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.)

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.

Preparations and crystal structures of 8 coordinate uranyl(VI) complexes having macrocyclic ligands derived from pyrroledicarboxialdehydes and diamines

International Nuclear Information System (INIS)

Komagine, J.; Takeda, M.; Takahashi, M.

2006-01-01

Six 8-coordinate uranyl(VI) complexes with macrocyclic Schiff base ligands derived from 2,6-pyrroledicarboxialdehyde and diamines are prepared and the crystal structures for two of them are determined focusing on the relation between the size of the ligands and U-N bond distances. No difference in average uranyl bond distances and bond angles are observed between [UO 2 (bipytn)](a) and [UO 2 (bipydmtn)](b). U-N bonds of these complexes are, however, not equal; the U-N(pyrrole) bonds [2.45(a), 2.44(b) A] are much shorter than the U-N(imine) bonds [2.67(a), 2.67(b) A]. (author)

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.

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

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.

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

Uranyl-organic assemblies with the macrocyclic ligand 1, 4, 8, 11-tetra-aza-cyclo-tetradecane-1, 4, 8, 11-tetraacetate (TETA)

International Nuclear Information System (INIS)

Thuery, Pierre

2010-01-01

Three uranyl ion complexes obtained from the reaction of uranyl nitrate hexahydrate and 1, 4, 8, 11-tetra-aza-cyclo-tetradecane-1, 4, 8, 11-tetraacetic acid (H 4 TETA) were characterized by their crystal structure. The centrosymmetric macrocycle, in the [3434] conformation with either carbon or nitrogen atoms as corners, is zwitterionic, with four carboxylate groups and two or four protonated nitrogen atoms. The complexes [(UO 2 ) 2 (H 2 TETA)(C 2 O 4 )(H 2 O) 2 ] (1) and [UO 2 (H 4 TETA)(H 2 O)].NO 3 .Cl (2) were synthesized under hydrothermal conditions and 1 includes additional oxalate ligands generated in situ. Both compounds are two-dimensional polymers in which the four-fold monodentate macrocyclic ligand unites either four uranyl oxalate dinuclear species (1) or isolated uranyl ions (2). Complex 3, [UO 2 (H 2 TETA)(H 2 O)].6H 2 O, was obtained at room temperature and, although it displays the same stoichiometry as 2, it differs from it by being a three-dimensional framework. Both 2 and 3 present channels containing either counter-ions or water molecules. As often observed, the water content of the low-temperature species, 3, is higher than that of the high-temperature one, 2. (author)

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)

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)

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

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)

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.

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)

Hyperpolarized 89Y NMR spectroscopic detection of yttrium ion and DOTA macrocyclic ligand complexation: pH dependence and Y-DOTA intermediates

Science.gov (United States)

Ferguson, Sarah; Kiswandhi, Andhika; Niedbalski, Peter; Parish, Christopher; Kovacs, Zoltan; Lumata, Lloyd

Dissolution dynamic nuclear polarization (DNP) is a rapidly emerging physics technique used to enhance the signal strength in nuclear magnetic resonance (NMR) and imaging (MRI) experiments for nuclear spins such as yttrium-89 by >10,000-fold. One of the most common and stable MRI contrast agents used in the clinic is Gd-DOTA. In this work, we have investigated the binding of the yttrium and DOTA ligand as a model for complexation of Gd ion and DOTA ligand. The macrocyclic ligand DOTA is special because its complexation with lanthanide ions such as Gd3+ or Y3+ is highly pH dependent. Using this physics technology, we have tracked the complexation kinetics of hyperpolarized Y-triflate and DOTA ligand in real-time and detected the Y-DOTA intermediates. Different kinds of buffers were used (lactate, acetate, citrate, oxalate) and the pseudo-first order complexation kinetic calculations will be discussed. The authors would like to acknowledge the support by US Dept of Defense Award No. W81XWH-14-1-0048 and Robert A. Welch Foundation Grant No. AT-1877.

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)

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.

Macrocyclic ligand decorated ordered mesoporous silica with large-pore and short-channel characteristics for effective separation of lithium isotopes: synthesis, adsorptive behavior study and DFT modeling.

Science.gov (United States)

Liu, Yuekun; Liu, Fei; Ye, Gang; Pu, Ning; Wu, Fengcheng; Wang, Zhe; Huo, Xiaomei; Xu, Jian; Chen, Jing

2016-10-18

Effective separation of lithium isotopes is of strategic value which attracts growing attention worldwide. This study reports a new class of macrocyclic ligand decorated ordered mesoporous silica (OMS) with large-pore and short-channel characteristics, which holds the potential to effectively separate lithium isotopes in aqueous solutions. Initially, a series of benzo-15-crown-5 (B15C5) derivatives containing different electron-donating or -withdrawing substituents were synthesized. Extractive separation of lithium isotopes in a liquid-liquid system was comparatively studied, highlighting the effect of the substituent, solvent, counter anion and temperature. The optimal NH 2 -B15C5 ligands were then covalently anchored to a short-channel SBA-15 OMS precursor bearing alkyl halides via a post-modification protocol. Adsorptive separation of the lithium isotopes was fully investigated, combined with kinetics and thermodynamics analysis, and simulation by using classic adsorption isotherm models. The NH 2 -B15C5 ligand functionalized OMSs exhibited selectivity to lithium ions against other alkali metal ions including K(i). Additionally, a more efficient separation of lithium isotopes could be obtained at a lower temperature in systems with softer counter anions and solvents with a lower dielectric constant. The highest value separation factor (α = 1.049 ± 0.002) was obtained in CF 3 COOLi aqueous solution at 288.15 K. Moreover, theoretical computation based on the density functional theory (DFT) was performed to elucidate the complexation interactions between the macrocyclic ligands and lithium ions. A suggested mechanism involving an isotopic exchange equilibrium was proposed to describe the lithium isotope separation by the functionalized OMSs.

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.

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

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.

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...

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.

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

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.

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...

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.

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".

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.

Repurposing a Library of Human Cathepsin L Ligands: Identification of Macrocyclic Lactams as Potent Rhodesain and Trypanosoma brucei Inhibitors.

Science.gov (United States)

Giroud, Maude; Dietzel, Uwe; Anselm, Lilli; Banner, David; Kuglstatter, Andreas; Benz, Jörg; Blanc, Jean-Baptiste; Gaufreteau, Delphine; Liu, Haixia; Lin, Xianfeng; Stich, August; Kuhn, Bernd; Schuler, Franz; Kaiser, Marcel; Brun, Reto; Schirmeister, Tanja; Kisker, Caroline; Diederich, François; Haap, Wolfgang

2018-04-26

Rhodesain (RD) is a parasitic, human cathepsin L (hCatL) like cysteine protease produced by Trypanosoma brucei ( T. b.) species and a potential drug target for the treatment of human African trypanosomiasis (HAT). A library of hCatL inhibitors was screened, and macrocyclic lactams were identified as potent RD inhibitors ( K i < 10 nM), preventing the cell-growth of Trypanosoma brucei rhodesiense (IC 50 < 400 nM). SARs addressing the S2 and S3 pockets of RD were established. Three cocrystal structures with RD revealed a noncovalent binding mode of this ligand class due to oxidation of the catalytic Cys25 to a sulfenic acid (Cys-SOH) during crystallization. The P-glycoprotein efflux ratio was measured and the in vivo brain penetration in rats determined. When tested in vivo in acute HAT model, the compounds permitted up to 16.25 (vs 13.0 for untreated controls) mean days of survival.

A new family of NxOy pyridine-containing macrocycles: synthesis and characterization of their Y(III), Ln(III), Zn(II), and Cd(II) coordination compounds

International Nuclear Information System (INIS)

Lodeiro, C.; Bastida, R.; Bertolo, E.; Rodriguez, A.

2004-01-01

Reaction between 2,6-bis(2-formylphenoxymethyl)pyridine and N,N-bis(3-aminopropyl)methylamine or tris(2-aminoethyl)amine has been used as the starting point for the synthesis of seven oxa-aza macrocyclic ligands, five of them never reported previously. They all feature different pendant arms, which provide a wide range of coordination possibilities. The Schiff base macrocycles L 1 and L 4 and their reduced ligands L 2 and L 5 are derived from 2,6-bis(2-formylphenoxymethyl)pyridine and tris(2-aminoethyl)amine or N,N-bis(3-aminopropyl)methylamine, respectively. The reaction of L 1 with salicylaldehyde forms L 3 , which features an imine bond in the pendant arm. The ligand L 5 has been the precursor for the pendant-armed L 6 and L 7 , by alkylation of the free NH groups with methyl-imidazole or methyl-indole. By a template or a nontemplate approach, we have synthesized different mono- and dinuclear complexes with Y(III), Ln(III), Zn(II), and Cd(II) cations. Both the free macrocyclic ligands and their corresponding metal complexes have been characterized by microanalysis, IR, UV-vis, 1 H and 13 C NMR spectroscopy, FAB mass spectrometry, MS electrospray, and conductivity measurements. (author)

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)

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.

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

“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.

Una introducción a los números complejos

OpenAIRE

Rivero, Francisco

2004-01-01

Una introducción a los números complejos (Rivero, Francisco) Historia de los números complejos 1.1 Los inicios del álgebra 1.2 Cardano 1.3 Bombelli 1.4 Números imaginarios Álgebra de los números complejos 2.1 Definición de número complejo 2.2 Suma de números complejos 2.3 Producto de números complejos 2.4 Representación geométrica 2.5 La forma polar 2.6 Potencias y raíces de números complejos 44 ciens-004 Primera Nivel monográ...

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.

Complejo Oficinas Cabanyal

OpenAIRE

CAMPOS CARCELLER, RAMÓN

2015-01-01

El proyecto es un complejo de oficinas con usos complementarios. Está ubicado en el barrio marítimo del Cabañal de Valencia. La zona más pública del complejo está abierta al barrio y permite el uso de sus instalaciones por parte de los vecinos. En esta planta se encuentran los usos complementarios: cafetería, restaurante, salón de actos, biblioteca, zonas de estudio en grupo, salas de exposiciones y guardería. La planta baja se divide en tres zonas: edificio de hall de las oficinas y comercio...

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.

Synthesis, spectroscopic and biological activities studies of acyclic and macrocyclic mono and binuclear metal complexes containing a hard-soft Schiff base.

Science.gov (United States)

Abou-Hussein, Azza A A; Linert, Wolfgang

2012-09-01

Mono- and bi-nuclear acyclic and macrocyclic complexes with hard-soft Schiff base, H(2)L, ligand derived from the reaction of 4,6-diacetylresorcinol and thiocabohydrazide, in the molar ratio 1:2 have been prepared. The H(2)L ligand reacts with Co(II), Ni(II), Cu(II), Zn(II), Mn(II) and UO(2)(VI) nitrates, VO(IV) sulfate and Ru(III) chloride to get acyclic binuclear complexes except for VO(IV) and Ru(III) which gave acyclic mono-nuclear complexes. Reaction of the acyclic mono-nuclear VO(IV) and Ru(III) complexes with 4,6-diacetylresorcinol afforded the corresponding macrocyclic mono-nuclear VO(IV) and Ru(IIII) complexes. Template reactions of the 4,6-diacetylresorcinol and thiocarbohydrazide with either VO(IV) or Ru(III) salts afforded the macrocyclic binuclear VO(IV) and Ru(III) complexes. The Schiff base, H(2)L, ligand acts as dibasic with two NSO-tridentate sites and can coordinate with two metal ions to form binuclear complexes after the deprotonation of the hydrogen atoms of the phenolic groups in all the complexes, except in the case of the acyclic mononuclear Ru(III) and VO(IV) complexes, where the Schiff base behaves as neutral tetradentate chelate with N(2)S(2) donor atoms. The ligands and the metal complexes were characterized by elemental analysis, IR, UV-vis (1)H-NMR, thermal gravimetric analysis (TGA) and ESR, as well as the measurements of conductivity and magnetic moments at room temperature. Electronic spectra and magnetic moments of the complexes indicate the geometries of the metal centers are either tetrahedral, square planar or octahedral. Kinetic and thermodynamic parameters were calculated using Coats-Redfern equation, for the different thermal decomposition steps of the complexes. The ligands and the metal complexes were screened for their antimicrobial activity against Staphylococcus aureus as Gram-positive bacteria, and Pseudomonas fluorescens as Gram-negative bacteria in addition to Fusarium oxysporum fungus. Most of the complexes exhibit

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.

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...

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

Experimental and Computational Studies of the Macrocyclic Effect of an Auxiliary Ligand on Electron and Proton Transfers Within Ternary Copper(II)-Histidine Complexes

International Nuclear Information System (INIS)

Song, Tao; Lam, Corey; Ng, Dominic C.; Orlova, G.; Laskin, Julia; Fang, De-Cai; Chu, Ivan K.

2009-01-01

The dissociation of [Cu II (L)His] -2+ complexes [L = diethylenetriamine (dien) or 1,4,7-triazacyclononane (9-aneN 3 )] bears a strong resemblance to the previously reported behavior of [Cu II (L)GGH] -2+ complexes. We have used low energy collision-induced dissociation experiments and density functional theory (DFT) calculations at the B3LYP/6-31+G(d) level to study the macrocyclic effect of the auxiliary ligands on the formation of His -+ from prototypical [Cu II (L)His] -2+ systems. DFT revealed that the relative energy barriers of the same electron transfer (ET) dissociation pathways of [Cu II (9-aneN 3 )His] -2+ and [Cu II (dien)His] -2+ are very similar, with the ET reactions of [Cu II (9-aneN 3 )His] -2+ leading to the generation of two distinct His -+ species; in contrast, the proton transfer (PT) dissociation pathways of [Cu II (9-aneN 3 )His] -2+ and [Cu II (dien)His] -2+ differ considerably. The PT reactions of [Cu II (9-aneN 3 )His] -2+ are associated with substantially higher barriers (>13 kcal/mol) than those of [Cu II (dien)His] -2+ . Thus, the sterically encumbered auxiliary 9-aneN3 ligand facilitates ET reactions while moderating PT reactions, allowing the formation of hitherto non-observable histidine radical cations.

New lanthanide(III) complexes of chiral nonadendate macrocyclic amine derived from (1R,2R)-1,2-diaminocyclohexane and 2,6-diformyl-4-methylphenol

Energy Technology Data Exchange (ETDEWEB)

Paluch, Marta [Department of Chemistry, University of Wroclaw, 14 F. Joliot-Curie, 50-383 Wroclaw (Poland); Lisowski, Jerzy [Department of Chemistry, University of Wroclaw, 14 F. Joliot-Curie, 50-383 Wroclaw (Poland)], E-mail: jurekl@wchuwr.chem.uni.wroc.pl

2008-02-28

The series of complexes [LnH{sub 4}L(NO{sub 3}){sub 2}](NO{sub 3}){sub 2}.nH{sub 2}O (Ln = La, Ce, Pr, Nd, Gd, Tb, Ho, Er, Tm) of the positively charged protonated form of a chiral macrocyclic amine H{sub 4}L{sup +}, derived from the 3 + 3 condensation product of (1R,2R)-1,2-diaminocyclohexane and 2,6-diformyl-4-methylphenol, have been synthesized. The series of complexes Na{sub x}[LnL](X){sub y}(OH){sub x-y}.n(solv) (X = NO{sup 3-} or Cl{sup -}, and Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) of the deprotonated anionic form of the ligand, L{sup 3-}, have also been synthesised. The complexes have been characterised by elemental analyses, {sup 1}H NMR and ESI MS spectra. The X-ray crystal structures of the [LaH{sub 4}L(NO{sub 3}){sub 2}](NO{sub 3}){sub 2}.5CH{sub 3}OH and [GdH{sub 4}L(NO{sub 3}){sub 2}](NO{sub 3}){sub 2}.5CH{sub 3}OH complexes have been determined. The two complexes are isostructural, and the protonated macrocycle acts as pentadentate ligand. The Ln(III) ion is bound to three phenolate oxygen atoms and two amine nitrogen atoms of the macrocyclic ligand and its coordination sphere is completed by the two axial bidendate nitrate anions.

Designer Ligands. Part 13. Synthesis and Catalytic Activity of ...

African Journals Online (AJOL)

Copper(I), copper(II), cobalt(II) and zinc(II) complexes of a macrocyclic, multidentate Schiff-base ligand have been prepared and, with the exception of the zinc(II) complex, have been shown to exhibit biomimetic catecholase activity. Keywords: Copper(II);Cobalt(II); Zinc(II); Biomimetic complexes; Catecholase activity

Evaluation of macrocyclic hydroxyisophthalamide ligands as chelators for zirconium-89.

Science.gov (United States)

Bhatt, Nikunj B; Pandya, Darpan N; Xu, Jide; Tatum, David; Magda, Darren; Wadas, Thaddeus J

2017-01-01

The development of bifunctional chelators (BFCs) for zirconium-89 immuno-PET applications is an area of active research. Herein we report the synthesis and evaluation of octadentate hydroxyisophthalamide ligands (1 and 2) as zirconium-89 chelators. While both radiometal complexes could be prepared quantitatively and with excellent specific activity, preparation of 89Zr-1 required elevated temperature and an increased reaction time. 89Zr-1 was more stable than 89Zr-2 when challenged in vitro by excess DTPA or serum proteins and in vivo during acute biodistribution studies. Differences in radiometal complex stability arise from structural changes between the two ligand systems, and suggest further ligand optimization is necessary to enhance 89Zr chelation.

Evaluation of macrocyclic hydroxyisophthalamide ligands as chelators for zirconium-89.

Directory of Open Access Journals (Sweden)

Nikunj B Bhatt

Full Text Available The development of bifunctional chelators (BFCs for zirconium-89 immuno-PET applications is an area of active research. Herein we report the synthesis and evaluation of octadentate hydroxyisophthalamide ligands (1 and 2 as zirconium-89 chelators. While both radiometal complexes could be prepared quantitatively and with excellent specific activity, preparation of 89Zr-1 required elevated temperature and an increased reaction time. 89Zr-1 was more stable than 89Zr-2 when challenged in vitro by excess DTPA or serum proteins and in vivo during acute biodistribution studies. Differences in radiometal complex stability arise from structural changes between the two ligand systems, and suggest further ligand optimization is necessary to enhance 89Zr chelation.

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

Synthesis and Crystal Structure of Dinuclear Cadmium(II) Complex with Dipodal Ligand

International Nuclear Information System (INIS)

Kang, Young Jin; Moon, Suk Hee; Byun, Jong Chul; Park, Ki Min

2010-01-01

the preparation and structural characterization of the discrete dinuclear cadmium(II) complex with the formula [Cd(μ 2 -Cl) 2 Cl 2 ]· 2 (H 2 O)·0.5(CH 3 OH)·0.5(CH 3 CN) obtained from the reaction of CdCl 2 ·2.5H 2 O and podal ligand with quinoline end-groups has been reported. In two cadmium ions are triply bridged by two chloride and one donor atoms of ligand L and adopt distorted pentagonal bipyramidal geometries with seven coordinations. It is notable that example of discrete dinuclear complex which one podal ligand accommodates simultaneously two metal ions is very rare. During the last four decades, the chemistry of macrocyclic and non-cyclic polyethers has attracted an increasing attention because of their selective complexation, cation transport and enzyme chemistry. In the field of coordination chemistry, generally, non-cyclic, crown-type polyether affords the low complexation ability because of its conformational freedom while macrocyclic polyethers such as 18-crown-6 show the excellent complexing ability

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.

Dissociation kinetics of open-chain and macrocyclic gadolinium(III)-aminopolycarboxylate complexes related to magnetic resonance imaging: catalytic effect of endogenous ligands.

Science.gov (United States)

Baranyai, Zsolt; Pálinkás, Zoltán; Uggeri, Fulvio; Maiocchi, Alessandro; Aime, Silvio; Brücher, Ernő

2012-12-14

The kinetics of the metal exchange reactions between open-chain Gd(DTPA)(2-) and Gd(DTPA-BMA), macrocyclic Gd(DOTA)(-) and Gd(HP-DO3A) complexes, and Cu(2+)  ions were investigated in the presence of endogenous citrate, phosphate, carbonate and histidinate ligands in the pH range 6-8 in NaCl (0.15 M) at 25 °C. The rates of the exchange reactions of Gd(DTPA)(2-) and Gd(DTPA-BMA) are independent of the Cu(2+) concentration in the presence of citrate and the reactions occur via the dissociation of Gd(3+)  complexes catalyzed by the citrate ions. The HCO(3)(-)/CO(3)(2-) and H(2)PO(4)(-) ions also catalyze the dissociation of complexes. The rates of the dissociation of Gd(DTPA-BMA), catalyzed by the endogenous ligands, are about two orders of magnitude higher than those of the Gd(DTPA)(2-). In fact near to physiological conditions the bicarbonate and carbonate ions show the largest catalytic effect, that significantly increase the dissociation rate of Gd(DTPA-BMA) and make the higher pH values (when the carbonate ion concentration is higher) a risk-factor for the dissociation of complexes in body fluids. The exchange reactions of Gd(DOTA)(-) and Gd(HP-DO3A) with Cu(2+) occur through the proton assisted dissociation of complexes in the pH range 3.5-5 and the endogenous ligands do not affect the dissociation rates of complexes. More insights into the interaction scheme between Gd(DTPA-BMA) and Gd(DTPA)(2-) and endogenous ligands have been obtained by acquiring the (13)C NMR spectra of the corresponding diamagnetic Y(III)-complexes, indicating the increase of the rates of the intramolecular rearrangements in the presence of carbonate and citrate ions. The herein reported results may have implications in the understanding of the etiology of nephrogenic systemic fibrosis, a rare disease that has been associated to the administration of Gd-containing agents to patients with impaired renal function. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Fabrication of reduced graphene oxide/macrocyclic cobalt complex nanocomposites as counter electrodes for Pt-free dye-sensitized solar cells

Science.gov (United States)

Tsai, Chih-Hung; Shih, Chun-Jyun; Wang, Wun-Shiuan; Chi, Wen-Feng; Huang, Wei-Chih; Hu, Yu-Chung; Yu, Yuan-Hsiang

2018-03-01

In this study, macrocyclic Co complexes were successfully grafted onto graphene oxide (GO) to produce GO/Co nanocomposites with a large surface area, high electrical conductivity, and excellent catalytic properties. The novel GO/Co nanocomposites were applied as counter electrodes for Pt-free dye-sensitized solar cells (DSSCs). Various ratios of macrocyclic Co complexes were used as the reductant to react with the GO, with which the surface functional groups of the GO were reduced and the macrocyclic ligand of the Co complexes underwent oxidative dehydrogenation, after which the conjugated macrocyclic Co systems were grafted onto the surface of the reduced GO to form GO/Co nanocomposites. The surface morphology, material structure, and composition of the GO/Co composites and their influences on the power-conversion efficiency of DSSC devices were comprehensively investigated. The results showed that the GO/Co (1:10) counter electrode (CE) exhibited an optimal power conversion efficiency of 7.48%, which was higher than that of the Pt CE. The GO/Co (1:10) CE exhibited superior electric conductivity, catalytic capacity, and redox capacity. Because GO/Co (1:10) CEs are more efficient and cheaper than Pt CEs, they could potentially be used as a replacement for Pt electrodes.

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.

Potent Inhibitors of the Hepatitis C Virus NS3 Protease: Design and Synthesis of Macrocyclic Substrate-Based [beta]-Strand Mimics

Energy Technology Data Exchange (ETDEWEB)

Goudreau, Nathalie; Brochu, Christian; Cameron, Dale R.; Duceppe, Jean-Simon; Faucher, Anne-Marie; Ferland, Jean-Marie; Grand-Maître, Chantal; Poirier, Martin; Simoneau, Bruno; Tsantrizos, Youla S. (Boehringer)

2008-06-30

The virally encoded NS3 protease is essential to the life cycle of the hepatitis C virus (HCV), an important human pathogen causing chronic hepatitis, cirrhosis of the liver, and hepatocellular carcinoma. The design and synthesis of 15-membered ring {beta}-strand mimics which are capable of inhibiting the interactions between the HCV NS3 protease enzyme and its polyprotein substrate will be described. The binding interactions between a macrocyclic ligand and the enzyme were explored by NMR and molecular dynamics, and a model of the ligand/enzyme complex was developed.

