of Root-Knot Nematodes on Tomato by the Endoparasitic Fungus Meria coniospora

    OpenAIRE

    Jansson, Hans-Börje; Jeyaprakash, A.; Zuckerman, Bert M.

    1985-01-01

    The endoparasitic nematophagous fungus Meria coniospora reduced root-knot nematode galling on tomatoes in greenhouse pot trials. The fungus was introduced to pots by addition of conidia at several inoculum levels directly to the soil or addition of nematodes infected with M. coniospora to the soil; both methods reduced root galling by root-knot nematodes. These studies represent a part of a recently initiated effort to evaluate the potential of endoparasitic nematophagous fungi for biocontrol...

  9. Knots: attractive places with high path tortuosity in mouse open field exploration.

    Directory of Open Access Journals (Sweden)

    Anna Dvorkin

    2010-01-01

    Full Text Available When introduced into a novel environment, mammals establish in it a preferred place marked by the highest number of visits and highest cumulative time spent in it. Examination of exploratory behavior in reference to this "home base" highlights important features of its organization. It might therefore be fruitful to search for other types of marked places in mouse exploratory behavior and examine their influence on overall behavior.Examination of path curvatures of mice exploring a large empty arena revealed the presence of circumscribed locales marked by the performance of tortuous paths full of twists and turns. We term these places knots, and the behavior performed in them-knot-scribbling. There is typically no more than one knot per session; it has distinct boundaries and it is maintained both within and across sessions. Knots are mostly situated in the place of introduction into the arena, here away from walls. Knots are not characterized by the features of a home base, except for a high speed during inbound and a low speed during outbound paths. The establishment of knots is enhanced by injecting the mouse with saline and placing it in an exposed portion of the arena, suggesting that stress and the arousal associated with it consolidate a long-term contingency between a particular locale and knot-scribbling.In an environment devoid of proximal cues mice mark a locale associated with arousal by twisting and turning in it. This creates a self-generated, often centrally located landmark. The tortuosity of the path traced during the behavior implies almost concurrent multiple views of the environment. Knot-scribbling could therefore function as a way to obtain an overview of the entire environment, allowing re-calibration of the mouse's locale map and compass directions. The rich vestibular input generated by scribbling could improve the interpretation of the visual scene.

  10. Peptide chemistry toolbox - Transforming natural peptides into peptide therapeutics.

    Science.gov (United States)

    Erak, Miloš; Bellmann-Sickert, Kathrin; Els-Heindl, Sylvia; Beck-Sickinger, Annette G

    2018-06-01

    The development of solid phase peptide synthesis has released tremendous opportunities for using synthetic peptides in medicinal applications. In the last decades, peptide therapeutics became an emerging market in pharmaceutical industry. The need for synthetic strategies in order to improve peptidic properties, such as longer half-life, higher bioavailability, increased potency and efficiency is accordingly rising. In this mini-review, we present a toolbox of modifications in peptide chemistry for overcoming the main drawbacks during the transition from natural peptides to peptide therapeutics. Modifications at the level of the peptide backbone, amino acid side chains and higher orders of structures are described. Furthermore, we are discussing the future of peptide therapeutics development and their impact on the pharmaceutical market. Copyright © 2018 Elsevier Ltd. All rights reserved.

  11. On-Surface Pseudo-High-Dilution Synthesis of Macrocycles: Principle and Mechanism.

    Science.gov (United States)

    Fan, Qitang; Wang, Tao; Dai, Jingya; Kuttner, Julian; Hilt, Gerhard; Gottfried, J Michael; Zhu, Junfa

    2017-05-23

    Macrocycles have attracted much attention due to their specific "endless" topology, which results in extraordinary properties compared to related linear (open-chain) molecules. However, challenges still remain in their controlled synthesis with well-defined constitution and geometry. Here, we report the successful application of the (pseudo-)high-dilution method to the conditions of on-surface synthesis in ultrahigh vacuum. This approach leads to high yields (up to 84%) of cyclic hyperbenzene ([18]-honeycombene) via an Ullmann-type reaction from 4,4″-dibromo-meta-terphenyl (DMTP) as precursor on a Ag(111) surface. The mechanism of macrocycle formation was explored in detail using scanning tunneling microscopy and X-ray photoemission spectroscopy. We propose that the dominant pathway for hyperbenzene (MTP) 6 formation is the stepwise desilverization of an organometallic (MTP-Ag) 6 macrocycle, which forms via cyclization of (MTP-Ag) 6 chains under pseudo-high-dilution conditions. The high probability of cyclization on the stage of the organometallic phase results from the reversibility of the C-Ag bond. The case is different from that in solution, in which cyclization typically occurs on the stage of a covalently bonded open-chain precursor. This difference in the cyclization mechanism on a surface compared to that in solution stems mainly from the 2D confinement exerted by the surface template, which hinders the flipping of chain segments necessary for cyclization.

  12. Design and synthesis of macrocyclic ligands and their complexes of lanthanides and actinides

    International Nuclear Information System (INIS)

    Alexander, V.

    1995-01-01

    A review article which covers the various design and synthetic strategies developed to synthesize macrocyclic complexes of lanthanides and actinides, their structural features, quantitative studies on the stabilities of these complexes, their applications, and the structure-reactivity principle would be an asset for those who are actively engaged in this area of research. This review is also purported to give a comprehensive view of the current status of this area of research to the beginners and to highlight the application of this chemical research to emerging nonchemical applications to lure the potential workers. The coordination template effect provides a general strategy for the synthesis of a wide variety of discrete metal complexes. The principal conceptual and experimental development that have established and exploited this strategy are briefly outlined. A brief review of the coordination template effect and subsequent developments in the design of macrocyclic complexes of alkali, alkaline earth, and transition metal ions is presented as an essential basis for the rational design of new macrocyclic complexes of lanthanides and actinides. The exciting aspect of this chemistry is that in the majority of cases the molecules meet the design criteria very well. It is evident that in an increasing number of cases the driving force behind the synthetic effort is the desire to create a molecule which will enable the user to make specific applications. 506 refs

  13. Hydrolyzable tannins of tamaricaceous plants. III. Hellinoyl- and macrocyclic-type ellagitannins from Tamarix nilotica.

    Science.gov (United States)

    Orabi, Mohamed A A; Taniguchi, Shoko; Yoshimura, Morio; Yoshida, Takashi; Kishino, Kaori; Sakagami, Hiroshi; Hatano, Tsutomu

    2010-05-28

    Three new hellinoyl-type ellagitannins, nilotinins M4 (7), D7 (8), and D8 (9), and a new macrocyclic-type, nilotinin D9 (10), together with eight known tannins, hirtellins B (2), C (11), and F (12), isohirtellin C (13), tamarixinin A (3), tellimagrandins I and II, and 1,2,6-tri-O-galloyl-beta-d-glucose (14), were isolated from an aqueous acetone extract of Tamarix nilotica dried leaves. Nilotinin M4 (7) is a monomeric tannin possessing a hellinoyl moiety. The structure of 8 demonstrated replacement of one of the HHDP groups at the glucose core O-4/O-6 in ordinary dimeric tannins with a galloyl moiety at O-6. This is a new structural feature among the tamaricaceous ellagitannins. On the basis of the results, reported spectroscopic assignments for 2, 3, and the macrocyclic tannins 11-13 were revised. Unusual shifts in the NMR spectra of these macrocyclic tannins are also discussed in relation to their conformations. Several tannins isolated from T. nilotica were assessed for possible cytotoxic activity against four human tumor cell lines, and nilotinin D8 (9) and hirtellin A (1) showed high cytotoxic effects.

  14. Synthesis of several tetraaza macrocyclic amine ligands and the biodistribution of their Tc-complexes

    International Nuclear Information System (INIS)

    Ketring, A.R.

    1982-01-01

    Several macrocyclic tetraaza ligands were synthesized and their /sup 99m/Tc-complexes prepared. The biological distribution of these complexes was examined to determine their possible utility as radiodiagnostic agents. The simplest of the macrocyclic tetraaza ligands studied, cyclam, forms a very stable cationic complex with Tc when pertechnetate is reduced with stannous ion in an aqueous solution of the ligand. When injected intravenously into mice Tc-cyclam was excreted predominantly by the urinary system. Derivatives of cyclam which were synthesized contained aromatic or aliphatic substituents and formed more lipophilic complexes with Tc. The complexes were formed in high yield as determined by paper chromatography, thin layer chromatography, electrophoresis and/or high performance liquid chromatography. Relative lipophilicities were determined for the complexes by octanol-to-water extractions. Animal studies using mice indicated there was an inverse relationship between the octanol-to-water extraction ratio and urinary excretion. Two of the complexes having relatively high octanol-to-water extraction ratios were significantly excreted by the hepatobiliary system with localization in the gall bladder. The complex having the highest octanol-to-water ratio was not excreted significantly by the hepatobiliary system, but cleared very slowly from the blood and localized in the liver, lungs, spleen and to some extent the heart. Derivatization of cyclam can be performed without greatly reducing its ability to complex Tc but greatly influencing the biological distribution of its Tc complex. This indicates that there is a potential for preparing radiodiagnostic agents using macrocyclic tetraaza ligands

  15. Chemical and Biological Significance of Oenothein B and Related Ellagitannin Oligomers with Macrocyclic Structure

    Directory of Open Access Journals (Sweden)

    Takashi Yoshida

    2018-03-01

    Full Text Available In 1990, Okuda et al. reported the first isolation and characterization of oenothein B, a unique ellagitannin dimer with a macrocyclic structure, from the Oenothera erythrosepala leaves. Since then, a variety of macrocyclic analogs, including trimeric–heptameric oligomers have been isolated from various medicinal plants belonging to Onagraceae, Lythraceae, and Myrtaceae. Among notable in vitro and in vivo biological activities reported for oenothein B are antioxidant, anti-inflammatory, enzyme inhibitory, antitumor, antimicrobial, and immunomodulatory activities. Oenothein B and related oligomers, and/or plant extracts containing them have thus attracted increasing interest as promising targets for the development of chemopreventive agents of life-related diseases associated with oxygen stress in human health. In order to better understand the significance of this type of ellagitannin in medicinal plants, this review summarizes (1 the structural characteristics of oenothein B and related dimers; (2 the oxidative metabolites of oenothein B up to heptameric oligomers; (3 the distribution of oenotheins and other macrocyclic analogs in the plant kingdom; and (4 the pharmacological activities hitherto documented for oenothein B, including those recently found by our laboratory.

  16. Knotting and unknotting proteins in the chaperonin cage: Effects of the excluded volume.

    Directory of Open Access Journals (Sweden)

    Szymon Niewieczerzal

    Full Text Available Molecular dynamics simulations are used to explore the effects of chaperonin-like cages on knotted proteins with very low sequence similarity, different depths of a knot but with a similar fold, and the same type of topology. The investigated proteins are VirC2, DndE and MJ0366 with two depths of a knot. A comprehensive picture how encapsulation influences folding rates is provided based on the analysis of different cage sizes and temperature conditions. Neither of these two effects with regard to knotted proteins has been studied by means of molecular dynamics simulations with coarse-grained structure-based models before. We show that encapsulation in a chaperonin is sufficient to self-tie and untie small knotted proteins (VirC2, DndE, for which the equilibrium process is not accessible in the bulk solvent. Furthermore, we find that encapsulation reduces backtracking that arises from the destabilisation of nucleation sites, smoothing the free energy landscape. However, this effect can also be coupled with temperature rise. Encapsulation facilitates knotting at the early stage of folding and can enhance an alternative folding route. Comparison to unknotted proteins with the same fold shows directly how encapsulation influences the free energy landscape. In addition, we find that as the size of the cage decreases, folding times increase almost exponentially in a certain range of cage sizes, in accordance with confinement theory and experimental data for unknotted proteins.

  17. A DECADE-BASELINE STUDY OF THE PLASMA STATES OF EJECTA KNOTS IN CASSIOPEIA A

    Energy Technology Data Exchange (ETDEWEB)

    Rutherford, John; Dewey, Daniel; Figueroa-Feliciano, Enectali; Heine, Sarah N. T.; Canizares, C. R.; Bastien, Fabienne A.; Sato, Kosuke, E-mail: enectali@mit.edu, E-mail: jmrv@mit.edu [Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2013-05-20

    We present the analysis of 21 bright X-ray knots in the Cassiopeia A supernova remnant from observations spanning 10 yr. We performed a comprehensive set of measurements to reveal the kinematic and thermal state of the plasma in each knot, using a combined analysis of two high energy resolution High Energy Transmission Grating (HETG) and four medium energy resolution Advanced CCD Imaging Spectrometer (ACIS) sets of spectra. The ACIS electron temperature estimates agree with the HETG-derived values for approximately half of the knots studied, yielding one of the first comparisons between high resolution temperature estimates and ACIS-derived temperatures. We did not observe the expected spectral evolution-predicted from the ionization age and density estimates for each knot-in all but three of the knots studied. The incompatibility of these measurements with our assumptions has led us to propose a dissociated ejecta model, with the metals unmixed inside the knots, which could place strong constraints on supernova mixing models.

  18. Confirming the nature of the knot near the pulsar B1951+32

    Science.gov (United States)

    Zyuzin, D. A.; Shibanov, Yu A.; Pavlov, G. G.; Danilenko, A. A.

    2017-12-01

    The energetic and fast-moving radio and γ-ray pulsar B1951+32 is associated with the supernova remnant CTB 80. It powers a complex pulsar wind nebula detected in the radio, Hα and X-rays (Moon et al 2004 ApJ 610 L33). A puzzling optical knot was detected about 0″.5 from the pulsar in the optical and near-IR (Moon et al 2004 ApJ 610 L33; Hester 2000 Bulletin of the AAS 32 1542). It is reminiscent of the unique “inner optical knot” located 0″.6 from the Crab pulsar. Until now there has been no evidence that B1951+32 knot is indeed associated with the pulsar. We observed the pulsar field with the Gemini-North telescope in 2016 to check the association. We performed first near-IR high spatial resolution imaging in the K s band using the NIRI+Altair instrument and deep optical imaging in the gr bands using the GMOS instrument. Our observations showed that the current knot position is shifted by ≈ 0″.6 from the position measured with the HST in 1997. This is consistent with the known pulsar proper motion and is direct evidence of the pulsar-knot connection. We compared the spectral energy distribution of the knot emission with that of the Crab knot. Possible implications of the results are discussed.

  19. Total curvature and total torsion of knotted random polygons in confinement

    Science.gov (United States)

    Diao, Yuanan; Ernst, Claus; Rawdon, Eric J.; Ziegler, Uta

    2018-04-01

    Knots in nature are typically confined spatially. The confinement affects the possible configurations, which in turn affects the spectrum of possible knot types as well as the geometry of the configurations within each knot type. The goal of this paper is to determine how confinement, length, and knotting affect the total curvature and total torsion of random polygons. Previously published papers have investigated these effects in the unconstrained case. In particular, we analyze how the total curvature and total torsion are affected by (1) varying the length of polygons within a fixed confinement radius and (2) varying the confinement radius of polygons with a fixed length. We also compare the total curvature and total torsion of groups of knots with similar complexity (measured as crossing number). While some of our results fall in line with what has been observed in the studies of the unconfined random polygons, a few surprising results emerge from our study, showing some properties that are unique due to the effect of knotting in confinement.

  20. Knot positioning during McDonald cervical cerclage, does it make a difference? A cohort study.

    Science.gov (United States)

    Atia, Hytham; Ellaithy, Mohamed; Altraigey, Ahmed; Ibrahim, Heba

    2018-05-15

    To study the effect of McDonald cerclage knot position on the different maternal and neonatal outcomes. This historical cohort study included women with singleton pregnancy who had a prophylactic McDonald cervical cerclage between 1 May 2010 and 31 September 2017. Maternal and neonatal outcome parameters were compared between the anterior and posterior knot cerclage procedures. The primary outcome measure was the rate of term birth. 550 Women had a prophylactic McDonald cervical cerclage, 306 with anterior knot (Group A) and 244 with posterior knot (Group B). There were no statistically significant differences regarding gestational age (GA) at delivery (36.3 ± 4.2 versus 35.8 ± 5.3 for groups A and B respectively), term birth rate, post-cerclage cervical length, symptomatic vaginitis, urinary tract infection, difficult cerclage removal and cervical lacerations. Similarly, there were no statistically significant differences as regards the studied neonatal outcomes including take home babies, neonatal intensive care admission, respiratory distress syndrome and neonatal sepsis. Survival analysis on GA at delivery demonstrated no statistically significant difference as regards the proportion of term deliveries in the anterior and posterior knot cerclage groups (log-rank test p-value = .478). Knot positioning during McDonald cervical cerclage, anteriorly or posteriorly, didn't significantly impact the studied maternal and neonatal outcomes.

  1. Freely Expanding Knots of X-Ray-emitting Ejecta in Kepler’s Supernova Remnant

    Science.gov (United States)

    Sato, Toshiki; Hughes, John P.

    2017-08-01

    We report measurements of proper motion, radial velocity, and elemental composition for 14 compact X-ray-bright knots in Kepler’s supernova remnant (SNR) using archival Chandra data. The knots with the highest speed show both large proper motions (μ ˜ 0.″11-0.″14 yr-1) and high radial velocities (v ˜ 8700-10,020 km s-1). For these knots the estimated space velocities (9100 km s-1 ≲ v 3D ≲ 10,400 km s-1) are similar to the typical Si velocity seen in supernovae (SNe) Ia near maximum light. High-speed ejecta knots appear only in specific locations and are morphologically and kinematically distinct from the rest of the ejecta. The proper motions of five knots extrapolate back over the age of Kepler’s SNR to a consistent central position. This new kinematic center agrees well with previous determinations, but is less subject to systematic errors and denotes a location about which several prominent structures in the remnant display a high degree of symmetry. These five knots are expanding at close to the free expansion rate (expansion indices of 0.75 ≲ m ≲ 1.0), which we argue indicates either that they were formed in the explosion with a high density contrast (more than 100 times the ambient density) or that they have propagated through regions of relatively low density (n H ruled out.

  2. The magnetic resonance appearance of surfers' knots: a case report

    Directory of Open Access Journals (Sweden)

    Luke J. McManus, BMBS, PhD

    2016-09-01

    Full Text Available Athletes are at increased risk of developing soft-tissue lesions of the lower limbs. Although the majority of these will be benign, the differential diagnosis is broad and increasingly, doctors are turning to magnetic resonance imaging (MRI as a first-line investigation when presented with these sorts of lesions, both to narrow the differential diagnosis and exclude malignancy. We report the case of a 28-year-old Caucasian man who presented with 2 soft-tissue lesions of the right foot. History and examination of the nodules fitted with a diagnosis of surfers' knots, an unusual form of acquired, benign, connective tissue nodule that may appear over the tibial tuberosities, dorsum of the feet, and occasionally on the chest of surfers in association with repetitive microtrauma during surfing. MRI findings were consistent with this diagnosis with both lesions exhibiting T1 hypointensity and speckled T2 hypointensity with no significant blooming artifact on gradient echo imaging. When imaged with gadolinium, they demonstrated only mild contrast enhancement. MRI is a valuable tool when investigating athletes with soft-tissue lesions over the lower limbs where the possibility of malignancy must be addressed. In selected cases, MRI may be sufficient to permit a conservative approach to the management of these patients.

  3. Quandles and topological pairs symmetry, knots, and cohomology

    CERN Document Server

    Nosaka, Takefumi

    2017-01-01

    This book surveys quandle theory, starting from basic motivations and going on to introduce recent developments of quandles with topological applications and related topics. The book is written from topological aspects, but it illustrates how esteemed quandle theory is in mathematics, and it constitutes a crash course for studying quandles. More precisely, this work emphasizes the fresh perspective that quandle theory can be useful for the study of low-dimensional topology (e.g., knot theory) and relative objects with symmetry. The direction of research is summarized as “We shall thoroughly (re)interpret the previous studies of relative symmetry in terms of the quandle”. The perspectives contained herein can be summarized by the following topics. The first is on relative objects G/H, where G and H are groups, e.g., polyhedrons, reflection, and symmetric spaces. Next, central extensions of groups are discussed, e.g., spin structures, K2 groups, and some geometric anomalies. The third topic is a method to s...

  4. OH+ emission from cometary knots in planetary nebulae

    Science.gov (United States)

    Priestley, F. D.; Barlow, M. J.

    2018-05-01

    We model the molecular emission from cometary knots in planetary nebulae (PNe) using a combination of photoionization and photodissociation region (PDR) codes, for a range of central star properties and gas densities. Without the inclusion of ionizing extreme ultraviolet (EUV) radiation, our models require central star temperatures T* to be near the upper limit of the range investigated in order to match observed H2 and OH+ surface brightnesses consistent with observations - with the addition of EUV flux, our models reproduce observed OH+ surface brightnesses for T* ≥ 100 kK. For T* non-detection of this molecule in PNe with such central star temperatures. Our predicted level of H2 emission is somewhat weaker than commonly observed in PNe, which may be resolved by the inclusion of shock heating or fluorescence due to UV photons. Some of our models also predict ArH+ and HeH+ rotational line emission above detection thresholds, despite neither molecule having been detected in PNe, although the inclusion of photodissociation by EUV photons, which is neglected by our models, would be expected to reduce their detectability.

  5. Feedback in clinical education: untying the Gordian knot.

    Science.gov (United States)

    Weinstein, Debra F

    2015-05-01

    Feedback is essential to clinical education, especially in the era of competencies, milestones, and entrustable professional activities. It is, however, an area where medical educators often fall short. Although educational leaders and faculty supervisors provide feedback in a variety of clinical settings, surveys show important gaps in medical student and resident satisfaction with the feedback received, suggesting lost opportunities to identify performance problems as well as to help each learner reach his or her greatest potential.In this issue of Academic Medicine, Telio and colleagues extend the empirically validated concept of a "therapeutic alliance" to propose the "educational alliance" as a framework for enhancing feedback in medical education. They highlight the importance of source credibility, which depends on the teacher-learner relationship and alignment of values, the teacher's understanding of the learner's role and goals, the teacher's direct observation of the learner, and the learner's perception of the teacher's good intentions. The author of this Commentary suggests that the educational alliance framework should prompt medical educators to reconsider feedback and explore opportunities for optimizing it. Most medical schools and graduate medical education programs are not designed in a way that supports the education alliance model, but the Commentary author offers suggestions for cultivating educational alliances, including rethinking supervisor selection criteria. Such interventions should be combined with ongoing faculty development and efforts to improve coaching and mentoring for students, residents, and fellows. Untying the Gordian knot of effective feedback will require innovative approaches, exchange of successful strategies, and continued research.

  6. Bounds for the minimum step number of knots confined to slabs in the simple cubic lattice

    International Nuclear Information System (INIS)

    Ishihara, K; Shimokawa, K; Scharein, R; Arsuaga, J; Vazquez, M; Diao, Y

    2012-01-01

    Volume confinement is a key determinant of the topology and geometry of a polymer. However, the direct relationship between the two is not fully understood. For instance, recent experimental studies have constructed P4 cosmids, i.e. P4 bacteriophages whose genome sequence and length have been artificially engineered and have shown that upon extraction their DNA knot distribution differs from that of wild-type bacteriophage P4. In particular, it was observed that the complexity of the knots decreases sharply with the length of the packed genome. This problem is the motivation of this paper. Here, a polymer is modeled as a self-avoiding polygon on the simple cubic lattice and the confining condition is such that the polygon is bounded between two parallel planes (i.e. bounded within a slab). We estimate the minimum length required for such a polygon to realize a knot type. Our numerical simulations show that in order to realize a prime knot (with up to ten crossings) in a 1-slab (i.e. a slab of height 1), one needs a polygon of length strictly longer than the minimum length needed to realize the same knot when there is no confining condition. In the case of the trefoil knot, we can in fact establish this result analytically by proving that the minimum length required to tie a trefoil in the 1-slab is 26, which is greater than 24, the known minimum length required to tie a trefoil without a confinement condition. Additionally, we find that in the 1-slab not all geometrical realizations of a given knot type are equivalent under BFACF moves. This suggests that in certain confined volumes, knowing the topology of a polymer is not enough to describe all its states. (paper)

  7. Use of tetraaza-macrocycles for complexation of actinides in aqueous solutions. Validation of the process for the treatment of waste waters

    International Nuclear Information System (INIS)

    Chollet, Herve

    1994-01-01

    This report makes one's contribution to the study of the reactivity of free or fixed tetraaza-macrocycles. The major interest of this work concerns the following key-points: - Synthesis, spectral characterization and X-ray diffraction study of tetraaza-macrocycles N-tetra-functionalized, - Synthesis, physicochemical, chemicals and X-ray studies of macrocyclic complex in lanthanides and actinides series, - Synthesis and characterization of tetraaza-macrocycles grafted on organic and inorganic polymers, - Reactivity of macrocyclic ligands grafted on Merrifield's resin or silica gel in cerium, europium, uranium, plutonium and americium series, - Extraction of heavy metals in a solid-liquid process and measurements of a pilot. (author) [fr

  8. Freely Expanding Knots of X-Ray-emitting Ejecta in Kepler’s Supernova Remnant

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Toshiki [Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan); Hughes, John P., E-mail: toshiki@astro.isas.jaxa.jp, E-mail: jph@physics.rutgers.edu [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854-8019 (United States)

    2017-08-20

    We report measurements of proper motion, radial velocity, and elemental composition for 14 compact X-ray-bright knots in Kepler’s supernova remnant (SNR) using archival Chandra data. The knots with the highest speed show both large proper motions ( μ ∼ 0.″11–0.″14 yr{sup −1}) and high radial velocities ( v ∼ 8700–10,020 km s{sup −1}). For these knots the estimated space velocities (9100 km s{sup −1} ≲ v {sub 3D} ≲ 10,400 km s{sup −1}) are similar to the typical Si velocity seen in supernovae (SNe) Ia near maximum light. High-speed ejecta knots appear only in specific locations and are morphologically and kinematically distinct from the rest of the ejecta. The proper motions of five knots extrapolate back over the age of Kepler’s SNR to a consistent central position. This new kinematic center agrees well with previous determinations, but is less subject to systematic errors and denotes a location about which several prominent structures in the remnant display a high degree of symmetry. These five knots are expanding at close to the free expansion rate (expansion indices of 0.75 ≲ m ≲ 1.0), which we argue indicates either that they were formed in the explosion with a high density contrast (more than 100 times the ambient density) or that they have propagated through regions of relatively low density ( n {sub H} < 0.1 cm{sup −3}) in the ambient medium. X-ray spectral analysis shows that the undecelerated knots have high Si and S abundances, a lower Fe abundance, and very low O abundance, pointing to an origin in the partial Si-burning zone, which occurs in the outer layer of the exploding white dwarf for models of SNe Ia. Other knots show lower speeds and expansion indices consistent with decelerated ejecta knots or features in the ambient medium overrun by the forward shock. Our new accurate location for the explosion site has well-defined positional uncertainties, allowing for a great reduction in the area to be searched for faint

  9. Long-slit spectrophotometry of the multiple knots of the polar ring galaxy IIZw71

    Science.gov (United States)

    Pérez-Montero, E.; García-Benito, R.; Díaz, A. I.; Pérez, E.; Kehrig, C.