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.

¿Inecuaciones en los complejos?

OpenAIRE

Guacaneme, Edgar Alberto

2000-01-01

En tanto profesores de matemáticas, presentamos aquí una reflexión que intenta cuestionar la imposibilidad de definir y solucionar inecuaciones en los números complejos. Así, en primer lugar, asumimos como objeto de provocación la existencia de un conjunto-solución para una determinada "inecuación" de variable compleja. En segundo lugar, como consecuencia de haber cuestionado el uso de la relación de orden usual de los números reales en el campo de los números complejos, recapitulamos un crit...

Magnetic behavior of MnPS3 phases intercalated by [Zn2L]2+ (LH2: macrocyclic ligand obtained by condensation of 2-hydroxy-5-methyl-1,3-benzenedicarbaldehyde and 1,2-diaminobenzene)

International Nuclear Information System (INIS)

Spodine, E.; Valencia-Galvez, P.; Fuentealba, P.; Manzur, J.; Ruiz, D.; Venegas-Yazigi, D.; Paredes-Garcia, V.; Cardoso-Gil, R.; Schnelle, W.; Kniep, R.

2011-01-01

The intercalation of the cationic binuclear macrocyclic complex [Zn 2 L] 2+ (LH 2 : macrocyclic ligand obtained by the template condensation of 2-hydroxy-5-methyl-1,3-benzenedicarbaldehyde and 1,2-diaminobenzene) was achieved by a cationic exchange process, using K 0.4 Mn 0.8 PS 3 as a precursor. Three intercalated materials were obtained and characterized: (Zn 2 L) 0.05 K 0.3 Mn 0.8 PS 3 (1), (Zn 2 L) 0.1 K 0.2 Mn 0.8 PS 3 (2) and (Zn 2 L) 0.05 K 0.3 Mn 0.8 PS 3 (3), the latter phase being obtained by an assisted microwave radiation process. The magnetic data permit to estimate the Weiss temperature θ of ∼-130 K for (1); ∼-155 K for (2) and ∼-130 K for (3). The spin canting present in the potassium precursor remains unperturbed in composite (3), and spontaneous magnetization is observed under 50 K in both materials. However composites (1) and (2) do not present this spontaneous magnetization at low temperatures. The electronic properties of the intercalates do not appear to be significantly altered. The reflectance spectra of the intercalated phases (1), (2) and (3) show a gap value between 1.90 and 1.80 eV, lower than the value observed for the K 0.4 Mn 0.8 PS 3 precursor of 2.8 eV. -- Graphical Abstract: Microwave assisted synthesis was used to obtain an intercalated MnPS 3 phase with a binuclear Zn(II) macrocyclic complex. A comparative magnetic study of the composites obtained by assisted microwave and traditional synthetic methods is reported. Display Omitted Highlights: → A rapid and efficient preparation of intercalated MnPS 3 composites by assisted microwave synthesis is described. → The exchange of potassium ions of the precursor by the macrocyclic Zn(II) complex is partial. → The composite obtained by assisted microwave synthesis retains the spontaneous magnetization, observed in the low temperature range of the magnetic susceptibility of the potassium precursor. → The materials obtained by the conventional method loose the spontaneous

Syntheses, structures, and properties of imidazolate-bridged Cu(II)-Cu(II) and Cu(II)-Zn(II) dinuclear complexes of a single macrocyclic ligand with two hydroxyethyl pendants.

Science.gov (United States)

Li, Dongfeng; Li, Shuan; Yang, Dexi; Yu, Jiuhong; Huang, Jin; Li, Yizhi; Tang, Wenxia

2003-09-22

The imidazolate-bridged homodinuclear Cu(II)-Cu(II) complex, [(CuimCu)L]ClO(4).0.5H(2)O (1), and heterodinuclear Cu(II)-Zn(II) complex, [(CuimZnL(-)(2H))(CuimZnL(-)(H))](ClO(4))(3) (2), of a single macrocyclic ligand with two hydroxyethyl pendants, L (L = 3,6,9,16,19,22-hexaaza-6,19-bis(2-hydroxyethyl)tricyclo[22,2,2,2(11,14)]triaconta-1,11,13,24,27,29-hexaene), have been synthesized as possible models for copper-zinc superoxide dismutase (Cu(2),Zn(2)-SOD). Their crystal structures analyzed by X-ray diffraction methods have shown that the structures of the two complexes are markedly different. Complex 1 crystallizes in the orthorhombic system, containing an imidazolate-bridged dicopper(II) [Cu-im-Cu](3+) core, in which the two copper(II) ions are pentacoordinated by virtue of an N4O environment with a Cu.Cu distance of 5.999(2) A, adopting the geometry of distorted trigonal bipyramid and tetragonal pyramid, respectively. Complex 2 crystallizes in the triclinic system, containing two similar Cu-im-Zn cores in the asymmetric unit, in which both the Cu(II) and Zn(II) ions are pentacoordinated in a distorted trigonal bipyramid geometry, with the Cu.Zn distance of 5.950(1)/5.939(1) A, respectively. Interestingly, the macrocyclic ligand with two arms possesses a chairlike (anti) conformation in complex 1, but a boatlike (syn) conformation in complex 2. Magnetic measurements and ESR spectroscopy of complex 1 have revealed the presence of an antiferromagnetic exchange interaction between the two Cu(II) ions. The ESR spectrum of the Cu(II)-Zn(II) heterodinuclear complex 2 displayed a typical signal for mononuclear trigonal bipyramidal Cu(II) complexes. From pH-dependent ESR and electronic spectroscopic studies, the imidazolate bridges in the two complexes have been found to be stable over broad pH ranges. The cyclic voltammograms of the two complexes have been investigated. Both of the two complexes can catalyze the dismutation of superoxide and show rather high activity.

Mutual control of axial and equatorial ligands: model studies with [Ni]-bacteriochlorophyll-a.

Science.gov (United States)

Yerushalmi, Roie; Noy, Dror; Baldridge, Kim K; Scherz, Avigdor

2002-07-17

Modification of the metal's electronic environment by ligand association and dissociation in metalloenzymes is considered cardinal to their catalytic activity. We have recently presented a novel system that utilizes the bacteriochlorophyll (BChl) macrocycle as a ligand and reporter. This system allows for charge mobilization in the equatorial plane and experimental estimate of changes in the electronic charge density around the metal with no modification of the metal's chemical environment. The unique spectroscopy, electrochemistry and coordination chemistry of [Ni]-bacteriochlorophyll ([Ni]-BChl) enable us to follow directly fine details and steps involved in the function of the metal redox center. This approach is utilized here whereby electro-chemical reduction of [Ni]-BChl to the monoanion [Ni]-BChl(-) results in reversible dissociation of biologically relevant axial ligands. Similar ligand dissociation was previously detected upon photoexcitation of [Ni]-BChl (Musewald, C.; Hartwich, G.; Lossau, H.; Gilch, P.; Pollinger-Dammer, F.; Scheer, H.; Michel-Beyerle, M. E. J. Phys. Chem. B 1999, 103, 7055-7060 and Noy, D.; Yerushalmi, R.; Brumfeld, V.; Ashur, I.; Baldridge, K. K.; Scheer, H.; Scherz, A. J. Am. Chem. Soc. 2000, 122, 3937-3944). The electrochemical measurements and quantum mechanical (QM) calculations performed here for the neutral, singly reduced, monoligated, and singly reduced, monoligated [Ni]-BChl suggest the following: (a) Electroreduction, although resulting in a pi anion [Ni]-BChl(-) radical, causes electron density migration to the [Ni]-BChl core. (b) Reduction of nonligated [Ni]-BChl does not change the macrocycle conformation, whereas axial ligation results in a dramatic expansion of the metal core and a flattening of the highly ruffled macrocycle conformation. (c) In both the monoanion and singly excited [Ni]-BChl ([Ni]-BChl*), the frontier singly occupied molecular orbital (SOMO) has a small but nonnegligible metal character. Finally, (d

Preparation and characterization of electroluminescent devices based on complexes of β-diketonates of Tb3+, Eu3+, Gd3+ ions with macrocyclic ligands and UO22+ films

International Nuclear Information System (INIS)

Gibelli, Edison Bessa

2010-01-01

Complexes containing Rare Earth ions are of great interest in the manufacture of electro luminescent devices as organic light emitting devices (OLED). These devices, using rare earth trivalent ions (TR 3+ ) as emitting centers, show high luminescence with extremely fine spectral bands due to the structure of their energy levels, long life time and high quantum efficiency. This work reports the preparation of Rare Earth β-diketonate complexes (Tb 3+ , Eu 3+ and Gd 3+ ) and (tta - thenoyltrifluoroacetonate and acac - acetylacetonate) containing a ligand macrocyclic crown ether (DB18C6 - dibenzo18coroa6) and polymer films of UO 2 2+ . The materials were characterized by complexometric titration with EDTA, CH elemental analysis, near infrared absorption spectroscopy, thermal analysis, X-ray diffraction (powder method) and luminescence spectroscopy. For manufacturing the OLED it was used the technique of deposition of thin films by physical vapor (PVD, Physical Vapor Deposition). (author)

A macrocyclic ligand as receptor and Zn(II)-complex receptor for anions in water: binding properties and crystal structures.

Science.gov (United States)

Ambrosi, Gianluca; Formica, Mauro; Fusi, Vieri; Giorgi, Luca; Macedi, Eleonora; Micheloni, Mauro; Paoli, Paola; Pontellini, Roberto; Rossi, Patrizia

2011-02-01

Binding properties of 24,29-dimethyl-6,7,15,16-tetraoxotetracyclo[19.5.5.0(5,8).0(14,17)]-1,4,9,13,18,21,24,29-octaazaenatriaconta-Δ(5,8),Δ(14,17)-diene ligand L towards Zn(II) and anions, such as the halide series and inorganic oxoanions (phosphate (Pi), sulfate, pyrophosphate (PPi), and others), were investigated in aqueous solution; in addition, the Zn(II)/L system was tested as a metal-ion-based receptor for the halide series. Ligand L is a cryptand receptor incorporating two squaramide functions in an over-structured chain that connects two opposite nitrogen atoms of the Me(2)[12]aneN(4) polyaza macrocyclic base. It binds Zn(II) to form mononuclear species in which the metal ion, coordinated by the Me(2)[12]aneN(4) moiety, lodges inside the three-dimensional cavity. Zn(II)-containing species are able to bind chloride and fluoride at the physiologically important pH value of 7.4; the anion is coordinated to the metal center but the squaramide units play the key role in stabilizing the anion through a hydrogen-bonding network; two crystal structures reported here clearly show this aspect. Free L is able to bind fluoride, chloride, bromide, sulfate, Pi, and PPi in aqueous solution. The halides are bound at acidic pH, whereas the oxoanions are bound in a wide range of pH values ranging from acidic to basic. The cryptand cavity, abundant in hydrogen-bonding sites at all pH values, allows excellent selectivity towards Pi to be achieved mainly at physiological pH 7.4. By joining amine and squaramide moieties and using this preorganized topology, it was possible, with preservation of the solubility of the receptor, to achieve a very wide pH range in which oxoanions can be bound. The good selectivity towards Pi allows its discrimination in a manner not easily obtainable with nonmetallic systems in aqueous environment. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Antitenascin antibody 81C6 armed with {sup 177}Lu: in vivo comparison of macrocyclic and acyclic ligands

Energy Technology Data Exchange (ETDEWEB)

Yordanov, Alexander T. [Department of Radiology, Duke University Medical Center Durham, NC 27710 (United States); Hens, Marc [Department of Radiology, Duke University Medical Center Durham, NC 27710 (United States); Pegram, Charles [Department of Pathology, Duke University Medical Center Durham, NC 27710 (United States); Bigner, Darell D. [Department of Pathology, Duke University Medical Center Durham, NC 27710 (United States); Zalutsky, Michael R. [Department of Radiology, Duke University Medical Center Durham, NC 27710 (United States)]. E-mail: zalut001@mc.duke.edu

2007-02-15

Introduction: When labeled with iodine-131, the antitenascin monoclonal antibody (mAb) 81C6 has shown promise as a targeted radiotherapeutic in patients with brain tumors. Because of its more favorable {gamma}-ray properties, lutetium-177 might be a better low-energy {beta}-emitter for this type of therapy. Materials and Methods: Chimeric 81C6 (ch81C6) was labeled with {sup 177}Lu using the acyclic 1B4M ligand and the macrocyclic ligands NHS-DOTA and MeO-DOTA and evaluated for binding to tenascin. Three paired-label tissue distribution experiments were performed in normal mice receiving one of the {sup 177}Lu-labeled immunoconjugates plus {sup 125}I-labeled ch81C6 labeled using Iodogen. Paired-label experiments in athymic mice bearing subcutaneous D54 MG human glioma xenografts were done to directly compare the biodistribution of ch81C6-1B4M-{sup 177}Lu and {sup 125}I-labeled ch81C6, and ch81C6-MeO-DOTA-{sup 177}Lu and {sup 125}I-labeled ch81C6. Similar comparisons were done using murine (mu) instead of ch81C6. The primary parameter utilized for evaluation was the {sup 177}Lu/{sup 125}I uptake ratio in each tissue. Results: In the studies performed in normal mice, the NHS-DOTA ligand yielded the highest {sup 177}Lu/{sup 125}I uptake ratios in tissues indicative of loss of label from the chelate; for this reason, only 1B4M and MeO-DOTA were evaluated further. The {sup 177}Lu/{sup 125}I ratio in bone increased gradually with time for the chimeric conjugates; however, there were no significant differences between ch81C6-1B4M-DTPA-{sup 177}Lu and ch81C6-MeO-DOTA-{sup 177}Lu. In contrast, mu81C6-1B4M-DTPA-{sup 177}Lu and mu81C6-MeO-DOTA-{sup 177}Lu showed a more dramatic increase in the {sup 177}Lu/{sup 125}I ratio in bone - from 2.4{+-}0.3 and 1.7{+-}0.2 at Day 1 to 8.5{+-}1.1 and 4.2{+-}0.5 at Day 7, respectively. Conclusion: With these antitenascin constructs, the nature of the mAb had a profound influence on the relative degree of loss of {sup 177}Lu from these

meso-Octamethylcalix[4]pyrrole as an effective macrocyclic receptor for the univalent thallium cation in the gas phase: Experimental and theoretical study

Science.gov (United States)

Polášek, Miroslav; Makrlík, Emanuel; Kvíčala, Jaroslav; Křížová, Věra; Vaňura, Petr

2018-02-01

By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the univalent thallium cation (Tl+) forms with meso-octamethylcalix[4]pyrrole (1) the cationic complex species 1 Tl+. When this kinetically stable cation-π complex 1 Tl+ is collisionally activated, it decomposes by elimination of the whole ligand 1 or small meso-octamethylcalix[4]pyrrole fragments. Further, applying quantum chemical DFT calculations, four different conformations of the resulting complex 1 Tl+ were derived. It means that under the present experimental conditions, this ligand 1 can be considered as a very effective macrocyclic receptor for the thallium cation.

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

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.

Fe4 cluster and a buckled macrocycle complex from the reduction of [(dmgBF2)2Fe(L)2] (L = MeCN, (t)Bu(i)NC).

Science.gov (United States)

Rose, Michael J; Winkler, Jay R; Gray, Harry B

2012-02-20

We report the syntheses, X-ray structures, and reductive electrochemistry of the Fe(II) complexes [(dmgBF(2))(2)Fe(MeCN)(2)] (1; dmg = dimethylglyoxime, MeCN = acetonitrile) and [(dmgBF(2))Fe((t)Bu(i)NC)(2)] (2; (t)Bu(i)NC = tert-butylisocyanide). The reaction of 1 with Na/Hg amalgam led to isolation and the X-ray structure of [(dmgBF(2))(2)Fe(glyIm)] (3; glyIm = glyimine), wherein the (dmgBF(2))(2) macrocyclic frame is bent to accommodate the binding of a bidentate apical ligand. We also report the X-ray structure of a rare mixed-valence Fe(4) cluster with supporting dmg-type ligands. In the structure of [(dmg(2)BF(2))(3)Fe(3)((1)/(2)dmg)(3)Fe(O)(6)] (4), the (dmgBF(2))(2) macrocycle has been cleaved, eliminating BF(2) groups. Density functional theory calculations and electron paramagnetic resonance data are in accordance with a central Fe(III) ion surrounded by three formally Fe(II)dmg(2)BF(2) units.

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

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.

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.

Development of electrochemical sensors for nano scale Tb(III) ion determination based on pendant macrocyclic ligands.

Science.gov (United States)

Singh, Ashok K; Singh, Prerna; Banerjee, Shibdas; Mehtab, Sameena

2009-02-02

The two macrocyclic pendant ligands 3,4,5:12,13,14-dipyridine-2,6,11,15-tetramethyl-1,7,10,16-tetramethylacrylate-1,4,7,10,13,16-hexaazacyclooctadeca-3,13-di ene (L(1)) and 3,4,5:12,13,14-dipyridine-2,6,11,15-tetramethyl-1,7,10,16-tetra(2-cyano ethane)-1,4,7,10,13,16-hexaazacyclooctadeca-3,13-diene (L(2)) have been synthesized and explored as neutral ionophores for preparing poly(vinylchloride) (PVC) based membrane sensors selective to Tb(III) ions. Effects of various plasticizers and anion excluders were studied in detail and improved performance was observed. The best performance was obtained for the membrane sensor having a composition of L(1): PVC:1-CN:NaTPB in the ratio of 6: 32: 58: 4 (w/w; mg). The performance of the membrane based on L(1) was compared with polymeric membrane electrode (PME) as well as with coated graphite electrode (CGE). The electrodes exhibit Nernstian slope for Tb(3+) ions with limits of detection of 3.4 x 10(-8)mol L(-1) for PME and 5.7 x 10(-9)mol L(-1) for CGE. The response time for PME and CGE was found to be 10s and 8s, respectively. The potentiometric responses are independent of the pH of the test solution in the pH range 3.0-7.5 for PME and 2.0-8.5 for CGE. The CGE has found to work satisfactorily in partially non-aqueous media upto 30% (v/v) content of methanol, ethanol and 20% (v/v) content of acetonitrile and could be used for a period of 5 months. The CGE was used as indicator electrode in the potentiometric titration of Tb(3+) ions with EDTA and in determination of fluoride ions in various samples. It can also be used in direct determination of Tb(3+) ions in tap water and various binary mixtures with quantitative results.

Development of electrochemical sensors for nano scale Tb(III) ion determination based on pendant macrocyclic ligands

Energy Technology Data Exchange (ETDEWEB)

Singh, Ashok K. [Department of Chemistry, Indian Institute of Technology-Roorkee, Roorkee 247 667 (India)], E-mail: akscyfcy@iitr.ernet.in; Singh, Prerna; Banerjee, Shibdas; Mehtab, Sameena [Department of Chemistry, Indian Institute of Technology-Roorkee, Roorkee 247 667 (India)

2009-02-02

The two macrocyclic pendant ligands 3,4,5:12,13,14-dipyridine-2,6,11, 15-tetramethyl-1,7,10,16-tetramethylacrylate -1,4,7,10,13, 16-hexaazacyclooctadeca-3,13-di ene (L{sub 1}) and 3,4,5:12,13,14-dipyridine-2,6,11,15-tetramethyl-1,7,10,16-tetra(2-cyano ethane)-1,4,7,10,13,16-hexaazacyclooctadeca-3,13-diene (L{sub 2}) have been synthesized and explored as neutral ionophores for preparing poly(vinylchloride) (PVC) based membrane sensors selective to Tb(III) ions. Effects of various plasticizers and anion excluders were studied in detail and improved performance was observed. The best performance was obtained for the membrane sensor having a composition of L{sub 1}: PVC:1-CN:NaTPB in the ratio of 6: 32: 58: 4 (w/w; mg). The performance of the membrane based on L{sub 1} was compared with polymeric membrane electrode (PME) as well as with coated graphite electrode (CGE). The electrodes exhibit Nernstian slope for Tb{sup 3+} ions with limits of detection of 3.4 x 10{sup -8} mol L{sup -1} for PME and 5.7 x 10{sup -9} mol L{sup -1} for CGE. The response time for PME and CGE was found to be 10 s and 8 s, respectively. The potentiometric responses are independent of the pH of the test solution in the pH range 3.0-7.5 for PME and 2.0-8.5 for CGE. The CGE has found to work satisfactorily in partially non-aqueous media upto 30% (v/v) content of methanol, ethanol and 20% (v/v) content of acetonitrile and could be used for a period of 5 months. The CGE was used as indicator electrode in the potentiometric titration of Tb{sup 3+} ions with EDTA and in determination of fluoride ions in various samples. It can also be used in direct determination of Tb{sup 3+} ions in tap water and various binary mixtures with quantitative results.

Development of electrochemical sensors for nano scale Tb(III) ion determination based on pendant macrocyclic ligands

International Nuclear Information System (INIS)

Singh, Ashok K.; Singh, Prerna; Banerjee, Shibdas; Mehtab, Sameena

2009-01-01

The two macrocyclic pendant ligands 3,4,5:12,13,14-dipyridine-2,6,11, 15-tetramethyl-1,7,10,16-tetramethylacrylate -1,4,7,10,13, 16-hexaazacyclooctadeca-3,13-di ene (L 1 ) and 3,4,5:12,13,14-dipyridine-2,6,11,15-tetramethyl-1,7,10,16-tetra(2-cyano ethane)-1,4,7,10,13,16-hexaazacyclooctadeca-3,13-diene (L 2 ) have been synthesized and explored as neutral ionophores for preparing poly(vinylchloride) (PVC) based membrane sensors selective to Tb(III) ions. Effects of various plasticizers and anion excluders were studied in detail and improved performance was observed. The best performance was obtained for the membrane sensor having a composition of L 1 : PVC:1-CN:NaTPB in the ratio of 6: 32: 58: 4 (w/w; mg). The performance of the membrane based on L 1 was compared with polymeric membrane electrode (PME) as well as with coated graphite electrode (CGE). The electrodes exhibit Nernstian slope for Tb 3+ ions with limits of detection of 3.4 x 10 -8 mol L -1 for PME and 5.7 x 10 -9 mol L -1 for CGE. The response time for PME and CGE was found to be 10 s and 8 s, respectively. The potentiometric responses are independent of the pH of the test solution in the pH range 3.0-7.5 for PME and 2.0-8.5 for CGE. The CGE has found to work satisfactorily in partially non-aqueous media upto 30% (v/v) content of methanol, ethanol and 20% (v/v) content of acetonitrile and could be used for a period of 5 months. The CGE was used as indicator electrode in the potentiometric titration of Tb 3+ ions with EDTA and in determination of fluoride ions in various samples. It can also be used in direct determination of Tb 3+ ions in tap water and various binary mixtures with quantitative results

[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) ↔ �

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

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.

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...

Presentación de los números complejos : enfoques e interpretaciones

OpenAIRE

Bustamante Donayre, Luis Alberto

2000-01-01

Desde que los números complejos aparecieron en el siglo XVI, tardaron dos siglos en ser, en cierta manera, aceptados. Aunque las aportaciones formales de Bombelli, Wessel, Argand, Gauss, Euler y Hamilton contribuyeron a una aceptación parcial de los matemáticos, los incomprendidos números complejos todavía eran considerados por los matemáticos del siglo XIX como entes espurios1 El presente trabajo tiene por objeto encontrar un enfoque en donde los números complejos aparez...

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

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....

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.

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.

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.

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.

Spectroscopic and biological approach in the characterization of a novel 14-membered [N4] macrocyclic ligand and its Palladium(II), Platinum(II), Ruthenium(III) and Iridium(III) complexes

Science.gov (United States)

Rani, Soni; Kumar, Sumit; Chandra, Sulekh

2014-01-01

A novel, tetradentate nitrogen donor [N4] macrocyclic ligand, i.e. 3,5,14,16-tetramethyl-2,6,13,17-tetraazatricyclo[12,0,07-12] cosa-1(22),2,5,7,9,11,13,16,18,20-decaene(L), has been synthesized and characterized by elemental analyses, IR, Mass, and 1H NMR spectral studies. Complexes of Pd(II), Pt(II), Ru(III) and Ir(III) have been prepared and characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, Mass, electronic spectral and thermal studies. On the basis of molar conductance the complexes may be formulated as [PdL]Cl2, [PtL]Cl2, [Ru(L)Cl2]Cl and [Ir(L)Cl2]Cl. The complexes are insoluble in most common solvents, including water, ethanol, carbon tetrachloride and acetonitrile, but soluble in DMF/DMSO. The value of magnetic moment indicates that all the complexes are diamagnetic except Ru(III) complex which shows magnetic moment corresponding to one unpaired electron. The magnetic moment of Ru(III) complex is 1.73 B.M. at room temperature. The antimicrobial activities of ligand and its complexes have been screened in vitro, as growth inhibiting agents. The antifungal and antibacterial screening were carried out using Food Poison and Disc Diffusion Method against plant pathogenic fungi and bacteria Alternaria porri, Fusarium oxysporum, Xanthomonas compestris and Pseudomonas aeruginosa respectively. The compounds were dissolved in DMSO to get the required solutions. The required medium used for these activities was PDA and nutrient agar.

Spectroscopic and biological approach in the characterization of a novel 14-membered [N4] macrocyclic ligand and its palladium(II), platinum(II), ruthenium(III) and iridium(III) complexes.

Science.gov (United States)

Rani, Soni; Kumar, Sumit; Chandra, Sulekh

2014-01-24

A novel, tetradentate nitrogen donor [N4] macrocyclic ligand, i.e. 3,5,14,16-tetramethyl-2,6,13,17-tetraazatricyclo[12,0,0(7-12)] cosa-1(22),2,5,7,9,11,13,16,18,20-decaene(L), has been synthesized and characterized by elemental analyses, IR, Mass, and (1)H NMR spectral studies. Complexes of Pd(II), Pt(II), Ru(III) and Ir(III) have been prepared and characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, Mass, electronic spectral and thermal studies. On the basis of molar conductance the complexes may be formulated as [PdL]Cl2, [PtL]Cl2, [Ru(L)Cl2]Cl and [Ir(L)Cl2]Cl. The complexes are insoluble in most common solvents, including water, ethanol, carbon tetrachloride and acetonitrile, but soluble in DMF/DMSO. The value of magnetic moment indicates that all the complexes are diamagnetic except Ru(III) complex which shows magnetic moment corresponding to one unpaired electron. The magnetic moment of Ru(III) complex is 1.73 B.M. at room temperature. The antimicrobial activities of ligand and its complexes have been screened in vitro, as growth inhibiting agents. The antifungal and antibacterial screening were carried out using Food Poison and Disc Diffusion Method against plant pathogenic fungi and bacteria Alternaria porri, Fusarium oxysporum, Xanthomonas compestris and Pseudomonas aeruginosa respectively. The compounds were dissolved in DMSO to get the required solutions. The required medium used for these activities was PDA and nutrient agar. Copyright © 2013 Elsevier B.V. All rights reserved.

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.

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)

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

Tailored synthesis of CuS nanodisks from a new macrocyclic precursor and their efficient catalytic properties on methylene blue dye degradation

International Nuclear Information System (INIS)

Islam, D. A.; Chakraborty, A.; Bhattacharya, B.; Sarkar, U.; Acharya, H.

2016-01-01

In this study, CuS nanodisks have been synthesized from a tetraaza (N_4) macrocyclic complex precursor by a facile wet chemical method. The crystallinity and morphology of the as-synthesized products were characterized by X-ray diffraction and transmission electron microscopy, which confirm a phase pure crystalline CuS nanostructures with ~15 to 20 nm in dimension with ~5 nm thickness. A possible formation mechanism and growth process of the CuS nanodisks are discussed using thiourea and tetraaza ligand as the sulfur donor and stabilizing agent, respectively. Cyclic N_4 ligand also acts as a binding agent to template-guide the oriented growth of CuS nanodisks. The optimized geometry of ligands and complexes was calculated using B3YLP functional, which indicates that the HOMO in the complex located on metal center and N atoms are weakly bonded to the metal center. The catalytic activity of CuS nanodisks toward MB degradation with light displays the higher MB degradation rate than under dark in the presence of H_2O_2. The C_t/C_0 plot as a function of time displays the higher MB degradation activity of CuS nanoparticles with H_2O_2. The recycle stability of CuS nanoparticles was even found to be >80 % after five cycles studied by repeating the MB degradation with same CuS nanoparticles sample.Graphical AbstractCuS nanostructures synthesized from a tetraaza macrocyclic complex precursor show the disk-like registry with average lateral dimension between 15 and 20 nm and thickness of 5 nm. The catalytic activity of CuS nanodisks toward MB degradation with light displays the higher MB degradation rate than in dark in the presence of H_2O_2.

Tailored synthesis of CuS nanodisks from a new macrocyclic precursor and their efficient catalytic properties on methylene blue dye degradation

Energy Technology Data Exchange (ETDEWEB)

Islam, D. A.; Chakraborty, A. [Assam University, Department of Chemistry, Centre for Soft Matters (India); Bhattacharya, B.; Sarkar, U. [Assam University, Department of Physics (India); Acharya, H., E-mail: himadriau@yahoo.co.in [Assam University, Department of Chemistry, Centre for Soft Matters (India)

2016-05-15

In this study, CuS nanodisks have been synthesized from a tetraaza (N{sub 4}) macrocyclic complex precursor by a facile wet chemical method. The crystallinity and morphology of the as-synthesized products were characterized by X-ray diffraction and transmission electron microscopy, which confirm a phase pure crystalline CuS nanostructures with ~15 to 20 nm in dimension with ~5 nm thickness. A possible formation mechanism and growth process of the CuS nanodisks are discussed using thiourea and tetraaza ligand as the sulfur donor and stabilizing agent, respectively. Cyclic N{sub 4} ligand also acts as a binding agent to template-guide the oriented growth of CuS nanodisks. The optimized geometry of ligands and complexes was calculated using B3YLP functional, which indicates that the HOMO in the complex located on metal center and N atoms are weakly bonded to the metal center. The catalytic activity of CuS nanodisks toward MB degradation with light displays the higher MB degradation rate than under dark in the presence of H{sub 2}O{sub 2}. The C{sub t}/C{sub 0} plot as a function of time displays the higher MB degradation activity of CuS nanoparticles with H{sub 2}O{sub 2}. The recycle stability of CuS nanoparticles was even found to be >80 % after five cycles studied by repeating the MB degradation with same CuS nanoparticles sample.Graphical AbstractCuS nanostructures synthesized from a tetraaza macrocyclic complex precursor show the disk-like registry with average lateral dimension between 15 and 20 nm and thickness of 5 nm. The catalytic activity of CuS nanodisks toward MB degradation with light displays the higher MB degradation rate than in dark in the presence of H{sub 2}O{sub 2}.

Novel bispidine ligands with a possible application in nuclear medicine; Neue Bispidin-Liganden mit potenzieller Anwendung in der Nuklearmedizin

Energy Technology Data Exchange (ETDEWEB)

Rudolf, Henning

2013-10-24

interesting structural properties like pentagonal bipyramidal geometries. For the development of stable and uncharged {sup 64}Cu{sup II} complex for positron emission tomography, three cyclic bispidine ligands containing amide donors were synthesized. These bispidine dioxo tetraaza macrocycles represent a new class of highly preorganized cyclic bispidine ligands by fusing the rigid bispidine backbone with the motif of a macrocyclic diamide. Due to the deprotonatable amides, they form stable, uncharged square-planar respectively square-pyramidal Cu{sup II} complexes and show also the stabilization of copper in the oxidation state +III. In evaluation experiments of the bispidine dioxo tetraaza macrocycles for a radiopharmaceutical application as {sup 64}Cu tracer for positron emission tomography, these ligands are showing an efficient radiolabeling with {sup 64}Cu >95% on benefiting timescale (60 min, tops) and a distinct specific activity up to 26 GBq/µmol. In particular the ligand H{sub 2}BBDT features a high stability versus EDTA and in human blood plasma. In radio challenge experiments, merely 8% of transchelation was detected against a 20fold excess of EDTA and nearly no decomplexation in human blood plasma after 48 h. Biodistribution studies in Kyoto-Wistar rats are showing a rapid and nearly complete clearance from blood and normal tissue after 60 min pi (post injection). The Cu{sup II} complex of the methyl propionate functionalized macrocycle H{sub 2}BBDTA-Me offers the opportunity to couple its saponificated methyl propionate linker to biovectors, nanoparticles or fluorescence labels.

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.

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.

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.

El complejo sinaptonémico en conejo cariotipo meiótico obtenido a partir de complejos sinaptonémicos en microesparcidos de espermatocitos paquiténicos

Directory of Open Access Journals (Sweden)

Juan José Filgueira D.

1986-10-01

Full Text Available Espermatocitos de conejo, fueron procesados mediante una técnica modificada de microesparcidos, que contribuyó a aumentar el conocimiento sobre el Complejo Sinaptonemico (CS y la sinapsis meiótica de los cromosomas del conejo. Los núcleos paquiténicos en microesparcidos, mostraron 22 Complejos inaptonémicos completamente formados que permitieron clasificarlos de acuerdo a la posición del centrómero; en los 22 grupos centroméricos, se determinaron las longitudes totales de los Complejos Sinaptonémicos, así como las correspondientes longitudes de los brazos de los bivalentes, para realizar un Idiograma. Los Complejos Sinaptonémicos (CS, aparecieron con restos de membrana nuclear en sus extremos y tres bivalentes presentaron residuos del nucleolo. El proceso de microesparcido fue seguido por microscopia óptica y se observe, como la técnica desarrollada para obtener los microesparcidos Hamada “de gota pendiente” aumentó la densidad de CSs por unidad de área. Las observaciones de los microesparcidos en grillas a traves del microscopio electrónico fueron corroboradas por observaciones de microesparcidos en placa, teñidos con plata, para microscopia de luz.

Grafting of aza-macrocyclic ligands onto organic fibres for the sequestering of radioelements and cadmium: application to industrial waste water treatment

International Nuclear Information System (INIS)

Rascalou, Frederic

2003-01-01

Within the frame of a preparation to the industrial transfer of a decontamination process for the processing of low-activity radioactive effluents of the Valduc nuclear centre, this research thesis reports research works which aimed at developing a new support for macrocyclic molecules in replacement of silica, in order to obtain a material which is steady in process conditions, can be incinerated at the end of the process, and could result in a higher production capacity. It also aimed at elaborating a sequestering material specific to cadmium. After a general presentation of challenges related to waste management and a presentation of the specific case of Valduc, the author gives an overview of earlier works, and discusses the validation of the selective solid-liquid extraction as additional technique to those provided by the existing processing plant. He justifies the selection of organic fibres as a new support. He reports the study of the grafting of macrocyclic molecules on viscose and polypropylene fibres, and describes ways of modification of these supports and the synthesis of the different molecular entities. The last part addresses the study of the performance of these new materials: results in static mode, performance in dynamic mode on pilot installations [fr

Nano-level monitoring of Yb(III) by fabrication of coated graphite electrode based on newly synthesized hexaaza macrocyclic ligand

International Nuclear Information System (INIS)

Singh, Ashok K.; Singh, Prerna

2009-01-01

The two macrocyclic ligands 2,12-(2-methoxyaniline) 2 -4,14-Me 2 -[20]-1,4,11,14-tetraene-1,5,8,11,15,18-N 6 (L 1 ) and 2,12-(2-methoxyaniline) 2 -4,14-Me 2 -8,18-dimethylacrylate-[20] -1,4,11,14-tetraene-1,5,8,11,15,18-N 6 (L 2 ) have been synthesized and explored as neutral ionophores for preparing poly(vinylchloride) (PVC) based membrane sensors selective to Yb(III) ions. Effects of various plasticizers and anion excluders were studied in detail and improved performance was observed. The best performance was obtained for the membrane sensor having a composition of L 2 :PVC:BA:NaTPB in the ratio of 5: 40: 52: 3 (w/w; mg). The performance of the membrane based on L 2 was compared with polymeric membrane electrode (PME) as well as with coated graphite electrode (CGE). The electrodes exhibit Nernstian slope for Yb 3+ ions with limits of detection of 4.3 x 10 -8 M for PME and 5.8 x 10 -9 M for CGE. The response time for PME and CGE was found to be 10 s and 8 s, respectively. The potentiometric responses are independent of the pH of the test solution in the pH range 3.0-8.0 for PME and 2.5-8.5 for CGE. The CGE has found to work satisfactorily in partially non-aqueous media upto 30% (v/v) content of methanol, ethanol and 20% (v/v) content of acetonitrile and could be used for a period of 5 months. The CGE was used as indicator electrode in the potentiometric titration of Yb 3+ ions with EDTA and in determination of fluoride ions in mouthwash samples. It can be used for determination of sulfite in red and white wine samples and also in determination of Yb 3+ in various binary mixtures with quantitative results.

Nano-level monitoring of Yb(III) by fabrication of coated graphite electrode based on newly synthesized hexaaza macrocyclic ligand

Energy Technology Data Exchange (ETDEWEB)

Singh, Ashok K., E-mail: akscyfcy@iitr.ernet.in [Department of Chemistry, Indian Institute of Technology-Roorkee, Roorkee 247667 (India); Singh, Prerna [Department of Chemistry, Indian Institute of Technology-Roorkee, Roorkee 247667 (India)

2009-06-08

The two macrocyclic ligands 2,12-(2-methoxyaniline){sub 2}-4,14-Me{sub 2}-[20]-1,4,11,14-tetraene-1,5,8,11,15,18-N{sub 6} (L{sub 1}) and 2,12-(2-methoxyaniline){sub 2}-4,14-Me{sub 2}-8,18-dimethylacrylate-[20] -1,4,11,14-tetraene-1,5,8,11,15,18-N{sub 6} (L{sub 2}) have been synthesized and explored as neutral ionophores for preparing poly(vinylchloride) (PVC) based membrane sensors selective to Yb(III) ions. Effects of various plasticizers and anion excluders were studied in detail and improved performance was observed. The best performance was obtained for the membrane sensor having a composition of L{sub 2}:PVC:BA:NaTPB in the ratio of 5: 40: 52: 3 (w/w; mg). The performance of the membrane based on L{sub 2} was compared with polymeric membrane electrode (PME) as well as with coated graphite electrode (CGE). The electrodes exhibit Nernstian slope for Yb{sup 3+} ions with limits of detection of 4.3 x 10{sup -8} M for PME and 5.8 x 10{sup -9} M for CGE. The response time for PME and CGE was found to be 10 s and 8 s, respectively. The potentiometric responses are independent of the pH of the test solution in the pH range 3.0-8.0 for PME and 2.5-8.5 for CGE. The CGE has found to work satisfactorily in partially non-aqueous media upto 30% (v/v) content of methanol, ethanol and 20% (v/v) content of acetonitrile and could be used for a period of 5 months. The CGE was used as indicator electrode in the potentiometric titration of Yb{sup 3+} ions with EDTA and in determination of fluoride ions in mouthwash samples. It can be used for determination of sulfite in red and white wine samples and also in determination of Yb{sup 3+} in various binary mixtures with quantitative results.

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.

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...

Salud: un sistema complejo adaptativo Health: an adaptive complex system

Directory of Open Access Journals (Sweden)

Luis Fernando Toro-Palacio

2012-02-01

Full Text Available Este artículo destaca la enorme distancia existente entre el pensamiento complejo de índole intelectual, difundido en nuestro medio, y el pensamiento complejo de índole experimental, que ha permitido lograr los desarrollos científico-tecnológicos que han cambiado radicalmente el mundo. Invita a considerar como sistemas complejos adaptativos entidades tales como la vida, el ser humano, la sociedad global y todo aquello que se llama salud, para lo cual resulta prioritario adoptar un enfoque diferente que amplíe su conocimiento. Al reconocer esta racionalidad, se sustentan las principales características y propiedades emergentes de la salud como sistema complejo adaptativo, siguiendo un modelo de prestación de cuidados y servicios. Finalmente, se plantean algunas preguntas de investigación pertinentes desde esta perspectiva, y se expresan una serie de apreciaciones que se espera sirvan para comprender todo lo que como individuos y como especie hemos llegado a ser. Se propone en este trabajo que la salud y la prestación de servicios de asistencia sanitaria se consideren como sistemas complejos adaptativos.This article points out the enormous gap that exists between complex thinking of an intellectual nature currently present in our environment, and complex experimental thinking that has facilitated the scientific and technological advances that have radically changed the world. The article suggests that life, human beings, global society, and all that constitutes health be considered as adaptive complex systems. This idea, in turn, prioritizes the adoption of a different approach that seeks to expand understanding. When this rationale is recognized, the principal characteristics and emerging properties of health as an adaptive complex system are sustained, following a care and services delivery model. Finally, some pertinent questions from this perspective are put forward in terms of research, and a series of appraisals are expressed that

Fractura triple del complejo suspensorio del hombro

Directory of Open Access Journals (Sweden)

Eraclio Delgado Rifá

2015-06-01

Full Text Available El complejo suspensorio del hombro es una estructura sumamente importante, compuesta por un anillo de huesos y tejidos blandos. Las lesiones aisladas de este complejo anatómico son frecuentes y no afectan su estabilidad. La interrupción doble conduce a la inestabilidad de esta estructura y usualmente requiere tratamiento quirúrgico. La triple interrupción, por su parte, es sumamente rara y es encontrada en casos de trauma de alta energía a menudo en asociación con otras lesiones. Se presenta una triple lesión del complejo suspensorio del hombro en un paciente de 46 años de edad, con una fractura de la glenoides, del acromion tipo III de Kuhn y de la coracoides tipo II de Ogawa. En este caso, la fractura del acromion fue tratada con fijación percutánea con alambres de Kirschner, por tener asociado lesiones de partes blandas que contraindicaron la reducción abierta. La fractura de la glenoides y de la apófisis coracoides fueron tratadas conservadoramente. Después de 6 meses de evolución, el paciente tuvo un resultado funcional aceptable, con una abducción de 90 grados, los 30 grados de rotación externa y 70 de rotación interna, además asintomático y consolidación de todas las fracturas. A pesar de ser catalogada de una lesión grave del cinturón escapular y estar asociada a otras lesiones se obtuvo un resultado satisfactorio al final del tratamiento.

Complejos de Cu(II: Alternativas en la terapia antineoplásica Complejos de Cu(II: Alternativas en la terapia

Directory of Open Access Journals (Sweden)

Myrna Sabanero López

2012-02-01

Full Text Available En el presente estudio, fué evaluada la actividad biológica de nuevos complejos de cobre (II fenantrolina unidos a aminoácidos, como ácido glutámico, isoleucina y α-metil-dopa. Para ésto se utilizaron células neoplásicas de pulmón humano y dos dosis (30 y 60 μg/ml de los compuestos fueron aplicadas a los cultivos celulares. También se realizaron ensayos inmunocitoquímicos para microtúbulos, microfi lamentos y electroforesis del DNA genómico. Los resultados obtenidos muestran que los complejos de Cu (II fenantrolina con ácido glutámico y α-metil-dopa afectan la adhesión celular (50% y 45%, respectivamente, alterando la distribución de los microtúbulos y microfi lamentos. La fragmentación del DNA, apoya el ensayo del efecto antitumoral del Cu (II fenantrolina con ácido glutámico y α-metil-dopa sobre los cultivos de células de pulmón humano in vitro, de manera dosis dependiente. En conclusión, los complejos de Cu (II fenantrolina con ácido glutámico y α-metil-dopa, presentan un efecto signifi cativo sobre la actividad celular, sugiriendo que estos complejos podrían ser potencialmente compuestos antitumorales. In this study, the biological activity of new copper (II phenanthroline compounds bound to amino acids such as glutamicacid, isoleucine and α-methyl dopa was evaluated. To accomplish this, tumor cells from the human lung and two doses of compounds (30 and 60 μg/ml were applied to cell cultures. Also, immunostaining of microtubules, phalloidin staining of microfilaments, and electrophoresis of genomic DNA were performed. The results showed that compounds of Cu(II phenanthroline with glutamic acid and α methyl-dopa significantly affected cellular adhesion (by 50% and 45%, respectively by altering the distribution of microtubules and microfilaments. Evaluation of DNA fragmentation supported the tumor suppressing effect of Cu (II Phenantroline with glutamicacid and α-Methyl Dopa on human lung cell cultures in

Self-assembly of metal-organic supramolecules: from a metallamacrocycle and a metal-organic coordination cage to 1D or 2D coordination polymers based on flexible dicarboxylate ligands.

Science.gov (United States)

Dai, Fangna; Dou, Jianmin; He, Haiyan; Zhao, Xiaoliang; Sun, Daofeng

2010-05-03

To assemble metal-organic supramolecules such as a metallamacrocycle and metal-organic coordination cage (MOCC), a series of flexible dicarboxylate ligands with the appropriate angle, 2,2'-(2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene)bis(sulfanediyl)dibenzoic acid (H(2)L(1)), 2,2'-(2,5-dimethyl-1,4-phenylene)bis(methylene)bis(sulfanediyl)dibenzoic acid (H(2)L(2)), 2,2'-(2,4,6-trimethyl-1,3-phenylene)bis(methylene)bis(sulfanediyl)dinicotinic acid (H(2)L(3)), and 2,2'-(2,4,6-trimethyl-1,3-phenylene)bis(methylene)bis(sulfanediyl)dibenzoic acid (H(2)L(4)), have been designed and synthesized. Using these flexible ligands to assemble with metal ions, six metal-organic supramolecules, Cd(2)(L(1))(2)(dmf)(4)(H(2)O)(2).H(2)O (1), Mn(3)((1)L(2))(2)((2)L(2))(dmf)(2)(H(2)O)(2).5dmf (2), Cu(4)(L(3))(4)(H(2)O)(4).3dmf (3), Cu(4)(L(4))(4)(dmf)(2)(EtOH)(2).8dmf.6H(2)O (4), Mn(4)(L(4))(4)(dmf)(4)(H(2)O)(4).6dmf.H(2)O (5), and Mn(3)(L(4))(3)(dmf)(4).2dmf.3H(2)O (6), possessing a rectangular macrocycle, MOCCs or their extensions, and 1D or 2D coordination polymers, have been isolated. All complexes have been characterized by single-crystal X-ray diffraction, elemental analysis, and thermogravimetric analysis. Complex 1 is a discrete rectangular macrocycle, while complex 2 is a 2D macrocycle-based coordination polymer in which the L(2) ligand adopts both syn and anti conformations. Complexes 3-5 are discrete MOCCs in which two binuclear metal clusters are engaged by four organic ligands. The different geometries of the secondary building units (SBUs) and the axial coordinated solvates on the SBUs result in their different symmetries. Complex 6 is a 1D coordination polymer, extended from a MOCC made up of two metal ions and three L(4) ligands. All of the flexible dicarboxylate ligands adopt a syn conformation except that in complex 2, indicating that the syn conformational ligand is helpful for the formation of a metallamacrocycle and a MOCC. The magnetic properties of complexes 5

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...

La teoría del granulado y su aplicación a sistemas moleculares complejos

OpenAIRE

Hijón de Miguel, Carmen

2009-01-01

El objetivo de esta tesis es el desarrollo de modelos de grano grueso para la simulación de sistemas moleculares complejos. Entendemos que un modelo de grano grueso es aquel que representa un sistema físico con menor número de grados de libertad que los que hay realmente en el sistema. Y por sistema molecular complejo entendemos aquel cuyos constituyentes son macromoléculas. El reto que plantea la simulación de los sistemas moleculares complejos es el desarrollo de modelos capaces de describi...