    2009-04-01

    Aims: The blue compact dwarf galaxy IIZw71 is catalogued as a probable polar-ring galaxy, and along its long axis it has several very luminous knots showing recent episodes of star formation. Our main aim is to study the physical properties, the stellar content, and the kinematics in the brightest knots of the polar ring. Methods: We carried out long-slit spectroscopic observations of the polar ring in the spectral range 3500-10 000 Å taken with the William Herschel Telescope (WHT). The spectroscopic observations complemented by the available photometry of the galaxy in narrow Hα filters. Results: We measured the rotation curve of the ring, from which we infer a ratio M/LB ≈ 3.9 inside the star-forming ring. We measured the auroral [Oiii] line in the two brightest knots, allowing us to measure oxygen, sulphur, nitrogen, argon, and neon chemical abundances following the direct method. Different empirical calibrators were used to estimate the oxygen abundance in the two faintest knots where the temperature sensitive lines could not be measured. The metallicities obtained are very similar for all the knots, but lower than previously reported in the literature from integrated spectra. The N/O abundance, as derived from the N2O2 parameter (the ratio of the [Nii] and [Oii] intensities), is remarkably constant over the ring, indicating that local polution processes are not conspicuous. Using synthetic stellar populations (SSPs) calculated with the code STARLIGHT, we studied the age distribution of the stellar populations in each knot, finding that in all of them there is a combination of a very young population with less than 10 Myr, responsible for the ionisation of the gas, with other populations older than 100 Myr, probably responsible for the chemical evolution of the knots. The small differences in metallicity and the age distributions among the different knots are indicative of a common chemical evolution, probably related to the process of interaction with the

  10. 360° virtual reality video for the acquisition of knot tying skills: A randomised controlled trial.

    Science.gov (United States)

    Yoganathan, S; Finch, D A; Parkin, E; Pollard, J

    2018-04-10

    360° virtual reality (VR) video is an exciting and evolving field. Current technology promotes a totally immersive, 3-dimensional (3D), 360° experience anywhere in the world using simply a smart phone and virtual reality headset. The potential for its application in the field of surgical education is enormous. The aim of this study was to determine knot tying skills taught with a 360-degree VR video compared to conventional 2D video teaching. This trial was a prospective, randomised controlled study. 40 foundation year doctors (first year postgraduate) were randomised to either the 360-degree VR video (n = 20) or 2D video teaching (n = 20). Participants were given 15 min to watch their allocated video. Ability to tie a single handed reef knot was then assessed against a marking criteria developed for the Royal College of Surgeons, England, (RCSeng) Basic Surgical Skills (BSS) course, by a blinded assessor competent in knot tying. Each candidate then underwent further teaching using Peyton's four step model. Knot tying technique was then re-assessed. Knot tying scores were significantly better in the VR video teaching arm when compared with conventional (median knot score 5.0 vs 4.0 p = 0.04). When used in combination with face to face skills teaching this difference persisted (median knot score 9.5 vs 9.0 p = 0.01). More people in the VR arm constructed a complete reef knot than in the 2D arm following face to face teaching (17/20 vs 12/20). No difference between the groups existed in the time taken to construct a reef knot following video and teaching (median time 31.0s vs 30.5s p = 0.89). This study shows there is significant merit in the application of 360-degree VR video technology in surgical training, both as an independent teaching aid and when used as an adjunct to traditional face to face teaching. Copyright © 2018 IJS Publishing Group Ltd. Published by Elsevier Ltd. All rights reserved.

  11. A novel knot selection method for the error-bounded B-spline curve fitting of sampling points in the measuring process

    International Nuclear Information System (INIS)

    Liang, Fusheng; Zhao, Ji; Ji, Shijun; Zhang, Bing; Fan, Cheng

    2017-01-01

    The B-spline curve has been widely used in the reconstruction of measurement data. The error-bounded sampling points reconstruction can be achieved by the knot addition method (KAM) based B-spline curve fitting. In KAM, the selection pattern of initial knot vector has been associated with the ultimate necessary number of knots. This paper provides a novel initial knots selection method to condense the knot vector required for the error-bounded B-spline curve fitting. The initial knots are determined by the distribution of features which include the chord length (arc length) and bending degree (curvature) contained in the discrete sampling points. Firstly, the sampling points are fitted into an approximate B-spline curve Gs with intensively uniform knot vector to substitute the description of the feature of the sampling points. The feature integral of Gs is built as a monotone increasing function in an analytic form. Then, the initial knots are selected according to the constant increment of the feature integral. After that, an iterative knot insertion (IKI) process starting from the initial knots is introduced to improve the fitting precision, and the ultimate knot vector for the error-bounded B-spline curve fitting is achieved. Lastly, two simulations and the measurement experiment are provided, and the results indicate that the proposed knot selection method can reduce the number of ultimate knots available. (paper)

  12. Prediction of the optimal set of contacts to fold the smallest knotted protein

    Science.gov (United States)

    Dabrowski-Tumanski, P.; Jarmolinska, A. I.; Sulkowska, J. I.

    2015-09-01

    Knotted protein chains represent a new motif in protein folds. They have been linked to various diseases, and recent extensive analysis of the Protein Data Bank shows that they constitute 1.5% of all deposited protein structures. Despite thorough theoretical and experimental investigations, the role of knots in proteins still remains elusive. Nonetheless, it is believed that knots play an important role in mechanical and thermal stability of proteins. Here, we perform a comprehensive analysis of native, shadow-specific and non-native interactions which describe free energy landscape of the smallest knotted protein (PDB id 2efv). We show that the addition of shadow-specific contacts in the loop region greatly enhances folding kinetics, while the addition of shadow-specific contacts along the C-terminal region (H3 or H4) results in a new folding route with slower kinetics. By means of direct coupling analysis (DCA) we predict non-native contacts which also can accelerate kinetics. Next, we show that the length of the C-terminal knot tail is responsible for the shape of the free energy barrier, while the influence of the elongation of the N-terminus is not significant. Finally, we develop a concept of a minimal contact map sufficient for 2efv protein to fold and analyze properties of this protein using this map.

  13. Prediction of the optimal set of contacts to fold the smallest knotted protein

    International Nuclear Information System (INIS)

    Dabrowski-Tumanski, P; Jarmolinska, A I; Sulkowska, J I

    2015-01-01

    Knotted protein chains represent a new motif in protein folds. They have been linked to various diseases, and recent extensive analysis of the Protein Data Bank shows that they constitute 1.5% of all deposited protein structures. Despite thorough theoretical and experimental investigations, the role of knots in proteins still remains elusive. Nonetheless, it is believed that knots play an important role in mechanical and thermal stability of proteins. Here, we perform a comprehensive analysis of native, shadow-specific and non-native interactions which describe free energy landscape of the smallest knotted protein (PDB id 2efv). We show that the addition of shadow-specific contacts in the loop region greatly enhances folding kinetics, while the addition of shadow-specific contacts along the C-terminal region (H3 or H4) results in a new folding route with slower kinetics. By means of direct coupling analysis (DCA) we predict non-native contacts which also can accelerate kinetics. Next, we show that the length of the C-terminal knot tail is responsible for the shape of the free energy barrier, while the influence of the elongation of the N-terminus is not significant. Finally, we develop a concept of a minimal contact map sufficient for 2efv protein to fold and analyze properties of this protein using this map. (paper)

  14. Particle on a torus knot: Constrained dynamics and semi-classical quantization in a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Das, Praloy, E-mail: praloydasdurgapur@gmail.com; Pramanik, Souvik, E-mail: souvick.in@gmail.com; Ghosh, Subir, E-mail: subirghosh20@gmail.com

    2016-11-15

    Kinematics and dynamics of a particle moving on a torus knot poses an interesting problem as a constrained system. In the first part of the paper we have derived the modified symplectic structure or Dirac brackets of the above model in Dirac’s Hamiltonian framework, both in toroidal and Cartesian coordinate systems. This algebra has been used to study the dynamics, in particular small fluctuations in motion around a specific torus. The spatial symmetries of the system have also been studied. In the second part of the paper we have considered the quantum theory of a charge moving in a torus knot in the presence of a uniform magnetic field along the axis of the torus in a semiclassical quantization framework. We exploit the Einstein–Brillouin–Keller (EBK) scheme of quantization that is appropriate for multidimensional systems. Embedding of the knot on a specific torus is inherently two dimensional that gives rise to two quantization conditions. This shows that although the system, after imposing the knot condition reduces to a one dimensional system, even then it has manifested non-planar features which shows up again in the study of fractional angular momentum. Finally we compare the results obtained from EBK (multi-dimensional) and Bohr–Sommerfeld (single dimensional) schemes. The energy levels and fractional spin depend on the torus knot parameters that specifies its non-planar features. Interestingly, we show that there can be non-planar corrections to the planar anyon-like fractional spin.

  15. Intra-vesical knot of bladder catheter in an extremely low birthweight neonate: A case report

    Directory of Open Access Journals (Sweden)

    Paula M.Y. Tang

    2015-07-01

    Full Text Available Premature and extremely low birth weight (ELBW neonates are at high risk of developing multiple co-morbidities and often require urinary catheterization for various medical indications. Intra-vesical knotting of bladder catheter is a known but uncommon complication of this procedure. We report a case of an ELBW baby boy with a knotted bladder catheter requiring surgical retrieval. After an elective operation for the closure of patent ductus arteriosus, a 4 French urinary catheter was inserted into an ELBW baby boy for urine output monitoring and left in-situ. Resistance was encountered in attempt to remove the urinary catheter. Abdominal X Ray confirmed intra-vesical knotting of the tube. Knot unravelling by interventional radiology was attempted but was unsuccessful. Open extra-peritoneal bladder exploration was performed for the retrieval of the tightly knotted catheter. A 6 French transurethral Foley catheter was inserted for bladder drainage. Upon removal of the Foley's catheter on day 5 post op, the baby was able to void spontaneously. With literature review, we postulated the potential risk factors resulting in this potentially avoidable iatrogenic unusual complication. Recommendations were suggested to avoid further incidences.

  16. The Synthesis, Structures and Chemical Properties of Macrocyclic Ligands Covalently Bonded into Layered Arrays

    International Nuclear Information System (INIS)

    Clearfield, Abraham

    2003-01-01

    OAK-B135 The immobilization of crown ethers tends to limit the leveling effect of solvents making the macrocycles more selective. In addition immobilization has the added advantage of relative ease of recovery of the otherwise soluble crown. We have affixed CH2PO3H2 groups to azacrown ethers. The resultant phosphorylated macrocycles may spontaneously aggregate into crystalline supramolecular linear arrays or contacted with cations produce layered or linear polymers. In the linear polymers the metal and phosphonic acids covalently bond into a central stem with the macrocyclic rings protruding from the stem as leaves on a twig. Two types of layered compounds were obtained with group 4 metals. Monoaza-crown ethers form a bilayer where the M4+ plus phosphonic acid groups build the layer and the rings fill the interlayer space. 1, 10-diazadiphosphonic acids cross-link the metal phosphonate layers forming a three-dimensional array of crown ethers. In order to improve diffusion into these 3-D arrays they are spaced by inclusion of phosphate or phosphate groups. Two series of azamacrocylic crown ethers were prepared containing rings with 20 to 32 atoms. These larger rings can complex two cations per ring. Methylene phosphonic acid groups have been bonded to the aza ring atoms to increase the complexing ability of these ligands. Our approach is to carry out acid-base titrations in the absence and presence of cations to determine the pKa values of the protons, both those bonded to aza groups and those associated with the phosphonic acid groups. From the differences in the titration curves obtained with and without the cations present we obtain the stoichiometry of complex formation and the complex stability constants. Some of the applications we are targeting include phase transfer catalysis, separation of cations and the separation of radioisotopes for diagnostic and cancer therapeutic purposes

  17. Immobilized copper(II) macrocyclic complex on MWCNTs with antibacterial activity

    Energy Technology Data Exchange (ETDEWEB)

    Tarlani, Aliakbar, E-mail: Tarlani@ccerci.ac.ir [Inorganic Nanostructures and Catalysts Research Lab., Chemistry & Chemical Engineering Research Center of Iran, Pajoohesh Blvd., km 17, Karaj Hwy, Tehran 14968-13151 (Iran, Islamic Republic of); Narimani, Khashayar [Inorganic Nanostructures and Catalysts Research Lab., Chemistry & Chemical Engineering Research Center of Iran, Pajoohesh Blvd., km 17, Karaj Hwy, Tehran 14968-13151 (Iran, Islamic Republic of); Mohammadipanah, Fatemeh; Hamedi, Javad [Department of Microbial Biotechnology, School of Biology and Center of Excellence in Phylogeny of Living Organisms, College of Science, University of Tehran, Tehran 14155-6455 (Iran, Islamic Republic of); University of Tehran Biocompound Collection (UTBC), Microbial Technology and Products Research Center, University of Tehran, Tehran (Iran, Islamic Republic of); Tahermansouri, Hasan [Department of Chemistry, Ayatollah Amoli Branch, Islamic Azad University, Amol (Iran, Islamic Republic of); Amini, Mostafa M. [Department of Chemistry, Shahid Behshti University, 1983963113, Tehran (Iran, Islamic Republic of)

    2015-06-30

    Graphical abstract: In an antibacterial test, grafted copper(II) macrocyclic complex on the surface of MWCNT showed higher antibacterial activity against Bacillus subtilis compared to the individual MWCNT-COOH and the complex. - Highlights: • Copper(II) tetraaza macrocyclic complex covalently bonded to modified MWCNT. • Grafting of the complex carried out via an interaction between −C(=O)Cl group and NH of the ligand. • The samples were subjected in an antibacterial assessment to compare their activity. • Immobilized complex showed higher antibacterial activity against Bacillus subtilis ATCC 6633 compared to separately MWCNT-C(C=O)-OH and CuTAM. - Abstract: In a new approach, a copper(II) tetraaza macrocyclic complex (CuTAM) was covalently bonded on modified multi-walled carbon nanotubes (MWCNTs). To achieve this purpose, MWCNTs were converted to MWCNT-COCl and then reacted to NH groups of TAM ligand. The prepared material was characterized by Fourier Transform Infrared (FT-IR), X-ray diffraction (XRD), Raman spectroscopy, thermal gravimetric analysis (TGA), and FESEM (field emission scanning electron microscopy). FT-IR and TGA demonstrated the presence of the organic moieties, and XRD proved that the structure of MWCNTs remained intact during the three modification steps. An increase in the I{sub D}/I{sub G} ratio in Raman spectra confirmed the surface modifications. Finally, the samples were subjected to an antibacterial assessment to compare their biological activity. The antibacterial test showed that the grafted complex on the surface of the nanotube (MWCNT-CO-CuTAM) has higher antibacterial activity against Bacillus subtilis ATCC 6633 than the MWCNT-COOH and CuTAM with 1000 and 2000 μg/mL.

  18. Cyclooctane metathesis catalyzed by silica-supported tungsten pentamethyl [(ΞSiO)W(Me)5]: Distribution of macrocyclic alkanes

    KAUST Repository

    Riache, Nassima

    2014-10-03

    Metathesis of cyclic alkanes catalyzed by the new surface complex [(ΞSiO)W(Me)5] affords a wide distribution of cyclic and macrocyclic alkanes. The major products with the formula CnH2n are the result of either a ring contraction or ring expansion of cyclooctane leading to lower unsubstituted cyclic alkanes (5≤n≤7) and to an unprecedented distribution of unsubstituted macrocyclic alkanes (12≤n≤40), respectively, identified by GC/MS and by NMR spectroscopies.

  19. Application of Calixarenes as Macrocyclic Ligands for Uranium(VI: A Review

    Directory of Open Access Journals (Sweden)

    Katarzyna Kiegiel

    2013-01-01

    Full Text Available Calixarenes represent a well-known family of macrocyclic molecules with broad range of potential applications in chemical, analytical, and engineering materials fields. This paper covers the use of calixarenes as complexing agents for uranium(VI. The high effectiveness of calix[6]arenes in comparison to other calixarenes in uranium(VI separation process is also presented. Processes such as liquid-liquid extraction (LLE, liquid membrane (LM separation, and ion exchange are considered as potential fields for application of calixarenes as useful agents for binding UO22+ for effective separation from aqueous solutions containing other metal components.

  20. Design and synthesis of binucleating macrocyclic clefts derived from Schiff-base calixpyrroles.

    Science.gov (United States)

    Givaja, Gonzalo; Volpe, Manuel; Leeland, James W; Edwards, Michael A; Young, Thomas K; Darby, S Barnie; Reid, Stuart D; Blake, Alexander J; Wilson, Claire; Wolowska, Joanna; McInnes, Eric J L; Schröder, Martin; Love, Jason B

    2007-01-01

    The syntheses, characterisation and complexation reactions of a series of binucleating Schiff-base calixpyrrole macrocycles are described. The acid-templated [2+2] condensations between meso-disubstituted diformyldipyrromethanes and o-phenylenediamines generate the Schiff-base pyrrolic macrocycles H(4)L(1) to H(4)L(6) upon basic workup. The single-crystal X-ray structures of both H(4)L(3).2 EtOH and H(4)L(6).H2O confirm that [2+2] cyclisation has occurred, with either EtOH or H2O hydrogen-bonded within the macrocyclic cleft. A series of complexation reactions generate the dipalladium [Pd2(L)] (L=L(1) to L(5)), dinickel [Ni2(L(1))] and dicopper [Cu2(L)] (L=L(1) to L(3)) complexes. All of these complexes have been structurally characterised in the solid state and are found to adopt wedged structures that are enforced by the rigidity of the aryl backbone to give a cleft reminiscent of the structures of Pacman porphyrins. The binuclear nickel complexes [Ni2(mu-OMe)2Cl2(HOMe)2(H(4)L(1))] and [Ni2(mu-OH)2Cl2(HOMe)(H(4)L(5))] have also been prepared, although in these cases the solid-state structures show that the macrocyclic ligand remains protonated at the pyrrolic nitrogen atoms, and the Ni(II) cations are therefore co-ordinated by the imine nitrogen atoms only to give an open conformation for the complex. The dicopper complex [Cu2(L(3))] was crystallised in the presence of pyridine to form the adduct [Cu2(py)(L(3))], in which, in the solid state, the pyridine ligand is bound within the binuclear molecular cleft. Reaction between H(4)L(1) and [Mn(thf){N(SiMe(3))2}2] results in clean formation of the dimanganese complex [Mn2(L(1))], which, upon crystallisation, formed the mixed-valent complex [Mn2(mu-OH)(L(1))] in which the hydroxo ligand bridges the metal centres within the molecular cleft.

  1. Molecular Rearrangement of an Aza-Scorpiand Macrocycle Induced by pH: A Computational Study

    Directory of Open Access Journals (Sweden)

    Jesus Vicente De Julián-Ortiz

    2016-07-01

    Full Text Available Rearrangements and their control are a hot topic in supramolecular chemistry due to the possibilities that these phenomena open in the design of synthetic receptors and molecular machines. Macrocycle aza-scorpiands constitute an interesting system that can reorganize their spatial structure depending on pH variations or the presence of metal cations. In this study, the relative stabilities of these conformations were predicted computationally by semi-empirical and density functional theory approximations, and the reorganization from closed to open conformations was simulated by using the Monte Carlo multiple minimum method.

  2. Biomechanical Assessment of the Strength of Volleyball Players in Different Stages of the Training Macrocycle

    Directory of Open Access Journals (Sweden)

    Śliwa Marcin

    2015-09-01

    Full Text Available Introduction. In order to help volleyball players achieve superior results, their coaches are constantly seeking new training methods. One of the methods used to improve the effectiveness of the training that is being implemented is conducting tests which make it possible to assess the player’s locomotor system in terms of its motor and biomechanical functions. The aim of the study was to determine the torque of the knee flexor and extensor muscles of volleyball players in three stages of the annual macrocycle.

  3. Kinetic Analysis for Macrocyclizations Involving Anionic Template at the Transition State

    Directory of Open Access Journals (Sweden)

    Vicente Martí-Centelles

    2012-01-01

    competitive oligomerization/polymerization processes yielding undesired oligomeric/polymeric byproducts. The effect of anions has also been included in the kinetic models, as they can act as catalytic templates in the transition state reducing and stabilizing the transition state. The corresponding differential equation systems for each kinetic model can be solved numerically. Through a comprehensive analysis of these results, it is possible to obtain a better understanding of the different parameters that are involved in the macrocyclization reaction mechanism and to develop strategies for the optimization of the desired processes.

  4. Hydrolysis of Letrozole catalyzed by macrocyclic Rhodium (I) Schiff-base complexes.

    Science.gov (United States)

    Reddy, P Muralidhar; Shanker, K; Srinivas, V; Krishna, E Ravi; Rohini, R; Srikanth, G; Hu, Anren; Ravinder, V

    2015-03-15

    Ten mononuclear Rhodium (I) complexes were synthesized by macrocyclic ligands having N4 and N2O2 donor sites. Square planar geometry is assigned based on the analytical and spectral properties for all complexes. Rh(I) complexes were investigated as catalysts in hydrolysis of Nitrile group containing pharmaceutical drug Letrozole. A comparative study showed that all the complexes are efficient in the catalysis. The percent yields of all the catalytic reaction products viz. drug impurities were determined by spectrophotometric procedures and characterized by spectral studies. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. "Nara" knot for suturing of cleft lip in children to make removal easy

    Directory of Open Access Journals (Sweden)

    Obaidullah

    2006-01-01

    Full Text Available Cleft patients usually go through a lifetime of repeated hospital admissions and multiple procedures. Suture removal at a tender age and on a sensitive area like the lip becomes a challenge for the nursing staff. It is also emotionally demanding on the part of the parents. Hence, in most centres these patients are at least sedated if not anaesthetised. We have been using a simple knot and running prolene material so that undoing of the knot becomes easy and suture removal more or less atraumatic. We would like to share our experience with readers through this article. An analysis of 53 cleft lip repairs has shown that this knot is safe and easily removable.

  6. Sensitivity of root-knot nematodes to gamma irradiation, salinity and plant growth regulator, cycocel

    Energy Technology Data Exchange (ETDEWEB)

    Sweelam, M E [Econ. Entomology Dept., Fac. Agric. Menoufia University Shebin El-Kom, (Egypt)

    1995-10-01

    The experiment was carried out at the experimental station of the faculty of agriculture, Menoufia Univ. To determine the sensitivity of root-knot nematode, Meloidogyne Javanica infecting tomato plants exposed to different doses of gamma irradiation 0,20,40,60,80 Gy, salinity levels 0. 1000, 2000, 4000 ppm and the plant growth regulator cycocel 0,200 ppm. Treated seeds were planted clay pots and salinity levels and cycocel concentrations were applied. Fresh weights and nematode populations were computed 3 months after application. Results indicated that 20 Gy, 1000 ppm salinity and cycocel gave the highest fresh weight of shoots and roots. The developmental stages and egg-laying females of nematode decreased by the increasing of irradiation dose and salinity levels. Root-knot galls decreased with 40 and 60 Gy, while significant increase was observed with 0 and 80 Gy, salinity levels decreased root galls. Cycocel decreased nematode population, egg-lying females and root-knot galls.

  7. Sensitivity of root-knot nematodes to gamma irradiation, salinity and plant growth regulator, cycocel

    International Nuclear Information System (INIS)

    Sweelam, M.E.

    1995-01-01

    The experiment was carried out at the experimental station of the faculty of agriculture, Menoufia Univ. To determine the sensitivity of root-knot nematode, Meloidogyne Javanica infecting tomato plants exposed to different doses of gamma irradiation 0,20,40,60,80 Gy, salinity levels 0. 1000, 2000, 4000 ppm and the plant growth regulator cycocel 0,200 ppm. Treated seeds were planted clay pots and salinity levels and cycocel concentrations were applied. Fresh weights and nematode populations were computed 3 months after application. Results indicated that 20 Gy, 1000 ppm salinity and cycocel gave the highest fresh weight of shoots and roots. The developmental stages and egg-laying females of nematode decreased by the increasing of irradiation dose and salinity levels. Root-knot galls decreased with 40 and 60 Gy, while significant increase was observed with 0 and 80 Gy, salinity levels decreased root galls. Cycocel decreased nematode population, egg-lying females and root-knot galls

  8. Avian influenza virus antibodies in Pacific Coast Red Knots (Calidris canutus rufa)

    Science.gov (United States)

    Johnson, James A.; DeCicco, Lucas H.; Ruthrauff, Daniel R.; Krauss, Scott; Hall, Jeffrey S.

    2014-01-01

    Prevalence of avian influenza virus (AIV) antibodies in the western Atlantic subspecies of Red Knot (Calidris canutus rufa) is among the highest for any shorebird. To assess whether the frequency of detection of AIV antibodies is high for the species in general or restricted only to C. c. rufa, we sampled the northeastern Pacific Coast subspecies of Red Knot (Calidris canutus roselaari) breeding in northwestern Alaska. Antibodies were detected in 90% of adults and none of the chicks sampled. Viral shedding was not detected in adults or chicks. These results suggest a predisposition of Red Knots to AIV infection. High antibody titers to subtypes H3 and H4 were detected, whereas low to intermediate antibody levels were found for subtypes H10 and H11. These four subtypes have previously been detected in shorebirds at Delaware Bay (at the border of New Jersey and Delaware) and in waterfowl along the Pacific Coast of North America.

  9. Food, feeding, and refuelling of Red Knots during northward migration at San Antonio Oeste, Rio Negro, Argentina

    NARCIS (Netherlands)

    Gonzalez, PM; Piersma, T; Verkuil, Y; González, Patricia M.

    1996-01-01

    We studied the food and feeding ecology of Red Knots Calidris canutus rufa on an area of rocky flat, or restinga, near San Antonio Oeste in the northwest of Golfo San Matias, Provincia de Rio Negro, Argentina in March 1992. These Red Knots are on their way north, from ''wintering'' areas in Tierra

  10. Red Knots (Calidris canutus piersmai and C. c. rogersi) depend on a small threatened staging area in Bohai Bay, China

    NARCIS (Netherlands)

    Rogers, Danny I.; Yang, Hong-Yan; Hassell, Chris J.; Boyle, Adrian N.; Rogers, Ken G.; Chen, Bing; Zhang, Zheng-Wang; Piersma, Theunis

    2010-01-01

    We monitored numbers of Red Knots (Calidris canutus) staging in Bohai Bay, China (39 degrees 02'N, 118 degrees 15'E) on northward migration. Knots were identified to subspecies, and we systematically searched for colour-banded birds from the non-breeding grounds. We modelled migratory turnover, and

  11. Being at the right time at the right place: interpreting the annual life cycle of Afro-Siberian red knots

    NARCIS (Netherlands)

    Leyrer, J.

    2011-01-01

    This thesis describes the possible selection pressures acting on survival and, indirectly, on reproduction of Afro-Siberian red knots Calidris canutus canutus while wintering and migrating. Afro-Siberian red knots are long-distance migrants. They travel between the West African wintering areas and

  12. Human peptide transporters

    DEFF Research Database (Denmark)

    Nielsen, Carsten Uhd; Brodin, Birger; Jørgensen, Flemming Steen

    2002-01-01

    Peptide transporters are epithelial solute carriers. Their functional role has been characterised in the small intestine and proximal tubules, where they are involved in absorption of dietary peptides and peptide reabsorption, respectively. Currently, two peptide transporters, PepT1 and PepT2, wh...

  13. Gaussian quadrature rules for C 1 quintic splines with uniform knot vectors

    KAUST Repository

    Barton, Michael; Ait-Haddou, Rachid; Calo, Victor Manuel

    2017-01-01

    We provide explicit quadrature rules for spaces of C1C1 quintic splines with uniform knot sequences over finite domains. The quadrature nodes and weights are derived via an explicit recursion that avoids numerical solvers. Each rule is optimal, that is, requires the minimal number of nodes, for a given function space. For each of nn subintervals, generically, only two nodes are required which reduces the evaluation cost by 2/32/3 when compared to the classical Gaussian quadrature for polynomials over each knot span. Numerical experiments show fast convergence, as nn grows, to the “two-third” quadrature rule of Hughes et al. (2010) for infinite domains.

  14. Post-breeding migration and connectivity of red knots in the Western Atlantic

    Science.gov (United States)

    Lyons, James E.; Winn, Bradford; Keyes, Timothy; Kalasz, Kevin S.

    2018-01-01

    Red knots (Calidris canutus rufa) have 3 distinct nonbreeding regions: 1 in the southeastern United States and Caribbean, another on the northeast coast of Brazil in the Maranhão region, and a third along the Patagonian coasts of Chile and Argentina. Effective conservation and recovery of this threatened long-distance migrant will require knowledge of population structure, migration ecology, and abundance and distribution throughout the annual cycle. We conducted a stopover population and biogeographic assessment of knots at the Altamaha River Delta, Georgia, an important stopover area in the southeastern United States. We estimated stopover population size and stopover duration during post-breeding migration in 2011 at the Altamaha study area using mark-resight data, and we inferred nonbreeding regions for this stopover population using stable isotope ratios of carbon and nitrogen in feathers, and observations (sightings and captures) during boreal winter from across the hemisphere. With an integrated Bayesian analysis of all these data, we also estimated the number of birds in the southeastern United States and northern Brazil during boreal winter. For mark-resight analyses in Georgia, we made observations of marked individuals during 14 weeks from early August to early November 2011 and detected 814 individually marked birds. We used the Jolly-Seber mark-recapture model and estimated the southbound passage population at approximately 23,400 red knots. In ongoing studies elsewhere, isotope samples were collected from 175 (21%) of the 814 birds detected in our study, and ≥1 sighting or capture record during boreal winter was located in data repositories for 659 birds (81%). Isotopic signatures and boreal winter records indicate that the majority (82–96%) of the birds that stopped at the Altamaha Delta spend the boreal winter in the northern part of the nonbreeding range (southeast USA, Caribbean, and northern Brazil). Knots migrating to the southeastern

  15. Intraurethral knot in a very-low-birth-weight infant: radiological recognition, surgical management and prevention

    International Nuclear Information System (INIS)

    Lodha, Abhay; Ly, Linh; McNamara, Patrick J.; Brindle, Mary; Daneman, Alan

    2005-01-01

    We report a case where a knot developed in a urinary catheter and became lodged within the urethra of a very-low-birth-weight (VLBW) preterm infant. The catheter was removed with the assistance of a urologist. We recommend using caution when placing urinary catheters in VLBW infants and question the appropriateness of feeding tubes as catheters. Recognition on radiographs of malpositioned bladder catheters is vital to the care of these patients. All staff involved in the insertion, maintenance or removal of these catheters should be suitably trained to minimize the risk of knots and related complications. (orig.)

  16. Gaussian quadrature rules for C 1 quintic splines with uniform knot vectors

    KAUST Repository

    Bartoň, Michael

    2017-03-21

    We provide explicit quadrature rules for spaces of C1C1 quintic splines with uniform knot sequences over finite domains. The quadrature nodes and weights are derived via an explicit recursion that avoids numerical solvers. Each rule is optimal, that is, requires the minimal number of nodes, for a given function space. For each of nn subintervals, generically, only two nodes are required which reduces the evaluation cost by 2/32/3 when compared to the classical Gaussian quadrature for polynomials over each knot span. Numerical experiments show fast convergence, as nn grows, to the “two-third” quadrature rule of Hughes et al. (2010) for infinite domains.

  17. DIRECT DETECTION OF THE HELICAL MAGNETIC FIELD GEOMETRY FROM 3D RECONSTRUCTION OF PROMINENCE KNOT TRAJECTORIES

    Energy Technology Data Exchange (ETDEWEB)

    Zapiór, Maciej; Martinez-Gómez, David, E-mail: zapior.maciek@gmail.com [Physics Department, University of the Balearic Islands, Cra. de Valldemossa, km 7.5. Palma (Illes Balears), E-07122 (Spain)

    2016-02-01

    Based on the data collected by the Vacuum Tower Telescope located in the Teide Observatory in the Canary Islands, we analyzed the three-dimensional (3D) motion of so-called knots in a solar prominence of 2014 June 9. Trajectories of seven knots were reconstructed, giving information of the 3D geometry of the magnetic field. Helical motion was detected. From the equipartition principle, we estimated the lower limit of the magnetic field in the prominence to ≈1–3 G and from the Ampère’s law the lower limit of the electric current to ≈1.2 × 10{sup 9} A.

  18. Direct Detection of the Helical Magnetic Field Geometry from 3D Reconstruction of Prominence Knot Trajectories

    Science.gov (United States)

    Zapiór, Maciej; Martínez-Gómez, David

    2016-02-01

    Based on the data collected by the Vacuum Tower Telescope located in the Teide Observatory in the Canary Islands, we analyzed the three-dimensional (3D) motion of so-called knots in a solar prominence of 2014 June 9. Trajectories of seven knots were reconstructed, giving information of the 3D geometry of the magnetic field. Helical motion was detected. From the equipartition principle, we estimated the lower limit of the magnetic field in the prominence to ≈1-3 G and from the Ampère’s law the lower limit of the electric current to ≈1.2 × 109 A.

  19. Knotting probabilities after a local strand passage in unknotted self-avoiding polygons

    International Nuclear Information System (INIS)

    Szafron, M L; Soteros, C E

    2011-01-01

    We investigate, both theoretically and numerically, the knotting probabilities after a local strand passage is performed in an unknotted self-avoiding polygon (SAP) on the simple cubic lattice. In the polygons studied, it is assumed that two polygon segments have already been brought close together for the purpose of performing a strand passage. This restricts the polygons considered to those that contain a specific pattern called Θ at a fixed location; an unknotted polygon containing Θ is called a Θ-SAP. It is proved that the number of n-edge Θ-SAPs grows exponentially (with n) at the same rate as the total number of n-edge unknotted SAPs (those with no prespecified strand passage structure). Furthermore, it is proved that the same holds for subsets of n-edge Θ-SAPs that yield a specific after-strand-passage knot-type. Thus, the probability of a given after-strand-passage knot-type does not grow (or decay) exponentially with n. Instead, it is conjectured that these after-strand-passage knot probabilities approach, as n goes to infinity, knot-type dependent amplitude ratios lying strictly between 0 and 1. This conjecture is supported by numerical evidence from Monte Carlo data generated using a composite (aka multiple) Markov chain Monte Carlo BFACF algorithm developed to study Θ-SAPs. A new maximum likelihood method is used to estimate the critical exponents relevant to this conjecture. We also obtain strong numerical evidence that the after-strand-passage knotting probability depends on the local structure around the strand-passage site. If the local structure and the crossing sign at the strand-passage site are considered, then we observe that the more 'compact' the local structure, the less likely the after-strand-passage polygon is to be knotted. This trend for compactness versus knotting probability is consistent with results obtained for other strand-passage models; however, we are the first to note the influence of the crossing-sign information. We

  20. Complexes of macrocyclic dibenzo-18-crown-6 polyether with nitrates of some rare earths

    International Nuclear Information System (INIS)

    Gren', A.I.; Zakhariya, N.F.; Vityuk, N.V.; Kalishevich, V.S.

    1984-01-01

    The purpose of the investigation is to obtain and study the structure of complexes of macrocyclic polyether dibenzo-18-crown-6(D-18-C-6) with REE nitrates (Ln, Pr, Nd, Er). Synthesis has been realized by mixing the solutions 2 mol Ln(NO 3 ) 3 and 2 mmol D-18-C-6 into 30-50 ml acetonitrile and boiling during 40-60 minutes. Study on the prepared compounds by means of UV- and IR-spectroscopy proved formation of D-18-C-6 complexes with lanthanide nitrates-Ln(NO 3 ) 3 D-18-C-6. Based on studying IR-spectra a conclusion is made on deformation of D-18-C-6 structure under complexing. Distortion of the ring structure of macrocyclic polyether manifests itself in increase of CH 2 -O-CH 2 bond lengths with simultaneous reduction of four other types of bonds C 6 H 5 -O-CH 2 . Synthesized complexes are stated to have different solubility in acetonitrile which increases in the La 3 ) 3 xD-18-C-6 is noted

  1. Adaptive self-assembly and induced-fit transformations of anion-binding metal-organic macrocycles

    Science.gov (United States)

    Zhang, Ting; Zhou, Li-Peng; Guo, Xiao-Qing; Cai, Li-Xuan; Sun, Qing-Fu

    2017-06-01

    Container-molecules are attractive to chemists due to their unique structural characteristics comparable to enzymes and receptors in nature. We report here a family of artificial self-assembled macrocyclic containers that feature induced-fit transformations in response to different anionic guests. Five metal-organic macrocycles with empirical formula of MnL2n (M=Metal L=Ligand n=3, 4, 5, 6, 7) are selectively obtained starting from one simple benzimidazole-based ligand and square-planar palladium(II) ions, either by direct anion-adaptive self-assembly or induced-fit transformations. Hydrogen-bonding interactions between the inner surface of the macrocycles and the anionic guests dictate the shape and size of the product. A comprehensive induced-fit transformation map across all the MnL2n species is drawn, with a representative reconstitution process from Pd7L14 to Pd3L6 traced in detail, revealing a gradual ring-shrinking mechanism. We envisage that these macrocyclic molecules with adjustable well-defined hydrogen-bonding pockets will find wide applications in molecular sensing or catalysis.

  2. Characterization and crystal structure of a 17-membered macrocyclic Schiff base compound MeO-sal-pn-bn

    Czech Academy of Sciences Publication Activity Database

    Khalaji, A.D.; Ghoran, S.H.; Rohlíček, Jan; Dušek, Michal

    2015-01-01

    Roč. 56, č. 2 (2015), s. 259-265 ISSN 0022-4766 Grant - others:AV ČR(CZ) Praemium Academiae Institutional support: RVO:68378271 Keywords : macrocyclic * Schiff base * spectroscopy * powder diffraction * orthorhombic Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.536, year: 2015

  3. Copper(i)-induced amplification of a [2]catenane in a virtual dynamic library of macrocyclic alkenes

    NARCIS (Netherlands)

    Berrocal, J.A.; Nieuwenhuizen, M.M.L.; Mandolini, L.; Meijer, E.W.; Di Stefano, S.

    2014-01-01

    Olefin cross-metathesis of diluted dichloromethane solutions (=0.15 M) of the 28-membered macrocyclic alkene C1, featuring a 1,10-phenanthroline moiety in the backbone, as well as of catenand 1, composed of two identical interlocked C1 units, generates families of noninterlocked oligomers Ci. The

  4. Organic carbonates as solvents in macrocyclic Mn(III) salen catalyzed asymmetric epoxidation of non-functionalized olefins

    Czech Academy of Sciences Publication Activity Database

    Maity, N. Ch.; Rao, G. V. S.; Prathap, Kaniraj Jeya; Abdi, S. H. R.; Kureshy, R. I.; Khan, N. H.; Bajaj, H. C.

    2013-01-01

    Roč. 366, January (2013), s. 380-389 ISSN 1381-1169 Institutional support: RVO:61388963 Keywords : asymmetric epoxidation * organic carbonate * macrocyclic Mn(III) salen complex Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.679, year: 2013

  5. Evaluation of potential bio-control agents on root-knot nematode ...

    African Journals Online (AJOL)

    Indigenous strains of Trichoderma viride (ITCC No. 6889), Pseudomonas fluorescens (ITCC No. B0034) and Purpureocillium lilacinum (ITCC No.6887) were isolated from undisturbed forest eco-system of Southern India. These three bio-mediators were evaluated for their antagonism towards root knot nematode, ...

  6. A new class of magnetic confinement device in the shape of a knot

    Energy Technology Data Exchange (ETDEWEB)

    Hudson, S. R., E-mail: shudson@pppl.gov; Startsev, E.; Feibush, E. [Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543 (United States)

    2014-01-15

    We describe a new class of magnetic confinement device, with the magnetic axis in the shape of a knot. We call such devices “knotatrons.” An example is given that has a large volume filled with magnetic surfaces, with significant rotational-transform, and with the magnetic field produced entirely by external circular coils.

  7. The mutual attraction of magnetic knots. [solar hydromagnetic instability in sunspot regions

    Science.gov (United States)

    Parker, E. N.

    1978-01-01

    It is observed that the magnetic knots associated with active regions on the sun have an attraction for each other during the formative period of the active regions, when new magnetic flux is coming to the surface. The attraction disappears when new flux ceases to rise through the surface. Then the magnetic spots and knots tend to come apart, leading to disintegration of the sunspots previously formed. The dissolution of the fields is to be expected, as a consequence of the magnetic repulsion of knots of like polarity and as a consequence of the hydromagnetic exchange instability. The purpose of this paper is to show that the mutual attraction of knots during the formative stages of a sunspot region may be understood as the mutual hydrodynamic attraction of the rising flux tubes. Two rising tubes attract each other, as a consequence of the wake of the leading tube when one is moving behind the other, and as a consequence of the Bernoulli effect when rising side by side.

  8. First report of the root-knot nematode Meloidogyne minor on turfgrass in Belgium

    NARCIS (Netherlands)

    Viaene, N.; Wiseborn, D.B.; Karssen, G.

    2007-01-01

    The root-knot nematode, Meloidogyne minor, was described during 2004 after it was found on potato roots in a field in the Netherlands and in golf courses in England, Wales, and Ireland (2). Since it is associated with yellow patch disease in turf grass and causes deformation of potato tubers (2), it

  9. Modelling phenotypic flexibility : an optimality analysis of gizzard size in Red Knots Calidris canutus

    NARCIS (Netherlands)

    van Gils, Jan A.; Piersma, Theunis; Dekinga, Anne; Battley, Phil F.

    2006-01-01

    Reversible phenotypic changes, such as those observed in nutritional organs of long-distance migrants, increasingly receive the attention of ornithologists. In this paper we review the cost-benefit studies that have been performed on the flexible gizzard of Red Knots Calidris cunutus. By varying the

  10. Modelling phenotypic flexibility: an optimality analysis of gizzard size in Red Knots (Calidris canutus)

    NARCIS (Netherlands)

    Van Gils, J.A.; Piersma, T.; Dekinga, A.; Battley, P.F.

    2006-01-01

    Reversible phenotypic changes, such as those observed in nutritional organs of long-distance migrants, increasingly receive the attention of ornithologists. In this paper we review the cost-benefit studies that have been performed on the flexible gizzard of Red Knots Calidris canutus. By varying the

  11. Quiet eye training improves surgical knot tying more than traditional technical training: a randomized controlled study.

    Science.gov (United States)

    Causer, Joe; Harvey, Adrian; Snelgrove, Ryan; Arsenault, Gina; Vickers, Joan N

    2014-08-01

    We examined the effectiveness of technical training (TT) and quiet eye training (QE) on the performance of one-handed square knot tying in surgical residents. Twenty surgical residents were randomly assigned to the 2 groups and completed pretest, training, retention, and transfer tests. Participants wore a mobile eye tracker that simultaneously recorded their gaze and hand movements. Dependent variables were knot tying performance (%), QE duration (%), number of fixations, total movement time (s), and hand movement phase time (s). The QE training group had significantly higher performance scores, a longer QE duration, fewer fixations, faster total knot tying times, and faster movement phase times compared with the TT group. The QE group maintained performance in the transfer test, whereas the TT group significantly decreased performance from retention to transfer. QE training significantly improved learning, retention, and transfer of surgical knot tying compared with a traditional technical approach. Both performance effectiveness (performance outcome) and movement efficiency (hand movement times) were improved using QE modeling, instruction, and feedback. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Day and night feeding habitat of Red Knots in Patagonia : Profitability versus safety?

    NARCIS (Netherlands)

    Sitters, HP; Gonzalez, PM; Piersma, T; Baker, AJ; Price, DJ; Sitters, Humphrey P.; González, Patricia M.; Baker, Allan J.; Price, David J.

    2001-01-01

    By radio-tracking and recording the movements of flocks. the distribution of feeding Red Knots (Calidris canutus rufa) was studied day and night at a migration stopover site near San Antonio Oeste, Rio Negro, Argentina in March and April 1998. By day, the birds fed in dense flocks of 500-4000 on an

  13. Azadirachtin powder for control of root-knot nematodes in tomato

    Science.gov (United States)

    USDA ARS Daniel K. Inouye U.S. Pacific Basin Agricultural Research Center, 64 Nowelo St., Hilo, HI 96720. Root-knot nematodes cause root galling and yield reductions in many vegetable crops, including tomato. Three organic treatments to improve root growth and reduce nematode infestation were eval...

  14. Fuzzy knot theory interpretation of Yang-Mills instantons and Witten's 5-Brane model

    International Nuclear Information System (INIS)

    El Naschie, M.S.

    2008-01-01

    A knot theory interpretation of 'tHooft's instanton based on hyperbolic volume, crossing numbers and exceptional Lie symmetry groups is given. Subsequently it is shown that although instantons and particle-like states of Heterotic super strings may appear to be different concepts, on a very deep fuzzy level they are not

  15. Percutaneous untying of a knot in a retained Swan-Ganz catheter

    International Nuclear Information System (INIS)

    Bhatti, Waqar A.; Sinha, Sankar; Rowlands, Peter

    2000-01-01

    A patient was referred to us with a tightly knotted Swan-Ganz catheter. The catheter could not be removed by conventional simple methods. We describe a minimally invasive means of removal of the catheter using an Amplatz gooseneck snare and an angioplasty balloon. This allowed the Catheter to be removed without trauma.

  16. Dissecting host plant manipulation by cyst and root-knot nematodes

    NARCIS (Netherlands)

    Karczmarek, A.

    2006-01-01

    Cyst ( Globodera spp. and Heterodera spp.) and root-knot nematodes ( Meloidogyne spp.), one of the most damaging crop pests, are a perfect example of highly adapted, sophisticated root parasites. These nematodes induces specialized feeding structures (cyst

  17. Effect of soil solarization using plastic mulch in controlling root-knot ...

    African Journals Online (AJOL)

    A field experiment was conducted from February to May, 2004 and 2005 planting seasons at the Vegetable Evaluation and Research Station Farm located at Anse Boileau, Seychelles to evaluate the effect of soil solarization using plastic mulch in controlling root-knot nematode infestation and yield of lettuce.

  18. Basal metabolic rate declines during long-distance migratory flight in great knots

    NARCIS (Netherlands)

    Battley, PF; Dekinga, A; Dietz, MW; Piersma, T; Tang, SX; Hulsman, K; Battley, Phil F.; Tang, Sixian

    2001-01-01

    Great Knots (Calidris tenuirostris) make one of the longest migratory flights in the avian world, flying almost 5500 km from Australia to China during northward migration. We measured basal metabolic rate (BMR) and body composition in birds before and after this flight and found that BMR decreased

  19. Endogenous circannual rhythmicity in body mass, molt, and plumage of Great Knots (Calidris tenuirostris)

    NARCIS (Netherlands)

    Piersma, Theunis; Brugge, Maarten; Spaans, Bernard; Battley, Phil F.; Handel, C.M.

    Four Great Knots (Calidris tenuirostris) were kept for six years in a constant-temperature indoor aviary. For two of those six years, they were kept under photoperiodic conditions that mimicked natural changes in daylength for wild birds, followed by four years under a constant photoperiod

  20. Hanseniaspora nodinigri, a new yeast species found in black knots (Dibotryon morbosum) of Prunus virginiana.

    Science.gov (United States)

    Lachance, M A

    1981-07-01

    The new yeast species Hanseniaspora nodinigri is described to accommodate members of the genus Hanseniaspora that are unable to assimilate glucono-sigma-lactone and isolated from stromatal tissue of black knots (Dobotryon morbosum) of chokecherry, Prunus virginiana. The newly described taxon shows much resemblance, by other criteria, to H. vineae van der Walt et Tscheuschner and H. osmophila (Niehaus) Phaff, Miller et Shifrine.

  1. Interference from adults forces young red knots to forage for longer and in dangerous places

    NARCIS (Netherlands)

    van den Hout, P.J.; van Gils, J.A.; Robin, F.; van der Geest, M.; Dekinga, A.; Piersma, T.

    2014-01-01

    In birds and mammals, juvenile and adult foragers are often found apart from each other. In this study, we found this is also true for red knots, Calidris canutus canutus, wintering on the intertidal flats of Banc d'Arguin, Mauritania. Not only did juveniles feed separately from adults, they also

  2. Evaluation of edible ginger and turmeric cultivars for root-knot nematode resistance

    Science.gov (United States)

    Edible ginger and turmeric roots are important agricultural commodities for the State of Hawaii. Bacterial wilt, Ralstonia solanacearum, and root-knot nematodes, Meloidogyne spp. are major factors hindering optimum production. An evaluation of tolerance and resistance to M. incognita was undertake...

  3. First report of the root-knot nematode Meloidogyne marylandi on Turfgrasses in Israel

    NARCIS (Netherlands)

    Oka, Y.; Karssen, G.; Mor, M.

    2004-01-01

    In a turfgrass nursery in Arava, Israel, a population of root-knot nematodes was isolated from poorly growing Zoysiagrass (Zoysia japonica Steud.) with symptoms of foliar chlorosis and roots with very small, smooth galls and protruding egg masses. The isolated population (genus Meloidogyne) included

  4. Evaluation of tomato genotypes for resistance to root-knot nematodes

    African Journals Online (AJOL)

    Tomato (Solanum lycopersicum) is one of the most popular vegetable crops worldwide, owing to its high nutritive value and diversified use. Tomato production in Ghana is threatened by plant parasitic nematodes, especially the root knot nematodes (Meloidogyne spp.), which are responsible for huge economic yield losses.

  5. Intravesical knotting of feeding tube used as urinary catheter in an infant

    Directory of Open Access Journals (Sweden)

    Mamatha Basavaraju

    2016-09-01

    Full Text Available Infant feeding tube is commonly used to temporarily drain the bladder in pediatric population. A case is described where the tube got knotted inside the bladder probably due to over insertion or bladder spasm caused by irritation of catheter.

  6. Hydrodynamic characteristics of knotted and knotless purse seine netting panels as determined in a flume tank.

    Science.gov (United States)

    Tang, Hao; Xu, Liuxiong; Hu, Fuxiang

    2018-01-01

    Nylon (PA) netting is widely used in purse seines and other fishing gears due to its high strength and good sinking performance. However, hydrodynamic properties of nylon netting of different characteristics are poorly understood. This study investigated hydrodynamic characteristics of nylon netting of different knot types and solidity ratios under different attack angles and flow velocities. It was found that the hydrodynamic coefficient of netting panels was related to Reynolds number, solidity ratio, attack angle, knot type and twine construction. The solidity ratio was found to positively correlate with drag coefficient when the netting was normal to the flow (CD90), but not the case when the netting was parallel to the flow (CD0). For netting panels inclined to the flow, the inclined drag coefficient had a negative relationship with the solidity ratio for attack angles between 0° and 50°, but a positive relationship for attack angles between 50° and 90°. The lift coefficient increased with the attack angle, reaching the culminating point at an attack angle of 50°, before subsequent decline. We found that the drag generated by knot accounted for 15-25% of total drag, and the knotted netting with higher solidity ratio exhibited a greater CD0, but it was not the case for the knotless netting. Compared to knotless polyethylene (PE) netting, the drag coefficients of knotless PA netting were dominant at higher Reynolds number (Re>2200).

  7. Hydrodynamic characteristics of knotted and knotless purse seine netting panels as determined in a flume tank.

    Directory of Open Access Journals (Sweden)

    Hao Tang

    Full Text Available Nylon (PA netting is widely used in purse seines and other fishing gears due to its high strength and good sinking performance. However, hydrodynamic properties of nylon netting of different characteristics are poorly understood. This study investigated hydrodynamic characteristics of nylon netting of different knot types and solidity ratios under different attack angles and flow velocities. It was found that the hydrodynamic coefficient of netting panels was related to Reynolds number, solidity ratio, attack angle, knot type and twine construction. The solidity ratio was found to positively correlate with drag coefficient when the netting was normal to the flow (CD90, but not the case when the netting was parallel to the flow (CD0. For netting panels inclined to the flow, the inclined drag coefficient had a negative relationship with the solidity ratio for attack angles between 0° and 50°, but a positive relationship for attack angles between 50° and 90°. The lift coefficient increased with the attack angle, reaching the culminating point at an attack angle of 50°, before subsequent decline. We found that the drag generated by knot accounted for 15-25% of total drag, and the knotted netting with higher solidity ratio exhibited a greater CD0, but it was not the case for the knotless netting. Compared to knotless polyethylene (PE netting, the drag coefficients of knotless PA netting were dominant at higher Reynolds number (Re>2200.

  8. Pierced Lasso Bundles are a new class of knot-like motifs.

    Directory of Open Access Journals (Sweden)

    Ellinor Haglund

    2014-06-01

    Full Text Available A four-helix bundle is a well-characterized motif often used as a target for designed pharmaceutical therapeutics and nutritional supplements. Recently, we discovered a new structural complexity within this motif created by a disulphide bridge in the long-chain helical bundle cytokine leptin. When oxidized, leptin contains a disulphide bridge creating a covalent-loop through which part of the polypeptide chain is threaded (as seen in knotted proteins. We explored whether other proteins contain a similar intriguing knot-like structure as in leptin and discovered 11 structurally homologous proteins in the PDB. We call this new helical family class the Pierced Lasso Bundle (PLB and the knot-like threaded structural motif a Pierced Lasso (PL. In the current study, we use structure-based simulation to investigate the threading/folding mechanisms for all the PLBs along with three unthreaded homologs as the covalent loop (or lasso in leptin is important in folding dynamics and activity. We find that the presence of a small covalent loop leads to a mechanism where structural elements slipknot to thread through the covalent loop. Larger loops use a piercing mechanism where the free terminal plugs through the covalent loop. Remarkably, the position of the loop as well as its size influences the native state dynamics, which can impact receptor binding and biological activity. This previously unrecognized complexity of knot-like proteins within the helical bundle family comprises a completely new class within the knot family, and the hidden complexity we unraveled in the PLBs is expected to be found in other protein structures outside the four-helix bundles. The insights gained here provide critical new elements for future investigation of this emerging class of proteins, where function and the energetic landscape can be controlled by hidden topology, and should be take into account in ab initio predictions of newly identified protein targets.