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.

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

Synthesis of macrocyclic polyamines; complexation of basic [{sup 99m}TcO{sub 2}{sup +}] and biodistribution of complexed forms; Synthese de polyamines macrocycliques. Complexation du coeur [{sup 99m}TcO{sub 2}{sup +}] et biodistribution des complexes formes

Energy Technology Data Exchange (ETDEWEB)

Riche, F.; Vidal, M. [Universite Joseph Fourier, 38 - Grenoble (France); Mathieu, J.P.; Fagret, D.; Comet, M. [Universite Joseph Fourier, 38 - La Tronche (France). Faculte de Medecine; Pasqualini, R. [CIS bio international, 91 - Gif-sur-Yvette (France)

1996-01-01

The synthesis of macrocyclic polyamines is described, as well as their complexation with technetium via pertechnetole ligands. Several pertechnetole reducing agents were studied, as well as their method of complexation with polyamines and their charge and lipophilicity. Their biodistribution in the mouse and the dog has been studied by scintiscanning which provides evidence of their excellence as hepatobiliary tracers. (UK).

Clinical, biological, and skin histopathologic effects of ionic macrocyclic and nonionic linear gadolinium chelates in a rat model of nephrogenic systemic fibrosis.

Science.gov (United States)

Fretellier, Nathalie; Idée, Jean-Marc; Guerret, Sylviane; Hollenbeck, Claire; Hartmann, Daniel; González, Walter; Robic, Caroline; Port, Marc; Corot, Claire

2011-02-01

the purpose of this study was to compare the clinical, pathologic, and biochemical effects of repeated administrations of ionic macrocyclic or nonionic linear gadolinium chelates (GC) in rats with impaired renal function. rats submitted to subtotal nephrectomy were allocated to single injections of 2.5 mmol/kg of gadodiamide (nonionic linear chelate), nonformulated gadodiamide (ie, without the free ligand caldiamide), gadoterate (ionic macrocyclic chelate), or saline for 5 consecutive days. Blinded semi-quantitative histopathologic and immunohistochemical examinations of the skin were performed, as well as clinical, hematological, and biochemical follow-up. Rats were killed at day 11. Long-term (up to day 32) follow-up of rats was also performed in an auxiliary study. epidermal lesions (ulcerations and scabs) were found in 4 of the 10 rats treated with nonformulated gadodiamide. Two rats survived the study period. Inflammatory signs were observed in this group. No clinical, hematological, or biochemical signs were observed in the saline and gadoterate- or gadodiamide-treated groups. Plasma fibroblast growth factor-23 levels were significantly higher in the gadodiamide group than in the gadoterate group (day 11). Decreased plasma transferrin-bound iron levels were measured in the nonformulated gadodiamide group. Histologic lesions were in the range: nonformulated gadodiamide (superficial epidermal lesions, inflammation, necrosis, and increased cellularity in papillary dermis) > gadodiamide (small superficial epidermal lesions and signs of degradation of collagen fibers in the dermis) > gadoterate (very few pathologic lesions, similar to control rats). repeated administration of the nonionic linear GC gadodiamide to renally impaired rats is associated with more severe histologic lesions and higher FGF-23 plasma levels than the macrocyclic GC gadoterate.

Synthesis and Characterization of Macrocyclic Polyether N,N'-Diallyl-7,16-diaza-1,4,10,13-tetraoxa-dibenzo-18-crown-6.

Science.gov (United States)

Toeri, Julius; Laborie, Marie-Pierre

2016-01-29

In this study an efficient and direct production procedure for a macrocyclic polyether N,N'-diallyl-7,16-diaza-1,4,10,13-tetraoxa-dibenzo-18-crown-6 from the reaction of catechol and N,N-bis(2-chloroethyl)prop-2-en-1-amine in n-butanol in the presence of a strong base is reported. The synthesis involves a two-step addition of sodium hydroxide to enhance the cyclization process, and at the end of the reaction, the reaction mixture is neutralized and the solvent replaced with water in-situ through distillation to afford a relatively pure precipitate that is easily recrystallized from acetone. The yield of the macrocycle was 36%-45% and could be scaled-up to one-mole quantities. The structure and purity of this compound was verified on the basis of elemental analysis, IR, UV-Vis, ¹H-, (13)C-NMR, 2D-NMR, mass spectroscopy, and thermal analysis. The white crystalline compound has a sharp melting point of 124 °C and a crystallization temperature of 81.4 °C determined by differential scanning calorimetry. Our motivation behind the synthesis of the bibracchial lariat azacrown polyether ligand was to examine its possible applications in ion-selective polymer-supported materials.

Synthesis and Characterization of Macrocyclic Polyether N,N′-Diallyl-7,16-diaza-1,4,10,13-tetraoxa-dibenzo-18-crown-6

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Julius Toeri

2016-01-01

Full Text Available In this study an efficient and direct production procedure for a macrocyclic polyether N,N′-diallyl-7,16-diaza-1,4,10,13-tetraoxa-dibenzo-18-crown-6 from the reaction of catechol and N,N-bis(2-chloroethylprop-2-en-1-amine in n-butanol in the presence of a strong base is reported. The synthesis involves a two-step addition of sodium hydroxide to enhance the cyclization process, and at the end of the reaction, the reaction mixture is neutralized and the solvent replaced with water in-situ through distillation to afford a relatively pure precipitate that is easily recrystallized from acetone. The yield of the macrocycle was 36%–45% and could be scaled-up to one-mole quantities. The structure and purity of this compound was verified on the basis of elemental analysis, IR, UV-Vis, 1H-, 13C-NMR, 2D-NMR, mass spectroscopy, and thermal analysis. The white crystalline compound has a sharp melting point of 124 °C and a crystallization temperature of 81.4 °C determined by differential scanning calorimetry. Our motivation behind the synthesis of the bibracchial lariat azacrown polyether ligand was to examine its possible applications in ion-selective polymer-supported materials.

Lanthanide complexes of macrocyclic polyoxovanadates by VO4 units: synthesis, characterization, and structure elucidation by X-ray crystallography and EXAFS spectroscopy.

Science.gov (United States)

Nishio, Masaki; Inami, Shinnosuke; Katayama, Misaki; Ozutsumi, Kazuhiko; Hayashi, Yoshihito

2012-01-16

Reactions of a tetravanadate anion, [V(4)O(12)](4-), with a series of lanthanide(III) salts yield three types of lanthanide complexes of macrocyclic polyoxovanadates: (Et(4)N)(6)[Ln(III)V(9)O(27)] [Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6)], (Et(4)N)(5)[(H(2)O)Ho(III)(V(4)O(12))(2)] (7), and (Et(4)N)(7)[Ln(III)V(10)O(30)] [Ln = Er (8), Tm (9), Yb (10), Lu (11)]. Lanthanide complexes 1-11 are isolated and characterized by IR, elemental analysis, single-crystal X-ray diffraction, and extended X-ray absorption fine structure spectroscopy (EXAFS). Lanthanide complexes 1-6 are composed of a square-antiprism eight-coordinated Ln(III) center with a macrocyclic polyoxovanadate that is constructed from nine VO(4) tetrahedra through vertex sharing. The structure of 7 is composed of a seven-coordinated Ho(III) center, which exhibits a capped trigonal-prism coordination environment by the sandwiching of two cyclic tetravanadates with a capping H(2)O ligand. Lanthanide complexes 8-11 have a six-coordinated Ln(III) center with a 10-membered vanadate ligand. The structural trend to adopt a larger coordination number for a larger lanthanide ion among the three types of structures is accompanied by a change in the vanadate ring sizes. These lanthanide complexes are examined by EXAFS spectroscopies on lanthanide L(III) absorption edges, and the EXAFS oscillations of each of the samples in the solid state and in acetonitrile are identical. The Ln-O and Ln···V bond lengths obtained from fits of the EXAFS data are consistent with the data from the single-crystal X-ray studies, reflecting retention of the structures in acetonitrile.

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...

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}.

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.

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.

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

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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.

Template synthesis and characterization of biologically active transition metal complexes comprising 14-membered tetraazamacrocyclic ligand

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DHARMPAL SINGH

2010-02-01

Full Text Available A novel series of complexes of the type [M(C28H24N4X2], whereM = Co(II, Ni(II, Cu(II, Zn(II and Cd(II, X = Cl–, NO3–, CH3COO– and (C28H24N4 corresponds to the tetradentate macrocyclic ligand, were synthe¬sized by template condensation of 1,8-diaminonaphthalene and diacetyl in the presence of divalent metal salts in methanolic medium. The complexes were characterized by elemental analyses, conductance and magnetic measurements, as well as by UV/Vis, NMR, IR and MS spectroscopy. The low values of the molar conductance indicate non-electrolyte type of complexes. Based on these spectral data, a distorted octahedral geometry may be proposed for all of these complexes. All the synthesized macrocyclic complexes were tested for in vitro antibacterial activity against some pathogenic bacterial strains, viz Bacillus cereus, Salmonella typhi, Escherichia coli and Staphylococcus aureus. The MIC values shown by the complexes against these bacterial strains were compared with the MIC shown by the standard antibiotics linezolid and cefaclor.

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

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.

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.

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)

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

Alkali metals and group IIA metals

International Nuclear Information System (INIS)

Fenton, D.E.

1987-01-01

This chapter on the coordination complexes of the alkali metals of group IIA starts with a historical perspective of their chemistry, from simple monodentate ligands, metal-β-diketonates to the macrocyclic polyethers which act as ligands to the alkali and akaline earth metals. Other macrocyclic ligands include quarterenes, calixarenes, porphyrins, phthalocyanines and chlorophylls. A section on the naturally occurring ionophores and carboxylic ionophores is included. (UK)

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).

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.

Separation of alkali, alkaline earth and rare earth cations by liquid membranes containing macrocyclic carriers. Third progress report, September 1, 1980-April 1, 1981

International Nuclear Information System (INIS)

Christensen, J.J.

1981-01-01

The overall objective of this project is to study the use of liquid membrane systems employing macrocyclic ligand carriers in making separations among metal cations. During the third year of the project, work continued in the development of a mathematical model to describe cation transport. The model was originally developed to describe the relationship between cation transport rate (J/sub M/) and the cation-macrocycle stability constant (K). The model was tested by determining the rates of transport of alkali and alkaline earth cations through chloroform membranes containing carrier ligands where the stability constants for their reaction with cations in methanol were known. From the results, it is clear that the model correctly describes the dependence of J/sub M/ on log K. The model also correctly describes the effect of cation concentration and carrier concentration on cation transport rates, as detailed in the previous progress report. During the third year of the project, the transport model was expanded so as to apply to competitive transport of cations from mixtures of two cations in the source aqueous phase. Data were collected under these conditions and the ability of the model to predict the flux of each cation was tested. Representative data of this type are presented along with corresponding data which were obtained when each cation was transported by the same carrier from a source phase containing only that cation. Comparison of transport rates determined under the two experimental conditions indicates that the relationship between the two sets of data is complex. To date, a few of these data involving transport from binary cation mixtures have been tested against the transport model. It was found that the model correctly predicts the cation fluxes from cation mixtures. These preliminary results indicate that the transport model can successfully predict separation factors when cation mixtures are used

Algunos complejos de carboxilatos de uranio (IV y 1-pirazolilborato

Directory of Open Access Journals (Sweden)

Omar Velasquez

2009-07-01

Full Text Available En este trabajo se presenta la síntesis y caracterización, mediante espectroscopia de infrarojo y H'—NMR de complejos de acetato de uranio, dietil carbamatos y dietilditiocarbamatos y 1—pirazolil—borato.

EL PENSAMIENTO COMPLEJO Y LA TRANSDISCIPLINARIEDAD: FENÓMENOS EMERGENTES DE UNA NUEVA RACIONALIDAD

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SERGIO NÉSTOR OSORIO GARCÍA

2012-01-01

Full Text Available Hoy tenemos que aprender a diferenciar y a distinguir, sin tener por ello que separar. En este sentido hay dos pares de conceptos claramente diferenciables y no por ello separables: por un lado, los conceptos complejidad y pensamiento complejo y por otro lado, conocimiento disciplinar (multi-poli e interdisciplinar y conocimiento transdisciplinar. Para la ciencia clásica el pensamiento complejo y el conocimiento transdisciplinar es un absurdo, pero para éstos, el ideal de racionalidad de la ciencia clásica es necesario y válido, pero insuficiente para comprender la Realidad en el tiempo actual. Se hace necesario un nuevo paradigma de racionalidad que permita pensar la unidad de los conocimientos fragmentados en disciplinas de cara a la supervivencia de la especie humana en esta era que se ha convertido en planetaria. La presente reflexión busca presentar desde las apuestas conceptuales de Edgar Morin (pensamiento complejo y de Basarab Nicolescu (conocimiento transdisciplinar la dimensión epistemológica, ontológica y metodológica de la emergencia de esta nueva racionalidad.

Las organizaciones de enfermería como sistemas complejos

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Caro Castillo Clara Virginia

2002-10-01

Full Text Available

This study takes into account some considerations about the classical logic when building knowledge. It states the logic of complexity, the complex thought and the rational, open and complex systems, as a new paradigm. In the light of the organization concept proposed by Morin, complex adaptative systems are emphasized, as well as other terms such as order, disorder, incidental events and noises. The self-eco-organizer process, takes the human being thinking as starting point and as dynamizer of simple and complex processes in the construction of knowledge about reality. Some research studies such as those of Erdmann, Meirelles and Pradebon show some ways in which one can learn from the organizational reality of nursing, the exercise of complex thinking in uncertainty, in tenous limits, in heterogeneity, diversity and pluralism of phenomena in its aspect, interactions and associations. The inter subjectivity states a new concept of space and of temporality. The care system organization in nursing visualizes several dimensions of "caríng": to care for himself, to care for himself together with the other, to be looked after by the other, to feel and the process of personal care system, the body itself as the nucleus of care, the fact of belonging to the system of multiple caring relations and the care for nature getting integrated to other beings and other social, natural systems, and in thisway strengthen the feeling of ownership, in search of a better survival, vitality, life human quality.

El presente estudio hace algunas consideraciones sobre la lógica clásica en la construcción del conocimiento. Señala la lógica de la complejidad, el pensamiento complejo y los sistemas racionales, abiertos y complejos como un nuevo paradigma. A la luz de la concepción de organización propuesta por Morin, enfatiza los sistemas adaptativos complejos, el orden, desorden, eventos, incidentes y ruidos. El proceso auto-eco-organizador toma como

Nuevos datos sobre la geologia del Complejo Intrusivo Alcalino de Monchique (SW de Portugal)

OpenAIRE

Valadares, V.; González Clavijo, Emilio J.

2004-01-01

Los estudios microscópicos complementarios de las rocas alcalinas han permitido confirmar la estructura anular groseramente concéntrica del Complejo de Monchique, semejante a la que presentan los complejos alcalinos coetáneos de Sintra y Sines. La zona central está constituida por sienitas nefelínicas de grano grueso, rodeadas por un anillo de sienitas nefelínicas heterogéneas de grano más fino. En esta unidad exterior, y localmente separando ambas unidades, existen cuerpos menores de rocas b...

La organización empresarial como sistema adaptativo complejo

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Luz Esperanza Bohórquez Arévalo

2013-01-01

Full Text Available El presente documento busca identificar las características de los sistemas adaptativos complejos (CAS, por su sigla en inglés Complexity Adaptative Systems , así como capturar las implicaciones de su aplica- ción en el estudio de las organizaciones. Para tal fin, se revisan resultados de investigación publicados en revistas académicas que han facilitado la introducción de las ciencias de la complejidad en la adminis- tración, al igual que se exploran los resultados de investigación de grupos e institutos que trabajan en el tema. A partir de los estudios comparativos de las propuestas observadas se plantea que los CAS pueden comprenderse desde la emergencia, la auto-organización y la evolución. La comprensión de la organiza- ción desde esta perspectiva genera líneas de investigación en liderazgo, estrategia, toma de decisiones y construcción de actuación conjunta; todo lo anterior en sistemas complejos.

La organización empresarial como sistema adaptativo complejo

Directory of Open Access Journals (Sweden)

Luz Esperanza Bohórquez Arévalo

2013-04-01

Full Text Available El presente documento busca identificar las características de los sistemas adaptativos complejos (CAS, por su sigla en inglés Complexity Adaptative Systems, así como capturar las implicaciones de su aplicación en el estudio de las organizaciones. Para tal fin, se revisan resultados de investigación publicados en revistas académicas que han facilitado la introducción de las ciencias de la complejidad en la administración, al igual que se exploran los resultados de investigación de grupos e institutos que trabajan en el tema. A partir de los estudios comparativos de las propuestas observadas se plantea que los CAS pueden comprenderse desde la emergencia, la auto-organización y la evolución. La comprensión de la organización desde esta perspectiva genera líneas de investigación en liderazgo, estrategia, toma de decisiones y construcción de actuación conjunta; todo lo anterior en sistemas complejos.

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

UV-visible spectroscopy of macrocyclic alkyl, nitrosyl and halide complexes of cobalt and rhodium. Experiment and calculation.

Science.gov (United States)

Hull, Emily A; West, Aaron C; Pestovsky, Oleg; Kristian, Kathleen E; Ellern, Arkady; Dunne, James F; Carraher, Jack M; Bakac, Andreja; Windus, Theresa L

2015-02-28

Transition metal complexes (NH3)5CoX(2+) (X = CH3, Cl) and L(H2O)MX(2+), where M = Rh or Co, X = CH3, NO, or Cl, and L is a macrocyclic N4 ligand are examined by both experiment and computation to better understand their electronic spectra and associated photochemistry. Specifically, irradiation into weak visible bands of nitrosyl and alkyl complexes (NH3)5CoCH3(2+) and L(H2O)M(III)X(2+) (X = CH3 or NO) leads to photohomolysis that generates the divalent metal complex and ˙CH3 or ˙NO, respectively. On the other hand, when X = halide or NO2, visible light photolysis leads to dissociation of X(-) and/or cis/trans isomerization. Computations show that visible bands for alkyl and nitrosyl complexes involve transitions from M-X bonding orbitals and/or metal d orbitals to M-X antibonding orbitals. In contrast, complexes with X = Cl or NO2 exhibit only d-d bands in the visible, so that homolytic cleavage of the M-X bond requires UV photolysis. UV-Vis spectra are not significantly dependent on the structure of the equatorial ligands, as shown by similar spectral features for (NH3)5CoCH3(2+) and L(1)(H2O)CoCH3(2+).

New 15-membered tetraaza (N4) macrocyclic ligand and its transition metal complexes: Spectral, magnetic, thermal and anticancer activity

Science.gov (United States)

El-Boraey, Hanaa A.; EL-Gammal, Ohyla A.

2015-03-01

Novel tetraamidemacrocyclic 15-membered ligand [L] i.e. naphthyl-dibenzo[1,5,9,12]tetraazacyclopentadecine-6,10,11,15-tetraoneand its transition metal complexes with Fe(II), Co(II), Ni(II), Cu(II), Ru(III) and Pd(II) have been synthesized and characterized by elemental analysis, spectral, thermal as well as magnetic and molar conductivity measurements. On the basis of analytical, spectral (IR, MS, UV-Vis, 1H NMR and EPR) and thermal studies distorted octahedral or square planar geometry has been proposed for the complexes. The antitumor activity of the synthesized ligand and some complexes against human breast cancer cell lines (MCF-7) and human hepatocarcinoma cell lines (HepG2) has been studied. The complexes (IC50 = 2.27-2.7, 8.33-31.1 μg/mL, respectively) showed potent antitumor activity, towards the former cell lines comparable with their ligand (IC50 = 13, 26 μg/mL, respectively). The results show that the activity of the ligand towards breast cancer cell line becomes more pronounced and significant when coordinated to the metal ion.

Evaluación in vitro de tabletas orales de complejos de cobre con antiinflamatorios no esteroideos

Directory of Open Access Journals (Sweden)

Julie Fernanda Benavides Arévalo

Full Text Available Introducción: los antiinflamatorios no esteroideos (AINES, son un grupo diverso y químicamente heterogéneo de fármacos analgésicos, antipiréticos y antiinflamatorios; sin embargo, su funcionamiento se ve afectado por su baja solubilidad acuosa y por la incidencia de efectos secundarios gastrointestinales. Como una alternativa a este problema, la formulación de tabletas orales con complejos de cobre con AINES muestra un adecuado comportamiento in vitro y podría tener efectos secundarios reducidos comparados con el fármaco antiinflamatorio no complejado. Objetivo: evaluar los procesos de desintegración y de disolución de tabletas orales de complejos de cobre con AINES. Métodos: luego de la síntesis y la caracterización instrumental de los complejos, se evaluó por microscopia óptica el efecto de la morfología, el tamaño de partícula y las características superficiales en el proceso de disolución; estos resultados fueron considerados para la formulación de los complejos y permitieron junto con la adecuada elección de un desintegrarte, un modificador de flujo, un lubricante y un aglutinante, la obtención de tabletas por compresión directa. Finalmente, en los comprimidos se evaluaron propiedades fisicomecánicas y los procesos de desintegración y disolución. Resultados: las tabletas de los complejos mostraron tiempos de desintegración entre 5 y 15 min y una liberación in vitro del 75 al 93 %. Conclusiones: la disolución de los AINES se vio favorecida por la formación de complejos, el menor tamaño de partícula, la presencia de poros y grietas en la superficie de las partículas y la inclusión de excipientes para la formulación de tabletas orales.

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.

Arquitectura y anatomía foliar del complejo Polypodium plesiosorum sensu Moran (Polypodiaceae

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J. Daniel Tejero-Díez

2010-09-01

Full Text Available El complejo Polypodium plesisorum es un grupo de morfología heterogénea. Se estudió la arquitectura y anatomía foliar de 12 especies que constituyen el complejo de Polypodium plesiosorum reconocidas por Moran, y otras 23 especies de Polypodium (complejos P. dulce, P. polypodioides y P. vulgare sunsu Moran y géneros relacionados taxonómicamente (Goniophlebium, Phlebodium, Pleopeltis, Serpocaulon, Synammia con fines comparativos. Dos grupos de especies homogéneas fueron establecidos en el complejo P. plesisorum. Uno de ellos se reconoce por el tipo de anastomosis de las venas (tipo III: Polypodium conterminans (originalmente considerado en el grupo de P. dulce de venación libre según Moran, P. hispidulum, P. plesiosorum y P. rhodopleuron. El segundo grupo formado por Polypodium arcanum, P. castaneum, P. colpodes, P. eatonii y P. flagellare, se reconoce por el tipo de anastomosis de las venas (tipo IV y la forma en que se fusionan los cordones vasculares a lo largo del eje pecíoloraquis de la hoja. Los caracteres estudiados ayudaron a relacionar las especies restantes con otros grupos fuera del complejo estudiado.Architecture and leaf anatomy of the Polypodium plesiosorum sensu Moran complex (Polypodiaceae. The Polypodium plesisorum complex is a heterogeneous morphology group. We studied leaf architecture and anatomy of 12 species of this group, in addition to other 23 species of Polypodium (P. dulce, P. polypodioides and P. vulgare complex sensu Moran and related genera (Goniophlebium, Phlebodium, Pleopeltis, Serpocaulon, Synammia, for comparative purposes. Two homogeneous groups of species were established in P. plesiosorum complex. One of them is recognized based on the type of anastomosis of the veins (Type III: Polypodium conterminans (originally considered in the group of P. dulce with free venation by Moran, P. hispidulum, P. plesiosorum and P. rhodopleuron. The second group with Polypodium arcanum, P. castaneum, P. colpodes, P

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.

Síndrome doloroso regional complejo: Conceptos actuales

OpenAIRE

Ferrer Lozano, Yovanny; Oquendo Vázquez, Pablo; Ferrer Lozano, Dunia

2006-01-01

Se realizó una revisión bibliográfica de los conceptos actuales que se les atribuyen al síndrome doloroso regional complejo, término propuesto en 1994 por la International Association for Study of Pain. En la aparición del síndrome intervienen varios factores como son los sistemas nerviosos periférico, central y vegetativo; el sistema endocrino, los factores psicológicos, históricos, ambientales y circunstanciales; que permiten en conjunto personalizar el dolor en cada paciente.El tratamiento...

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...

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.

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.

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.

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).

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.

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.

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...

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.

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 ...

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

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.

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....

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

Spectral manifestation of substitution of out-of-plane ligands in metallophtalocyanines

Directory of Open Access Journals (Sweden)

Starukhin A.

2017-01-01

Full Text Available In our study, we demonstrate the splitting effect of long-wavelength bands in absorption spectra (excitation of fluorescence of the series of Zn(II, Ti(IV, Zr(IV and Hf(IV phthalocyanines at low temperatures. The effect has been explained by the shift of metal ion out of the plane of phthalocyanine macrocycle, the transformation of macrocycle to nonplanar “dome” conformation and additional loss the high symmetry of macrocycle.

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...

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

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.

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.

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.

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...

El estudio de sistemas económicos complejos

Directory of Open Access Journals (Sweden)

Guillermo De León Lázaro

2012-01-01

Full Text Available Una y otra vez, un año tras otro, una generación después de otra, los investigadores que trabajan en el ámbito de la economía y gestión de empresas, han intentado encauzar sus esfuerzos hacía la búsqueda de un cuerpo científico capaz de comprender mejor, explicar más adecuadamente y tratar con rigor los fenómenos, cada vez más complejos, que mueven la vida de los estados, de las instituciones y de las empresas.

SIMULACIÓN DE MECANISMOS COMPLEJOS DE REACCIÓN.

Directory of Open Access Journals (Sweden)

Daniel A Barragán R.

2010-10-01

Full Text Available Se propone un método para la interpretación de mecanismos complejos de reacción, el cual es aplicado a la simulación del mecanismo de Gyórgyi-Field, (GF desarrollado para la reacción química oscilante de Belousov-Zhabotinsky (BZ. El método basado en la ley de acción de masas y en el principio de independencia y coexistencia de los pasos elementales, reproduce el comportamiento oscilatorio en la concentración de los intermediarios de reacción.

Fixation of carbon dioxide by macrocyclic lanthanide(III) complexes under neutral conditions producing self-assembled trimeric carbonato-bridged compounds with μ3-η2:η2:η2 bonding.

Science.gov (United States)

Bag, Pradip; Dutta, Supriya; Biswas, Papu; Maji, Swarup Kumar; Flörke, Ulrich; Nag, Kamalaksha

2012-03-28

A series of mononuclear lanthanide(III) complexes [Ln(LH(2))(H(2)O)(3)Cl](ClO(4))(2) (Ln = La, Nd, Sm, Eu, Gd, Tb, Lu) of the tetraiminodiphenolate macrocyclic ligand (LH(2)) in 95 : 5 (v/v) methanol-water solution fix atmospheric carbon dioxide to produce the carbonato-bridged trinuclear complexes [{Ln(LH(2))(H(2)O)Cl}(3)(μ(3)-CO(3))](ClO(4))(4)·nH(2)O. Under similar conditions, the mononuclear Y(III) complex forms the dimeric compound [{Y(LH(2))(H(2)O)Cl}(μ(2)-CO(3)){Y(LH(2))(H(2)O)(2)}](ClO(4))(3)·4H(2)O. These complexes have been characterized by their IR and NMR ((1)H, (13)C) spectra. The X-ray crystal structures have been determined for the trinuclear carbonato-bridged compounds of Nd(III), Gd(III) and Tb(III) and the dinuclear compound of Y(III). In all cases, each of the metal centers are 8-coordinate involving two imine nitrogens and two phenolate oxygens of the macrocyclic ligand (LH(2)) whose two other imines are protonated and intramolecularly hydrogen-bonded with the phenolate oxygens. The oxygen atoms of the carbonate anion in the trinuclear complexes are bonded to the metal ions in tris-bidentate μ(3)-η(2):η(2):η(2) fashion, while they are in bis-bidentate μ(2)-η(2):η(2) mode in the Y(III) complex. The magnetic properties of the Gd(III) complex have been studied over the temperature range 2 to 300 K and the magnetic susceptibility data indicate a very weak antiferromagnetic exchange interaction (J = -0.042 cm(-1)) between the Gd(III) centers (S = 7/2) in the metal triangle through the carbonate bridge. The luminescence spectral behaviors of the complexes of Sm(III), Eu(III), and Tb(III) have been studied. The ligand LH(2) acts as a sensitizer for the metal ions in an acetonitrile-toluene glassy matrix (at 77 K) and luminescence intensities of the complexes decrease in the order Eu(3+) > Sm(3+) > Tb(3+).

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

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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.

Consideraciones básicas del pensamiento complejo de Edgar Morin, en la educación

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José Miguel Pereira-Chaves

2010-06-01

Full Text Available Recibido 18 de noviembre de 2009 • Aceptado 02 de diciembre de 2009 • Corregido 09 de mayo de 2010     Este ensayo consiste en una breve descripción y un análisis del pensamiento complejo de Edgar Morin; para ello se hace mención al enfoque sistémico el cual se refiere a la interconexión y a las interacciones entre los objetos, las personas y el ambiente como un todo, lo cual sirve de fundamento para la propuesta educativa, en la que el conocimiento se debe abordar de manera integral y no fragmentado. Por lo anterior, el conocimiento humano debe fomentar la toma de conciencia de que somos tan sólo una parte componente de un sistema más general (complejo, y en constante interacción, en el que la educación puede ser el medio efectivo para que los alumnos desarrollen la capacidad de comprender otros sistemas complejos, además de los seres vivos. Aquí cobran importante interés las “nuevas ciencias” y las humanidades.

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...

10,21-Dimethyl-2,7,13,18-tetraphenyl-3,6,14,17-tetraazatricyclo[17.3.1.18,12]tetracosa-1(23,2,6,8(24,9,11,13,17,19,21-decaene-23,24-diol cyclohexane 0.33-solvate

Directory of Open Access Journals (Sweden)

Sushil K. Gupta

2011-10-01

Full Text Available The title compound, C46H40N4O2·0.33C6H12, was obtained unintentionally as a product of an attempted synthesis of a cadmium(II complex of the [2,6-{PhSe(CH22N=CPh}2C6H2(4-Me(OH] ligand. The full tetraiminodiphenol macrocyclic ligand is generated by the application of an inversion centre. The macrocyclic ligand features strong intramolecular O—H...N hydrogen bonds. The dihedral angles formed between the phenyl ring incorporated within the macrocycle and the peripheral phenyl rings are 82.99 (8 and 88.20 (8°. The cyclohexane solvent molecule lies about a site of overline{3} symmetry. Other solvent within the lattice was disordered and was treated with the SQUEEZE routine [Spek (2009. Acta Cryst. D65, 148–155].

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

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).

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

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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.

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...

Comparison of two cross-bridged macrocyclic chelators for the evaluation of 64Cu-labeled-LLP2A, a peptidomimetic ligand targeting VLA-4-positive tumors

International Nuclear Information System (INIS)

Jiang, Majiong; Ferdani, Riccardo; Shokeen, Monica; Anderson, Carolyn J.

2013-01-01

Integrin α 4 β 1 (also called very late antigen-4 or VLA-4) plays an important role in tumor growth, angiogenesis and metastasis, and there has been increasing interest in targeting this receptor for cancer imaging and therapy. In this study, we conjugated a peptidomimetic ligand known to have good binding affinity for α 4 β 1 integrin to a cross-bridged macrocyclic chelator with a methane phosphonic acid pendant arm, CB-TE1A1P. CB-TE1A1P-LLP2A was labeled with 64 Cu under mild conditions in high specific activity, in contrast to conjugates based on the “gold standard” di-acid cross-bridged chelator, CB-TE2A, which require high temperatures for efficient radiolabeling. Saturation binding assays demonstrated that 64 Cu-CB-TE1A1P-LLP2A had comparable binding affinity (1.2 nM vs 1.6 nM) but more binding sites (B max = 471 fmol/mg) in B16F10 melanoma tumor cells than 64 Cu-CB-TE2A-LLP2A (B max = 304 fmol/mg, p 64 Cu-CB-TE1A1P-LLP2A had less renal retention but higher uptake in tumor (11.4 ± 2.3 %ID/g versus 3.1 ± 0.6 %ID/g, p 64 Cu-CB-TE2A-LLP2A. At 2 h post-injection, 64 Cu-CB-TE1A1P-LLP2A also had significantly higher tumor:blood and tumor:muscle ratios than 64 Cu-CB-TE2A-LLP2A (CB-TE1A1P = 19.5 ± 3.0 and 13.0 ± 1.4, respectively, CB-TE2A = 4.2 ± 1.4 and 5.5 ± 0.9, respectively, p 64 Cu-CB-TE1A1P-LLP2A is an excellent PET radiopharmaceutical for the imaging of α 4 β 1 positive tumors and also has potential for imaging other α 4 β 1 positive cells such as those of the pre-metastatic niche

A Macrocyclic Agouti-Related Protein/[Nle4, DPhe7]α-Melanocyte Stimulating Hormone Chimeric Scaffold Produces Sub-nanomolar Melanocortin Receptor Ligands

OpenAIRE

Ericson, Mark D.; Freeman, Katie T.; Schnell, Sathya M.; Haskell-Luevano, Carrie

2017-01-01

The melanocortin system consists of five receptor subtypes, endogenous agonists, and naturally occurring antagonists. These receptors and ligands have been implicated in numerous biological pathways including processes linked to obesity and food intake. Herein, a truncation structure-activity relationship study of chimeric agouti-related protein (AGRP)/[Nle4, DPhe7]α-Melanocyte Stimulating Hormone (NDP-MSH) ligands is reported. The tetrapeptide His-DPhe-Arg-Trp or tripeptide DPhe-Arg-Trp repl...

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.

An enantiomerically pure siderophore type ligand for the diastereoselective 1 : 1 complexation of lanthanide(III ions

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Markus Albrecht

2009-12-01

Full Text Available A facile synthesis of a highly preorganized tripodal enterobactine-type ligand 1a-H3 consisting of a chiral C3-symmetric macrocyclic peptide and three tridentate 2-amido-8-hydroxyquinoline coordinating units is presented. Complex formation with various metal ions (Al3+, Ga3+, Fe3+, La3+ and Eu3+ was investigated by spectrophotometric methods. Only in the case of La3+ and Eu3+ were well defined 1 : 1 complexes formed. On the basis of CD spectroscopy and DFT calculations the configuration at the metal centre of the La3+ complex was determined to show Λ helicity. The coordination compounds [(1aLn] presented should be prototypes for further lanthanide(III complexes with an enterobactine analogue binding situation.

Chemistry Department, Faculty of Science, Alexandria University

African Journals Online (AJOL)

well defined coordination environments. Moreover, variation of functional groups on the equatorial macrocyclic ligand has provided a means for manipulating the reactivity of the metal centre. Herein, the dynamics of the reaction of oxygen with cobalt tetraaza macrocyclic complexes are reported. The complex investigated ...

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...

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

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.

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

The effect of heterocyclic S,S’-ligands on the electrochemical properties of some cobalt(III complexes in acid

Directory of Open Access Journals (Sweden)

V. M. JOVANOVIC

2005-02-01

Full Text Available Eight mixed-ligand cobalt(III complexes with the macrocyclic amine 1,4,8,11-tetraazacyclotetradecane (cyclam and a heterocyclic dithiocarbamate (Rdtc- i.e., morpholine- (Morphdtc, thiomorpholine- (Timdtc, piperazine- (Pzdtc, N-methylpiperazine-(Mepzdtc, piperidine- (Pipdtc, 2-, 3- or 4-methylpiperidine- (2-, 3- and 4-Mepipdtc carbodithionato-S,S ions, of the general formula [Co(cyclamRdtc](ClO42, were investigated in deoxygenated 0.1MHClO4 solutions. Cyclic voltammetry data at a glassy carbon (GC electrode demonstrate a redox reaction of cobalt(III from the complexes at potentials strongly influenced by the presence of different heterocyclic Rdtc- ligands. In this respect, the complexes were separated into two groups: the first, with a heteroatom O, S or N in the heterocyclic ring, and the second, with a methyl group on the piperidine ring of the Rdtc- ligand. Anodic polarization of an Fe electrode in the presence of the complexes shows their influence not only on the dissolution of iron but also on the hydrogen evolution reactions and on this basis complexes the complexes could be divided into the same two groups. It was found that the weaker the inhibiting effect of the free heterocyclic amines is, the significantly higher is the efficiency of the corresponding complexes.

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...

μ-Acetato-κ2O:O′-[7,23-dibenzyl-15,31-dichloro-3,7,11,19,23,27-hexaazatricyclo[27.3.1.113,17]tetratriconta-1(32,2,11,13,15,17(34,18,27,29(33,30-decaene-33,34-diolato-κ10N4,N5,N6,O1,O2:N1,N2,N3,O1,O2]dinickel(II perchlorate acetonitrile disolvate

Directory of Open Access Journals (Sweden)

Juan Kong

2008-01-01

Full Text Available The title complex, [Ni2(C42H46Cl2N6O2(C2H3O2]ClO4·2CH3CN, was synthesized by condensation of 2,6-diformyl-4-chlorophenol with N,N-bis(aminopropylbenzylamine in the presence of NiII ions. The ligand is a 28-membered macrocycle with two identical pendant arms. The coordination geometries of the Ni atoms are both octahedral. The two Ni atoms are bridged by two phenolate O atoms of the macrocyclic ligand and one acetate ligand, with an Ni...Ni distance of 3.147 (4 Å.

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.

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.

Cadmium (II) macrocyclic Schiff-base complexes containing piperazine moiety: Synthesis, spectroscopic, X-ray structure, theoretical and antibacterial studies

Science.gov (United States)

Keypour, Hassan; Mahmoudabadi, Masoumeh; Shooshtari, Amir; Bayat, Mehdi; Mohsenzadeh, Fariba; Gable, Robert William

2018-03-01

The new Cd(II) macrocyclic Schiff-base complexes were prepared via the metal templated [1 + 1] cyclocondensation of 2,2'-(piperazine-1,4-diylbis (methylene))dianiline (A) and 2,6-pyridinedicarbaldehyde or 2,6-diacetylpyridine. The products were characterized by elemental analysis, mass spectrometry and spectroscopic methods such as: FT-IR, 1H and 13C-NMR, the crystal structure of [CdL1(ClO4)2](CH3CN) (1) complex was also obtained by single-crystal X-ray crystallography. The complexes were tested for in vitro antibacterial properties against some bacteria. The complexes had antibacterial properties and in some cases were active even more than standards. The geometries of the [CdLn (ClO4)2], (n = 1,2) complexes have been optimized at the BP86/def2-SVP level of theory. Also the nature of Cd←Ln (n = 1, 2) bonds in [CdLn (ClO4)2], (n = 1,2) complexes are studied with the help of NBO and Energy decomposition analysis (EDA). Results showed that the nature of metal-ligand bond in the complexes is slightly more electrostatic with a contribution of about 52% in total interaction energy.

A Macrocyclic Agouti-Related Protein/[Nle4,DPhe7]α-Melanocyte Stimulating Hormone Chimeric Scaffold Produces Subnanomolar Melanocortin Receptor Ligands.

Science.gov (United States)

Ericson, Mark D; Freeman, Katie T; Schnell, Sathya M; Haskell-Luevano, Carrie

2017-01-26

The melanocortin system consists of five receptor subtypes, endogenous agonists, and naturally occurring antagonists. These receptors and ligands have been implicated in numerous biological pathways including processes linked to obesity and food intake. Herein, a truncation structure-activity relationship study of chimeric agouti-related protein (AGRP)/[Nle4,DPhe7]α-melanocyte stimulating hormone (NDP-MSH) ligands is reported. The tetrapeptide His-DPhe-Arg-Trp or tripeptide DPhe-Arg-Trp replaced the Arg-Phe-Phe sequence in the AGRP active loop derivative c[Pro-Arg-Phe-Phe-Xxx-Ala-Phe-DPro], where Xxx was the native Asn of AGRP or a diaminopropionic (Dap) acid residue previously shown to increase antagonist potency at the mMC4R. The Phe, Ala, and Dap/Asn residues were successively removed to generate a 14-member library that was assayed for agonist activity at the mouse MC1R, MC3R, MC4R, and MC5R. Two compounds possessed nanomolar agonist potency at the mMC4R, c[Pro-His-DPhe-Arg-Trp-Asn-Ala-Phe-DPro] and c[Pro-His-DPhe-Arg-Trp-Dap-Ala-DPro], and may be further developed to generate novel melanocortin probes and ligands for understanding and treating obesity.

Plan de mantenimiento integral del Complejo de Castejón

OpenAIRE

Eslava Zaragüeta, Óscar

2016-01-01

Este proyecto de Fin de Grado está enfocado hacia el control y seguimiento del mantenimiento en el Complejo de Castejón, ya que en dicho establecimiento no hay ningún tipo de control ni un plan de mantenimiento establecido. Este hecho, provoca gastos económicos elevados ya que el mantenimiento que se realiza es un mantenimiento correctivo, es decir, cuando se rompe un equipo o componente, se arregla o se sustituye, lo que provoca un gasto mucho mayor, además de posibles in...

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

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

ESTUDIO TERMODINÁMICO Y CINÉTICO DE LA FORMACIÓN DEL COMPLEJO 2' (OHACETOFENONA-Al(III

Directory of Open Access Journals (Sweden)

Yamina A. Dávila

2011-01-01

Full Text Available En este trabajo se realizó un estudio experimental basado en la velocidad de formación, estabilidad y estructura del complejo formado entre el Al(III y 2 ́(OHacetofenona en metanol y etanol usando espectroscopía UV- visible. Fueron estudiadas las influencias de la temperatura (15-35°C, fuerza iónica (1,7x10-3 – 7,8x10-3 M y permitividad relativa del solvente (ε r = 24,55 y 32,63 sobre la velocidad de reacción. Aplicando el método de la relación molar, se determinó la formación de un complejo de estequiometría 1:1. Además, fue calculada la constante de formación del complejo en metanol (KC= 6,08x105. Para la reacción de complejación (usando la Teoría del estado de transición los valores obtenidos fueron: MeOH ΔH‡ 18,7 kcal/mol y ΔS‡ 9,75 cal/K mol, y para EtOH ΔH‡ 23,0 kcal/mol y ΔS‡ 24,9 cal/K mol. Estas experiencias muestran que la velocidad específica de reacción aumenta con el descenso de la permitividad del medio y disminuye cuando la fuerza iónica del medio es mayor.

SISTEMAS COMPLEJOS, COMPUTACION EVOLUTIVA Y APLICACIONES A LA PLANIFICACION MINERA

OpenAIRE

Goles Chacc, Eric Antonio

2013-01-01

El secuenciamiento óptimo (extracción sucesiva en el tiempo de los bloques de la mina, en términos económicamente más conveniente) está directamente asociado a la parte más relevante del negocio minero. Del punto de vista del Modelamiento y su resolución por medio de algoritmos complejos, este problema no está bien resuelto en la industria actual, constituyéndose así en un dominio de investigación aplicada muy relevante. El objetivo del proyecto es generar una plataforma de servicios de...

Modelado lingüístico de fenómenos complejos

OpenAIRE

Álvarez Álvarez, Alberto

2012-01-01

Actualmente, es posible adquirir y almacenar grandes volúmenes de datos sobre diferentes fenómenos complejos en muchas áreas importantes. Con el fin de ser útil, esta información debe ser explicada de la manera más comprensible posible, incluyendo los conocimientos previos disponibles sobre el fenómeno que se estudia. Estos objetivos sólo pueden lograrse mediante el uso de lenguaje natural, especialmente si la información final va a ser utilizada por personas no expertas. Por lo tanto, e...

Isotopic shifts in chemical exchange systems. 1. Large isotope effects in the complexation of Na+ isotopes by macrocyclic polyethers

International Nuclear Information System (INIS)

Knoechel, A.; Wilken, R.D.

1981-01-01

The complexation of 24 Na + and 22 Na + by 18 of the most widely used macrocyclic polyethers (crown ethers and monocyclic and bicyclic aminopolyethers) has been investigated in view of possible equilibrium isotope shifts. Solvated salts and polyether complexes were distributed differently into two phases and isotope ratios determined in both phases. Chloroform/water systems were shown to be particularly suitable to the investigations allowing favorable distribution for Na + and 13 of the 18 polyethers employed. With crown ethers 24 Na + enrichment varied from nonsignficant values (for large crown ethers) up to 3.1 +- 0.4% (18-crown-6). In the case of bicyclic aminopolyethers, ligands with cages of optimum size to accommodate Na + showed 24 Na + enrichment between O (nonsignificant) (2.2/sub B/2./sub B/) and 5.2 +- 1.8% (2.2.1). In contrast, for 2.2.2. and its derivatives, being too large for Na + , 22 Na + enrichment varying from O (nonsignificant) (2.2.2.p) up to 5.4 +- 0.5% (2.2.2.) has been observed. These values are remarkably high. They are explained by different bonding in solvate structure and polyether complex by using the theoretical approach of Bigeleisen

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....

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

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.

Synthesis and characterization of Ni(II, Cu(II and Co(III complexes with polyamine-containing macrocycles bearing an aminoethyl pendant arm

Directory of Open Access Journals (Sweden)

K. S. SIDDIQI

2004-09-01

Full Text Available Reaction of [M(ppn2]X2 (where M = Cu(II, Ni(II, Co(II and ppn = 1,3-diaminopropane with formaldehyde and ethylenediamine in methanol results in the ready formation of a 16-membered macrocyclic complex. The complexes were characterized by elemental anlysis, IR, EPR, electronic spectral data, magnetic moments and conductance measurements. The Cu(II, Ni(II and Co(III complexes are coordinated axially with both pendant groups of the hexadentate macrocycle. These pendant donors are attached to the macrocycle by a carbon chain. The electrical conductivities of the Cu(II and Ni(II chelates indicated them to be 1:2 electrolytes whilst those of Co(III is a 1:3 electrolyte in DMSO. The EPR spectrum of the copper complex exhibited G at 3.66, which indicates a considerable exchange interaction in the complex. Spectroscopic evidence suggests that in all of the complexes the metal ion is in an octahedral environment.

Complejo residencial económico y popular - P.E.E.P. - Nueva Liguria – Italia

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Ceroni, Eugenio

1979-03-01

Full Text Available This article describes the construction of a building compound, built with government funds. This group contains, besides the housing units, both in 21 m-high tower form and in 18 m-high elongated building, a series of public and private services, namely: — Parking lots. — Underground garages. — Landscaped areas. — Play and sports grounds. — Religious, social, medical, cultural, and shopping centres, etc.

Se describe en este artículo la realización de un complejo de edificios, construidos con ayuda estatal. Este complejo, además de los edificios destinados a viviendas —cuya tipología varía desde edificios-torre, con una altura de 21 m, hasta edificios lineales con una altura de 18 m—, está dotado de una serie de servicios públicos y privados tales como: — Aparcamientos. — Garajes subterráneos. — Zonas verdes. — Campos de juego. — Centros religioso, social, médico, cultural, comercial, etc.

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

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.

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

Simulaciones hidrodinámicas de flujos complejos

Science.gov (United States)

María Ibáñez Cabanell, José

Son muchos los escenarios astrofísicos en que los procesos hidrodinámicos juegan un papel clave. En la complejidad que encierra la descripción de dichos procesos destaca el de la correcta simulación de flujos complejos donde la presencia de ondas de choque fuertes que, eventualmente, interaccionan entre ellas o también la presencia de inestabilidades (Kelvin-Helmholtz, Rayleigh-Taylor, etc.) suponen un verdadero desafío numérico. Los códigos hidrodinámicos basados en la solución de un problema de valores iniciales discontinuo (problema de Riemann) son, en la actualidad, los más robustos en el campo de la dinámica de fluidos computacional. En esta charla se dará un resumen de los fundamentos de dichas técnicas numéricas (esquemas de alta resolución de captura de choques) y se ilustrará su potencialidad mostrando una amplia gama de resultados en diferentes aplicaciones astrofísicas.