  9. Management of Root Knot Nematode on Tomato through Grafting Root Stock of Solanum sisymbriifolium

    Directory of Open Access Journals (Sweden)

    Suraj Baidya

    2017-05-01

    Full Text Available The root-knot nematodes (Meloidogyne spp are difficult to manage once established in the field because of their wide host range, and soil-borne nature. Thus, the aim of the present study was to examine the use of resistant root stock of wild brinjal (Solanum sisymbriifolium to reduce the loss caused by the nematodes on tomato. For the management of root-knot nematodes, grafted plant with resistant root stock of the wild brinjal was tested under farmers’ field conditions at Hemza of Kaski district. Grafted and non-grafted plants were produced in root-knot nematode-free soil. Around three week-old grafted and non-grafted tomato plants were transplanted in four different plastic tunnels where root-knot nematodes had been reported previously. The plants were planted in diagonal position to each other as a pair plot in 80 × 60 cm2 spacing in an average of 20 × 7 m2 plastic tunnels. Galling Index (GI was recorded three times in five randomly selected plants in each plot at 60 days intervals. The first observation was recorded two months after transplanting. Total fruit yield was recorded from same plants. In the grafted plants, the root system was totally free from gall whereas in an average of 7.5 GI in 0-10 scale was recorded in the non-grafted plants. Fruits were harvested from time to time and cumulated after final harvest to calculate the total fruit yield. It was estimated that on an average tomato fruit yield was significantly (P>0.05 increased by 37 percent in the grafted plants compared with the non-grafted plants. Grafting technology could be used effectively for cultivation of commonly grown varieties, which are susceptible to root-knot nematodes in disease prone areas. This can be used as an alternative technology for reducing the use of hazardous pesticides for enhancing commercial organic tomato production.

  10. Synthesis and optoelectronic properties of a monodispersed macrocycle oligomer consisting of three triarylamine units

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Qinggang, E-mail: gangq0172@163.com [Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, College of Environmental Science and Engineering, Nanjing University of Information Science and Technology, 219 Ningliu Road, Pukou District, Nanjing 210044 (China); Qian, Haiyan, E-mail: qianhaiy@163.com [College of Material Science and Technology, Nanjing University of Technology, 5 Xinmofan Road, Nanjing 210009 (China); Zhou, Yonghui; Li, Jun; Xiao, Huining [Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, College of Environmental Science and Engineering, Nanjing University of Information Science and Technology, 219 Ningliu Road, Pukou District, Nanjing 210044 (China)

    2012-08-15

    A monodispersed macrocyclic oligomer constructed by three triarylmine units ((TPAT){sub 3}) was designed and readily synthesized from the monomer of 3-(4 Prime -(phenyl(4 Double-Prime -methylphenyl)amino)-phenyl)pentan-3-ol (TPAT) by means of a simple Friedel-Crafts alkylation reaction. The structure of the resultant macrocycle was examined using FT-IR, NMR and MALDI-TOF mass spectroscopy. Compared with 1,10-bis(di-4-tolylaminophenyl) cyclohexane (TAPC) and tri-p-tolylamine (TTA), (TPAT){sub 3} possesses the three-dimensional chair conformation and the higher T{sub g}. In the photoluminescence (PL) spectrum of (TPAT){sub 3} film, there are no excimer emission peaks in the range of 400-550 nm region as those of TAPC and TTA. Besides an EL peak at 386 nm, the single-layer device occured only the 438 nm excimer emission peak, whose intensity increased with the excitation voltage increase. Using 1,3,5-Tris(N-phenylbenzimidazol-2-yl)-benzene (TPBI) as the electron-transporting layer, the resulting double-layer device ITO/(TPAT){sub 3} (40 nm)/TPBI (40 nm)/Mg:Ag (10:1; 50 nm)/Ag (100 nm) only exhibited a 438 nm maximum symmetrical emission peak under an excitation voltage of 14 V. However, as the applied voltage was increased from 14 V to 19 V, the intensity of the symmetrical curve with a 468 nm peak from exciplex emission gets stronger and stronger. In fact, the resultant emission curve was asymmetrical, due to the overlap of two symmetrical curves with 438 nm and 468 nm peaks, respectively. The maximum luminance and luminous efficiency are 2240 cd m{sup -2} at 18.8 V and 1.73 cd A{sup -1} at 1878 cd m{sup -2} (13.9 V). Highlights: Black-Right-Pointing-Pointer The monodispersed macrocyclic oligomer constructed by three triarylamine units was synthesized and characterized. Black-Right-Pointing-Pointer The PL of (TPAT){sub 3} film does not emerge TAPC and TTA's emission peaks of over 400 nm region. Black-Right-Pointing-Pointer The 438 nm emission peak was found from

  11. Safety and clinical efficacy of tenvermectin, a novel antiparasitic 16-membered macrocyclic lactone antibiotics.

    Science.gov (United States)

    Fei, Chenzhong; She, Rufeng; Li, Guiyu; Zhang, Lifang; Fan, Wushun; Xia, Suhan; Xue, Feiqun

    2018-05-30

    Tenvermectin (TVM) is a novel 16-membered macrocyclic lactone antibiotics, which contains component TVM A and TVM B. However there is not any report on safety and clinical efficacy of TVM for developing as a potential drug. In order to understand the part of safety and clinical efficacy of TVM, we conducted the acute toxicity test, the standard bacterial reverse mutation (Ames) test and the clinical deworming test. In the acute toxicity studies, TVM, TVM A and ivermectin (IVM) were administrated once by oral gavage to mice and rats. Results showed that the oral LD 50 values of TVM, TVM A and IVM in mice were 74.41, 106.95 and 53.06 mg/kg respectively. The oral LD 50 values of TVM and TVM A in rats were determined to be 164.22 and 749.34 mg/kg respectively. TVM and IVM are moderately toxic substances, meanwhile the TVM A belongs to low toxic compounds, implying that the acute toxicity is highly related to the length of side chain of TVM at position C25. In the Ames test, results showed that TVM did not induce mutagenicity in Salmonella typhimurium TA97a, TA98, TA100, TA102 and TA1535 with and without metabolic activation system, speculating that the mutagenicity is probably not related to the side chain at position C25 of 16-membered macrocyclic lactone antibiotics. In the efficacy trail of TVM against swine nematodes, growing pigs natural infection of Ascaris suum and Trichuris suis were treated with a single subcutaneous injection 0.3 mg/kg b.w.. Results showed that TVM and IVM had excellent effect in expelling Ascaris suum, and TVM had potential efficacy against Trichuris suis, however IVM had no effect on Trichuris suis. This study suggests that the side chain of TVM at position C25 may have important biological functions, which is one of the key sites of the studies on structure-activity relationship of 16-membered macrocyclic lactone compounds. TVM is a new compound exhibited some advantages worthy of developing. Copyright © 2018 Elsevier B.V. All

  12. Design, synthesis, X-ray studies, and biological evaluation of novel macrocyclic HIV-1 protease inhibitors involving the P1'-P2' ligands

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Arun K.; Sean Fyvie, W.; Brindisi, Margherita; Steffey, Melinda; Agniswamy, Johnson; Wang, Yuan-Fang; Aoki, Manabu; Amano, Masayuki; Weber, Irene T.; Mitsuya, Hiroaki

    2017-11-01

    Design, synthesis, and evaluation of a new class of HIV-1 protease inhibitors containing diverse flexible macrocyclic P1'-P2' tethers are reported. Inhibitor 5a with a pyrrolidinone-derived macrocycle exhibited favorable enzyme inhibitory and antiviral activity (Ki = 13.2 nM, IC50 = 22 nM). Further incorporation of heteroatoms in the macrocyclic skeleton provided macrocyclic inhibitors 5m and 5o. These compounds showed excellent HIV-1 protease inhibitory (Ki = 62 pM and 14 pM, respectively) and antiviral activity (IC50 = 5.3 nM and 2.0 nM, respectively). Inhibitor 5o also remained highly potent against a DRV-resistant HIV-1 variant.

  13. PeptideAtlas

    Data.gov (United States)

    U.S. Department of Health & Human Services — PeptideAtlas is a multi-organism, publicly accessible compendium of peptides identified in a large set of tandem mass spectrometry proteomics experiments. Mass...

  14. Great isotope effects in compounding of sodium isotopes by macrocyclic polyether

    International Nuclear Information System (INIS)

    Knoechel, A.; Wilken, R.D.

    1978-01-01

    Isotope effects appear in the compounding of the two sodium isotopes 24 Na + and 22 Na + with macrocyclic polyethers, whose value was determined for the 13 best known polyethers. A radiometric process was used for determining the different half life periods of the nuclides used. To separate the compound and non-compound types, these were distributed between water and chloroform. The isotope ratio in the chloroform phase was compared with the output isotope ratio and the separation facfor determined from this. When using crown ethers, there was enrichment of 24 Na + by a significant amount (large crown ether) up to 3.1 +- 0.4% for 18 crown 6. The remarkably high results can be correlated by Biegeleisen's theory with other chemical conditions. There is a report on the first results of transferring these conditions to the H + /T + system. (orig.) [de

  15. Versatile protein recognition by the encoded display of multiple chemical elements on a constant macrocyclic scaffold

    Science.gov (United States)

    Li, Yizhou; De Luca, Roberto; Cazzamalli, Samuele; Pretto, Francesca; Bajic, Davor; Scheuermann, Jörg; Neri, Dario

    2018-03-01

    In nature, specific antibodies can be generated as a result of an adaptive selection and expansion of lymphocytes with suitable protein binding properties. We attempted to mimic antibody-antigen recognition by displaying multiple chemical diversity elements on a defined macrocyclic scaffold. Encoding of the displayed combinations was achieved using distinctive DNA tags, resulting in a library size of 35,393,112. Specific binders could be isolated against a variety of proteins, including carbonic anhydrase IX, horseradish peroxidase, tankyrase 1, human serum albumin, alpha-1 acid glycoprotein, calmodulin, prostate-specific antigen and tumour necrosis factor. Similar to antibodies, the encoded display of multiple chemical elements on a constant scaffold enabled practical applications, such as fluorescence microscopy procedures or the selective in vivo delivery of payloads to tumours. Furthermore, the versatile structure of the scaffold facilitated the generation of protein-specific chemical probes, as illustrated by photo-crosslinking.

  16. Tunable photophysical processes of porphyrin macrocycles on the surface of ZnO nanoparticles

    KAUST Repository

    Parida, Manas R.

    2015-01-23

    We investigated the impact of the molecular structure of cationic porphyrins on the degree of electrostatic interactions with zinc oxide nanoparticles (ZnO NPs) using steady-state and time-resolved fluorescence and transient absorption spectroscopy. Our results demonstrate that the number of cationic pyridinium units has a crucial impact on the photophysics of the porphyrin macrocycle. Fluorescence enhancement, relative to initial free porphyrin fluorescence, was found to be tuned from 3.4 to 1.3 times higher by reducing the number of cationic substituents on the porphyrin from 4 to 2. The resulting enhancement of the intensity of the fluorescence is attributed to the decrease in the intramolecular charge transfer (ICT) character between the porphyrin cavity and its meso substituent. The novel findings reported in this work provide an understanding of the key variables involved in nanoassembly, paving the way toward optimizing the interfacial chemistry of porphyrin-ZnO NP assembly for photodynamic therapy and energy conversion.

  17. tetrapyrrole macrocycle

    African Journals Online (AJOL)

    ... 3(1), 17-24 (1989). CATALYTIC OXIDATION OF 3,5-DI-TERTBUTYL CATECHOL (3,5-DTBC) .... (C13) in 25 ml of methanol. To the stirred .... and electrochemical properties (15) since these properties are very similar for all the complexes.

  18. Virtual libraries of tetrapyrrole macrocycles. Combinatorics, isomers, product distributions, and data mining.

    Science.gov (United States)

    Taniguchi, Masahiko; Du, Hai; Lindsey, Jonathan S

    2011-09-26

    A software program (PorphyrinViLiGe) has been developed to enumerate the type and relative amounts of substituted tetrapyrrole macrocycles in a virtual library formed by one of four different classes of reactions. The classes include (1) 4-fold reaction of n disubstituted heterocycles (e.g., pyrroles or diiminoisoindolines) to form β-substituted porphyrins, β-substituted tetraazaporphyrins, or α- or β-substituted phthalocyanines; (2) combination of m aminoketones and n diones to form m × n pyrroles, which upon 4-fold reaction give β-substituted porphyrins; (3) derivatization of an 8-point tetrapyrrole scaffold with n reagents, and (4) 4-fold reaction of n aldehydes and pyrrole to form meso-substituted porphyrins. The program accommodates variable ratios of reactants, reversible or irreversible reaction (reaction classes 1 and 2), and degenerate modes of formation. Pólya's theorem (for enumeration of cyclic entities) has also been implemented and provides validation for reaction classes 3 and 4. The output includes the number and identity of distinct reaction-accessible substituent combinations, the number and identity of isomers thereof, and the theoretical mass spectrum. Provisions for data mining enable assessment of the number of products having a chosen pattern of substituents. Examples include derivatization of an octa-substituted phthalocyanine with eight reagents to afford a library of 2,099,728 members (yet only 6435 distinct substituent combinations) and reversible reaction of six distinct disubstituted pyrroles to afford 2649 members (yet only 126 distinct substituent combinations). In general, libraries of substituted tetrapyrrole macrocycles occupy a synthetically accessible region of chemical space that is rich in isomers (>99% or 95% for the two examples, respectively).

  19. Co-N-macrocyclic modified graphene with excellent electrocatalytic activity for lithium-thionyl chloride batteries

    International Nuclear Information System (INIS)

    Li, Bimei; Yuan, Zhongzhi; Xu, Ying; Liu, Jincheng

    2016-01-01

    Highlights: • A Co-N-graphene catalyst composed of CoN 4 -macrocyclic-like (CoN x ) structure is synthesized. • Co-N x -Graphene has effective electrocatalytic activity for Li/SOCl 2 batteries. • The storage stability of the catalyst is attributed to its insolubility in electrolyte. - Abstract: A mixture of cobalt phthalocyanine (CoPc) and graphene is thermally decomposed at 800 °C to synthesize a novel catalyst. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) show that the catalyst retains the lamellar structure of graphene. X-ray diffraction (XRD) reveals that the catalyst is no longer composed of CoPc and high-resolution TEM (HRTEM), X-ray photoelectron spectra (XPS) prove that Co and N elements have entered the graphene molecular structure, thus forming a Co-N x -graphene (Co-N x -G) catalyst composed of a CoN 4 -macrocyclic-like structure. This catalyst serves as an excellent catalyst of thionyl chloride (SOCl 2 ) reduction. Cyclic voltammetry and battery discharge tests reveal that Co-N x -G-800 substantially increases the discharge voltage and capacity of a Li/SOCl 2 battery. Moreover, Co-N x -G-800 exhibits stable catalytic activity during battery storage. Ultraviolet–visible spectroscopy shows that CoPc is soluble in a SOCl 2 electrolyte solution, whereas Co-N x -G-800 is not, this characteristic contributes to the stable catalytic property of Co-N x -G.

  20. Peptide-Carrier Conjugation

    DEFF Research Database (Denmark)

    Hansen, Paul Robert

    2015-01-01

    To produce antibodies against synthetic peptides it is necessary to couple them to a protein carrier. This chapter provides a nonspecialist overview of peptide-carrier conjugation. Furthermore, a protocol for coupling cysteine-containing peptides to bovine serum albumin is outlined....

  1. PH dependent adhesive peptides

    Science.gov (United States)

    Tomich, John; Iwamoto, Takeo; Shen, Xinchun; Sun, Xiuzhi Susan

    2010-06-29

    A novel peptide adhesive motif is described that requires no receptor or cross-links to achieve maximal adhesive strength. Several peptides with different degrees of adhesive strength have been designed and synthesized using solid phase chemistries. All peptides contain a common hydrophobic core sequence flanked by positively or negatively charged amino acids sequences.

  2. Peptide Nucleic Acids

    DEFF Research Database (Denmark)

    2003-01-01

    A novel class of compounds, known as peptide nucleic acids, bind complementary ssDNA and RNA strands more strongly than a corresponding DNA. The peptide nucleic acids generally comprise ligands such as naturally occurring DNA bases attached to a peptide backbone through a suitable linker....

  3. Peptide Nucleic Acids

    DEFF Research Database (Denmark)

    1998-01-01

    A novel class of compounds, known as peptide nucleic acids, bind complementary ssDNA and RNA strands more strongly than a corresponding DNA. The peptide nucleic acids generally comprise ligands such as naturally occurring DNA bases attached to a peptide backbone through a suitable linker....

  4. Peptide Nucleic Acids (PNA)

    DEFF Research Database (Denmark)

    2002-01-01

    A novel class of compounds, known as peptide nucleic acids, bind complementary ssDNA and RNA strands more strongly than a corresponding DNA. The peptide nucleic acids generally comprise ligands such as naturally occurring DNA bases attached to a peptide backbone through a suitable linker....

  5. Peptide Nucleic Acid Synthons

    DEFF Research Database (Denmark)

    2004-01-01

    A novel class of compounds, known as peptide nucleic acids, bind complementary ssDNA and RNA strands more strongly than a corresponding DNA. The peptide nucleic acids generally comprise ligands such as naturally occurring DNA bases attached to a peptide backbone through a suitable linker....

  6. Antimicrobial Peptides in 2014

    Directory of Open Access Journals (Sweden)

    Guangshun Wang

    2015-03-01

    Full Text Available This article highlights new members, novel mechanisms of action, new functions, and interesting applications of antimicrobial peptides reported in 2014. As of December 2014, over 100 new peptides were registered into the Antimicrobial Peptide Database, increasing the total number of entries to 2493. Unique antimicrobial peptides have been identified from marine bacteria, fungi, and plants. Environmental conditions clearly influence peptide activity or function. Human α-defensin HD-6 is only antimicrobial under reduced conditions. The pH-dependent oligomerization of human cathelicidin LL-37 is linked to double-stranded RNA delivery to endosomes, where the acidic pH triggers the dissociation of the peptide aggregate to release its cargo. Proline-rich peptides, previously known to bind to heat shock proteins, are shown to inhibit protein synthesis. A model antimicrobial peptide is demonstrated to have multiple hits on bacteria, including surface protein delocalization. While cell surface modification to decrease cationic peptide binding is a recognized resistance mechanism for pathogenic bacteria, it is also used as a survival strategy for commensal bacteria. The year 2014 also witnessed continued efforts in exploiting potential applications of antimicrobial peptides. We highlight 3D structure-based design of peptide antimicrobials and vaccines, surface coating, delivery systems, and microbial detection devices involving antimicrobial peptides. The 2014 results also support that combination therapy is preferred over monotherapy in treating biofilms.

  7. Binding of carbon dioxide to metal macrocycles: Toward a mechanistic understanding of electrochemical and photochemical carbon dioxide reduction

    Energy Technology Data Exchange (ETDEWEB)

    Fujita, E.

    1993-01-01

    Efforts were made to find effective catalysts for photochemical and electrochemical reduction of CO[sub 2]. We are studying the factors controlling excited-state lifetimes, electron-transfer rates to mediators/catalysts, properties of reduced mediators, binding of small molecules to reduced mediators, and reactivity of the mediators to yield the desired products. This document describes some of the results of binding on CO[sub 2] to metal macrocycles. The electrocatalytic activity of cobalt macrocycle complexes in reduction of CO[sub 2] in CO[sub 2]-saturated water at the Hg electrode is being studied. We are ready to study the mechanism and kinetics of the photochemical CO[sub 2] reduction in order to design more efficient photo-energy conversion systems. 19 refs.

  8. Binding of carbon dioxide to metal macrocycles: Toward a mechanistic understanding of electrochemical and photochemical carbon dioxide reduction

    Energy Technology Data Exchange (ETDEWEB)

    Fujita, E.

    1993-07-01

    Efforts were made to find effective catalysts for photochemical and electrochemical reduction of CO{sub 2}. We are studying the factors controlling excited-state lifetimes, electron-transfer rates to mediators/catalysts, properties of reduced mediators, binding of small molecules to reduced mediators, and reactivity of the mediators to yield the desired products. This document describes some of the results of binding on CO{sub 2} to metal macrocycles. The electrocatalytic activity of cobalt macrocycle complexes in reduction of CO{sub 2} in CO{sub 2}-saturated water at the Hg electrode is being studied. We are ready to study the mechanism and kinetics of the photochemical CO{sub 2} reduction in order to design more efficient photo-energy conversion systems. 19 refs.

  9. Construction of Orthonormal Piecewise Polynomial Scaling and Wavelet Bases on Non-Equally Spaced Knots

    Directory of Open Access Journals (Sweden)

    Jean Pierre Astruc

    2007-01-01

    Full Text Available This paper investigates the mathematical framework of multiresolution analysis based on irregularly spaced knots sequence. Our presentation is based on the construction of nested nonuniform spline multiresolution spaces. From these spaces, we present the construction of orthonormal scaling and wavelet basis functions on bounded intervals. For any arbitrary degree of the spline function, we provide an explicit generalization allowing the construction of the scaling and wavelet bases on the nontraditional sequences. We show that the orthogonal decomposition is implemented using filter banks where the coefficients depend on the location of the knots on the sequence. Examples of orthonormal spline scaling and wavelet bases are provided. This approach can be used to interpolate irregularly sampled signals in an efficient way, by keeping the multiresolution approach.

  10. Examining the High-energy Radiation Mechanisms of Knots and Hotspots in Active Galactic Nucleus Jets

    Science.gov (United States)

    Zhang, Jin; Du, Shen-shi; Guo, Sheng-Chu; Zhang, Hai-Ming; Chen, Liang; Liang, En-Wei; Zhang, Shuang-Nan

    2018-05-01

    We compile the radio–optical–X-ray spectral energy distributions (SEDs) of 65 knots and 29 hotspots in 41 active galactic nucleus jets to examine their high-energy radiation mechanisms. Their SEDs can be fitted with the single-zone leptonic models, except for the hotspot of Pictor A and six knots of 3C 273. The X-ray emission of 1 hotspot and 22 knots is well explained as synchrotron radiation under the equipartition condition; they usually have lower X-ray and radio luminosities than the others, which may be due to a lower beaming factor. An inverse Compton (IC) process is involved for explaining the X-ray emission of the other SEDs. Without considering the equipartition condition, their X-ray emission can be attributed to the synchrotron-self-Compton process, but the derived jet powers (P jet) are not correlated with L k and most of them are larger than L k, with more than three orders of magnitude, where L k is the jet kinetic power estimated with their radio emission. Under the equipartition condition, the X-ray emission is well interpreted with the IC process for the cosmic microwave background photons (IC/CMB). In this scenario, the derived P jet of knots and hotspots are correlated with and comparable to L k. These results suggest that the IC/CMB model may be a promising interpretation of the X-ray emission. In addition, a tentative knot–hotspot sequence in the synchrotron peak-energy–peak-luminosity plane is observed, similar to the blazar sequence, which may be attributed to the different cooling mechanisms of electrons.

  11. Sprouty gene dosage influences temporal-spatial dynamics of primary enamel knot formation

    Czech Academy of Sciences Publication Activity Database

    Lochovská, Kateřina; Peterková, Renata; Pavlíková, Zuzana; Hovořáková, Mária

    2015-01-01

    Roč. 15, APR 22 (2015), s. 21 ISSN 1471-213X R&D Projects: GA ČR(CZ) GAP305/12/1766; GA ČR GB14-37368G Institutional support: RVO:68378041 Keywords : enamel knot * tooth development * mouse molar * sprouty genes * sonic hedgehog * cre-loxp system * supernumerary tooth Subject RIV: EA - Cell Biology Impact factor: 2.096, year: 2015

  12. Protection of olive planting stocks against parasitism of root-knot nematodes by arbuscular mycorrhizal fungi

    OpenAIRE

    Castillo, Pablo; Nico, Andrés I.; Azcón González de Aguilar, Concepción; Río Rincón, C. del; Calvet, Cinta; Jiménez-Díaz, Rafael M.

    2006-01-01

    The effects were investigated, under controlled conditions, of single and joint inoculation of olive planting stocks cvs Arbequina and Picual with the arbuscular mycorrhizal fungi (AMF) Glomus intraradices, Glomus mosseae or Glomus viscosum, and the root-knot nematodes Meloidogyne incognita and Meloidogyne javanica, on plant performance and nematode infection. Establishment of the fungal symbiosis significantly increased growth of olive plants by 88·9% within a range of 11·9–214·0%, ...

  13. Effect of Emamectin Benzoate on Root-Knot Nematodes and Tomato Yield

    OpenAIRE

    Cheng, Xingkai; Liu, Xiumei; Wang, Hongyan; Ji, Xiaoxue; Wang, Kaiyun; Wei, Min; Qiao, Kang

    2015-01-01

    Southern root-knot nematode (Meloidogyne incognita) is an obligate, sedentary endoparasite of more than 3000 plant species, that causes heavy economic losses and limit the development of protected agriculture of China. As a biological pesticide, emamectin benzoate has effectively prevented lepidopteran pests; however, its efficacy to control M. incognita remains unknown. The purpose of the present study was to test soil application of emamectin benzoate for management of M. incognita in labor...

  14. Explicit Gaussian quadrature rules for C^1 cubic splines with symmetrically stretched knot sequence

    KAUST Repository

    Ait-Haddou, Rachid

    2015-06-19

    We provide explicit expressions for quadrature rules on the space of C^1 cubic splines with non-uniform, symmetrically stretched knot sequences. The quadrature nodes and weights are derived via an explicit recursion that avoids an intervention of any numerical solver and the rule is optimal, that is, it requires minimal number of nodes. Numerical experiments validating the theoretical results and the error estimates of the quadrature rules are also presented.

  15. A farmer friendly and economic IPM strategy to combat root-knot nematodes infesting lentil

    OpenAIRE

    Rose Rizvi; Rizwan Ali Ansari; Gulshan Zehra; Irshad Mahmood

    2015-01-01

    An experiment was conducted to assess the effect of Rhizobium sp., waste tea leaves, eggshell powder, and composted cow dung manure on the root-knot nematode, Meloidogyne incognita, on lentil in Botany department AMU, Aligarh, India. When used alone, composted cow dung was better in reducing galling and nematode multiplication and improving lentil growth followed by eggshell powder, Rhizobium sp., and waste tea leaves. Significant result in the integrated management of M. incognita was obtain...

  16. Root-knot nematodes in golf course greens of the western United States

    Science.gov (United States)

    A survey of 238 golf courses in ten of the Western U.S. found root-knot nematodes (Meloidogyne spp.) in 60 % of the putting greens sampled. Sequence and phylogenetic analyses of 18S rRNA, D2-D3 of 28S rRNA, ITS-rRNA and mtDNA gene sequences were used to identify specimens from 110 golf courses. The...

  17. HOMFLY for twist knots and exclusive Racah matrices in representation [333

    Science.gov (United States)

    Morozov, A.

    2018-03-01

    Next step is reported in the program of Racah matrices extraction from the differential expansion of HOMFLY polynomials for twist knots: from the double-column rectangular representations R = [ rr ] to a triple-column and triple-hook R = [ 333 ]. The main new phenomenon is the deviation of the particular coefficient f[ 332 ][ 21 ] from the corresponding skew dimension, what opens a way to further generalizations.

  18. Developing an Objective Structured Assessment of Technical Skills for Laparoscopic Suturing and Intracorporeal Knot Tying.

    Science.gov (United States)

    Chang, Olivia H; King, Louise P; Modest, Anna M; Hur, Hye-Chun

    2016-01-01

    To develop a teaching and assessment tool for laparoscopic suturing and intracorporeal knot tying. We designed an Objective Structured Assessment of Technical Skills (OSATS) tool that includes a procedure-specific checklist (PSC) and global rating scale (GRS) to assess laparoscopic suturing and intracorporeal knot-tying performance. Obstetrics and Gynecology residents at our institution were videotaped while performing a laparoscopic suturing and intracorporeal knot-tying task at a surgical simulation workshop. A total of 2 expert reviewers assessed resident performance using the OSATS tool during live performance and 1 month later using the videotaped recordings. OSATS scores were analyzed using the Wilcoxon rank-sum test. Data are presented as median scores (interquartile range [IQR]). Intrarater and interrater reliabilities were assessed using a Spearman correlation and are presented as an r correlation coefficient and p value. An r ≥ 0.8 was considered as a high correlation. After testing, we received feedback from residents and faculty to improve the OSATS tool as part of an iterative design process. In all, 14 of 21 residents (66.7%) completed the study, with 9 junior residents and 5 senior residents. Junior residents had a lower score on the PSC than senior residents did; however, this was not statistically significant (median = 6.0 [IQR: 4.0-10.0] and median = 13.0 [IQR: 10.0-13.0]; p = 0.09). There was excellent intrarater reliability with our OSATS tool (for PSC component, r = 0.88 for Rater 1 and 0.93 for Rater 2, both p assessment and teaching tool for laparoscopic suturing and intracorporeal knot-tying skills. Overall, good intrarater reliability was demonstrated, suggesting that this tool may be useful for longitudinal assessment of surgical skills. Copyright © 2015 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.

  19. Automated knot detection with visual post-processing of Douglas-fir veneer images

    Science.gov (United States)

    C.L. Todoroki; Eini C. Lowell; Dennis Dykstra

    2010-01-01

    Knots on digital images of 51 full veneer sheets, obtained from nine peeler blocks crosscut from two 35-foot (10.7 m) long logs and one 18-foot (5.5 m) log from a single Douglas-fir tree, were detected using a two-phase algorithm. The algorithm was developed using one image, the Development Sheet, refined on five other images, the Training Sheets, and then applied to...

  20. Caspase 3 activation in the primary enamel knot of developing molar tooth

    Czech Academy of Sciences Publication Activity Database

    Matalová, Eva; Kovářů, František; Míšek, Ivan

    2006-01-01

    Roč. 55, 2 (2006), s. 183-188 ISSN 0862-8408 R&D Projects: GA ČR GA304/04/0101; GA AV ČR KJB500450503; GA MŠk OC B23.001 Institutional research plan: CEZ:AV0Z50450515 Keywords : apoptosis * caspase 3 * primary enamel knot Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.093, year: 2006

  1. Dinuclear Silver(I) and Copper(II) Complexes of Hexadentate Macrocyclic Ligands Containing p-Xylyl Spacers

    DEFF Research Database (Denmark)

    McKenzie, Christine J.; Nielsen, Lars Preuss; Søtofte, Inger

    1998-01-01

    The cyclocondensation of terephthalic aldehyde with N,N-bis(3-aminopropyl)-methylamine in the presence of silver(I) gives the dinuclear tetramine Schiff base macrocyclic complex, [Ag2L1](NO3)2 (L1=7,22-N,N'-dimethyl-3,7,11,18, 22,26-hexaazatricyclo[26.2.21.18.213.16]-tetratricosa-2,11,13,15,1 7...

  2. Tools for Chemical Biology: New Macrocyclic Compounds from Diversity-Oriented Synthesis and Toward Materials from Silver(I) Acetylides

    DEFF Research Database (Denmark)

    Madsen, Charlotte Marie

    Part I The formation of a library of diverse macrocyclic compounds with different functionalities and ring sizes in a few steps from two easily accessible α,ω-diol building blocks is presented. The building blocks are combined by esteriffcations in four different ways leading to the formation of ...... of uoro-iodoadamantanes. However, overall the results provide a good starting point for the synthesis of new triptycene and adamantane-containing molecules that can interact with carbon nanotubes....

  3. Green chemistry for preparation of oligopyrrole macrocycles precursors: Novel methodology for dipyrromethanes and tripyrromethanes synthesis in water

    Czech Academy of Sciences Publication Activity Database

    Král, Vladimír; Vašek, P.; Dolenský, B.

    2004-01-01

    Roč. 69, č. 5 (2004), s. 1126-1136 ISSN 0010-0765 R&D Projects: GA ČR GA203/02/0933; GA ČR GA203/02/0420; GA ČR GP203/03/D049 Grant - others:QLRT(XE) 2000-02360 Keywords : oligopyrrole macrocycles * porphyrins * calixpyrrols Subject RIV: CC - Organic Chemistry Impact factor: 1.062, year: 2004

  4. [Plant signaling peptides. Cysteine-rich peptides].

    Science.gov (United States)

    Ostrowski, Maciej; Kowalczyk, Stanisław

    2015-01-01

    Recent bioinformatic and genetic analyses of several model plant genomes have revealed the existence of a highly abundant group of signaling peptides that are defined as cysteine-rich peptides (CRPs). CRPs are usually in size between 50 and 90 amino acid residues, they are positively charged, and they contain 4-16 cysteine residues that are important for the correct conformational folding. Despite the structural differences among CRP classes, members from each class have striking similarities in their molecular properties and function. The present review presents the recent progress in research on signaling peptides from several families including: EPF/EPFL, SP11/SCR, PrsS, RALF, LURE, and some other peptides belonging to CRP group. There is convincing evidence indicating multiple roles for these CRPs as signaling molecules during the plant life cycle, ranging from stomata development and patterning, self-incompatibility, pollen tube growth and guidance, reproductive processes, and nodule formation.

  5. Linked and knotted beams of light, conservation of helicity and the flow of null electromagnetic fields

    International Nuclear Information System (INIS)

    Irvine, William T M

    2010-01-01

    Maxwell's equations allow for some remarkable solutions consisting of pulsed beams of light which have linked and knotted field lines. The preservation of the topological structure of the field lines in these solutions has previously been ascribed to the fact that the electric and magnetic helicities, a measure of the degree of linking and knotting between field lines, are conserved. Here we show that the elegant evolution of the field is due to the stricter condition that the electric and magnetic fields be everywhere orthogonal. The field lines then satisfy a 'frozen field' condition and evolve as if they were unbreakable filaments embedded in a fluid. The preservation of the orthogonality of the electric and magnetic field lines is guaranteed for null, shear-free fields such as the ones considered here by a theorem of Robinson. We calculate the flow field of a particular solution and find it to have the form of a Hopf fibration moving at the speed of light in a direction opposite to the propagation of the pulsed light beam, a familiar structure in this type of solution. The difference between smooth evolution of individual field lines and conservation of electric and magnetic helicities is illustrated by considering a further example in which the helicities are conserved, but the field lines are not everywhere orthogonal. The field line configuration at time t = 0 corresponds to a nested family of torus knots but unravels upon evolution.

  6. Hair-on-hair static friction coefficient can be determined by tying a knot.

    Science.gov (United States)

    Chevalier, Nicolas R

    2017-11-01

    Characterizing the tribological properties of the hair-hair interface is important to quantify the manageability of hair and to assess the performance of hair care products. Audoly et al. (Phys. Rev. Lett. 99, 164301, 2007) derived an equation relating the self-friction coefficient of an elastic fiber to the dimensions of a simple, relaxed overhand knot made from this fiber. I experimentally tested and validated their equation using nylon thread and an independent measurement of its self-friction coefficient. I show that this methodology can be applied to provide high-throughput data on the static self-friction coefficient of single hair fibers in various conditions and to quantitatively assess how hair care treatments (conditioner, relaxant) alter frictional properties. I find that treatment of hair with 1M sodium hydroxide leads to a quick, irreversible self-friction coefficient increase; the resulting fine frictional fibers can be used to form very small knots for microsurgical vessel and organ ligature in medicine or embryology. The relaxed overhand knot method can more generally be used to measure the self-friction coefficients of a wide range of elastic fibers from the nano- (e.g. proteins, nanotubes) to the macro-scale (e.g. textile fiber, fiberglass). Copyright © 2017 Elsevier B.V. All rights reserved.

  7. A novel platform based on defect-rich knotted graphene nanotubes for detection of small biomolecules

    International Nuclear Information System (INIS)

    Lan, Shumin; Song, Yingpan; Chen, Qidi; Guo, Zhiyong; Zhan, Hongbing

    2016-01-01

    Highlights: • Curvature of the SC-CNTs’ cavities had more local pressure, leading to form k-GNTs. • k-GNTs are divided into sections by knots with abundant edge-plane sites/defects. • k-GNTs exhibited excellent catalytic activity, sensitivity and reproducibility. - Abstract: Detection of disease-related small biomolecules was of great significance for clinical diagnostics and treatment. In this work, we synthesized defect-rich knotted graphene nanotubes (k-GNTs) via chemical oxidative etching of stacked-up carbon nanotubes (SC-CNTs) followed by chemical reduction, to detect disease-related small biomolecules. We further studied the electrochemical properties using three representative redox probes and analyzed their biosensitivity using five biomolecules. The k-GNT-modified electrodes exhibited excellent electrochemical response, with the lowest ΔE p and the highest k 0 . Besides, the modified electrodes could simultaneously detect and discriminate between dopamine (DA), ascorbic acid and uric acid (UA), as well as differentiate phenethylamine (PEA) and epinephrine (EP) existed in newborn rat serum, providing the wide linear detection ranges with high sensitivities for DA, UA, PEA, and EP. These excellent electrocatalytic properties could be ascribe to the unique knotted graphene nanotube structure with high proportion of defect/edge sites, large, accessible, three-dimensional, accessible surface area, fewer oxygen-containing groups and doped N atoms. Our work reveals defect-rich k-GNTs as a promising platform for further applications in electrochemical biosensing and electrocatalysis.

  8. Blue optical continuum associated with a radio knot in 3C346

    Science.gov (United States)

    Dey, Arjun; van Breugel, Wil J. M.

    1994-06-01

    We report the discovery of extremely luminous near-UV continuum emission associated with a bright radio knot in the radio galaxy 3C346 (zeta = 0.162). Photometric measurements from U and r' band images and longslit spectra show a spectral energy distribution that steepens at higher frequencies, with radio and optical spectral indices alphar = -0.37 +/- 0.02 and alphao = -1.8 +/- 0.2, respectively. Based on a comparison of the optical properties of this knot with other known cases of optical emission associated with radio structures, we conclude that the continuum emission is optical synchrotron radiation. Our observations are consistent with the suggestion that 3C346 is a foreshortened FR-II radio galaxy with its radio axis oriented close to the line of sight. The optical and radio emission from the knot appear to be associated with a hotspot (at the end of a jet) on the near side. Finally, our U and r' images of 3C346 provide a striking illustration that the optical morphologies of nearby radio galaxies also depend upon wavelength and that studies of these objects are relevant to the interpretation of the alignment effect seen in the high redshift radio galaxies.

  9. [Controlling effect of antagonist bioorganic fertilizer on tomato root-knot nematode].

    Science.gov (United States)

    Zhu, Zhen; Chen, Fang; Xiao, Tong-jian; Wang, Xiao-hui; Ran, Wei; Yang, Xing-ming; Shen, Qi-rong

    2011-04-01

    Indoor in vitro culture experiment and greenhouse pot experiment were conducted to evaluate the capabilities of three bacterial strains XZ-173 (Bacillus amyloliquefaciens), SL-25 (B. gibsonii), and KS-62 (Paenibacillus polymyxa) that can hydrolyze collagen protein in controlling tomato root-knot nematode. In the in vitro culture experiment, suspensions of XZ-173, SL-25, and KS-62 induced a mortality rate of 75.9%, 66.7%, and 50.0% to the second-stage junior nematode within 24 h, and decreased the egg hatching rate to 17.8%, 28.9% and 37.6% after 7-day incubation, respectively, in contrast to the 17.4% mortality rate and 53.6% egg hatching rate in the control (sterilized water). In the greenhouse pot experiment, the bioorganic fertilizer mixed with equal parts of fermented XZ-173, SL-25, and KS-62 gained the best result, with the root-knot nematode population in rhizosphere soil decreased by 84.0% as compared with the control. The bioorganic fertilizer also decreased the numbers of galls and eggs on tomato roots significantly, and increased the underground and aboveground biomass of tomato. Therefore, antagonist bioorganic fertilizer has promising potential in controlling root-knot nematode.

  10. Knot probability of polygons subjected to a force: a Monte Carlo study

    International Nuclear Information System (INIS)

    Rensburg, E J Janse van; Orlandini, E; Tesi, M C; Whittington, S G

    2008-01-01

    We use Monte Carlo methods to study the knot probability of lattice polygons on the cubic lattice in the presence of an external force f. The force is coupled to the span of the polygons along a lattice direction, say the z-direction. If the force is negative polygons are squeezed (the compressive regime), while positive forces tend to stretch the polygons along the z-direction (the tensile regime). For sufficiently large positive forces we verify that the Pincus scaling law in the force-extension curve holds. At a fixed number of edges n the knot probability is a decreasing function of the force. For a fixed force the knot probability approaches unity as 1 - exp(-α 0 (f)n + o(n)), where α 0 (f) is positive and a decreasing function of f. We also examine the average of the absolute value of the writhe and we verify the square root growth law (known for f = 0) for all values of f

  11. Diversity of Knot Solitons in Liquid Crystals Manifested by Linking of Preimages in Torons and Hopfions

    Directory of Open Access Journals (Sweden)

    Paul J. Ackerman

    2017-01-01

    Full Text Available Topological solitons are knots in continuous physical fields classified by nonzero Hopf index values. Despite arising in theories that span many branches of physics, from elementary particles to condensed matter and cosmology, they remain experimentally elusive and poorly understood. We introduce a method of experimental and numerical analysis of such localized structures in liquid crystals that, similar to the mathematical Hopf maps, relates all points of the medium’s order parameter space to their closed-loop preimages within the three-dimensional solitons. We uncover a surprisingly large diversity of naturally occurring and laser-generated topologically nontrivial solitons with differently knotted nematic fields, which previously have not been realized in theories and experiments alike. We discuss the implications of the liquid crystal’s nonpolar nature on the knot soliton topology and how the medium’s chirality, confinement, and elastic anisotropy help to overcome the constraints of the Hobart-Derrick theorem, yielding static three-dimensional solitons without or with additional defects. Our findings will establish chiral nematics as a model system for experimental exploration of topological solitons and may impinge on understanding of such nonsingular field configurations in other branches of physics, as well as may lead to technological applications.

  12. Diversity of Knot Solitons in Liquid Crystals Manifested by Linking of Preimages in Torons and Hopfions

    Science.gov (United States)

    Ackerman, Paul J.; Smalyukh, Ivan I.

    2017-01-01

    Topological solitons are knots in continuous physical fields classified by nonzero Hopf index values. Despite arising in theories that span many branches of physics, from elementary particles to condensed matter and cosmology, they remain experimentally elusive and poorly understood. We introduce a method of experimental and numerical analysis of such localized structures in liquid crystals that, similar to the mathematical Hopf maps, relates all points of the medium's order parameter space to their closed-loop preimages within the three-dimensional solitons. We uncover a surprisingly large diversity of naturally occurring and laser-generated topologically nontrivial solitons with differently knotted nematic fields, which previously have not been realized in theories and experiments alike. We discuss the implications of the liquid crystal's nonpolar nature on the knot soliton topology and how the medium's chirality, confinement, and elastic anisotropy help to overcome the constraints of the Hobart-Derrick theorem, yielding static three-dimensional solitons without or with additional defects. Our findings will establish chiral nematics as a model system for experimental exploration of topological solitons and may impinge on understanding of such nonsingular field configurations in other branches of physics, as well as may lead to technological applications.

  13. Investigation of the potential of silica-bonded macrocyclic ligands for separation of metal ions from nuclear waste

    International Nuclear Information System (INIS)

    Camaioni, D.M.; Colton, N.G.; Bruening, R.L.

    1992-01-01

    This report describes the testing of some novel separations materials known as SuperLig trademark materials for their ability to separate efficiently and selectively certain metal ions from a synthetic, nonradioactive nuclear waste solution. The materials, developed and patented by IBC Advanced Technologies, are highly selective macrocyclic ligands that have been covalently bonded to silica gel. The SuperLig trademark materials that were tested are: (1) SuperLig trademark 601 for barium (Ba 2+ ) and strontium (Sr 2+ ) separation, (2) SuperLig trademark 602 for cesium (Cs + ) and rubidium (Rb + ) separation, (3) SuperLig trademark 27 for palladium (Pd 2+ ) separation, and (4) SuperLig trademark II for silver (Ag + ) and ruthenium (Ru 3+ ) separation. Our observations show that the technology for separating metal ions using silica-bonded macrocycles is essentially sound and workable to varying degrees of success that mainly depend on the affinity of the macrocycle for the metal ion of interest. It is expected that ligands will be discovered or synthesized that are amenable to separating metal ions of interest using this technology. Certainly more development, testing, and evaluation is warranted. 3 figs., 11 tabs

  14. Dinuclear Silver(I) and Copper(II) Complexes of Hexadentate Macrocyclic Ligands Containing p-Xylyl Spacers

    DEFF Research Database (Denmark)

    McKenzie, Christine J.; Nielsen, Lars Preuss; Søtofte, Inger

    1998-01-01

    The cyclocondensation of terephthalic aldehyde with N,N-bis(3-aminopropyl)-methylamine in the presence of silver(I) gives the dinuclear tetramine Schiff base macrocyclic complex, [Ag2L1](NO3)2 (L1=7,22-N,N'-dimethyl-3,7,11,18, 22,26-hexaazatricyclo[26.2.21.18.213.16]-tetratricosa-2,11,13,15,1 7......,26,28,30,31,33-decaene). [Ag2L1](NO3)2 crystallizes in the monoclinic space group P21/c, with a=14.153(6), b=12.263(4), c=9.220(2) Å, beta=97.52(3) Å and Z=2. The silver ions are strongly coordinated at each end of the macrocycle by the two imine nitrogen atoms [2.177(3) and 2.182(3) Å] with close interatomic...... interactions to an oxygen atom of a nitrate ion and an amine nitrogen atom [2.580(2) and 2.690(2) Å]. The Ag...Ag distance is 6.892(3) Å. The free tetraimine macrocycle, L1, was obtained by treatment of [Ag2L1](NO3)2 with an excess of iodide, and the reduced derivative 7,22-N,N'-dimethyl-3...

  15. Spectroscopic and electrochemical investigation with coordination stabilities: Mononuclear manganese(II) complexes derived from different constituents macrocyclic ligands

    Science.gov (United States)

    Kumar, Rajiv; Chnadra, S.; Mishra, Parashuram

    2007-12-01

    Since the manganese(II) complexes are known as having a high degree of stability, some of them may be able to play a very important role in biosystems. We prepared manganese(II) complexes with different chromospheres containing macrocyclic ligands bearing N, S and O like functional donor atoms in order to obtain different models of compounds. So these new manganese(II) complexes were derived from macrocyclic ligands by chelating them with metal ions. Thus, two macrocyclic ligands, L 1: 2,4-diphenyl-1,5-diaza-8,12-dioxo-6,7:13,14-dibenzocyclo tetradeca-1,4-diene[N 2O 2]ane; L 2: 2,4,9,11-tetraphenyl-6,13-dimethyl-1,5,8,12-traazacyclotertr-adeca-1,4,8,11-tetraene[N 4]ane; and two more different form first one viz.—L 3: 1,7-diaza-4-monothia-10,14-dioxo-8,9:15,16-cyclohexadecane[N 2O 2S]ane and L 4: 4,13-diaoxa-1,7,10,16-hexazacyclooctadecane[N 4O 2]ane were prepared and their capacity to retain the manganese(II) ion in solid as well as aqueous solution was determined from various physiochemical techniques viz: characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, mass, IR, electronic, ESR spectral studies and cyclic voltammetric measurements.

  16. Through-Space Paramagnetic NMR Effects in Host-Guest Complexes: Potential Ruthenium(III) Metallodrugs with Macrocyclic Carriers.

    Science.gov (United States)

    Chyba, Jan; Novák, Martin; Munzarová, Petra; Novotný, Jan; Marek, Radek

    2018-04-05

    The potential of paramagnetic ruthenium(III) compounds for use as anticancer metallodrugs has been investigated extensively during the past several decades. However, the means by which these ruthenium compounds are transported and distributed in living bodies remain relatively unexplored. In this work, we prepared several novel ruthenium(III) compounds with the general structure Na + [ trans-Ru III Cl 4 (DMSO)(L)] - (DMSO = dimethyl sulfoxide), where L stands for pyridine or imidazole linked with adamantane, a hydrophobic chemophore. The supramolecular interactions of these compounds with macrocyclic carriers of the cyclodextrin (CD) and cucurbit[ n]uril (CB) families were investigated by NMR spectroscopy, X-ray diffraction analysis, isothermal titration calorimetry, and relativistic DFT methods. The long-range hyperfine NMR effects of the paramagnetic guest on the host macrocycle are related to the distance between them and their relative orientation in the host-guest complex. The CD and CB macrocyclic carriers being studied in this account can be attached to a vector that attracts the drug-carrier system to a specific biological target and our investigation thus introduces a new possibility in the field of targeted delivery of anticancer metallodrugs based on ruthenium(III) compounds.

  17. Selecting highly structure-specific antibodies using structured synthetic mimics of the cystine knot protein sclerostin

    NARCIS (Netherlands)

    Back, J.W.; Frisch, C.; Van Pee, K.; Boschert, V.; van Vught, R.; Puijk, W.; Mueller, T. D.; Knappik, A.; Timmerman, P.

    2012-01-01

    Antibodies directed against specific regions of a protein have traditionally been raised against full proteins, protein domains or simple unstructured peptides, containing contiguous stretches of primary sequence. We have used a new approach of selecting antibodies against restrained peptides

  18. Unsaturated macrocyclic dihydroxamic acid siderophores produced by Shewanella putrefaciens using precursor-directed biosynthesis.

    Science.gov (United States)

    Soe, Cho Z; Codd, Rachel

    2014-04-18

    To acquire iron essential for growth, the bacterium Shewanella putrefaciens produces the macrocyclic dihydroxamic acid putrebactin (pbH2; [M + H(+)](+), m/zcalc 373.2) as its native siderophore. The assembly of pbH2 requires endogenous 1,4-diaminobutane (DB), which is produced from the ornithine decarboxylase (ODC)-catalyzed decarboxylation of l-ornithine. In this work, levels of endogenous DB were attenuated in S. putrefaciens cultures by augmenting the medium with the ODC inhibitor 1,4-diamino-2-butanone (DBO). The presence in the medium of DBO together with alternative exogenous non-native diamine substrates, (15)N2-1,4-diaminobutane ((15)N2-DB) or 1,4-diamino-2(E)-butene (E-DBE), resulted in the respective biosynthesis of (15)N-labeled pbH2 ((15)N4-pbH2; [M + H(+)](+), m/zcalc 377.2, m/zobs 377.2) or the unsaturated pbH2 variant, named here: E,E-putrebactene (E,E-pbeH2; [M + H(+)](+), m/zcalc 369.2, m/zobs 369.2). In the latter system, remaining endogenous DB resulted in the parallel biosynthesis of the monounsaturated DB-E-DBE hybrid, E-putrebactene (E-pbxH2; [M + H(+)](+), m/zcalc 371.2, m/zobs 371.2). These are the first identified unsaturated macrocyclic dihydroxamic acid siderophores. LC-MS measurements showed 1:1 complexes formed between Fe(III) and pbH2 ([Fe(pb)](+); [M](+), m/zcalc 426.1, m/zobs 426.2), (15)N4-pbH2 ([Fe((15)N4-pb)](+); [M](+), m/zcalc 430.1, m/zobs 430.1), E,E-pbeH2 ([Fe(E,E-pbe)](+); [M](+), m/zcalc 422.1, m/zobs 422.0), or E-pbxH2 ([Fe(E-pbx)](+); [M](+), m/zcalc 424.1, m/zobs 424.2). The order of the gain in siderophore-mediated Fe(III) solubility, as defined by the difference in retention time between the free ligand and the Fe(III)-loaded complex, was pbH2 (ΔtR = 8.77 min) > E-pbxH2 (ΔtR = 6.95 min) > E,E-pbeH2 (ΔtR = 6.16 min), which suggests one possible reason why nature has selected for saturated rather than unsaturated siderophores as Fe(III) solubilization agents. The potential to conduct multiple types of ex situ chemical

  19. Biomechanical Assessment of Motor Abilities in Male Handball Players During the Annual Training Macrocycle

    Directory of Open Access Journals (Sweden)

    Sacewicz Tomasz

    2016-12-01

    Full Text Available Introduction. The aim of the study was to determine the torque of the knee extensors and flexors of the lead lower limb, the torque of the shoulder extensors and flexors of the dominant upper limb, and the torque generated by the muscles of the kinematic chain going from the trail lower limb to the hand of the dominant limb in male handball players during the annual training macrocycle. Changes in jump height and throwing velocity were also investigated. Material and methods. The study involved 13 handball players from a Polish second-league team. The measurements were performed four times: at the beginning of the preparation period, at the beginning of the season, at the end of the first part of the season, and at the end of the second part of the season. Torque was measured in isokinetic and isometric conditions. Jumping ability was tested using a piezoelectric platform, and throwing velocity was measured with a speed radar gun. Results. The study found statistically significant differences between the relative torque values of the knee extensors (p < 0.002 and flexors (p < 0.003 of the lead leg measured in isokinetic conditions between the first three measurements and the final one. Isokinetic measurement of the torque of the muscles of the kinematic chain going from the trail leg to the hand of the dominant arm decreased in a statistically significant way at the end of the season. As for the results of the measurement of the torque of the shoulder extensors and flexors in static conditions, no statistically significant differences were observed between the four measurements. However, statistically significant differences were noted in jumping ability and throwing velocity in the annual training macrocycle. Conclusions. The results of the study indicate that there is a need to perform regular assessments of players’ strength and jumping ability during the competition period. There is a need to modify the training methods used during the

  20. Vaccatides: Antifungal Glutamine-Rich Hevein-Like Peptides from Vaccaria hispanica

    Directory of Open Access Journals (Sweden)

    Ka H. Wong

    2017-06-01

    Full Text Available Hevein and hevein-like peptides are disulfide-constrained chitin-binding cysteine-rich peptides. They are divided into three subfamilies, 6C-, 8C-, and 10C-hevein-like peptides, based on the number of cysteine residues. In addition, hevein-like peptides can exist in two forms, short and long. The long C-terminal form found in hevein and 10C-hevein-like peptides contain a C-terminal protein cargo. In contrast, the short form without a protein cargo is found in all three subfamilies. Here, we report the discovery and characterization of two novel glutamine-rich and protein cargo-free 8C-hevein-like peptides, vaccatides vH1 and vH2, from Vaccaria hispanica of the Caryophyllaceae family. Proteomic analyses showed that the vaccatides are 40–41 amino acids in length and contain a chitin-binding domain. NMR determination revealed that vaccatide vH2 displays a highly compact structure with a N-terminal cystine knot and an addition C-terminal disulfide bond. Stability studies showed that this compact structure renders vaccatide vH2 resistant to thermal, chemical and proteolytic degradation. The chitin-binding vH2 was shown to inhibit the mycelium growth of four phyto-pathogenic fungal strains with IC50 values in the micromolar range. Our findings show that vaccatides represent a new family of 8C-hevein-like peptides, which are protein cargo-free and glutamine-rich, characteristics that differentiate them from the prototypic hevein and the 10C-hevein-like peptides. In summary, this study enriches the existing library of hevein-like peptides and provides insight into their molecular diversity in sequence, structure and biosynthesis. Additionally, their highly disulfide-constrained structure could be used as a scaffold for developing metabolically and orally active peptidyl therapeutics.