Adenopatía supraclavicular como forma de presentación de un carcinoma de cérvix asociado al complejo esclerosis tuberosa con linfangioleiomiomatosis

OpenAIRE

Pablo López Mato; Alfonso Varela Fariña; Elena Seco Hernández; Antonio J. Chamorro Fernández

2013-01-01

La linfangioleiomiomatosis es una proliferación del tejido muscular broncovascular que recientemente se ha definido como una expresión incompleta de la entidad “complejo esclerosis tuberosa”, una facomatosis a la que se asocian diversas neoplasias. Presentamos un caso de carcinoma de cérvix con metástasis supraclaviculares y cervicales, asociado a linfangioleiomiomatosis en el contexto de un “complejo esclerosis tuberosa”.

Congruencia del pensamiento complejo de Edgar Morín en la metodología de la educación a distancia

Directory of Open Access Journals (Sweden)

Monica de Jesus Chacón-Prado

2015-09-01

Full Text Available El filósofo francés Edgar Morín propone estudiar la verdad a través del pensamiento complejo. Este es un abordaje al conocimiento que apoya el uso de múltiples perspectivas o enfoques y niega la fragmentación del objeto durante su estudio. Por ello, este documento escribe desde la visión filosófica como el pensamiento complejo es especialmente útil en la educación a distancia porque fomenta convivir con la incertidumbre y la inestabilidad del mundo de hoy.

Supramolecular Allosteric Cofacial Porphyrin Complexes

International Nuclear Information System (INIS)

Oliveri, Christopher G.; Gianneschi, Nathan C.; Nguyen, Son Binh T.; Mirkin, Chad A.; Stern, Charlotte L.; Wawrzak, Zdzislaw; Pink, Maren

2008-01-01

Nature routinely uses cooperative interactions to regulate cellular activity. For years, chemists have designed synthetic systems that aim toward harnessing the reactivity common to natural biological systems. By learning how to control these interactions in situ, one begins to allow for the preparation of man-made biomimetic systems that can efficiently mimic the interactions found in Nature. To this end, we have designed a synthetic protocol for the preparation of flexible metal-directed supramolecular cofacial porphyrin complexes which are readily obtained in greater than 90% yield through the use of new hemilabile porphyrin ligands with bifunctional ether-phosphine or thioether-phosphine substituents at the 5 and 15 positions on the porphyrin ring. The resulting architectures contain two hemilabile ligand-metal domains (Rh I or Cu I sites) and two cofacially aligned porphyrins (Zn II sites), offering orthogonal functionalities and allowing these multimetallic complexes to exist in two states, 'condensed' or 'open'. Combining the ether-phosphine ligand with the appropriate Rh I or Cu I transition-metal precursors results in 'open' macrocyclic products. In contrast, reacting the thioether-phosphine ligand with RhI or CuI precursors yields condensed structures that can be converted into their 'open' macrocyclic forms via introduction of additional ancillary ligands. The change in cavity size that occurs allows these structures to function as allosteric catalysts for the acyl transfer reaction between X-pyridylcarbinol (where X = 2, 3, or 4) and 1-acetylimidazole. For 3- and 4-pyridylcarbinol, the 'open' macrocycle accelerates the acyl transfer reaction more than the condensed analogue and significantly more than the porphyrin monomer. In contrast, an allosteric effect was not observed for 2-pyridylcarbinol, which is expected to be a weaker binder and is unfavorably constrained inside the macrocyclic cavity.

Complejos de halógeno acetatos de uranio (IV y torio (IV con sulfoxidos y fosfinoxidos

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Omar Velasquez

2010-09-01

Full Text Available En este trabajo se ha Investigado el efecto sterico sobre los modos de coordinación del grupo carboxilato (unidentado, bidentado y puente, en complejos de halógeno acetato con fosfinóxidos y sulfóxidos y la correlación de los resultadoscon el modelo "Cone Angle" e\\ cual ha sido descrito en otra publicación previa' Los complejos preparados son: M(RCO ^ .nL donde n = 4, M = Th ó U, L = Me^SO (dmso, R = CF,3 y L = Me3P0 (tmpo; n = 3, M = Th, L = tmpo, R = CF3 y L = ppo o dmso, R OCCI3; M = U, L = t p p o , R =CF3 y L =dmso, dpso, R = C C l 3 ; n = 2 , M = T h , L = tppo, R = CF3, CHCI^On^ 1, M = Th ó U, L =dmso.

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...

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

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).

Adenopatía supraclavicular como forma de presentación de un carcinoma de cérvix asociado al complejo esclerosis tuberosa con linfangioleiomiomatosis

Directory of Open Access Journals (Sweden)

Pablo López Mato

2013-09-01

Full Text Available La linfangioleiomiomatosis es una proliferación del tejido muscular broncovascular que recientemente se ha definido como una expresión incompleta de la entidad “complejo esclerosis tuberosa”, una facomatosis a la que se asocian diversas neoplasias. Presentamos un caso de carcinoma de cérvix con metástasis supraclaviculares y cervicales, asociado a linfangioleiomiomatosis en el contexto de un “complejo esclerosis tuberosa”.

Reduction reactions of water soluble cyano-cobalt(III)-porphyrins: Metal versus ligand centered processes

International Nuclear Information System (INIS)

Mosseri, S.; Neta, P.; Harriman, A.; Hambright, P.

1990-01-01

Reduction reactions of dicyano-cobalt(III)-porphyrins [potential in vivo cyanide scavenger drugs] were studied by radiolytic and electrochemical methods using the water soluble tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and tetrakis(N-methyl-4-pyridyl)porphyrin (TMPyP). For [(CN)2CoIIITPPS]-, reduction occurs stepwise to the CoII, CoI, and finally to the phlorin anion. This behavior is similar to that of the cobalt porphyrins in the absence of cyanide, except that the cyanide ligand shifts the reduction potentials to much more negative values. On the other hand, under radiolytic conditions, [(CN)2CoIIITMPyP]- is reduced on the porphyrin macrocycle by one electron to give the CoIII pi-radical anion, which disproportionates into the initial complex and the two-electron ring reduced CoIII phlorin. The radical anion is also formed by intramolecular electron transfer subsequent to the reaction of CoIITMPyP and cyanide. The results are compared with the chemistry of Vitamin B-12

Synthesis and Characterization of Some Macrocylic Complexes Incorporating Indole and 2,2'-Bipyridine or 1,10-Phenanthroline

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Muhammad S. Khan

2015-06-01

Full Text Available Complexes of anionic pentadentate macrocyclic ligands by the template condensation of bis(hydrazino2,2'-bipyridine or 1,10-phenanthroline with an indoledialdehyde have been synthesized. The new Mn(II, Fe(II, Co(II, Ni(II, Cu(II and Zn(II macrocyclic complexes have been characterized by analytical and spectroscopic techniques and by conductivity and magnetic susceptibility measurements.

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

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.

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.

VARIABILIDAD MORFOLÓGICA DE LAS ESPECIES DEL COMPLEJO POA RESINULOSA (POACEAE Y SU RELACIÓN CON LAS ESPECIES DE LA SECCIÓN DIOICOPOA

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M. Gabriela Fernández Pepi

2008-01-01

Full Text Available El complejo Poa resinulosa incluye un grupo de especies conformado por P. calchaquiensis, P. pedersenii y P. resinulosa, de difícil delimitación debido a que las entidades son afines en cuanto a su morfología, aunque presentan distribución disyunta. Para evaluar y analizar a las especies del complejo Poa resinulosa y especies afines al mismo complejo, se midieron 40 caracteres morfológicos y anatómicos en ejemplares de Poa calchaquiensis, P. lanigera, P. pilcomayensis y P. resinulosa. Esos datos se incorporaron a la matriz del conjunto de especies de Poa sección Dioicopoa confeccionada por Giussani (2000, incluyendo también a P. nubensis una nueva especie afín a P. calchaquiensis. Mediante el análisis de componentes principales y pruebas estadísticas, se circunscribió a las especies del complejo Poa resinulosa. Se describió a P. resinulosa como una variedad de P. ligularis, de la que se diferencia por poseer lígula corta, hojas y cañas de menor longitud, menor ancho de la lámina y estomas de menor tamaño. Se presenta una clave para la identificación de Poa ligularis var. resinulosa y taxones afines, y un mapa con la distribución geográfica de ambas variedades de P. ligularis.

De sistema mecánico a sistema tecnológico complejo. El caso de los automóviles

Directory of Open Access Journals (Sweden)

Arturo Ángel Lara Rivero

2014-01-01

Full Text Available La mayoría de los trabajos de investigación relacionados con el sector automotriz se ha concentrado en el análisis de la naturaleza mecánica de los vehículos y, de una manera muy escasa, al estudio de su naturaleza electrónica. Para dar cuenta de las transformaciones profundas ocurridas en las últimas cuatro décadas es necesario integrar en la explicación la manera en que los componentes y los sistemas electrónicos han transformado la naturaleza de los vehículos automotores. El objetivo de este trabajo es analizar la naturaleza de los procesos evolutivos implicados en la transición del vehículo automotor: de un sistema complejo a un sistema complejo adaptable.

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

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

Preparation and characterization of electroluminescent devices based on complexes of {beta}-diketonates of Tb{sup 3+}, Eu{sup 3+}, Gd{sup 3+} ions with macrocyclic ligands and UO{sub 2}{sup 2+} films; Preparacao e caracterizacao de dispositivos eletroluminescentes de complexos de {beta}-dicetonados de ions Tb{sup 3+}, Eu{sup 3+}, Gd{sup 3+} com ligantes macrociclicos e filmes de UO{sub 2}{sup 2+}

Energy Technology Data Exchange (ETDEWEB)

Gibelli, Edison Bessa

2010-07-01

Complexes containing Rare Earth ions are of great interest in the manufacture of electro luminescent devices as organic light emitting devices (OLED). These devices, using rare earth trivalent ions (TR{sup 3+}) as emitting centers, show high luminescence with extremely fine spectral bands due to the structure of their energy levels, long life time and high quantum efficiency. This work reports the preparation of Rare Earth {beta}-diketonate complexes (Tb{sup 3+}, Eu{sup 3+} and Gd{sup 3+}) and (tta - thenoyltrifluoroacetonate and acac - acetylacetonate) containing a ligand macrocyclic crown ether (DB18C6 - dibenzo18coroa6) and polymer films of UO{sub 2}{sup 2+}. The materials were characterized by complexometric titration with EDTA, CH elemental analysis, near infrared absorption spectroscopy, thermal analysis, X-ray diffraction (powder method) and luminescence spectroscopy. For manufacturing the OLED it was used the technique of deposition of thin films by physical vapor (PVD, Physical Vapor Deposition). (author)

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

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

Catalytic hydrogenation of carbon monoxide

International Nuclear Information System (INIS)

Wayland, B.B.

1993-12-01

Focus of this project is on developing new approaches for hydrogenation of carbon monoxide to produce organic oxygenates at mild conditions. The strategies to accomplish CO reduction are based on favorable thermodynamics manifested by rhodium macrocycles for producing a series of intermediates implicated in the catalytic hydrogenation of CO. Metalloformyl complexes from reactions of H 2 and CO, and CO reductive coupling to form metallo α-diketone species provide alternate routes to organic oxygenates that utilize these species as intermediates. Thermodynamic and kinetic-mechanistic studies are used in guiding the design of new metallospecies to improve the thermodynamic and kinetic factors for individual steps in the overall process. Electronic and steric effects associated with the ligand arrays along with the influences of the reaction medium provide the chemical tools for tuning these factors. Non-macrocyclic ligand complexes that emulate the favorable thermodynamic features associated with rhodium macrocycles, but that also manifest improved reaction kinetics are promising candidates for future development

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.

Ambrona (Soria) : apuntes sobre la industria lítica del Complejo Superior

OpenAIRE

Rubio Jara, Susana

1996-01-01

La finalidad de este trabajo, resumen de mi tesis de licenciatura, es caracterizar tecnomorfológicamente la industria lítica del Complejo Superior de Ambrona, de la que hasta el momento sólo se ha publicado el número total de piezas pese haber sido objeto de estudio entre los años 60 y 80.This paper, summary of my gradúate thesis, characterizes in a technomorphological frame, the lithic industry of «The Upper Complex» in Ambrona site. This industry although it was exposing between the sixties...

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

Sistema de reconocimiento y diagnóstico de arritmias cardíacas aplicado a la identificación de taquicardias de complejos anchos a partir del ECG

Directory of Open Access Journals (Sweden)

Oscar Javier Olarte

2009-01-01

Full Text Available Se presenta una herramienta software como soporte al diagnóstico diferencial de taquicardias de complejos anchos basado en la metodología clínica de diagnóstico Bayesiano. El sistema consta de módulos independientes para: a Detección de complejos, con sensibilidad (Sn de 94% y valor predictivo positivo (VP+ de 97,5%. b cómputo de la duración del complejo, con error cuadrático medio (ERMS de 25,2 ms c determinación del eje eléctrico del complejo QRS, con error RMS de 5,89º d determinación de morfología de bloqueo de rama, con Sn 89,9% y VP+ 93,3% y e clasificación de morfologías de QRS, donde se obtuvo clasificación completa. La técnica empleada se basa en detección de cruces por cero y valores singulares (máximos y mínimos en la transformada wavelet. Por su parte, el sistema de clasificación de morfologías se desarrolla con redes neuronales artificiales.

Syn-anti conformational switching in an ethane-bridged Co(II)bisporphyrin induced by external stimuli: effects of inter-macrocyclic interactions, axial ligation and chemical and electrochemical oxidations.

Science.gov (United States)

Dey, Soumyajit; Rath, Sankar Prasad

2014-02-07

The syn-anti conformational switching has been demonstrated in the ethane-bridged dicobalt(II)bisporphyrin which is present in the syn-form only. The addition of either perylene or axial ligands to Co(II)(bisporphyrin) completely transforms the syn form into the anti because of strong π-π interaction and axial coordination, respectively. The complex undergoes four 1e-oxidations in CH2Cl2 which are indicative of strong through space interactions between the two cofacial Co-porphyrins at 295 K. The first oxidation is a metal centered one and occurs at a potential much lower than that of the monomeric analog. However, the second oxidation, which is again metal centered, was at a significantly higher potential. The large difference between the first two oxidations, as observed here, is due to much stronger inter-porphyrin interactions. The step-wise oxidations have been performed both chemically and electro-chemically while the progress of the reactions was monitored by UV-visible and (1)H NMR spectroscopy. After 1e-oxidation, a very broad (1)H NMR signal results with increased difference between two meso resonances, which indicates that the two macrocycles are in the syn-form with lesser interplanar separation as also observed by DFT. However, 2e-oxidation results in the stabilization of the anti form. The addition of axial ligands to Co(II)(bisporphyrin) also completely transforms the syn form into the anti form. While additions of THF and I2/I(-) both result in the formation of five-coordinate complexes, Co(II) is oxidized to Co(III) in the case of the latter. However, additions of 1-methylimidazole, pyridine and pyrazine as axial ligands result in the formation of a six-coordinate complex in which Co(II) is spontaneously oxidized to Co(III) in air.

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

A diversity-oriented synthesis strategy enabling the combinatorial-type variation of macrocyclic peptidomimetic scaffolds† †Electronic supplementary information (ESI) available: Experimental procedures, characterization data and details of the computational analyses. See DOI: 10.1039/c5ob00371g Click here for additional data file.

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.

2015-01-01

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. PMID:25778821

Adipocinas y síndrome metabólico: múltiples facetas de un proceso fisiopatológico complejo

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Julio C. Sánchez N., MD., PhD

2010-07-01

Full Text Available Debido a la alta morbimortalidad de las enfermedades cardiovasculares y a su relación con trastornos de base como la obesidad y el síndrome metabólico, es crucial entender cuáles son los mecanismos y procesos que desencadenan la alteración del metabolismo y a su vez la generación de dichas enfermedades. En tal sentido, el tejido adiposo y el adipocito tienen un papel fundamental en este proceso, mediante la producción de múltiples adipocinas, algunas clásicas y otras de reciente descripción, pero que hasta ahora empieza a dilucidarse en medio del complejo panorama de interacciones fisiopatológicas conducentes al desarrollo de resistencia a la insulina y del complejo desequilibrio metabólico que conlleva un sinnúmero de complicaciones clínicas. Un grupo de estas adipocinas tiene claros efectos proinflamatorios, mientras que otras pueden clasificarse como anti-inflamatorias, las cuales contrarrestan en cierta medida y hasta cierto punto las acciones de las otras. Cuando esta homeostasis se rompe, la cascada de inflamación crónica allí originada desencadena resistencia a la insulina y se inicia el desarrollo del síndrome metabólico a partir de la obesidad, que a su vez genera alteraciones de la respuesta del adipocito a diferentes estímulos. Esto, sumado a los efectos de otros elementos, configura un complejo cuadro de factores que es necesario tener en cuenta para el abordaje correcto de la obesidad y sus patologías asociadas.

Caracterización del complejo productivo de la madera de la Provincia de Córdoba, Argentina. Factores que dificultan su competitividad

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Gerardo Andrés Denegri

2016-01-01

Full Text Available El objetivo del trabajo es determinar y analizar las cadenas foresto-industriales que componen el complejo productivo de la madera de la provincia de Córdoba, y discutir las variables que afectan su competitividad. Para recabar los datos se recurrió a encuestas semiestructuradas a informantes claves y revisión bibliográfica. Se identificaron y analizaron tres cadenas: la del mueble de madera, la de productos para la construcción y la de envases y tarimas. Del análisis del comportamiento de los actores, surge que la rentabilidad de las empresas del eslabón industrial se logra transfiriendo la ineficiencia del complejo a las forestaciones y, en menor medida, a los bosques nativos, maximizando la ganancia individual. Se sostiene como conclusión que sin la intervención de diferentes niveles del Estado, la posibilidad de obtener una cierta rentabilidad de corto plazo y una fuerte cultura individualista no son incentivos para cooperar y generar procesos sostenibles de integración. La cooperación entre los distintos actores facilitaría una mayor integración entre las cadenas, la incorporación de valor, elevar la eficiencia y la competitividad sistémica del complejo.

Copper(II) and Zinc(II) Complexes of Conformationally Constrained Polyazamacrocycles as Efficient Catalysts for RNA Model Substrate Cleavage in Aqueous Solution at Physiological pH

Czech Academy of Sciences Publication Activity Database

Bím, Daniel; Svobodová, E.; Eigner, V.; Rulíšek, Lubomír; Hodačová, J.

2016-01-01

Roč. 22, č. 30 (2016), s. 10426-10437 ISSN 0947-6539 R&D Projects: GA ČR(CZ) GA14-31419S Institutional support: RVO:61388963 Keywords : cleavage reactions * density functional calculations * ligand design * macrocyclic ligands * reaction mechanisms Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.317, year: 2016

Ambrona (Soria : apuntes sobre la industria lítica del Complejo Superior

Directory of Open Access Journals (Sweden)

Susana Rubio Jara

1996-01-01

Full Text Available La finalidad de este trabajo, resumen de mi tesis de licenciatura, es caracterizar tecnomorfológicamente la industria lítica del Complejo Superior de Ambrona, de la que hasta el momento sólo se ha publicado el número total de piezas pese haber sido objeto de estudio entre los años 60 y 80.This paper, summary of my gradúate thesis, characterizes in a technomorphological frame, the lithic industry of «The Upper Complex» in Ambrona site. This industry although it was exposing between the sixties and eigthies, untll this moment it was unpublished.

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

Separation and characterization of metallosupramolecular libraries by ion mobility mass spectrometry.

Science.gov (United States)

Li, Xiaopeng; Chan, Yi-Tsu; Casiano-Maldonado, Madalis; Yu, Jing; Carri, Gustavo A; Newkome, George R; Wesdemiotis, Chrys

2011-09-01

The self-assembly of Zn(II) ions and bis(terpyridine) (tpy) ligands carrying 120° or 180° angles between their metal binding sites was utilized to prepare metallosupramolecular libraries with the connectivity. These combinatorial libraries were separated and characterized by ion mobility mass spectrometry (IM MS) and tandem mass spectrometry (MS(2)). The 180°-angle building blocks generate exclusively linear complexes, which were used as standards to determine the architectures of the assemblies resulting from the 120°-angle ligands. The latter ligand geometry promotes the formation of macrocyclic hexamers, but other n-mers with smaller (n = 5) or larger ring sizes (n = 7-9) were identified as minor products, indicating that the angles in the bis(terpyridine) ligand and within the coordinative tpy-Zn(II)-tpy bonds are not as rigid, as previously believed. Macrocyclic and linear isomers were detected in penta- and heptameric assemblies; in the larger octa- and nonameric assemblies, ring-opened conformers with compact and folded geometries were observed in addition to linear extended and cyclic architectures. IM MS(2) experiments provided strong evidence that the macrocycles present in the libraries were already formed in solution, during the self-assembly process, not by dissociation of larger complexes in the gas phase. The IM MS/MS(2) methods provide a means to analyze, based on size and shape (architecture), supramolecular libraries that are not amenable to liquid chromatography, LC-MS, NMR, and/or X-ray techniques.

Synthesis and study of lipophilic crown ethers and thia-ligands. Application to nuclear fuel reprocessing

International Nuclear Information System (INIS)

Guyon, Vincent

1992-01-01

In the field of metal extraction from the solutions of nuclear fuel reprocessing, new specific complexing agents that are more efficient than tributyl phosphate must possess a high lipophilic character. The use of lipophilic crown ethers and thia-ligands has eliminated the problem related to their loss in the aqueous media. Moreover, it has made their complexes more soluble in organic solvents. The increase of lipophilic character of monocyclic polyethers has been realized with the addition of an alkyl chain and the development of a new process has made possible the separation of cis-syn-cis and cis-anti-cis isomers of dicyclohexano 18 crown 6 on an industrial scale. The creation of a rapid NMR method of analysis has permitted to study the extracting capacity of those crown ethers in relation to monovalent and divalent cations in nitric acid media and also to demonstrate the influence brought by different substituents. Some new lipophilic thia-ligands (macrocycles and podands) have also been prepared and the study of palladium extraction in nitric acid media by these compounds has led to a better understanding of the relation between the structure and the extracting capacity. Of easy access, some podands have an extracting selectivity and an extracting kinetic for this metal which are highly superior than those of dialkyl sulphides actually employed in the industry. This makes their use possible in the nuclear area. (author) [fr

Suplementos nutricionales orales a base de nuevos complejos de cobre, magnesio, manganeso y zinc

OpenAIRE

Benavides Arévalo, Julie Fernanda; Tobón Zapata, Gloria Elena

2011-01-01

Suplementos nutricionales orales a base de nuevos complejos de cobre, magnesio, manganeso y zinc Los oligoelementos cobre, magnesio, manganeso y zinc intervienen en numerosos procesos metabólicos, enzimáticos, inmunológicos y tisulares, forman parte estructural de proteínas y pueden participar en la regulación de la expresión genética. La deficiencia de estos elementos esenciales dificulta el apropiado funcionamiento del organismo e induce el desarrollo de diversas enfermedades. Se debe garan...

Macrocyclic receptor showing extremely high Sr(II)/Ca(II) and Pb(II)/Ca(II) selectivities with potential application in chelation treatment of metal intoxication.