  1. Peptides in melanoma therapy.

    Science.gov (United States)

    Mocellin, Simone

    2012-01-01

    Peptides derived from tumor associated antigens can be utilized to elicit a therapeutically effective immune response against melanoma in experimental models. However, patient vaccination with peptides - although it is often followed by the induction of melanoma- specific T lymphocytes - is rarely associated with tumor response of clinical relevance. In this review I summarize the principles of peptide design as well as the results so far obtained in the clinical setting while treating cutaneous melanoma by means of this active immunotherapy strategy. I also discuss some immunological and methodological issues that might be helpful for the successful development of peptide-based vaccines.

  2. Antimicrobial Peptides in Reptiles

    Science.gov (United States)

    van Hoek, Monique L.

    2014-01-01

    Reptiles are among the oldest known amniotes and are highly diverse in their morphology and ecological niches. These animals have an evolutionarily ancient innate-immune system that is of great interest to scientists trying to identify new and useful antimicrobial peptides. Significant work in the last decade in the fields of biochemistry, proteomics and genomics has begun to reveal the complexity of reptilian antimicrobial peptides. Here, the current knowledge about antimicrobial peptides in reptiles is reviewed, with specific examples in each of the four orders: Testudines (turtles and tortosises), Sphenodontia (tuataras), Squamata (snakes and lizards), and Crocodilia (crocodilans). Examples are presented of the major classes of antimicrobial peptides expressed by reptiles including defensins, cathelicidins, liver-expressed peptides (hepcidin and LEAP-2), lysozyme, crotamine, and others. Some of these peptides have been identified and tested for their antibacterial or antiviral activity; others are only predicted as possible genes from genomic sequencing. Bioinformatic analysis of the reptile genomes is presented, revealing many predicted candidate antimicrobial peptides genes across this diverse class. The study of how these ancient creatures use antimicrobial peptides within their innate immune systems may reveal new understandings of our mammalian innate immune system and may also provide new and powerful antimicrobial peptides as scaffolds for potential therapeutic development. PMID:24918867

  3. Synthesis, characterization and biological activity of symmetric dinuclear complexes derived from a novel macrocyclic compartmental ligand

    Energy Technology Data Exchange (ETDEWEB)

    Mruthyunjayaswamy, B.H.M.; Ijare, Omkar B.; Jadegoud, Y. [Gulbarga University (India). Dept. of Chemistry]. E-mail: bhmmswamy53@rediffmail.com

    2005-07-15

    A phenol based novel macrocyclic binucleating compartmental ligand N,N-bis(2,6-diiminomethyl-4-methyl-1-hydroxyphenyl)malonoyldicarboxamide was prepared. The complexes were prepared by template method by reacting 2,6-diformyl-4-methylphenol, malonoyl dihydrazide and the metal chlorides of Cu(II), Ni(II), Co(II), Cd(II), Zn(II) and Hg(II) in methanol to get a series of dinuclear complexes. The complexes were characterized by elemental analyses, conductivity measurements, magnetic susceptibility data, IR, UV-Vis, ESR, NMR and FAB mass spectral data. The dinuclear nature of the complexes was confirmed on the basis of elemental analyses, magnetic susceptibility, ESR and FAB mass spectral data. The ligand as well as Cu(II), Ni(II), Co(II) and Zn(II) complexes were tested for their antibacterial and antifungal properties against Escherichia coli, Staphyloccocus aureus, Aspergillus niger and Fusarium oxysporum. Magnetic susceptibility measurements of Cu(II), Ni(II) and Co(II) complexes reveal that these complexes exhibit antiferromagnetic coupling behavior due to the presence of two metal ions in close proximity. FAB mass spectrum of the Cu(II) complex gave a clear evidence for the dinuclear nature. The ligand and the complexes were found to be less active against the tested bacteria, but the ligand alone was found active against the fungus Fusarium oxysporum. (author)

  4. An eighteen-membered macrocyclic ligand for actinium-225 targeted alpha therapy

    International Nuclear Information System (INIS)

    Thiele, Nikki A.; MacMillan, Samantha N.; Wilson, Justin J.; Rodriguez-Rodriguez, Cristina

    2017-01-01

    The 18-membered macrocycle H 2 macropa was investigated for 225 Ac chelation in targeted alpha therapy (TAT). Radiolabeling studies showed that macropa, at submicromolar concentration, complexed all 225 Ac (26 kBq) in 5 min at RT. [ 225 Ac(macropa)] + remained intact over 7 to 8 days when challenged with either excess La 3+ ions or human serum, and did not accumulate in any organ after 5 h in healthy mice. A bifunctional analogue, macropa-NCS, was conjugated to trastuzumab as well as to the prostate-specific membrane antigen-targeting compound RPS-070. Both constructs rapidly radiolabeled 225 Ac in just minutes at RT, and macropa-Tmab retained >99 % of its 225 Ac in human serum after 7 days. In LNCaP xenograft mice, 225 Ac-macropa-RPS-070 was selectively targeted to tumors and did not release free 225 Ac over 96 h. These findings establish macropa to be a highly promising ligand for 225 Ac chelation that will facilitate the clinical development of 225 Ac TAT for the treatment of soft-tissue metastases. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Grafted chromium 13-membered dioxo-macrocyclic complex into aminopropyl-based nanoporous SBA-15

    Energy Technology Data Exchange (ETDEWEB)

    Tarlani, Aliakbar, E-mail: Tarlani@ccerci.ac.ir [Inorganic Nanostructures and Catalysts Research Laboratory, Chemistry and Chemical Engineering Research Center of Iran, Pajoohesh Boulevard, km 17, Karaj Highway, Tehran 14968-13151 (Iran, Islamic Republic of); Joharian, Monika; Narimani, Khashayar [Inorganic Nanostructures and Catalysts Research Laboratory, Chemistry and Chemical Engineering Research Center of Iran, Pajoohesh Boulevard, km 17, Karaj Highway, Tehran 14968-13151 (Iran, Islamic Republic of); Muzart, Jacques [Institut de Chimie Moléculaire de Reims, CNRS-Université de Reims Champagne-Ardenne, BP 1039, 51687 Reims Cedex 2 (France); Fallah, Mahtab [Inorganic Nanostructures and Catalysts Research Laboratory, Chemistry and Chemical Engineering Research Center of Iran, Pajoohesh Boulevard, km 17, Karaj Highway, Tehran 14968-13151 (Iran, Islamic Republic of)

    2013-07-15

    In a new approach, chromium (III) tetraaza dioxo ligand was grafted onto functionalized SBA-15 after four step reactions by using coordinating ability of anchored amino functionalized SBA-15. After the termination of each step, the obtained product was characterized by FT-IR, low-angle X-ray diffraction (LA-XRD), N{sub 2} adsorption–desorption isotherms (Brunauer–Emmett–Teller (BET)–Barret–Joyner–Halenda (BJH)) and thermogravimetric analysis (TGA), and used as catalyst for the efficient and regioselective alcoholysis of styrene oxide to 2-alkoxy-1-phenylethanol product at ambient temperature. - Graphical abstract: Chromium (III) tetraaza dioxo ligand was grafted onto functionalized SBA-15 using coordinating ability of anchored amino functionalized SBA-15. Preparation of the catalyst is depicted in Scheme 1. - Highlights: • Dioxo tetraazachromium macrocyclic complex grafted into the SBA-15-NH{sub 2} channels. • The bond is created by coordinating ability of anchored amino functionalized SBA-15. • The prepared nanocatalyst has superior activity in the alcoholysis of styrene oxide. • The catalyst is reusable at ambient temperature for the mentioned reaction.

  6. Synthesis and hydrogenation application of Pt-Pd bimetallic nanocatalysts stabilized by macrocycle-modified dendrimer

    Science.gov (United States)

    Jin, Zhijun; Xiao, Haiyan; Zhou, Wei; Zhang, Dongqiao; Peng, Xiaohong

    2017-12-01

    Different generations of poly(propylene imine) (Gn-PPI) terminated with N-containing 15-membered triolefinic macrocycle (GnM) (n = 2, 3, 4, 5) were prepared. The bimetallic nanoparticle catalysts GnM-(Ptx/Pd10-x) (x = 0, 3, 5, 7, 10) were prepared by the synchronous ligand-exchange reaction between GnM and the complexes of Pt(PPh3)4 and Pd(PPh3)4. The structure and catalytic properties of GnM-(Ptx/Pd10-x) were characterized via Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, energy-dispersive spectroscopy and inductively coupled plasma atomic emission spectroscopy. The novel bimetallic Pd-Pt nanoparticle catalysts stabilized by dendrimers (DSNs) present higher catalytic activities for the hydrogenation of dimeric acid (DA) than that of nitrile butadiene rubber (NBR). It can be concluded that bimetallic Pd-Pt DSNs possess alloying and synergistic electronic effects on account of the hydrogenation degree (HD) of DA and NBR. Furthermore, the HD of DA and NBR shows a remarkable decrease with the incremental generations (n) of GnM-(Pt3/Pd7) (n = 2, 3, 4, 5).

  7. Tetraazacyclohexadeca Macrocyclic Ligand as a Neutral Carrier in a Cr Ion-selective Electrode

    Directory of Open Access Journals (Sweden)

    Puja Saxena

    2004-12-01

    Full Text Available Abstract: A polystyrene-based membrane of 2,10-dimethyl-4,12-diphenyl-1,5,9,13-tetraazacyclohexadeca-1,4,9,12-tetraene macrocyclic ionophore was prepared and investigated as Cr(III-selective electrode. The best performance was observed with the membrane having the polystyrene-ligand-dibutylphthalate-sodiumtetraphenyl borate composition 1:4:1:1 with a Nernstian slope of 19.0 mV per decade of concentration between pH 3.0 and 6.5. This electrode has been found to be chemically inert and of adequate stability with a response time of 20 s and was used over a period of 100 d with good reproducibility (S= 0.3 mV. The membrane works satisfactorily in a partially non-aqueous medium up to a maximum 30% (v/v content of methanol and ethanol. The potentiometric selectivity coefficient values indicate that the membrane sensor is highly selective for Cr(III ions over a number of monovalent, divalent and trivalent cations. The membrane electrode has also been successfully used to determine Cr3+ in various food materials.

  8. Macrocyclic Gd(3+) complexes with pendant crown ethers designed for binding zwitterionic neurotransmitters.

    Science.gov (United States)

    Oukhatar, Fatima; Meudal, Hervé; Landon, Céline; Logothetis, Nikos K; Platas-Iglesias, Carlos; Angelovski, Goran; Tóth, Éva

    2015-07-27

    A series of Gd(3+) complexes exhibiting a relaxometric response to zwitterionic amino acid neurotransmitters was synthesized. The design concept involves ditopic interactions 1) between a positively charged and coordinatively unsaturated Gd(3+) chelate and the carboxylate group of the neurotransmitters and 2) between an azacrown ether appended to the chelate and the amino group of the neurotransmitters. The chelates differ in the nature and length of the linker connecting the cyclen-type macrocycle that binds the Ln(3+) ion and the crown ether. The complexes are monohydrated, but they exhibit high proton relaxivities (up to 7.7 mM(-1)  s(-1) at 60 MHz, 310 K) due to slow molecular tumbling. The formation of ternary complexes with neurotransmitters was monitored by (1) H relaxometric titrations of the Gd(3+) complexes and by luminescence measurements on the Eu(3+) and Tb(3+) analogues at pH 7.4. The remarkable relaxivity decrease (≈80 %) observed on neurotransmitter binding is related to the decrease in the hydration number, as evidenced by luminescence lifetime measurements on the Eu(3+) complexes. These complexes show affinity for amino acid neurotransmitters in the millimolar range, which can be suited to imaging concentrations of synaptically released neurotransmitters. They display good selectivity over non-amino acid neurotransmitters (acetylcholine, serotonin, and noradrenaline) and hydrogenphosphate, but selectivity over hydrogencarbonate was not achieved. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Synthesis and hydrogenation application of Pt–Pd bimetallic nanocatalysts stabilized by macrocycle-modified dendrimer

    Science.gov (United States)

    Xiao, Haiyan; Zhou, Wei; Zhang, Dongqiao; Peng, Xiaohong

    2017-01-01

    Different generations of poly(propylene imine) (Gn-PPI) terminated with N-containing 15-membered triolefinic macrocycle (GnM) (n = 2, 3, 4, 5) were prepared. The bimetallic nanoparticle catalysts GnM-(Ptx/Pd10−x) (x = 0, 3, 5, 7, 10) were prepared by the synchronous ligand-exchange reaction between GnM and the complexes of Pt(PPh3)4 and Pd(PPh3)4. The structure and catalytic properties of GnM-(Ptx/Pd10−x) were characterized via Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, energy-dispersive spectroscopy and inductively coupled plasma atomic emission spectroscopy. The novel bimetallic Pd–Pt nanoparticle catalysts stabilized by dendrimers (DSNs) present higher catalytic activities for the hydrogenation of dimeric acid (DA) than that of nitrile butadiene rubber (NBR). It can be concluded that bimetallic Pd–Pt DSNs possess alloying and synergistic electronic effects on account of the hydrogenation degree (HD) of DA and NBR. Furthermore, the HD of DA and NBR shows a remarkable decrease with the incremental generations (n) of GnM-(Pt3/Pd7) (n = 2, 3, 4, 5). PMID:29308263

  10. Some aspects of the extraction separation of actinides by macrocyclic crown compounds

    International Nuclear Information System (INIS)

    Kumar, Anil; Singh, R.K.; Bajpai, D.D.; Shukla, J.P.

    1994-01-01

    Selective and effective extraction-separation of U(VI) and Pu(IV) from aqueous nitric acid media by several crown ethers have been investigated in detail. The critical study of various parameters namely aqueous phase acidity, reagent concentration, diluent, period of equilibration, aqueous to organic phase ratio, strippant and diverse ions, have established the conditions for their optimum extraction. Influence of the introduction of sulfur into a crown ether ring forming a mixed sulfur-oxygen containing macrohetrocycle for improved extraction of actinides is also studied. The species extracted appear to be of ion-pair type, UO 2 (CE) 2+ .2NO 3- and Pu(CE) 2 4+ .4NO 3- formed with U(VI) and Pu(IV), respectively. The apparent extraction equilibrium constant, log Kex, into toluene by DC18C6 with U(VI) is 0.44 and 4.44 for Pu(IV). Recovery of actinides from loaded macrocycles is easily accomplished using dilute oxalic acid, perchloric acid, sulphuric acid or sodium carbonate as the strippants. The lack of interference from even appreciable amounts of possible fission product contaminants is a notable feature of this separation procedure. (author). 20 refs., 6 figs., 6 tabs

  11. Structural, spectral, DFT and biological studies on macrocyclic mononuclear ruthenium (II) complexes

    Science.gov (United States)

    Muthukkumar, M.; Kamal, C.; Venkatesh, G.; Kaya, C.; Kaya, S.; Enoch, Israel V. M. V.; Vennila, P.; Rajavel, R.

    2017-11-01

    Macrocyclic mononuclear ruthenium (II) complexes have been synthesized by condensation method [Ru (L1, L2, L3) Cl2] L1 = (C36 H31 N9), L2= (C42H36N8), L3= (C32H32 N8)]. These ruthenium complexes have been established by elemental analyses and spectroscopic techniques (Fourier transform infrared spectroscopy (FT-IR), 1H- nuclear magnetic resonance (NMR), 13C- NMR and Electrospray ionization mass spectrometry (ESI-MS)). The coordination mode of the ligand has been confirmed and the octahedral geometry around the ruthenium ion has been revealed. Binding affinity and binding mode of ruthenium (II) complexes with Bovine serum Albumin (BSA) have been characterized by Emission spectra analysis. UV-Visible and fluorescence spectroscopic techniques have also been utilized to examine the interaction between ligand and its complexes L1, L2, & L3 with BSA. Chemical parameters and molecular structure of Ru (II) complexes L1H, L2H, & L3H have been determined by DFT coupled with B3LYP/6-311G** functional in both the gaseous and aqueous phases.

  12. An eighteen-membered macrocyclic ligand for actinium-225 targeted alpha therapy

    Energy Technology Data Exchange (ETDEWEB)

    Thiele, Nikki A.; MacMillan, Samantha N.; Wilson, Justin J. [Cornell Univ., Ithaca, NY (United States). Chemistry and Chemical Biology; Brown, Victoria; Jermilova, Una; Ramogida, Caterina F.; Robertson, Andrew K.H.; Schaffer, Paul; Radchenko, Valery [TRIUMF, Vancouver, BC (Canada). Life Science Div.; Kelly, James M.; Amor-Coarasa, Alejandro; Nikolopoulou, Anastasia; Ponnala, Shashikanth; Williams, Clarence Jr.; Babich, John W. [Radiology, Weill Cornell Medicine, New York, NY (United States); Rodriguez-Rodriguez, Cristina [British Columbia Univ., Vancouver, BC (Canada). Dept. of Physics and Astronomy and Centre for Comparative Medicine

    2017-11-13

    The 18-membered macrocycle H{sub 2}macropa was investigated for {sup 225}Ac chelation in targeted alpha therapy (TAT). Radiolabeling studies showed that macropa, at submicromolar concentration, complexed all {sup 225}Ac (26 kBq) in 5 min at RT. [{sup 225}Ac(macropa)]{sup +} remained intact over 7 to 8 days when challenged with either excess La{sup 3+} ions or human serum, and did not accumulate in any organ after 5 h in healthy mice. A bifunctional analogue, macropa-NCS, was conjugated to trastuzumab as well as to the prostate-specific membrane antigen-targeting compound RPS-070. Both constructs rapidly radiolabeled {sup 225}Ac in just minutes at RT, and macropa-Tmab retained >99 % of its {sup 225}Ac in human serum after 7 days. In LNCaP xenograft mice, {sup 225}Ac-macropa-RPS-070 was selectively targeted to tumors and did not release free {sup 225}Ac over 96 h. These findings establish macropa to be a highly promising ligand for {sup 225}Ac chelation that will facilitate the clinical development of {sup 225}Ac TAT for the treatment of soft-tissue metastases. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Zn and Fe complexes containing a redox active macrocyclic biquinazoline ligand.

    Science.gov (United States)

    Banerjee, Priyabrata; Company, Anna; Weyhermüller, Thomas; Bill, Eckhard; Hess, Corinna R

    2009-04-06

    A series of iron and zinc complexes has been synthesized, coordinated by the macrocyclic biquinazoline ligand, 2-4:6-8-bis(3,3,4,4-tetramethyldihydropyrrolo)-10-15-(2,2'-biquinazolino)-[15]-1,3,5,8,10,14-hexaene-1,3,7,9,11,14-N(6) (Mabiq). The Mabiq ligand consists of a bipyrimidine moiety and two dihydropyrrole units. The electronic structures of the metal-Mabiq complexes have been characterized using spectroscopic and density-functional theory (DFT) computational methods. The parent zinc complex exhibits a ligand-centered reduction to generate the metal-coordinated Mabiq radical dianion, establishing the redox non-innocence of this ligand. Iron-Mabiq complexes have been isolated in three oxidation states. This redox series includes low-spin ferric and low-spin ferrous species, as well as an intermediate-spin Fe(II) compound. In the latter complex, the iron ion is antiferromagnetically coupled to a Mabiq-centered pi-radical. The results demonstrate the rich redox chemistry and electronic properties of metal complexes coordinated by the Mabiq ligand.

  14. Enantioseparation and chiral recognition mechanism of new chiral derivatives of xanthones on macrocyclic antibiotic stationary phases.

    Science.gov (United States)

    Fernandes, Carla; Tiritan, Maria Elizabeth; Cass, Quezia; Kairys, Visvaldas; Fernandes, Miguel Xavier; Pinto, Madalena

    2012-06-08

    A chiral HPLC method using four macrocyclic antibiotic chiral stationary phases (CSPs) has been investigated for determination of the enantiomeric purity of fourteen new chiral derivatives of xanthones (CDXs). The separations were performed with the CSPs Chirobiotic T, Chirobiotic TAG, Chirobiotic V and Chirobiotic R under multimodal elution conditions (normal-phase, reversed-phase and polar ionic mode). The analyses were performed at room temperature in isocratic mode and UV and CD detection at a wavelength of 254 nm. The best enantioselectivity and resolution were achieved on Chirobiotic R and Chirobiotic T CSPs, under normal elution conditions, with R(S) ranging from 1.25 to 2.50 and from 0.78 to 2.06, respectively. The optimized chromatographic conditions allowed the determination of the enantiomeric ratio of eight CDXs, always higher than 99%. In order to better understand the chromatographic behavior at a molecular level, and the structural features associated with the chiral recognition mechanism, computational studies by molecular docking were carried out using VDock. These studies shed light on the mechanisms involved in the enantioseparation for this important class of chiral compounds. Copyright © 2012 Elsevier B.V. All rights reserved.

  15. Synthesis, characterization and biological activity of symmetric dinuclear complexes derived from a novel macrocyclic compartmental ligand

    International Nuclear Information System (INIS)

    Mruthyunjayaswamy, B.H.M.; Ijare, Omkar B.; Jadegoud, Y.

    2005-01-01

    A phenol based novel macrocyclic binucleating compartmental ligand N,N-bis(2,6-diiminomethyl-4-methyl-1-hydroxyphenyl)malonoyldicarboxamide was prepared. The complexes were prepared by template method by reacting 2,6-diformyl-4-methylphenol, malonoyl dihydrazide and the metal chlorides of Cu(II), Ni(II), Co(II), Cd(II), Zn(II) and Hg(II) in methanol to get a series of dinuclear complexes. The complexes were characterized by elemental analyses, conductivity measurements, magnetic susceptibility data, IR, UV-Vis, ESR, NMR and FAB mass spectral data. The dinuclear nature of the complexes was confirmed on the basis of elemental analyses, magnetic susceptibility, ESR and FAB mass spectral data. The ligand as well as Cu(II), Ni(II), Co(II) and Zn(II) complexes were tested for their antibacterial and antifungal properties against Escherichia coli, Staphyloccocus aureus, Aspergillus niger and Fusarium oxysporum. Magnetic susceptibility measurements of Cu(II), Ni(II) and Co(II) complexes reveal that these complexes exhibit antiferromagnetic coupling behavior due to the presence of two metal ions in close proximity. FAB mass spectrum of the Cu(II) complex gave a clear evidence for the dinuclear nature. The ligand and the complexes were found to be less active against the tested bacteria, but the ligand alone was found active against the fungus Fusarium oxysporum. (author)

  16. Insulin C-peptide test

    Science.gov (United States)

    C-peptide ... the test depends on the reason for the C-peptide measurement. Ask your health care provider if ... C-peptide is measured to tell the difference between insulin the body produces and insulin someone injects ...

  17. Peptide Vaccines for Leishmaniasis

    Directory of Open Access Journals (Sweden)

    Rory C. F. De Brito

    2018-05-01

    Full Text Available Due to an increase in the incidence of leishmaniases worldwide, the development of new strategies such as prophylactic vaccines to prevent infection and decrease the disease have become a high priority. Classic vaccines against leishmaniases were based on live or attenuated parasites or their subunits. Nevertheless, the use of whole parasite or their subunits for vaccine production has numerous disadvantages. Therefore, the use of Leishmania peptides to design more specific vaccines against leishmaniases seems promising. Moreover, peptides have several benefits in comparison with other kinds of antigens, for instance, good stability, absence of potentially damaging materials, antigen low complexity, and low-cost to scale up. By contrast, peptides are poor immunogenic alone, and they need to be delivered correctly. In this context, several approaches described in this review are useful to solve these drawbacks. Approaches, such as, peptides in combination with potent adjuvants, cellular vaccinations, adenovirus, polyepitopes, or DNA vaccines have been used to develop peptide-based vaccines. Recent advancements in peptide vaccine design, chimeric, or polypeptide vaccines and nanovaccines based on particles attached or formulated with antigenic components or peptides have been increasingly employed to drive a specific immune response. In this review, we briefly summarize the old, current, and future stands on peptide-based vaccines, describing the disadvantages and benefits associated with them. We also propose possible approaches to overcome the related weaknesses of synthetic vaccines and suggest future guidelines for their development.

  18. Peptide Vaccines for Leishmaniasis.

    Science.gov (United States)

    De Brito, Rory C F; Cardoso, Jamille M De O; Reis, Levi E S; Vieira, Joao F; Mathias, Fernando A S; Roatt, Bruno M; Aguiar-Soares, Rodrigo Dian D O; Ruiz, Jeronimo C; Resende, Daniela de M; Reis, Alexandre B

    2018-01-01

    Due to an increase in the incidence of leishmaniases worldwide, the development of new strategies such as prophylactic vaccines to prevent infection and decrease the disease have become a high priority. Classic vaccines against leishmaniases were based on live or attenuated parasites or their subunits. Nevertheless, the use of whole parasite or their subunits for vaccine production has numerous disadvantages. Therefore, the use of Leishmania peptides to design more specific vaccines against leishmaniases seems promising. Moreover, peptides have several benefits in comparison with other kinds of antigens, for instance, good stability, absence of potentially damaging materials, antigen low complexity, and low-cost to scale up. By contrast, peptides are poor immunogenic alone, and they need to be delivered correctly. In this context, several approaches described in this review are useful to solve these drawbacks. Approaches, such as, peptides in combination with potent adjuvants, cellular vaccinations, adenovirus, polyepitopes, or DNA vaccines have been used to develop peptide-based vaccines. Recent advancements in peptide vaccine design, chimeric, or polypeptide vaccines and nanovaccines based on particles attached or formulated with antigenic components or peptides have been increasingly employed to drive a specific immune response. In this review, we briefly summarize the old, current, and future stands on peptide-based vaccines, describing the disadvantages and benefits associated with them. We also propose possible approaches to overcome the related weaknesses of synthetic vaccines and suggest future guidelines for their development.