Science.gov (United States)

Ferreirós-Martínez, Raquel; Esteban-Gómez, David; Tóth, Éva; de Blas, Andrés; Platas-Iglesias, Carlos; Rodríguez-Blas, Teresa

2011-04-18

Herein we report a detailed investigation of the complexation properties of the macrocyclic decadentate receptor N,N'-Bis[(6-carboxy-2-pyridil)methyl]-4,13-diaza-18-crown-6 (H(2)bp18c6) toward different divalent metal ions [Zn(II), Cd(II), Pb(II), Sr(II), and Ca(II)] in aqueous solution. We have found that this ligand is especially suited for the complexation of large metal ions such as Sr(II) and Pb(II), which results in very high Pb(II)/Ca(II) and Pb(II)/Zn(II) selectivities (in fact, higher than those found for ligands widely used for the treatment of lead poisoning such as ethylenediaminetetraacetic acid (edta)), as well as in the highest Sr(II)/Ca(II) selectivity reported so far. These results have been rationalized on the basis of the structure of the complexes. X-ray crystal diffraction, (1)H and (13)C NMR spectroscopy, as well as theoretical calculations at the density functional theory (B3LYP) level have been performed. Our results indicate that for large metal ions such as Pb(II) and Sr(II) the most stable conformation is Δ(δλδ)(δλδ), while for Ca(II) our calculations predict the Δ(λδλ)(λδλ) form being the most stable one. The selectivity that bp18c6(2-) shows for Sr(II) over Ca(II) can be attributed to a better fit between the large Sr(II) ions and the relatively large crown fragment of the ligand. The X-ray crystal structure of the Pb(II) complex shows that the Δ(δλδ)(δλδ) conformation observed in solution is also maintained in the solid state. The Pb(II) ion is endocyclically coordinated, being directly bound to the 10 donor atoms of the ligand. The bond distances to the donor atoms of the pendant arms (2.55-2.60 Å) are substantially shorter than those between the metal ion and the donor atoms of the crown moiety (2.92-3.04 Å). This is a typical situation observed for the so-called hemidirected compounds, in which the Pb(II) lone pair is stereochemically active. The X-ray structures of the Zn(II) and Cd(II) complexes show that

Complejo tubo-ovárico: revisión de casos en el Hospital Nacional Cayetano Heredia (1990-1999

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Ronald Roberto Sanchez Silva Torriani

2003-07-01

Full Text Available Objetivo: Determinar las características epidemiológicas, clínicas y de manejo del complejo tubo-ovárico (CTO.Material y métodos: Se realizó un estudio retrospectivo en 65 pacientes hospitalizadas con diagnóstico de complejo tubo-ovárico (CTO en el Servicio de Ginecología del Hospital Nacional Cayetano Heredia de Lima, Perú, entre Enero de 1990 y Diciembre de 1999. Se registraron datos demográficos, antecedentes patológicos, cuadro clínico, exámenes auxiliares, tratamiento médico, quirúrgico, hallazgos operatorios, complicaciones quirúrgicas, tiempo de hospitalización y seguimiento. Resultados: El complejo tubo-ovárico correspondió al 0.72% de las pacientes hospitalizadas en el servicio de Ginecología de este hospital. Este fue más frecuente entre la tercera y cuarta década de la vida (promedio = 31.9 años, en casadas (44.6% y multigestas (53.8%. El uso de dispositivos intrauterinos no tuvo relación estadísticamente significativa con la localización del CTO confirmado quirúrgicamente. Las manifestaciones clínicas más frecuentes fueron dolor pélvico (96.9%, fiebre (76.9%, dolor a la movilización cervical (60% y masa anexial (58.5%. La ecografía pélvica presentó mayor positividad en el diagnóstico de CTO (91.3%, luego de la laparoscopía (100%, aunque ésta se realizó solo en 4 casos. El drenaje de absceso más lavado de cavidad peritoneal tuvo similar porcentaje de complicaciones que las demás técnicas, pero en el seguimiento 2 pacientes (14.3% fueron reoperadas. En el seguimiento de 24 pacientes el dolor pélvico fue el problema más frecuente en 40% de casos. No hubo mortalidad en este estudio. Conclusiones: El complejo tubo-ovárico es una patología que compromete la capacidad reproductiva y función ovárica de la mujer. La ecografía es un examen que presentó alta positividad en el diagnóstico. La laparotomía exploratoria más drenaje de absceso y lavado de cavidad peritoneal es un tratamiento quir

La producción familiar en el complejo avícola entrerriano: trayectoria, estrategias y transformaciones

OpenAIRE

García , Ana Laura

2012-01-01

El presente trabajo aborda el análisis de las estrategias desplegadas por los productores familiares integrados contractualmente al complejo avícola entrerriano a lo largo de sus cursos de vida. En particular, interesa profundizar tres ejes: los cambios y continuidades en sus estrategias, sus implicancias en términos de la permanencia de la agricultura familiar y su reconfiguración interna.

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

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.

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

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.

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.

Escolecita de aglomerados basálticos del complejo basal de Fuerteventura (Islas Canarias)

OpenAIRE

La Iglesia, Á.; Fernández Santín, Soledad; Hernández-Pacheco, A.

1990-01-01

Se caracteriza por análisis químico, microscopía óptica, difracción de Rayos X, análisis térmico diferencial, termogravimetría y espectroscopía de infrarrojos, una zeolita fibrosa perteneciente a la formación volcánica aglomerática del Complejo Basal de la isla de Fuerteventura. Los datos analíticos obtenidos confirman la identidad de esta zeolita fibrosa como escolecita. El análisis químico del mineral pone de manifiesto un elevado contenido en sodio, superior a los que aparecen en la biblio...

Bioética global y pensamiento complejo. Hacia una emergente manera de ser

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Sergio Néstor Osorio García

2008-01-01

Full Text Available La Bioética global como el pensamiento complejo sólo pueden entenderse en su novedad, si las comprendemos como estrategias emergentes que buscan enfrentar y responder a los desafíos de nuestra era planetaria. Desafíos que retan como nunca nuestra creatividad histórica para habitar la tierra. La consolidación y desarrollo de estas dos importantes estrategias del pensamiento y la acción, nos podrían ayudar en la construcción de un mundo más decente para los humanos y menos destructivo para con los ecosistemas no-humanos.

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.

Sales de imidazolio funcionalizadas: síntesis y formación de complejos metálicos

OpenAIRE

Sol Sánchez, Daniel

2014-01-01

El presente trabajo describe la síntesis de una sal de imidazolio funcionalizada con un grupo difenilfosfino en el carbono de la posición 4 del anillo heterocíclico y el estudio de su reactividad orientada a la formación de complejos metálicos, singularmente aquellos que contienen el carbeno N-heterocíclico derivado de la desprotonación del catión imidazolio.

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

Bromido(1,4,7,10,13-pentaazacyclohexadecanecobalt(III dibromide dihydrate

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Tsutomu Kurisaki

2013-04-01

Full Text Available The title salt, [CoBr(C11H27N5]Br2·2H2O, contains a complex cation with mirror symmetry and two Br− counter-anions that are likewise located on the mirror plane. The central CoIII atom of the complex cation has one Br− ion in an axial position, one N atom of the pentadentate macrocyclic ligand in the other axial position and four N atoms of the ligand in equatorial positions, defining a distorted octahedral coordination geometry. The macrocyclic ligand is coordinated to the CoIII atom within a 5, 6, 5 arrangement of chelate rings in the equatorial plane of the four N atoms. Due to symmetry, the configuration of the chiral N atoms is 1RS, 4SR, 10RS, 13SR. In the crystal, N—H...Br, O—H...Br and N—H...O hydrogen bonds between the complex cation, anions and lattice water molecules generate a three-dimensional network.

EL PROCESO DE FORMACIÓN PROFESIONAL DESDE UN PUNTO DE VISTA COMPLEJO E HISTÓRICO-CULTURAL

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Odalia Llerena Companioni

2015-01-01

Full Text Available En este ensayo se valoran conceptos e ideas centrales en la obra de Lev. S. Vigotsky y Edgar Morin y se expresan algunos puntos de enlace entre ellas que pueden servir de base al reconocimiento de la formación profesional como proceso complejo, a partir de la Teoría de la Complejidad y el Enfoque Histórico-Cultural como bases teóricas-metodológicas que permiten valorar el desarrollo del proceso de formación profesional, desde una perspectiva crítica, integral y contextualizada culturalmente. Los puntos de referencia que tradicionalmente, caracterizaron el análisis del proceso de formación son objeto de significativas modificaciones en lo que puede denominarse la era de la educación global. Dichos cambios provienen tanto de la evolución científica y tecnológica, como de una concepción educativa que pone en el centro el desarrollo integral del ser humano. Para responder a esta realidad se precisa observar dicho proceso de formación a partir de las peculiaridades individuales y las condiciones en que este se produce, así como las relaciones de mutua influencia entre todos estos aspectos que le otorgan un carácter complejo.

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).

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.

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)

Rigid versus Flexible Ligands on Carbon Nanotubes for the Enhanced Sensitivity of Cobalt Ions

Energy Technology Data Exchange (ETDEWEB)

Gou, Pingping; Kraut, Nadine D.; Feigel, Ian Matthew; Star, Alexander

2013-02-26

Carbon nanotubes have shown great promise in the fabrication of ultra-compact and highly sensitive chemical and biological sensors. Additional chemical functionalization schemes can controllably improve selectivity of the carbon nanotube-based sensors; however the exact transduction mechanism is still under debate. In this article we detail the synthesis and selective response of single-walled carbon nanotubes (SWNTs) functionalized with polyazomethine (PAM) polymer towards the application of a specific trace metal ion detector. The response of the polymer system was compared to shape persistent macrocycle (MAC) comprised of identical ion coordination ligands. While ion detection with rigid MAC/SWNT chemiresistor was comparable to bare SWNT, flexible PAM offers significant SWNT signal amplification, allowing for picomolar detection of Co{sup 2+} ions with both selectivity and a fast response. We hypothesized that rearrangement of the flexible PAM on the SWNT network is a sensing mechanism which allows for ultrasensitive detection of metal ions. The electron transfer and polymer rearrangement on the SWNT was studied by a combination of optical spectroscopy and electrical measurements - ultimately allowing for a better understanding of fundamental mechanisms that prompt device response.

Complejidad, interdisciplina y política en la teoría de los sistemas complejos, de Rolando García

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Leonardo G. Rodríguez Zoya

2017-07-01

Full Text Available Con su teoría de los Sistemas complejos, Rolando García establece un enfoque teórico-metodológico para la investigación interdisciplinaria de sistemas complejos, fundamentado en la epistemología constructivista de Jean Piaget. El objetivo de este artículo es analizar tres conceptos que subyacen en esta teoría: complejidad, interdisciplina y política. La estrategia argumental está organizada en dos etapas: en la primera se examina la relación entre complejidad e interdisciplina, y las tres concepciones de complejidad que este vínculo arroja (como concepto metodológico, como concepto organizacional y como concepto evolutivo. En la segunda etapa argumental se explora, particularmente, la dimensión política; también, las finalidades prácticas del enfoque planteado por García y las implicaciones del concepto de marco epistémico.

Abordar lo complejo desde el diseño: una mirada hacia la transdisciplinariedad

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Leonardo Andrés Moreno Toledano

2017-07-01

Full Text Available El presente ensayo plantea una reflexión sobre la dificultad que las disciplinas actuales presentan al enfrentarse a los problemas complejos de nuestra era. Para ello, se plantea la necesidad de abordar los fenómenos actuales desde enfoques no tradicionales y desarrollados a raíz de algunas teorías que han sido creadas con el fin de explicar este tipo de problemas. Asimismo, en el artículo se resalta el potencial del diseño, como disciplina orientada a la práctica, para encontrar soluciones a diversos fenómenos que se suceden en nuestras sociedades a partir de visiones no unidisciplinares.

Diez pasos para el aprendizaje complejo: Un acercamiento sistemático al diseňo instruccional de los cuatro componentes

NARCIS (Netherlands)

Van Merriënboer, Jeroen; Kirschner, Paul A.

2011-01-01

Van Merriënboer, J. J. G., & Kirschner, P. A. (2010). Diez pasos para el aprendizaje complejo: Un acercamiento sistemático al diseňo instruccional de los cuatro componentes (translation from English). Cuajimalpa, México: Aseguramiento de la Calidad en la Educacion y en el Trabajo.

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

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.

Interaction of d(10) metal ions with thioether ligands: a thermodynamic and theoretical study.

Science.gov (United States)

Melchior, Andrea; Peralta, Elena; Valiente, Manuel; Tavagnacco, Claudio; Endrizzi, Francesco; Tolazzi, Marilena

2013-05-07

Thermodynamic parameters of complex formation between d(10) metal ions, such as Zn(2+), Cd(2+), Hg(2+) and Ag(+), and the macrocyclic thioether 1,4,7-trithiacyclononane ([9]AneS3) or the monodentate diethylsulfide (Et(2)S), in acetonitrile (AN) at 298.15 K, were studied by a systematic methodology including potentiometry, calorimetry and polarography. [9]AneS3 is able to form complexes with all the target cations, Et(2)S only reacts with Hg(2+) and Ag(+). Mononuclear ML(j) (j = 1, 2) complexes are formed with all the metal ions investigated, where the affinity order is Hg(2+) > Ag(+) > Cd(2+) ≈ Zn(2+) when L = [9]AneS3 and Hg(2+) > Ag(+) when L = Et(2)S. Enthalpy and entropy values are generally negative, as a consequence of both metal ion interactions with neutral ligands, the reagents' loss of degrees of freedom and the release of solvating molecules. DFT calculations on the complexes formed with [9]AneS3 in vacuum and in AN are also carried out, to correlate experimental and theoretical thermodynamic values and to highlight the interplay between the direct metal-thioether interaction and the solvation effects. Trends obtained for the stability constants and enthalpies of the 1 : 1 and 1 : 2 complexes in solvent well reproduce the experimental ones for all the divalent metal ion complexes with [9]AneS3 and indicate the release of 3 AN molecules in the formation of each consecutive octahedral complex. In addition, calculated and experimental values for Ag(+) complex formation in solution suggest that in AgL(2) species [9]AneS3 ligands are not both tridentate.

Caracterización tecnomorfológica del complejo inferior de Ambrona

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Joaquín Panera Gallego

1996-01-01

Full Text Available La industria achelense correspondiente al Complejo Inferior de Ambrona, atribuida al Pleistoceno medio, se sitúa en la órbita de la de Áridos, La Maya II, El Sartalejo y Torralba. Mediante su caracterización tecnomorfológica y su contextualización en el Paleolítico inferior de la Península Ibérica, pretendemos paliar la carencia originada por la falta de trabajos en profundidad sobre su estudio.The Acheulian industry of «The Lower Compiex» in Ambrona, appointed to the Middle Pleistocene, is situated in the orbit of Áridos, La Maya II, El Sartalejo and Torralba. We propose palliate the lacks, originated for the non-existence ofjobs about his study, by his technomorphological analysis in the Lower Paleolithic of the Iberian Península.

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

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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.

La educación de la mirada: Percepción, pensamiento complejo y competencias visuales

OpenAIRE

Jiménez-Montano, M. (Mayra); Flores-Ramos, J.E. (José E.)

2016-01-01

Los autores proponen un modelo pedagógico para los estudiantes de diseño arquitectónico de primer año que parte de la interacción de la triada de la problematización de la percepción visual, el pensamiento complejo de Edgar Morin y el desarrollo de las competencias visuales. A partir de estos preceptos se diseñan actividades pedagógicas que estimulan experiencias significativas en el alumnado para el desarrollo de una mirada educada, profunda y analítica. La herramienta utiliza...

Exploración sobre las decisiones estratégicas desde el pensamiento complejo.

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Luz María Rivas Montoya

2013-12-01

Full Text Available La racionalidad, las decisiones estratégicas y el pensamiento complejo motivaron la construcción del problema de esta investigación, planteado en términos del carácter limitado y reduccionista de los criterios y referentes de decisión en la visión gerencial tradicional frente a una visión compleja de la realidad humana. La exploración de este problema se realizó desde y para el campo académico de la estrategia, con el propósito de mostrar algunas de las dificultades que se presentan en la definición e implementación de una estrategia corporativa en particular. El trabajo de campo se realizó en una empresa multinegocio del sector asegurador colombiano; los datos se obtuvieron a través de entrevistas semiestructuradas realizadas adiversos actores de la organización. El pensamiento complejo desde la perspectiva de Edgar Morin (1990 se constituyó en el marco de referencia teórica.   La hermenéutica de la acción de Ricœur (2010 iluminó la interpretación de los datos cualitativos; para su análisis se utilizó el sistema de codificación abierta, axial, selectiva y de procesoque proponen Strauss y Corbin (2002. En términos generales, tres fueron las categorías que emergieron de los datos: sinergia, como decisión estratégica relevante; des-humanización,como uno de los efectos de la decisión estratégica en los individuos, y rupturas de tejidos relacionales, como uno de los impactos que deja la sinergia en la organización bajo estudio.

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)

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)

Two novel mixed-ligand complexes containing organosulfonate ligands.

Science.gov (United States)

Li, Mingtian; Huang, Jun; Zhou, Xuan; Fang, Hua; Ding, Liyun

2008-07-01

The structures reported herein, viz. bis(4-aminonaphthalene-1-sulfonato-kappaO)bis(4,5-diazafluoren-9-one-kappa(2)N,N')copper(II), [Cu(C(10)H(8)NO(3)S)(2)(C(11)H(6)N(2)O)(2)], (I), and poly[[[diaquacadmium(II)]-bis(mu-4-aminonaphthalene-1-sulfonato)-kappa(2)O:N;kappa(2)N:O] dihydrate], {[Cd(C(10)H(8)NO(3)S)(2)(H(2)O)(2)].2H(2)O}(n), (II), are rare examples of sulfonate-containing complexes where the anion does not fulfill a passive charge-balancing role, but takes an active part in coordination as a monodentate and/or bridging ligand. Monomeric complex (I) possesses a crystallographic inversion center at the Cu(II) atom, and the asymmetric unit contains one-half of a Cu atom, one complete 4-aminonaphthalene-1-sulfonate (ans) ligand and one 4,5-diazafluoren-9-one (DAFO) ligand. The Cu(II) atom has an elongated distorted octahedral coordination geometry formed by two O atoms from two monodentate ans ligands and by four N atoms from two DAFO molecules. Complex (II) is polymeric and its crystal structure is built up by one-dimensional chains and solvent water molecules. Here also the cation (a Cd(II) atom) lies on a crystallographic inversion center and adopts a slightly distorted octahedral geometry. Each ans anion serves as a bridging ligand linking two Cd(II) atoms into one-dimensional infinite chains along the [010] direction, with each Cd(II) center coordinated by four ans ligands via O and N atoms and by two aqua ligands. In both structures, there are significant pi-pi stacking interactions between adjacent ligands and hydrogen bonds contribute to the formation of two- and three-dimensional networks.

Información, señal, comunidad y contexto: su importancia al tratar con sistemas adaptativos complejos

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Jordi Guzman

2007-07-01

Full Text Available El artículo trata de las diferencias entre información y conocimiento, así como de la relevancia del contexto en el aprendizaje, el cual se da dentro de una cultura en competencia por su supervivencia con otras culturas. Estas características definen un sistema adaptativo complejo, que se asemeja a la conducta de las especies que luchan por sobrevivir a los cambios de un entorno en continuo movimiento.

Breve historia del Complejo Industrial Sahagún, 1948-1988/95

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ADRIÁN ESCAMILLA TREJO

2013-10-01

Full Text Available En este trabajo se analiza el funcionamiento económico de un importante complejo paraestatal, a través de tres de sus principales empresas: Diesel Nacional (DINA, Constructora Nacional de Carros de Ferrocarril (CONCARRIL y Siderúrgica Nacional (SIDENA, las cuales integraron durante algún tiempo uno de los ejes de la industria de bienes de capital y duraderos en México. El objetivo del ensayo es presentar los límites y alcances de esta experiencia industrial de Estado, proponiendo una forma de acercarse de manera más objetiva a la historia de este complejo industrial y sus empresas. La conclusión central es que las tres empresas cumplieron con el objetivo para el que fueron creadas: satisfacer la demanda creciente de los bienes que producían, con calidad y a bajo costo. Sin embargo, con altos niveles de endeudamiento por el subsidio otorgado a otras entidades estatales y a empresas privadas; y sin poder conformar un sólido núcleo tecnológico que les permitiera adaptar, innovar y reproducir endógenamente nuevos y mejores productos, por lo que las tres empresas continuaron dependiendo en mayor o menor medida de la asesoría tecnológica de firmas transnacionales líderes en su ramo. Abstract This paper analyzes the economic operation of an important “industrial state complex”, through its three main companies: National Diesel (DINA, National Construction Railcars (CONCARRIL and National Steel (SIDENA, which integrated for some time one of the axes of the capital goods and durable goods industry in Mexico. The article objective is to present the limits and scope of the State's industrial experience, proposing a way of getting more objectively at the history of this industrial complex and its companies. The central conclusion is that the three companies met the objective for which they were created: to satisfy the growing demand for the goods they produced, quality and cost. However, with high levels of indebtedness due the subsidy

AutoSite: an automated approach for pseudo-ligands prediction—from ligand-binding sites identification to predicting key ligand atoms

Science.gov (United States)

Ravindranath, Pradeep Anand; Sanner, Michel F.

2016-01-01

Motivation: The identification of ligand-binding sites from a protein structure facilitates computational drug design and optimization, and protein function assignment. We introduce AutoSite: an efficient software tool for identifying ligand-binding sites and predicting pseudo ligand corresponding to each binding site identified. Binding sites are reported as clusters of 3D points called fills in which every point is labelled as hydrophobic or as hydrogen bond donor or acceptor. From these fills AutoSite derives feature points: a set of putative positions of hydrophobic-, and hydrogen-bond forming ligand atoms. Results: We show that AutoSite identifies ligand-binding sites with higher accuracy than other leading methods, and produces fills that better matches the ligand shape and properties, than the fills obtained with a software program with similar capabilities, AutoLigand. In addition, we demonstrate that for the Astex Diverse Set, the feature points identify 79% of hydrophobic ligand atoms, and 81% and 62% of the hydrogen acceptor and donor hydrogen ligand atoms interacting with the receptor, and predict 81.2% of water molecules mediating interactions between ligand and receptor. Finally, we illustrate potential uses of the predicted feature points in the context of lead optimization in drug discovery projects. Availability and Implementation: http://adfr.scripps.edu/AutoDockFR/autosite.html Contact: sanner@scripps.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:27354702

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

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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.

Amarre, rendimiento y calidad del fruto en naranja con aplicación de un complejo hormonal

OpenAIRE

Galván-Luna, Juan José; Briones-Encinia, Florencio; Rivera-Ortiz, Patricio; Valdes-Aguilar, Luis Alonso; Soto-Hernández, Marcos; Rodríguez-Alcázar, Jorge; Salazar-Salazar, Ovidio

2009-01-01

En cítricos el uso de reguladores de crecimiento incrementa el amarre de frutos y en consecuencia la productividad. El objetivo del presente trabajo fue determinar el efecto de un complejo hormonal de origen natural (auxinas, giberelinas y citocininas) en el amarre, rendimiento y calidad del fruto en naranja (Citrus sinensis (L.) Osb) del grupo navel cvs. "Washington" y "Thomson", en árboles de 15 años de edad. El estudio se realizó en el municipio de Ciudad Victoria, Tamaulipas, México duran...

Hydrolyzable tannins of tamaricaceous plants. V. Structures of monomeric-trimeric tannins and cytotoxicity of macrocyclic-type tannins isolated from Tamarix nilotica (1).

Science.gov (United States)

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

2013-05-24

Three new ellagitannin monomers, nilotinins M5-M7 (1-3), a dimer, nilotinin D10 (4), and a trimer, nilotinin T1 (5), together with three known dimers, hirtellin D (7) and tamarixinins B (8) and C (9), and a trimer, hirtellin T2 (6), were isolated from Tamarix nilotica dried leaves. The structures of the tannins were elucidated by intensive spectroscopic methods and chemical conversions into known tannins. The new trimer (5) is a unique macrocyclic type whose monomeric units are linked together by an isodehydrodigalloyl and two dehydrodigalloyl moieties. Additionally, dimeric and trimeric macrocyclic-type tannins isolated from T. nilotica in this study were assessed for possible cytotoxic activity against four human tumor cell lines. Tumor-selective cytotoxicities of the tested compounds were higher than those of synthetic and natural potent cytotoxic compounds, including polyphenols, and comparable with those of 5-fluorouracil and melphalan.