  19. Peptide Nucleic Acids

    DEFF Research Database (Denmark)

    2004-01-01

    A novel class of compounds known as peptide nucleic acids, bind complementary DNA and RNA strands, and generally do so more strongly than the corresponding DNA or RNA strands while exhibiting increased sequence specificity and solubility. The peptide nucleic acids comprise ligands selected from...

  20. A class of non-null toroidal electromagnetic fields and its relation to the model of electromagnetic knots

    International Nuclear Information System (INIS)

    Arrayás, Manuel; Trueba, José L

    2015-01-01

    An electromagnetic knot is an electromagnetic field in vacuum in which the magnetic lines and the electric lines coincide with the level curves of a pair of complex scalar fields ϕ and θ (see equations (A.1), (A.2)). When electromagnetism is expressed in terms of electromagnetic knots, it includes mechanisms for the topological quantization of the electromagnetic helicity, the electric charge, the electromagnetic energy inside a cavity and the magnetic flux through a superconducting ring. In the case of electromagnetic helicity, its topological quantization depends on the linking number of the field lines, both electric and magnetic. Consequently, to find solutions of the electromagnetic knot equations with nontrivial topology of the field lines has important physical consequences. We study a new class of solutions of Maxwell's equations in vacuum Arrayás and Trueba (2011 arXiv:1106.1122) obtained from complex scalar fields that can be interpreted as maps S 3 →S 2 , in which the topology of the field lines is that of the whole torus-knot set. Thus this class of solutions is built as electromagnetic knots at initial time. We study some properties of those fields and consider if detection based on the energy and momentum observables is possible. (paper)

  1. EXPANSION OF HYDROGEN-POOR KNOTS IN THE BORN-AGAIN PLANETARY NEBULAE A30 AND A78

    Energy Technology Data Exchange (ETDEWEB)

    Fang, X.; Guerrero, M. A.; Marquez-Lugo, R. A.; Toalá, J. A. [Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, E-18008 Granada (Spain); Arthur, S. J. [Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Campus Morelia, 58090 Morelia (Mexico); Chu, Y.-H.; Gruendl, R. A. [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States); Blair, W. P. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Hamann, W.-R.; Oskinova, L. M.; Todt, H., E-mail: fangx@iaa.es [Institute for Physics and Astronomy, Universität Potsdam, D-14476 Potsdam (Germany)

    2014-12-20

    We analyze the expansion of hydrogen-poor knots and filaments in the born-again planetary nebulae A30 and A78 based on Hubble Space Telescope (HST) images obtained almost 20 yr apart. The proper motion of these features generally increases with distance to the central star, but the fractional expansion decreases, i.e., the expansion is not homologous. As a result, there is not a unique expansion age, which is estimated to be 610-950 yr for A30 and 600-1140 yr for A78. The knots and filaments have experienced complex dynamical processes: the current fast stellar wind is mass loaded by the material ablated from the inner knots; the ablated material is then swept up until it shocks the inner edges of the outer, hydrogen-rich nebula. The angular expansion of the outer filaments shows a clear dependence on position angle, indicating that the interaction of the stellar wind with the innermost knots channels the wind along preferred directions. The apparent angular expansion of the innermost knots seems to be dominated by the rocket effect of evaporating gas and by the propagation of the ionization front inside them. Radiation-hydrodynamical simulations show that a single ejection of material followed by a rapid onset of the stellar wind and ionizing flux can reproduce the variety of clumps and filaments at different distances from the central star found in A30 and A78.

  2. Preclinical evaluation of somatostatin analogs bearing two macrocyclic chelators for high specific activity labeling with radiometals

    International Nuclear Information System (INIS)

    Storch, D.; Schmitt, J.S.; Waldherr, C.; Maecke, H.R.; Waser, B.; Reubi, J.C.

    2007-01-01

    Radiometallated analogues of the regulatory peptide somatostatin are of interest in the in vivo localization and targeted radiotherapy of somatostatin receptor-overexpressing tumors. An important aspect of their use in vivo is a fast and efficient labeling (complexation) protocol for radiometals along with a high specific activity. We describe in this manuscript synthetic methods for the coupling of two chelators (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid = DOTA) to the bioactive peptide [Tyr 3 ,Thr 8 ]-octreotide (TATE) in order to increase the specific activity (radioactivity in Bq per mole peptide). The full chelator-linker-peptide conjugate was assembled on solid support using standard Fmoc chemistry. Two DOTA-chelators were linked to the peptide using lysine or N,N'-bis(3-aminopropyl)-glycine (Apg); in addition, pentasarcosine (Sar 5 ) was used as a spacer between the chelators and the peptide to probe its influence on biology and pharmacology. Complexation rates with In 3+ and Y 3+ salts and the corresponding radiometals were high, the bis-DOTA-derivatives showed higher complexation rates and gave higher specific activity than DOTA-TATE. Pharmacological and biological data of the complexed molecules did not show significant differences if compared to the parent peptide [ 111/nat In-DOTA]-TATE except for [( 111/nat In-DOTA) 2 -Apg]-TATE which showed a lower binding affinity and rate of internalization into tumor cells. The biodistribution of [( 111/nat In-DOTA)-Lys( 111/nat In-DOTA)]-TATE in the rat tumor model (AR4-2J) showed a high and specific (as shown by a blocking experiment) tracer uptake in somatostatin receptor-positive tissue but a lower tumor uptake compared to [ 111/nat In-DOTA]-TATE. (orig.)

  3. Personalized Video Feedback and Repeated Task Practice Improve Laparoscopic Knot-Tying Skills: Two Controlled Trials.

    Science.gov (United States)

    Abbott, Eduardo F; Thompson, Whitney; Pandian, T K; Zendejas, Benjamin; Farley, David R; Cook, David A

    2017-11-01

    Compare the effect of personalized feedback (PF) vs. task demonstration (TD), both delivered via video, on laparoscopic knot-tying skills and perceived workload; and evaluate the effect of repeated practice. General surgery interns and research fellows completed four repetitions of a simulated laparoscopic knot-tying task at one-month intervals. Midway between repetitions, participants received via e-mail either a TD video (demonstration by an expert) or a PF video (video of their own performance with voiceover from a blinded senior surgeon). Each participant received at least one video per format, with sequence randomly assigned. Outcomes included performance scores and NASA Task Load Index (NASA-TLX) scores. To evaluate the effectiveness of repeated practice, scores from these trainees on a separate delayed retention test were compared against historical controls who did not have scheduled repetitions. Twenty-one trainees completed the randomized study. Mean change in performance scores was significantly greater for those receiving PF (difference = 23.1 of 150 [95% confidence interval (CI): 0, 46.2], P = .05). Perceived workload was also significantly reduced (difference = -3.0 of 20 [95% CI: -5.8, -0.3], P = .04). Compared with historical controls (N = 93), the 21 with scheduled repeated practice had higher scores on the laparoscopic knot-tying assessment two weeks after the final repetition (difference = 1.5 of 10 [95% CI: 0.2, 2.8], P = .02). Personalized video feedback improves trainees' procedural performance and perceived workload compared with a task demonstration video. Brief monthly practice sessions support skill acquisition and retention.

  4. Optimizing the efficacy of Paecilomyces lilacinus (strain 251) for the control of root-knot nematodes.

    Science.gov (United States)

    Kiewnick, S; Sikora, R A

    2004-01-01

    The egg pathogenic fungus Paecilomyces lilacinus (strain 251) is a biocontrol fungus with a potential range of activity to control the worldwide most important plant parasitic nematodes. This biological nematicide may be an useful tool in an integrated approach to control mainly sedentary nematodes. Greenhouse experiments were conducted with the root-knot nematodes Meloidogyne incognita and M. hapla on tomato. P. lilacinus, formulated as WG (BIOACT WG), was incorporated into soil inoculated with root-knot nematode eggs prior to transplanting the susceptible tomato cultivar "Hellfrucht". Furthermore, soil treatments were combined with seedling treatments 24 hours before transplanting and a soil drench 2 weeks after planting, respectively. Seedling and post planting treatment was also combined with a soil treatment at planting. All single or combination treatments tested decreased the gall index and the number of egg masses compared to the untreated control 12 weeks after planting. However, the combination of the seedling treatment with a pre- or at-planting application of P. lilacinus was necessary to achieve higher levels of control. Additional post plant drenching resulted in only a slight increase In efficacy. To the feasibility of this modified application system for the control of root-knot nematodes, a yield experiment was conducted with M. hapla and the susceptible cultivar "Gnom F1 Hybrid". It could be demonstrated that the above mentioned combination of pre-planting application plus the seedling and one post plant drench gave the best control and resulted in a significant fruit yield increase in concurrence with a decrease in number of galls per root.

  5. “One Ring to Bind Them All”—Part I: The Efficiency of the Macrocyclic Scaffold for G-Quadruplex DNA Recognition

    Directory of Open Access Journals (Sweden)

    David Monchaud

    2010-01-01

    Full Text Available Macrocyclic scaffolds are particularly attractive for designing selective G-quadruplex ligands essentially because, on one hand, they show a poor affinity for the “standard” B-DNA conformation and, on the other hand, they fit nicely with the external G-quartets of quadruplexes. Stimulated by the pioneering studies on the cationic porphyrin TMPyP4 and the natural product telomestatin, follow-up studies have developed, rapidly leading to a large diversity of macrocyclic structures with remarkable-quadruplex binding properties and biological activities. In this review we summarize the current state of the art in detailing the three main categories of quadruplex-binding macrocycles described so far (telomestatin-like polyheteroarenes, porphyrins and derivatives, polyammonium cyclophanes, and in addressing both synthetic issues and biological aspects.

  6. Spermatic Cord Knot: A Clinical Finding in Patients with Spermatic Cord Torsion

    Directory of Open Access Journals (Sweden)

    Abdullatif Al-Terki

    2011-01-01

    Full Text Available Pertinent history taking and careful examination often taper the differentials of the acute scrotum; congruently the ability to diagnose acute spermatic cord torsion (SCT when radiological adjuncts are not available is highly imperative. This observational study serves to present a series of 46 cases of spermatic cord torsion whereby we hypothesize the identification of a clinical knot on scrotal examination as an important clinical aid in making a decision to surgical exploration in patients with acute and subacute SCT, especially in centers where imaging resources are unavailable.

  7. On knottings in the physical Hilbert space of LQG as given by the EPRL model

    International Nuclear Information System (INIS)

    Bahr, Benjamin

    2011-01-01

    We consider the EPRL spin foam amplitude for arbitrary embedded two-complexes. Choosing a definition of the face- and edge amplitudes which lead to spin foam amplitudes invariant under trivial subdivisions, we investigate invariance properties of the amplitude under consistent deformations, which are deformations of the embedded two-complex where faces are allowed to pass through each other in a controlled way. Using this surprising invariance, we are able to show that the physical Hilbert space, as defined by the sum over all spin foams, contains no information about knotting classes of graphs anymore.

  8. Finite-size and asymptotic behaviors of the gyration radius of knotted cylindrical self-avoiding polygons.

    Science.gov (United States)

    Shimamura, Miyuki K; Deguchi, Tetsuo

    2002-05-01

    Several nontrivial properties are shown for the mean-square radius of gyration R2(K) of ring polymers with a fixed knot type K. Through computer simulation, we discuss both finite size and asymptotic behaviors of the gyration radius under the topological constraint for self-avoiding polygons consisting of N cylindrical segments with radius r. We find that the average size of ring polymers with the knot K can be much larger than that of no topological constraint. The effective expansion due to the topological constraint depends strongly on the parameter r that is related to the excluded volume. The topological expansion is particularly significant for the small r case, where the simulation result is associated with that of random polygons with the knot K.

  9. Cocomplexation of urea and UO22+ in a Schiff base macrocycle: a mimic of an enzyme binding site

    International Nuclear Information System (INIS)

    van Staveren, C.J.; Fenton, D.E.; Reinhoudt, D.N.; van Eerden, J.; Harkema, S.

    1987-01-01

    As part of the authors work on the complexation of neutral molecules by macrocyclic ligands, they are particularly interested in the complexation of urea. They have shown that urea can form complexes with (aza-)18-crown but the association constants of these complexes in water are very small (18-crown-6-urea, log K/sub s/ = 0.1). Protonation of urea effects stronger binding especially when the crown ether is sufficiently large to form an encapsulated complex (e.g., the complex benzo-27-crown-9-urea-HClO 4 ). Protonation of the weakly basic urea (pK/sub a/ = 0.1, water, 25 0 C) requires strongly acidic conditions and to avoid this they have introduced a covalently linked carboxylic group in the cavity of the macrocycle. A strong hydrogen bond of urea with 2-carboxyl-1,3-xylyl-30-crown-9 results in an encapsulated complex. The concept of using an electrophilic center to bind urea in the cavity of a crown ether proved to be a more general concept. A metal cation can serve as the electrophile as was shown by the isolation and single-crystal X-ray analysis of the 2,6-pyrido-27-crown-9-urea-LiClO 4 (1:2:1) complex in which one of the urea molecules is encapsulated. In an effort to bind an electrophilic metal ion in the crown ethers irreversibly they have concentrated their work on macrocycles of type 1, since the strong binding of quadridentate (salen type) Schiff bases with soft metal ions is well-known

  10. Macrocyclic receptors immobilized to monodisperse porous polymer particles by chemical grafting and physical impregnation for strontium capture: A comparative study

    Energy Technology Data Exchange (ETDEWEB)

    Song, Yang [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing (China); Du, Yi [Department of Chemical Engineering, Laboratory for Advanced Materials, Tsinghua University, Beijing (China); Lv, Dachao [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing (China); Ye, Gang, E-mail: yegang@tsinghua.edu.cn [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing (China); Wang, Jianchen [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing (China)

    2014-06-01

    Graphical abstract: Macrocyclic receptors grafted to monodisperse porous polymer particles for Sr(II) capture. - Highlights: • Synthesis of novel selective Sr adsorbent grafted with macrocyclic receptors. • New monodisperse porous polymer particles used to promote Sr adsorption. • Comparative study and discussion on adsorption behaviour and mechanism. • A chromatographic process proposed for Sr separation in simulated HLLW. - Abstract: Separation of strontium is of great significance for radioactive waste treatment and environmental remediation after nuclear accidents. In this work, a novel class of adsorbent (Crown-g-MPPPs) was synthesized by chemical grafting a macrocyclic ether receptor to monodisperse porous polymer particles (MPPPs) for strontium adsorption. Meanwhile, a counterpart material (Crown@MPPPs) with the receptor molecules immobilized to the MPPPs substrate by physical impregnation was prepared. To investigate how the immobilization manner and distribution of the receptors influence the adsorption ability, a comparative study on the adsorption behaviour of the two materials towards Sr(II) in HNO{sub 3} media was accomplished. Due to the shorter diffusion path and covalently-bonded structure, Crown-g-MPPPs showed faster adsorption kinetics and better stability for cycle use. While Crown@MPPPs had the advantages of facile synthesis and higher adsorption capacity, owing to the absence of conformational constraint to form complexation with Sr(II). Kinetic functions (Lagergren pseudo-first-order/pseudo-second-order functions) and adsorption isotherm models (Langmuir/Freundlich models) were used to fit the experimental data and examine the adsorption mechanism. On this basis, a chromatographic process was proposed by using Crown@MPPPs for an effective separation of Sr(II) (91%) in simulated high level liquid waste (HLLW)

  11. Thermodynamic studies of the complexation of plutonium(IV) by linear and macrocyclic poly-amino-carboxylate ligands

    International Nuclear Information System (INIS)

    Burgat, Romain

    2007-01-01

    In the framework of a collaboration between the CEA (Commissariat a l Energie Atomique) of Valduc and the ICMUB (Institut de Chimie Moleculaire de l Universite de Bourgogne), a study platform of the structural and physico-chemical properties of the radioelements U, Pu and Am complexes has been implemented. The plutonium(IV) complexation has been studied in a molar nitrate medium. The affinity of three linear poly-amino-carboxylates (EDTA, CDTA and DTPA) towards plutonium(IV) has then been estimated. For the three ligands, the formation constants of the monoleptic complexes Pu(EDTA), Pu(CDTA) and [Pu(DTPA)] - have been determined in a (H,K)NO 3 1 M medium and then extrapolated at a zero ionic force with the specific interactions theory (SIT). For the three complexes, mono-hydroxylated monoleptic species have been observed. With the EDTA and the CDTA, protonated dileptic complexes of a general formula [Pu(L) 2 H h ] (4-h)- have been revealed too. Nevertheless, the steric hindrance around the metallic center is too important to allow to a second molecule of DTPA to coordinate the Pu 4+ cation. The exclusive formation of the species [Pu(DTPA)] - and [Pu(DTPA)(OH)] 2- has been confirmed by capillary electrophoresis (EC-ICP-MS). On account of the preliminary results obtained during the titration of the cyclame tetraacetic product (TETRA) in presence of plutonium(IV), the adding of a competitive ligand such as EDTA has been considered for the study of the complexation of this radioelement by macrocyclic ligands. At last, the affinity of different macrocyclic ligands containing either four amide functions (TETAMMe 2 and TETAMMEt 2 ) or carboxylate groups (TETA, DOTPr and TETPr) towards lanthanides(III) has been estimated too. Although the complexation reaction be fast with the two first ligands, these complexes are less stable than those formed with the carboxylic macrocycles. (O.M.)

  12. Macrocyclic trichothecenes are undetectable in kudzu (Pueraria montana) plants treated with a high-producing isolate of Myrothecium verrucaria.

    Science.gov (United States)

    Abbas, H K; Tak, H; Boyette, C D; Shier, W T; Jarvis, B B

    2001-09-01

    Myrothecium verrucaria was found to be an effective pathogen against kudzu grown in the greenhouse and the field. M. verrucaria produced large amounts of macrocyclic trichothecenes when cultured on solid rice medium, including epiroridin E (16.8 mg/g crude extract), epiisororidin E (1 mg/g), roridin E (8.7 mg/g), roridin H (31.3 mg/g), trichoverrin A (0.6 mg/g), trichoverrin B (0.1 mg/g), verrucarin A (37.4 mg/g), and verrucarin J (2.2 mg/g). Most of these toxins were also isolated from M. verrucaria spores and mycelia grown on potato dextrose agar medium, including epiroridin E (32.3 mg/g), epiisororidin E (28.6 mg/g), roridin E (0 mg/g), roridin H (60 mg/g), trichoverrin A (1.3 mg/g), trichoverrin B (1.8 mg/g), verrucarin A (13.8 mg/g), and verrucarin J (131 mg/g). When M. verrucaria was cultured on liquid media, the numbers but not the amounts of toxins decreased. Only epiroridin E (28.3 mg/g), epiisororidin E (29.6 mg/g), verrucarin B (195 mg/g) and verrucarin J (52.6 mg/g) were measured when the fungus was cultured on cornsteep medium. On soyflour-cornmeal broth M. verrucaria produced several toxins, including epiroridin E (58.1 mg/g), epiisororidin E (5.8 mg/g), verrucarin B (29.9 mg/g) and verrucarin J (32 mg/g). In contrast, no macrocyclic trichothecenes were detected by HPLC analysis of plant tissues of kudzu, sicklepod, and soybean treated with aqueous suspensions of M. verrucaria spores formulated with a surfactant. Chloroform-methanol extracts of kudzu leaves and stems treated with M. verrucaria spores were less cytotoxic to four cultured mammalian cell lines than the corresponding extracts from control plants. Purified macrocyclic trichothecenes (verrucarin A and T-2 toxin) were very cytotoxic to the same cell lines (< or = 2 ng/ml). These results show that neither intact macrocyclic trichothecenes nor toxic metabolites could be detected in plant tissues after treatment with M. verrucaria spores. These results argue for both safety and efficacy for the

  13. Synthesis of Cycloveratrylene Macrocycles and Benzyl Oligomers Catalysed by Bentonite under Microwave/Infrared and Solvent-Free Conditions

    Directory of Open Access Journals (Sweden)

    Manuel Salmón

    2013-10-01

    Full Text Available Tonsil Actisil FF, which is a commercial bentonitic clay, promotes the formation of cycloveratrylene macrocycles and benzyl oligomers from the corresponding benzyl alcohols in good yields under microwave heating and infrared irradiation in the absence of solvent in both cases. The catalytic reaction is sensitive to the type of substituent on the aromatic ring. Thus, when benzyl alcohol was substituted with a methylenedioxy, two methoxy or three methoxy groups, a cyclooligomerisation process was induced. Unsubstituted, methyl and methoxy benzyl alcohols yielded linear oligomers. In addition, computational chemistry calculations were performed to establish a validated mechanistic pathway to explain the growth of the obtained linear oligomers.

  14. Evaluation of the larval migration inhibition assay for detecting macrocyclic lactone resistance in Dirofilaria immitis.

    Science.gov (United States)

    Evans, Christopher C; Moorhead, Andrew R; Storey, Bobby E; Blagburn, Byron L; Wolstenholme, Adrian J; Kaplan, Ray M

    2017-11-15

    Anthelmintics of the macrocyclic lactone (ML) drug class are widely used as preventives against the canine heartworm (Dirofilaria immitis). Over the past several years, however, reports of ML lack of efficacy (LOE) have emerged, in which dogs develop mature heartworm infection despite the administration of monthly prophylactics. More recently, isolates from LOE cases have been used to infect laboratory dogs and the resistant phenotype has been confirmed by the establishment of adult worms in the face of ML treatment at normally preventive dosages. Testing for and monitoring resistance in D. immitis requires a validated biological or molecular diagnostic assay. In this study, we assessed a larval migration inhibition assay (LMIA) that we previously optimized for use with D. immitis third-stage larvae (L 3 ). We used this assay to measure the in vitro ML susceptibilities of a known-susceptible laboratory strain of D. immitis and three highly suspected ML-resistant isolates originating from three separate LOE cases; progeny from two of these isolates have been confirmed ML-resistant by treatment of an infected dog in a controlled setting. A nonlinear regression model was fit to the dose-response data, from which IC 50 values were calculated. The D. immitis LMIA yielded consistent and reproducible dose-response data; however, no statistically significant differences in drug susceptibility were observed between control and LOE parasites. Additionally, the drug concentrations needed to paralyze the L 3 were much higher than those third- and fourth-stage larvae would experience in vivo. IC 50 values ranged from 1.57 to 5.56μM (p≥0.19). These data could suggest that ML resistance in this parasite is not mediated through a reduced susceptibility of L 3 to the paralytic effects of ML drugs, and therefore motility-based assays are likely not appropriate for measuring the effects of MLs against D. immitis in this target stage. Published by Elsevier B.V.

  15. Development of an in vitro bioassay for measuring susceptibility to macrocyclic lactone anthelmintics in Dirofilaria immitis.

    Science.gov (United States)

    Evans, Christopher C; Moorhead, Andrew R; Storey, Bobby E; Wolstenholme, Adrian J; Kaplan, Ray M

    2013-12-01

    For more than 20 years, anthelmintics of the macrocyclic lactone (ML) drug class have been widely and effectively used as preventives against the canine heartworm, Dirofilaria immitis. However, in recent years an increased number of lack of efficacy (LOE) cases are being reported, in which dogs develop mature heartworm infections despite receiving monthly prophylactic doses of ML drugs. While this situation is raising concerns that heartworms may be developing resistance to MLs, compelling evidence for this is still lacking. Resolution of this dilemma requires validated biological or molecular diagnostic assays, but, unfortunately, no such tests currently exist. To address this need, we developed and optimized a larval migration inhibition assay (LMIA) for use with D. immitis third-stage larvae. The LMIA was used to measure the in vitro dose-response of two ML drugs (ivermectin and eprinomectin) on a known ML-susceptible laboratory strain of D. immitis. A nonlinear regression model was fit to the dose-response data, from which IC50 values were calculated; the mean IC50 and 95% confidence interval for IVM was 4.56 μM (1.26-16.4 μM), greater than that for EPR at 2.02 μM (1.68-2.42 μM), and this difference was significant (p = 0.0428). The R (2) value for EPR assays (0.90) was also greater than that for IVM treatment (0.71). The consistency and reproducibility of the dose-response data obtained with this assay suggests that it may be a useful technique for investigating the relative susceptibilities to ML drugs in other D. immitis populations.

  16. Dysprosium complexes with the tetraphenylporphyrin macrocyclic ligand; Complejos de disprosio con el ligante macrociclico tetrafenilporfirina

    Energy Technology Data Exchange (ETDEWEB)

    Martinez M, V.; Padilla, J.; Ramirez, F.M

    1992-04-15

    In this report, the results obtained on the synthesis, characterization and study of the chemical behavior of dysprosium complex with the acetylacetone chelating agent (Hacac) and the tetraphenylporphyrin macrocyclic ligand (H{sub 2}TFP) are given. Based on the literature but according to our necessities and interest, the appropriate methodology settled down from the synthesis of prime matters until the obtaining and characterization of the products. The acetyl acetonate complex was obtained of mono hydrated dysprosium [Dy(acac){sub 3}. H{sub 2}0] and trihydrated [Dy(acac){sub 3} .3 H{sub 2}0], the mono tetra phenyl porphyrinate [Dy(TFP)(acac). 2 ac] the double sandwich of the dysprosium porphyrinate [Dy(TFP){sub 2}] and the triple sandwich of the dysprosium porphyrinate [Dy(TFP){sub 3}. 2 TCB] (TCB = trichlorobenzene). Its were characterized by their melting points, solubility, IR, UV, TGA and DTA both first and besides the techniques already mentioned for NMR'H, RPE and Magnetic susceptibility the three last complexes. From the spectroscopic point of view, IR and RPE its suggested the existence of a complex of inverse mixed valence [Dy(TFP){sup 2-} (TFP) {sup 1-}] for the Dy(TFP){sub 2} as a result of the existence of the free radical (TFP' {sup 1-} and that it was not in none of the other porphyrin compounds. In the NMR'H spectra of the compounds were not observed signals in the region from 0 to 10 ppm that which shows that the dysprosium complexes in special those of the porphyrin type are highly paramagnetic and its could be used as displacement reagents, creators of images and contrast agents of great utility in these days in studies of NMR, technique today by today used in medical diagnoses. (Author)

  17. Dysprosium complexes with the tetraphenylporphyrin macrocyclic ligand; Complejos de disprosio con el ligante macrociclico tetrafenilporfirina

    Energy Technology Data Exchange (ETDEWEB)

    Martinez M, V; Padilla, J; Ramirez, F M

    1992-04-15

    In this report, the results obtained on the synthesis, characterization and study of the chemical behavior of dysprosium complex with the acetylacetone chelating agent (Hacac) and the tetraphenylporphyrin macrocyclic ligand (H{sub 2}TFP) are given. Based on the literature but according to our necessities and interest, the appropriate methodology settled down from the synthesis of prime matters until the obtaining and characterization of the products. The acetyl acetonate complex was obtained of mono hydrated dysprosium [Dy(acac){sub 3}. H{sub 2}0] and trihydrated [Dy(acac){sub 3} .3 H{sub 2}0], the mono tetra phenyl porphyrinate [Dy(TFP)(acac). 2 ac] the double sandwich of the dysprosium porphyrinate [Dy(TFP){sub 2}] and the triple sandwich of the dysprosium porphyrinate [Dy(TFP){sub 3}. 2 TCB] (TCB = trichlorobenzene). Its were characterized by their melting points, solubility, IR, UV, TGA and DTA both first and besides the techniques already mentioned for NMR'H, RPE and Magnetic susceptibility the three last complexes. From the spectroscopic point of view, IR and RPE its suggested the existence of a complex of inverse mixed valence [Dy(TFP){sup 2-} (TFP) {sup 1-}] for the Dy(TFP){sub 2} as a result of the existence of the free radical (TFP' {sup 1-} and that it was not in none of the other porphyrin compounds. In the NMR'H spectra of the compounds were not observed signals in the region from 0 to 10 ppm that which shows that the dysprosium complexes in special those of the porphyrin type are highly paramagnetic and its could be used as displacement reagents, creators of images and contrast agents of great utility in these days in studies of NMR, technique today by today used in medical diagnoses. (Author)

  18. The geometry of periodic knots, polycatenanes and weaving from a chemical perspective: a library for reticular chemistry.

    Science.gov (United States)

    Liu, Yuzhong; O'Keeffe, Michael; Treacy, Michael M J; Yaghi, Omar M

    2018-05-04

    The geometry of simple knots and catenanes is described using the concept of linear line segments (sticks) joined at corners. This is extended to include woven linear threads as members of the extended family of knots. The concept of transitivity that can be used as a measure of regularity is explained. Then a review is given of the simplest, most 'regular' 2- and 3-periodic patterns of polycatenanes and weavings. Occurrences in crystal structures are noted but most structures are believed to be new and ripe targets for designed synthesis.

  19. Possible configuration of two-knot auto-localized exciton in strainless and deformed alkali halide crystals

    International Nuclear Information System (INIS)

    Dzhumanov, S.; Tulepbergenov, S.K.; Shunkeev, K.Sh.

    2002-01-01

    In the paper molecular component of two-knot auto-localized exciton (TALE) occupying centrosymmetric state in alkali halide crystal cubic lattice with local D 2h symmetry is considered. In is suggested that the symmetry lowering of forming small radius auto-localized exciton (ALE) is realizing in order configuration transformation by the scenario: multi-knot continual ALE (with O h symmetry)→six-halide ALE (with O h symmetry)→TALE (with O h symmetry) or by the scenario O h →D 2h . Then for TALE with local D 2h symmetry normal molecular ion shifts are considered as well

  20. Diversity-oriented peptide stapling

    DEFF Research Database (Denmark)

    Tran, Thu Phuong; Larsen, Christian Ørnbøl; Røndbjerg, Tobias

    2017-01-01

    as a powerful method for peptide stapling. However, to date CuAAC stapling has not provided a simple method for obtaining peptides that are easily diversified further. In the present study, we report a new diversity-oriented peptide stapling (DOPS) methodology based on CuAAC chemistry. Stapling of peptides...

  1. The impact of solarisation integrated with plant bio-fermentation on root knot nematodes

    International Nuclear Information System (INIS)

    Ibrahim, S. K.; Traboulsi, A. F.

    2009-01-01

    The impact of different freshly/dried chopped medicinal or aromatic plant materials as an organic amendment in pot cultures, as well as integrated with solarisation under greenhouse conditions on the root knot nematodes population was evaluated. Results indicated that application of solarisation alone gave good control (72%) but when integrated with different plant materials, the control level increased to 95% with Allium sativum and 90% with Mentha microphylla and slightly less with other plant materials which ranged from75 to 80%. The results of pot experiments revealed that the most significant effect on the number of nematodes was achieved with Tagetes patula followed by Pimpinella anisum, Melia azadirach and Origanium syriacum reaching 0.0, 1.2, 1.2 and 2.5/g of roots, respectively. Total control was obtained with Allium sativum. Origanium syriacum contained the highest amount of essential oil (6%). Results obtained indicated that integrated approach using solarisation combined with plant materials could be the best alternative control for the root-knot nematodes. (author)

  2. Adhering Pasteuria penetrans endospores affect movements of root-knot nematode juveniles

    Directory of Open Access Journals (Sweden)

    Ioannis VAGELAS

    2013-01-01

    Full Text Available Pasteuria penetrans is a biological control agent of root-knot nematodes (Meloidogyne spp., preventing root invasion by second-stage juveniles (J2s, and eventually causing females sterility and death. greatest control effects for P. penetrans depend on the numbers of endospores attached to nematode cuticles. a method based on digital image analysis was used to record the effects of endospore attachment on the movements of juvenile root-knot nematodes, using a model based on the centroid point. Data showed that the numbers of endospores attached to the cuticle influenced nematode movement. At high endospore attachment levels (20‒30 per J2, nematodes did not show directional movement, whereas nematodes encumbered with five to eight spores showed limited directional movement, compared to those without endospores. nematode cephalic region turns were modelled using a markov chain, showing that P. penetrans endospores affected movements. Less nematodes invaded and established on tomato root systems when encumbered with low (five to eight or high numbers (20‒30 of P. penetrans endospores, compared with unencumbered nematodes.

  3. Topological Vortex and Knotted Dissipative Optical 3D Solitons Generated by 2D Vortex Solitons.

    Science.gov (United States)

    Veretenov, N A; Fedorov, S V; Rosanov, N N

    2017-12-29

    We predict a new class of three-dimensional (3D) topological dissipative optical one-component solitons in homogeneous laser media with fast saturable absorption. Their skeletons formed by vortex lines where the field vanishes are tangles, i.e., N_{c} knotted or unknotted, linked or unlinked closed lines and M unclosed lines that thread all the closed lines and end at the infinitely far soliton periphery. They are generated by embedding two-dimensional laser solitons or their complexes in 3D space after their rotation around an unclosed, infinite vortex line with topological charge M_{0} (N_{c}, M, and M_{0} are integers). With such structure propagation, the "hula-hoop" solitons form; their stability is confirmed numerically. For the solitons found, all vortex lines have unit topological charge: the number of closed lines N_{c}=1 and 2 (unknots, trefoils, and Solomon knots links); unclosed vortex lines are unknotted and unlinked, their number M=1, 2, and 3.

  4. A baseline correction algorithm for Raman spectroscopy by adaptive knots B-spline

    International Nuclear Information System (INIS)

    Wang, Xin; Fan, Xian-guang; Xu, Ying-jie; Wang, Xiu-fen; He, Hao; Zuo, Yong

    2015-01-01

    The Raman spectroscopy technique is a powerful and non-invasive technique for molecular fingerprint detection which has been widely used in many areas, such as food safety, drug safety, and environmental testing. But Raman signals can be easily corrupted by a fluorescent background, therefore we presented a baseline correction algorithm to suppress the fluorescent background in this paper. In this algorithm, the background of the Raman signal was suppressed by fitting a curve called a baseline using a cyclic approximation method. Instead of the traditional polynomial fitting, we used the B-spline as the fitting algorithm due to its advantages of low-order and smoothness, which can avoid under-fitting and over-fitting effectively. In addition, we also presented an automatic adaptive knot generation method to replace traditional uniform knots. This algorithm can obtain the desired performance for most Raman spectra with varying baselines without any user input or preprocessing step. In the simulation, three kinds of fluorescent background lines were introduced to test the effectiveness of the proposed method. We showed that two real Raman spectra (parathion-methyl and colza oil) can be detected and their baselines were also corrected by the proposed method. (paper)

  5. Knot wormholes and the dimensional invariant of exceptional Lie groups and Stein space hierarchies

    International Nuclear Information System (INIS)

    Elokaby, Ayman

    2009-01-01

    The present short note points out a most interesting and quite unexpected connection between the number of distinct knot as a function of their crossing number and exceptional Lie groups and Stein space hierarchies. It is found that the crossing number 7 plays the role of threshold similar to 4 and 5 in E-infinity theory and for the 11 crossing the number of distinct knots is very close to 4α-bar 0 +1=548+1=549, where α-bar 0 =137 is the inverse integer electromagnetic fine structure constant. This is particularly intriguing in view of a similar relation pertinent to the 17 two and three Stein spaces where the total dimension is Σ 1 17 Stein=5α-bar 0 +1=685+1=686, as well as the sum of the eight exceptional Lie symmetry groups Σ i=1 8 |E i |=4α-bar 0 =548. The slight discrepancy of one is explained in both cases by the inclusion of El Naschie's transfinite corrections leading to Σ i=1 8 |E i |=(4)(137+k 0 )=548.328157 and Σ i=1 17 Stein=(5)(137+k 0 )=685.41097, where k o = φ 5 (1 - φ 5 ) and φ=(√(5)-1)/2.

  6. The temporal outcomes of open versus arthroscopic knotted and knotless rotator cuff repair over 5 years

    Science.gov (United States)

    Lucena, Thomas R; Lam, Patrick H; Millar, Neal L

    2015-01-01

    Background The present study aimed to determine how repair technique influenced structural and clinical outcomes at 5 years post-surgery. Methods Three cohorts of patients had repair of a symptomatic rotator cuff tear using (i) an open double-row mattress repair technique (n = 25); (ii) arthroscopic single-row simple suture knotted technique (n = 25); or (iii) arthroscopic single-row inverted mattress knotless technique (n = 36) by one surgeon. Standardized patient- and examiner-determined outcomes were obtained pre-operatively and postoperatively with a validated protocol, ultrasound were also performed at the same time. Results Retear occurred more often after open repair (48%) at 5 years than after arthroscopic knotted (33%) and arthroscopic knotless (26%) repair. Retear was associated with increasing age, pre-operative tear size and weaker pre-operative and 5 years postoperative cuff strength. Between 2 years and 5 years, the open repair group experienced an increase in the frequency of pain during activity, as well as in the difficulty experienced and the severity of pain during overhead activities (p repair group. Conclusions At 5-year follow-up, arthroscopic rotator cuff repair techniques resulted in fewer retears and better outcomes compared to an open double-row technique. PMID:27582985

  7. Sustainable management of root-knot disease of tomato by neem cake and Glomus fasciculatum

    Directory of Open Access Journals (Sweden)

    Rose Rizvi

    2015-12-01

    Full Text Available A pot experiment was conducted during winter season of 2009–2010 in the department of Botany, AMU, Aligarh, India, to determine the nematicidal potential of organic matter, neem cake at third level of dose, and bioagent, Glomus fasciculatum in terms of various growth parameters of tomato, when inoculated individually as well as concomitantly with respect to root-knot development. Neem cake and G. fasciculatum showed potential for sustainable management while providing nutrient sources for proper plant growth. Disease intensity of root-knot nematode decreased while increasing the doses of neem cake along with the G. fasciculatum. Chlorophyll contents have been found to be increased in single and combined application as well. There is a progressive increase in growth parameters raised in soil amended with 10, 20, and 30 g neem cake/kg soil and inoculated with G. fasciculatum. Significant improvement in the plant growth was observed when G. fasciculatum and neem cake were inoculated simultaneously. Neem cake plus G. fasciculatum reduced the nematodes’ multiplication and root-galling, and increased the plant growth of tomato as compared to unamended and Meloidogyne incognita-inoculated plants. Mycorrhyzation and agronomic parameters were increased due to application of G. fasciculatum alone, but enhanced further when inoculated with neem cake.

  8. PNA Peptide chimerae

    DEFF Research Database (Denmark)

    Koch, T.; Næsby, M.; Wittung, P.

    1995-01-01

    Radioactive labelling of PNA has been performed try linking a peptide segment to the PNA which is substrate for protein kinase A. The enzymatic phosphorylation proceeds in almost quantitative yields....

  9. Tumor penetrating peptides

    Directory of Open Access Journals (Sweden)

    Tambet eTeesalu

    2013-08-01

    Full Text Available Tumor-homing peptides can be used to deliver drugs into tumors. Phage library screening in live mice has recently identified homing peptides that specifically recognize the endothelium of tumor vessels, extravasate, and penetrate deep into the extravascular tumor tissue. The prototypic peptide of this class, iRGD (CRGDKGPDC, contains the integrin-binding RGD motif. RGD mediates tumor homing through binding to αv integrins, which are selectively expressed on various cells in tumors, including tumor endothelial cells. The tumor-penetrating properties of iRGD are mediated by a second sequence motif, R/KXXR/K. This C-end Rule (or CendR motif is active only when the second basic residue is exposed at the C-terminus of the peptide. Proteolytic processing of iRGD in tumors activates the cryptic CendR motif, which then binds to neuropilin-1 activating an endocytic bulk transport pathway through tumor tissue. Phage screening has also yielded tumor-penetrating peptides that function like iRGD in activating the CendR pathway, but bind to a different primary receptor. Moreover, novel tumor-homing peptides can be constructed from tumor-homing motifs, CendR elements and protease cleavage sites. Pathologies other than tumors can be targeted with tissue-penetrating peptides, and the primary receptor can also be a vascular zip code of a normal tissue. The CendR technology provides a solution to a major problem in tumor therapy, poor penetration of drugs into tumors. The tumor-penetrating peptides are capable of taking a payload deep into tumor tissue in mice, and they also penetrate into human tumors ex vivo. Targeting with these peptides specifically increases the accumulation in tumors of a variety of drugs and contrast agents, such as doxorubicin, antibodies and nanoparticle-based compounds. Remarkably the drug to be targeted does not have to be coupled to the peptide; the bulk transport system activated by the peptide sweeps along any compound that is

  10. Peptide aldehyde inhibitors of bacterial peptide deformylases.

    Science.gov (United States)

    Durand, D J; Gordon Green, B; O'Connell, J F; Grant, S K

    1999-07-15

    Bacterial peptide deformylases (PDF, EC 3.5.1.27) are metalloenzymes that cleave the N-formyl groups from N-blocked methionine polypeptides. Peptide aldehydes containing a methional or norleucinal inhibited recombinant peptide deformylase from gram-negative Escherichia coli and gram-positive Bacillus subtilis. The most potent inhibitor was calpeptin, N-CBZ-Leu-norleucinal, which was a competitive inhibitor of the zinc-containing metalloenzymes, E. coli and B. subtilis PDF with Ki values of 26.0 and 55.6 microM, respectively. Cobalt-substituted E. coli and B. subtilis deformylases were also inhibited by these aldehydes with Ki values for calpeptin of 9.5 and 12.4 microM, respectively. Distinct spectral changes were observed upon binding of calpeptin to the Co(II)-deformylases, consistent with the noncovalent binding of the inhibitor rather than the formation of a covalent complex. In contrast, the chelator 1,10-phenanthroline caused the time-dependent inhibition of B. subtilis Co(II)-PDF activity with the loss of the active site metal. The fact that calpeptin was nearly equipotent against deformylases from both gram-negative and gram-positive bacterial sources lends further support to the idea that a single deformylase inhibitor might have broad-spectrum antibacterial activity. Copyright 1999 Academic Press.

  11. Knotted pipeline

    International Nuclear Information System (INIS)

    Beer, G.; Slovak, K.

    2006-01-01

    It is too early to speculate on where the Transpetrol shares will end up. The bankruptcy trustee of Yukos, Eduard Rebgun, has so far received three offers from Gazprom, the Rusneft oil company and the Penta private equity group via its Cyprian company. All three would like to gain control over the Slovak oil transporting company. As yet, no formal request from the Slovak Republic has been delivered to Moscow. By Trend's deadline, President Ivan Gasparovic and the Minister of Economy, Lubomir Jahnatek, were still negotiating in Moscow with the Russian President, Vladimir Putin. One of the topics on the agenda was the future of the company which transports Russian oil to Europe. Both Slovakia and Russia aim to gain control over the stock and the situation is locked in stalemate The stock in question is owned by the Dutch company, Yukos Finance. And although this company is owned by the bankrupt Yukos, the property rights are in the hands of foundation, Stichting Administratiekantoor Yukos International. Yukos Finance is not in bankruptcy and it is therefore difficult to detach the Yukos shares from the company assets. (authors)

  12. Tying Knots

    DEFF Research Database (Denmark)

    Bødker, Susanne; Dindler, Christian; Iversen, Ole Sejer

    2017-01-01

    dispersed within these networks. To illustrate and discuss the process of participatory infrastructuring we use a case study from an educational context. This particular project contains a diverse set of design activities at many organizational levels revolving around technology, decision-making, competence...... of the literature on infrastructuring, participatory design, and activity theory, and leads to a revised understanding of, for example, learning and conflicts in participatory infrastructuring....

  13. Template synthesis of poly aza macrocyclic copper(II) and nickel(II) complexes: Spectral characterization and antimicrobial studies

    Energy Technology Data Exchange (ETDEWEB)

    Gurumoorthy, P.; Ravichandran, J.; Kaliur Rahiman, A. [The New College, Chennai (India); Karthikeyan, N.; Palani, P. [Univ. of Madras, Chennai (India)

    2012-07-15

    The template synthesis of copper(II) and nickel(II) complexes derived from 2,6-diformyl-4-methylphenol with diethylenetriamine or 1,2-bis(3-amino propylamino)ethane produce the 12-membered N{sub 3}O and 17-membered N{sub 4}O macrocyclic complexes, respectively. The geometry of the complexes has been determined with the help of electronic and EPR spectroscopic values and found to be five coordinated square pyramidal and, six coordinated distorted tetragonal for 12-membered and 17-membered macrocyclic complexes, respectively. Electrochemical studies of the mononuclear N{sub 3}O and N{sub 4}O copper(II) complexes show one irreversible one electron reduction wave at E{sup pc} = .1.35 and .1.15 V respectively, and the corresponding nickel(II) complexes show irreversible one-electron reduction wave at E{sup pc} = .1.25 and .1.22 V, respectively. The nickel(II) complexes show irreversible one-electron oxidation wave at Epa = +0.84 and +0.82 V, respectively. All the complexes were evaluated for in vitro antimicrobial activity against the human pathogenic bacteria and fungi.

  14. Hydrophobic, Hydrophilic, and Amphiphilic Polyglycocarbonates with Linear and Macrocyclic Architectures from Bicyclic Glycocarbonates Derived from CO2 and Glucoside

    KAUST Repository

    Pati, Debasis

    2017-02-09

    Two bicyclic glycocarbonates were synthesized in five steps from α-methyl-d-glucoside without resorting to phosgene or to its derivatives for the first time. The 4- and 6-positions of glucose were modified to introduce a six-membered carbonate ring, using CO as the carbonylating reagent; the 2- and 3-positions of the same glucoside substrate were first transformed into either methyl or triethylene glycol monomethyl ether groups to protect these positions from undesirable reactions and also to impart hydrophobicity in the first case and hydrophilicity in the second. The polymerization behavior of these bicyclic glycocarbonates was then investigated under different conditions. On the one hand, through ring-opening polymerization of the above monomers, linear polyglycocarbonate homopolymers and diblock copolymers were obtained initiated by p-methylbenzyl alcohol using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst; on the other hand, macrocyclic polyglycocarbonate homopolymers and diblock copolymers were grown using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) which served as zwitterionic initiator. The various architectures derived were all thoroughly characterized by NMR, GPC, and MALDI-tof and shown to exhibit the expected structure. Finally, the self-assembly of linear and macrocyclic amphiphilic copolyglycocarbonates in water was investigated and characterized by cryo-TEM.

  15. Hydrophobic, Hydrophilic, and Amphiphilic Polyglycocarbonates with Linear and Macrocyclic Architectures from Bicyclic Glycocarbonates Derived from CO2 and Glucoside

    KAUST Repository

    Pati, Debasis; Feng, Xiaoshuang; Hadjichristidis, Nikolaos; Gnanou, Yves

    2017-01-01

    Two bicyclic glycocarbonates were synthesized in five steps from α-methyl-d-glucoside without resorting to phosgene or to its derivatives for the first time. The 4- and 6-positions of glucose were modified to introduce a six-membered carbonate ring, using CO as the carbonylating reagent; the 2- and 3-positions of the same glucoside substrate were first transformed into either methyl or triethylene glycol monomethyl ether groups to protect these positions from undesirable reactions and also to impart hydrophobicity in the first case and hydrophilicity in the second. The polymerization behavior of these bicyclic glycocarbonates was then investigated under different conditions. On the one hand, through ring-opening polymerization of the above monomers, linear polyglycocarbonate homopolymers and diblock copolymers were obtained initiated by p-methylbenzyl alcohol using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst; on the other hand, macrocyclic polyglycocarbonate homopolymers and diblock copolymers were grown using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) which served as zwitterionic initiator. The various architectures derived were all thoroughly characterized by NMR, GPC, and MALDI-tof and shown to exhibit the expected structure. Finally, the self-assembly of linear and macrocyclic amphiphilic copolyglycocarbonates in water was investigated and characterized by cryo-TEM.

  16. Covalent lanthanide(III) macrocyclic complexes: the bonding nature and optical properties of a promising single antenna molecule.

    Science.gov (United States)

    Rabanal-León, Walter A; Páez-Hernández, Dayán; Arratia-Pérez, Ramiro

    2014-12-21

    The present work is focused on the elucidation of the electronic structure, bonding nature and optical properties of a series of low symmetry (C2) coordination compounds of type [Ln(III)HAM](3+), where "Ln(III)" are the trivalent lanthanide ions: La(3+), Ce(3+), Eu(3+) and Lu(3+), while "HAM" is the neutral six-nitrogen donor macrocyclic ligand [C22N6H26]. This systematic study has been performed in the framework of the Relativistic Density Functional Theory (R-DFT) and also using a multi-reference approach via the Complete Active Space (CAS) wavefunction treatment with the aim of analyzing their ground state and excited state electronic structures as well as electronic correlation. Furthermore, the use of the energy decomposition scheme proposed by Morokuma-Ziegler and the electron localization function (ELF) allows us to characterize the bonding between the lanthanide ions and the macrocyclic ligand, obtaining as a result a dative-covalent interaction. Due to a great deal of lanthanide optical properties and their technological applications, the absorption spectra of this set of coordination compounds were calculated using the time-dependent density functional theory (TD-DFT), where the presence of the intense Ligand to Metal Charge Transfer (LMCT) bands in the ultraviolet and visible region and the inherent f-f electronic transitions in the Near-Infra Red (NIR) region for some lanthanide ions allow us to propose these systems as "single antenna molecules" with potential applications in NIR technologies.

  17. Oxidative diversification of amino acids and peptides by small-molecule iron catalysis.

    Science.gov (United States)

    Osberger, Thomas J; Rogness, Donald C; Kohrt, Jeffrey T; Stepan, Antonia F; White, M Christina

    2016-09-08

    Secondary metabolites synthesized by non-ribosomal peptide synthetases display diverse and complex topologies and possess a range of biological activities. Much of this diversity derives from a synthetic strategy that entails pre- and post-assembly oxidation of both the chiral amino acid building blocks and the assembled peptide scaffolds. The vancomycin biosynthetic pathway is an excellent example of the range of oxidative transformations that can be performed by the iron-containing enzymes involved in its biosynthesis. However, because of the challenges associated with using such oxidative enzymes to carry out chemical transformations in vitro, chemical syntheses guided by these principles have not been fully realized in the laboratory. Here we report that two small-molecule iron catalysts are capable of facilitating the targeted C-H oxidative modification of amino acids and peptides with preservation of α-centre chirality. Oxidation of proline to 5-hydroxyproline furnishes a versatile intermediate that can be transformed to rigid arylated derivatives or flexible linear carboxylic acids, alcohols, olefins and amines in both monomer and peptide settings. The value of this C-H oxidation strategy is demonstrated in its capacity for generating diversity: four 'chiral pool' amino acids are transformed to twenty-one chiral unnatural amino acids representing seven distinct functional group arrays; late-stage C-H functionalizations of a single proline-containing tripeptide furnish eight tripeptides, each having different unnatural amino acids. Additionally, a macrocyclic peptide containing a proline turn element is transformed via late-stage C-H oxidation to one containing a linear unnatural amino acid.

  18. RECONSTRUCTING DIET COMPOSITION ON THE BASIS OF FECES IN A MOLLUSK-EATING WADER, THE KNOT CALIDRIS-CANUTUS

    NARCIS (Netherlands)

    DEKINGA, A; PIERSMA, T

    Methods are described to assess the molluscan diet of Knots feeding on intertidal flats in western Europe from their faecal output. The size distributions of two common bivalve prey, Macoma balthica and Cerastoderma edule, can be estimated from the heights of shell hinges retrieved from droppings.

  19. Reconstructing diet composition on the basis of faeces in a mollusc-eating wader, the Knot Calidris canutus

    NARCIS (Netherlands)

    Dekinga, A.; Piersma, T.

    1993-01-01

    Methods are described to assess the molluscan diet of Knots feeding on intertidal flats in western Europe from their faecal output. The size distributions of two common bivalve prey, Macoma balthica and Cerastoderma edule, can be estimated from the heights of shell hinges retrieved from droppings.

  20. Incidence and Identification of Root-Knot Nematode in Plastic-House Fields of Central Area of Korea

    Directory of Open Access Journals (Sweden)

    Hyoung Rai Ko

    2017-12-01

    Full Text Available To investigate occurrence of root-knot nematode (RKN in plastic house of central area of Korea, 132 soil samples were collected in cucumber, water melon, tomato, red pepper and strawberry fields from 2013 to 2015. Among 132 soil samples, 65 soil samples (49% were infested with RKN and mean density of RKN was 178 second-stage juveniles per 100 cm³ soil (min. 1 ~ max. 3,947. The frequency of RKN by regional was the highest in Chuncheon with 80%, followed by Cheonan (68%, Nonsan (36%, Buyeo (33% and Yesan (30%. The frequency of RKN by crops was the highest in tomato with 83%, followed by cucumber (61%, strawberry (41%, red pepper (30%, watermelon (26%. To identify the species of RKN, fifteen populations were selected for representative populations. As a phylogenetic analysis of 15 populations, southern root-knot nematode (Meloidogyne incognita, peanut root-knot nematode (M. arenaria and northern root-knot nematode (M. hapla were identified with 47%, 20% and 33% ratio, respectively. In crops, M. incognita, M. arenaria and M. hapla were detected in tomato, M. incognita and M. arenaria were detected in cucumber and watermelon, and M. hapla was detected in strawberry and lettuce. Thus, there should be a continuous management to major species of each crops to prevent dispersal of RKN damages.