Estimación de profundidades del Complejo Plutónico Navarrete mediante procesamiento gravimétrico

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Flavia A Croce

2009-06-01

Full Text Available Se presenta el estudio gravimétrico en la región noreste del macizo de Somuncurá provincia de Río Negro con el objetivo de modelar la geometría y estimar las máximas profundidades del Complejo Plutónico Navarrete, emplazado en corteza superior. A la carta de anomalías de Bouguer se la filtró con el objeto de separar dichas anomalías en anomalía regional (que responde a características corticales profundas y anomalía residual (la cual contiene efectos de masas locales y cercanas a la superficie. Para ello se optó por el método de prolongación ascendente de campos potenciales, ya que en un estudio cualitativo fue el más apropiado para la resolución de dicho problema en particular. El afloramiento oeste del Complejo Plutónico Navarrete muestra un valor positivo de anomalía de gravedad de +5 mGal. Por el contrario el afloramiento este de dicho granito, presenta valores negativos entre -5 y -10 mGal. A partir del espectro de frecuencia radial aplicado a la carta de anomalías residuales de Bouguer, se estimaron las máximas profundidades de los afloramientos este y oeste del complejo intrusivo Navarrete, con valores de 8 km y de 6,5 km respectivamente.A gravimetric study is presented in the northeast region of the Somuncurá massif, with the objective of analyzing the geometry and maximum depths of the Navarrete Plutonic Complex, located in the upper crust. A Bouguer anomaly map was filtered in order to separating these anomalies in regional anomaly (which should contain the effects of deep crustal features and residual anomaly (which should contain the effects of local and near surface masses. The process used was the upward continuation method of the potential field. As a result, the west Navarrete granite formation shows a positive value of +5 mGal for gravity anomalies. On the contrary, the east Navarrete granite formation presents negative values between -5 and -10 mGal. A two dimensional power spectrum was applied to the

Complejo administrativo comercial – Lausana, Suiza

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Willomet, R.

1976-07-01

Full Text Available Administrative and commercial complex - Lausanne - Switzerland In an area which is being rebuilt in the centre of Lausanne, a 145,000 m2 administrative and commercial complex has been built. It consists of a low body with 3 levels, arranged as platforms above the street and in the shape of terraces with gardens whereby a 4,000 m2 area reserved for pedestrians has been created. On this lower part, high buildings have been constructed in harmony with each other. The building system consists of an upper structure with big beams and ribs which support the façade panels. The structure rests upon 4 big central columns and two on the side, whereby a diaphanous look has been achieved, further increased by mobile partition walls by which future needs also can be attended to. The light exterior enclosures were thoroughly studied and tested so as to provide total protection against dust and outer noise. Further the construction is equipped with interior heating and cooling installations and insulation from sound. This new urban complex does not attempt to adapt itself to the surrounding environment, but its lines are rather an expression of the architecture of tomorrow.En la ciudad de Lausana se ha construido un complejo administrativo y comercial de 145.000 m2, en una zona urbana del centro sujeta a remodelación. Consta de un cuerpo bajo, con tres niveles, a modo de plataformas sobre la calle, creándose así una zona de 4.000 m2 reservada a los peatones, con lugares para pasear, hacer compras o descansar entre terrazas ajardinadas. Sobre este volumen bajo se elevaron cuerpos en altura, combinados adecuadamente para constituir un conjunto estético y armonioso.

Complejo Omni - Atlanta – (EE. UU.

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Housworth, Marvin

1976-12-01

Full Text Available This complex of buildings, situated in the centre of Atlanta City, forms a dynamic nucleus for various social activities, such as recreational, commercial and business activities. These buildings are constructed above railway nets, due to special property rights for this lot, which constituted one of the main determinants for the characteristics of the property. The unit is made up by a luxurious hotel, two restaurants, office buildings and shopping arcades, arranged around a spacious inner yard. This patio is covered by means of an exceedingly big glass roof, supported by beams and steel framework and is provided with walls of big glazed surfaces. Thus, an intimate and friendly atmosphere is created, free from the contamination and noise of the big city whereby the square displays the typical characteristics of open squares in smaller towns.Este conjunto de edificios, emplazado en el centro de la ciudad de Atlanta, conforma un núcleo dinámico en donde se encuentran diversas actividades de tipo social: recreativas, comerciales y empresariales. Se ha construido sobre ruedas ferroviarias, en virtud de derechos especiales de propiedad que conservaba la parcela, lo que constituyó uno de los principales condicionamientos de fas características del proyecto. El complejo dispone de un hotel de lujo, dos restaurantes, edificios de oficinas y galerías comerciales, dispuestos en torno a un amplio espacio interior, cerrado por una enorme cubierta acristalada, apoyada en vigas y entramados metálicos, y por grandes ventanales corridos entre bloques. Conforma así un ambiente íntimo y acogedor, liberado del ruido y de la atmósfera turbulenta de la gran ciudad, con características propias de las pequeñas plazas populares.

Diversidad alfa y beta de la comunidad de reptiles en el complejo cenagoso de Zapatosa, Colombia

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Guido Fabián Medina-Rangel

2011-06-01

Full Text Available La diversidad es una propiedad de las comunidades, permite describir, caracterizar y entender el funcionamiento de los ecosistemas. Para estudiar la riqueza, abundancia y el recambio de especies de reptiles entre hábitats circundantes al complejo cenagoso de Zapatosa, se realizaron cuatro salidas de campo (noviembre de 2006 y octubre de 2007. Se invirtieron 640h/hombre de muestreo repartido en cinco tipos de hábitat: bosque casmófito, bosque seco, bosque de ribera, palmar y sabana arbolada. Se encontraron 847 individuos de 48 especies, la familia más rica fue Colubridae, se registraron cinco especies endémicas y ocho con algún grado de amenaza en conservación a nivel nacional. El hábitat más diverso fue el bosque de ribera. La representatividad del muestreo en total y para cada hábitat fue superior al 80%, con excepción del palmar (<75%. La composición de especies fue diferente entre la sabana arbolada y los hábitats bosque de ribera, palmar y bosque seco. El recambio promedio de especies fue del 50%. El bosque casmófito mostró la mayor complementariedad y número de especies únicas. El complejo cenagoso presentó 2/3 de los reptiles registrados hasta hoy para la región Caribe y más del 80% de los encontrados para el departamento del Cesar.

Flotación en columnas de complejos cobre - amilxantato en función del pH

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Francisco J. Tavera-Miranda

2009-03-01

Full Text Available La diferencia de solubilidad de los complejos amilxantato de cobre(I y de cobre(II es un elemento determinante en la implementación de procesos de flotación para recuperar cobre disuelto, aspecto en el que no se ha profundizado. En este trabajo se estudia el comportamiento de ambos complejos en función del pH del medio, evaluando los resultados a partir de su contribución específica en la recuperación y la cinética del proceso de flotación, el cual se lleva a cabo en una columna de laboratorio utilizando amilxantato de potasio como colector. El rango de pH utilizado (4 a 13 permite evaluar el efecto de las transformaciones que tienen lugar en el sistema amilxantato- cobre-agua. Los resultados indican el incremento de la recuperación de cobre con el incremento del pH del medio hasta valores de pH 11 y muestran una fuerte dependencia de la recuperación con las características químicas del sistema, el cobre flotado se incrementa marcadamente al incrementarse la concentración de la especie cristalina amilxantato de cobre(I, asociado a esto se manifiesta un incremento de la fracción de gas retenido y el flujo de superficie de las burbujas, las cuales tienen una incidencia directa sobre la cinética del proceso de flotación.

Ligand Depot: a data warehouse for ligands bound to macromolecules.

Science.gov (United States)

Feng, Zukang; Chen, Li; Maddula, Himabindu; Akcan, Ozgur; Oughtred, Rose; Berman, Helen M; Westbrook, John

2004-09-01

Ligand Depot is an integrated data resource for finding information about small molecules bound to proteins and nucleic acids. The initial release (version 1.0, November, 2003) focuses on providing chemical and structural information for small molecules found as part of the structures deposited in the Protein Data Bank. Ligand Depot accepts keyword-based queries and also provides a graphical interface for performing chemical substructure searches. A wide variety of web resources that contain information on small molecules may also be accessed through Ligand Depot. Ligand Depot is available at http://ligand-depot.rutgers.edu/. Version 1.0 supports multiple operating systems including Windows, Unix, Linux and the Macintosh operating system. The current drawing tool works in Internet Explorer, Netscape and Mozilla on Windows, Unix and Linux.

Paramagnetic F-19 Relaxation Enhancement in Nickel(II) Complexes of N-Trifluoroethyl Cyclam Derivatives and Cell Labeling for F-19 MRI

Czech Academy of Sciences Publication Activity Database

Blahut, J.; Bernášek, K.; Gálisová, A.; Herynek, V.; Císařová, I.; Kotek, J.; Lang, J.; Matějková, Stanislava; Hermann, P.

2017-01-01

Roč. 56, č. 21 (2017), s. 13337-13348 ISSN 0020-1669 Institutional support: RVO:61388963 Keywords : magnetic resonance * clinical applications * macrocyclic ligands Subject RIV: CA - Inorganic Chemistry OBOR OECD: Inorganic and nuclear chemistry Impact factor: 4.857, year: 2016

Evaluación de complejos enzimáticos en alimentación de pollos de engorde

OpenAIRE

García Jiménez, Mario

2011-01-01

El objetivo de esta tesis doctoral ha sido evaluar la adición de diversos complejos enzimáticos a dietas basadas en cereales que contenían diferentes cantidades de polisacáridos no amiláceos (PNA), sobre la productividad y parametros digestivos de pollos de engorde. Asimismo se ha estudiado la variación de la respuesta a la suplementación enzimática(SE) en función de otros factores tales como el periodo de ayuno posterior al nacimiento, el procesamiento termico del cereal, el tipo de cereal u...

Complejo parroquial de Santa Ana, en Moratalaz, Madrid

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Fisac, Miguel

1967-06-01

Full Text Available This church is sited at Moratalaz, a modern district of low rent houses in Madrid, and the architect has attempted to represent in the design the liturgical concepts developed in the Vatican II Council. These precise ideas have been expressed in the architecture by means of highly plastic symbols. In addition, the planform is very functional and the reinforced and prestressed concrete have been almost the only material used: so that the construction medium is also in accord with the modern nature of the design. The shapes, the space arrangement and everything which might seem a capricious creation of the artist in fact are the result of a detailed analysis of function and reason.Este complejo parroquial se ha levantado en Moratalaz, que es un barrio popular de la capital de España, procurando imprimir y recoger todas las premisas litúrgicas marcadas por el Concilio Vaticano II. El arquitecto ha plasmado sus precisas ideas en un edificio de gran expresividad plástica y de planta orgánica y eficaz, utilizando, casi exclusivamente, un material de nuestro tiempo: hormigón armado y pretensado. Las formas, la disposición de espacios y todo cuanto puede parecer caprichosa creación del artista, no son, en realidad, sino resultado de un cuidadoso estudio de funcionalismo racional y utilitario.

Nickel(I) and nickel(III) complexes of substituted tetraaza macrocycles formed by pulse radiolysis and electrochemistry of nickel(II) precursors

International Nuclear Information System (INIS)

Bernhardt, P.V.; Lawrance, G.A.; Sangster, D.F.

1988-01-01

The square-planar nickel(II) complexes of the ligands 8-methyl-8-nitro-1,3,6,10,13,15-hexaazatricyclo[13.1.1.1/sup 13,15/]octadecane, 8-amino-8-methyl-1,3,6,10,13,15-hexaazatricyclo[13.1.1.1/sup 13,15/]octadecane, 3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo[3.3.1]nonane, and 9-methyl-9-nitro-1,4,7,11-tetraazacyclotridecane (I-IV) react rapidly with hydroxyl radicals and aquated electrons (e/sub aq/). The initial transient products of these reactions decay via first-order kinetics within a few milliseconds in neutral aqueous solution at 22/degrees/C in all cases. Electronic spectra and decay rate constants, as well as formation rate constants, are reported for all transients. Reaction of the nitro-substituted complexes with e/sub aq/ led to electron addition to the nitro group rather than to the metal center; otherwise, a Ni/sup I/ transient is observed. Following reaction with OH, the product of the initial decay remains a Ni/sup III/ species. This is more long-lived, and stabilization of Ni/sup III/ by axial coordination of the pendant amine in II is indicated. No notable stabilization of Ni/sup I/ or Ni/sup III/ from the presence of the bicyclic azamethylene football in I-III occurs. Cyclic voltammetry in acetonitrile identified both one-electron oxidation and one-electron reduction processes for the nickel(II) complexes, as well as nitro group reduction, where this group was pendant to the macrocycle. 34 references, 3 figures, 3 tables

Impact of protein and ligand impurities on ITC-derived protein-ligand thermodynamics.

Science.gov (United States)

Grüner, Stefan; Neeb, Manuel; Barandun, Luzi Jakob; Sielaff, Frank; Hohn, Christoph; Kojima, Shun; Steinmetzer, Torsten; Diederich, François; Klebe, Gerhard

2014-09-01

The thermodynamic characterization of protein-ligand interactions by isothermal titration calorimetry (ITC) is a powerful tool in drug design, giving valuable insight into the interaction driving forces. ITC is thought to require protein and ligand solutions of high quality, meaning both the absence of contaminants as well as accurately determined concentrations. Ligands synthesized to deviating purity and protein of different pureness were titrated by ITC. Data curation was attempted also considering information from analytical techniques to correct stoichiometry. We used trypsin and tRNA-guanine transglycosylase (TGT), together with high affinity ligands to investigate the effect of errors in protein concentration as well as the impact of ligand impurities on the apparent thermodynamics. We found that errors in protein concentration did not change the thermodynamic properties obtained significantly. However, most ligand impurities led to pronounced changes in binding enthalpy. If protein binding of the respective impurity is not expected, the actual ligand concentration was corrected for and the thus revised data compared to thermodynamic properties obtained with the respective pure ligand. Even in these cases, we observed differences in binding enthalpy of about 4kJ⋅mol(-1), which is considered significant. Our results indicate that ligand purity is the critical parameter to monitor if accurate thermodynamic data of a protein-ligand complex are to be recorded. Furthermore, artificially changing fitting parameters to obtain a sound interaction stoichiometry in the presence of uncharacterized ligand impurities may lead to thermodynamic parameters significantly deviating from the accurate thermodynamic signature. Copyright © 2014 Elsevier B.V. All rights reserved.

Complexation behaviour of DADCA and DAPDA with dysprosium-166/holmium-166 parent daughter system and its potential for use in radioimmunotherapy

International Nuclear Information System (INIS)

Orsini, S.; University of Technology, Broadway, NSW; Di Bartolo, N.; Smith, S.; Baker, T.

1998-01-01

Full text: A novel approach for the delivery of therapeutic doses from 166 Ho to cancerous tissue is via the decay of its parent, 166 Dy. When designing radioimmunoconjugte, a crucial question is to determine whether the ligand used in the radiolabeling process is capable of holding the 166 Ho on decay of the parent, 166 Dy. In this study, two pendant arm macrocycles 1, 10-Diaza-4, 7, 13, 16-tetraoxacyclooctadecane-N, N'-diacetic acid, (DACDA) and 1, 10-Diaza-4, 7, 13-trioxacyclopentadecane-N, N'-diacetic acid, (DAPDA) that were reported to forms reasonably stable complexes with Dy and Ho, were synthesised. The synthesis of the two pendant arm macrocycles was first attempted using methods outlined by Chang and Rowland. The yields obtained through this method were low (10 % for both ligands) and it was considered important to investigate alternative approaches to the synthesis. The new method involved an alkylation reaction in the presence of acetonitrile and sodium bicarbonate. The method took considerably less time and the yields increased to 88 %. The ligands were characterised using 1 H NMR, 13 C NMR and mass spectrometry. The chemical and radiolytic stabilities of 166 Dy and 166 Ho complexes of the two ligands were investigated at pH = 5 and the ligands potential for use in the in vivo generator system evaluated

Crítica desde el pensamiento complejo a los métodos cuantitativos para el análisis educativo. El caso de los rendimientos educativos

Directory of Open Access Journals (Sweden)

Carlos Ricardo Aguilar Astorga

2017-07-01

Full Text Available En materia de política educativa es común asociar el nivel salarial de un sujeto respecto de su nivel educativo: sin embargo, dicha relación no es tan lineal como parece, sino que, visto desde el pensamiento complejo, intervienen factores como los costos marginales -a los que cada individuo se enfrenta al asistir a su centro educativo-, los cuales comprueban otra reciprocidad de variables. La forma como se construyen las asignaciones presupuestales en materia educativa en México no se deriva de este hecho, sino que hallan una correlación entre rendimiento educativo y asignación presupuestal por nivel educativo, excluyendo factores explicativos que el pensamiento complejo permite destacar. Tomar esto en consideración, mejoraría la política pública educativa.

Global Journal of Pure and Applied Sciences - Vol 9, No 3 (2003)

African Journals Online (AJOL)

Syntheses and spectral properties of iron(II) complexes with tetraaza(12) macrocyclic ligands · EMAIL FULL TEXT EMAIL FULL TEXT ... Colorimetric determination of Chloramphenicol and metronidazole in pharmaceutical formulations after schiff-base formation with vanillin and anisaldehyde · EMAIL FULL TEXT EMAIL ...

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

Isotopic Ligand Exchange of Some Hexa-Coordinated Inorganic Complexes with Halide Ions in Solution and in Crystals; Echanges Isotopiques de Coordinats de Complexes Inorganiques Hexacoordonnes Avec des Ions Halogenures en Solution et dans les Cristaux; Izotopnyj obmen ligand v nekotorykh geksakoordinirovannykh ne- organicheskikh kompleksakh s ionami galoidov v rastvore i kristallakh; Intercambio Isotopico de Ligandos de Complejos Inorganicos Hexacoordinados y Iones Haluro en Solucion y en Cristales

Energy Technology Data Exchange (ETDEWEB)

Schmidt, G. B. [Institut fuer Kernchemie der Universitaet Koeln, Cologne, Federal Republic of Germany (Germany)

1965-10-15

deplacement dans le reseau de cis- et trans- [Co(en){sub 2}Cl*{sub 2}]Cl marque et de trans- [Rh(en){sub 2}Cl*{sub 2}] Cl marque. Le temps de demi-echange pour les deux complexes de cobalt isomeriques solides est d'environ 4 h a 150 Degree-Sign C. Pour le complexe au rhodium, l'auteur a trouve un temps de demi-echange d'environ 26 h a 225 Degree-Sign C. Il a calcule des energies d'activation de 30 a 35 kcal/mole. Sous l'effet d'une exposition aux rayons X, l'echange augmente avec la dose. En outre, l'echange thermique des cristaux irradies est accelere. Contrairement a ce qui se passe pour des complexes del'ethylene-diamine, les bromures ou chlorures de pentamminebromo-rhodium et de pentamminebromo-iridium solides ne s'echangent que lentement, meme si on augmente la temperature jusqu'a 210 Degree-Sign Ci Mais dans ces complexes solides il. se produit des echanges 'actives' si le complexe recoit une energie d'excitation d'un processus nucleaire, comme la transition isomerique {sup 80m}Br -> {sup 80}Br. Ce phenomene est etudie assez en detail. (author) [Spanish] La cinetica de los intercambios isotopicos proporciona informacion sobre la labilidad de los complejos en solucion y sobre los mecanismos de sustitucion. Se ha investigado en solucion acida el intercambio entre los complejos [Rh(NH{sub 3}){sub 5}Br]{sup 2+} and [Ii(NH{sub 3}){sub 5}Br]{sup 2+}, maracados con {sup 82}Br, y iones Br{sup -}, entre trans -[Rh(en){sub 2}Cl{sub 2}Rh(en)){sup +} y trans- [Co(en){sub 2}Cl{sub 2}]{sup +} con iones Cl{sup -}, entre trans- trans- [Co(en){sub 2}Cl{sub 2}]{sup +} con iones Br{sup -}, y entre [OsCl{sub 6}]{sup 2-} y [Osl{sub 6}]{sup 2-} con iones Cl- y I{sup -} respectivamente. El intercambio en el complejo de pentamminobromoiridio es unas 60 veces mas lento que en el complejo correspondiente del rodio. Se ha encontrado que la constante de velocidad para el complejo de Rh es k{sub 100 Degree-Sign C} = 1.7 x 10{sup -4} min{sup -1}, y para el complejo de Ir en las mismas condiciones, 1

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.

Ligands in PSI structures

International Nuclear Information System (INIS)

Kumar, Abhinav; Chiu, Hsiu-Ju; Axelrod, Herbert L.; Morse, Andrew; Elsliger, Marc-André; Wilson, Ian A.; Deacon, Ashley

2010-01-01

A survey of the types and frequency of ligands that are bound to PSI structures is analyzed as well as their utility in functional annotation of previously uncharacterized proteins. Approximately 65% of PSI structures report some type of ligand(s) that is bound in the crystal structure. Here, a description is given of how such ligands are handled and analyzed at the JCSG and a survey of the types, variety and frequency of ligands that are observed in the PSI structures is also compiled and analyzed, including illustrations of how these bound ligands have provided functional clues for annotation of proteins with little or no previous experimental characterization. Furthermore, a web server was developed as a tool to mine and analyze the PSI structures for bound ligands and other identifying features

El complejo cárnico uruguayo ante la realidad del MERCOSUR

Directory of Open Access Journals (Sweden)

Segrelles Serrano, José Antonio

2002-03-01

Full Text Available The agricultural origins of Uruguay are still a highly important factor in its present economy, although meat agrocomplex has a special weight concerning both production and foreign trade. The Uruguay meat agrocomplex will have to face progressive globalization of the economy and growing free trade around the world. Regional integration in Mercosur" will be an efficient instrument to entrance the comparative advantages of the different livestock subsectors. However, we should not forget the repercussions that proceed from economic power, competitivity and political, monetary and financial stability of Argentina and Brazil.

[es] Los orígenes agropecuarios de Uruguay continúan representando una realidad trascendental en su economía actual, aunque ante todo destaca el complejo cárnico, tanto por lo que respecta a la producción como al comercio exterior. El complejo cárnico uruguayo va a tener que hacer frente a la progresiva globalización de la economía y a la creciente liberalización comercial en el mundo. Su integración regional en el Mercosur puede ser un instrumento eficaz para resaltar las ventajas comparativas de sus distintos subsectores ganaderos. Sin embargo, no conviene olvidar las repercusiones que deriven del peso económico, posible competencia y estabilidad política, monetaria y financiera de Argentina y Brasil. [fr] Les origines du complexe agricole et de l'élevage représente encore aujourd'hui une réalité vitale pour son économia actuelle même si c'est surtout l'industrie de la vianda celle qui se détache aussi bien par sa production que par son commerce extérieur. Les industries de la viande à Uruguay doit affronter la progressive globalisation de l'économie et la libéralisation commerciale toujours croissante dans le monde. Leur intégration régionale dans Mercosur peut être un instrument efficace pour la mi se eu relief des avantages des différents sous-secteurs de l'élevage et la comparaison

¿Tecnofilia, alternidad o pensamiento ácrata? Metamediación y periodismo complejo

Directory of Open Access Journals (Sweden)

Yamile Haber Guerra

2014-09-01

Full Text Available Este documento contiene una discusión sobre el periodismo y la tecnología en la sociedad contemporánea. Trae a debate la relación entre el periodismo,  la internet y los nuevos lenguajes. En este contexto, la información asume nuevas funciones y fines informativos que el canon tradicional no había previsto. Las formas clásicas de construcción de la noticia se erigen sobre los nuevos paradigmas con efectividad y pertinencia aún no documentados del todo. El texto invita al reconocimiento de la complejidad como principio estructurante de todo saber comunicacional, y del lenguaje periodístico como objeto de estudio amplio, complejo y abierto a nuevos métodos no excluyentes, concurrentes e integrados.

Las ignimbritas del complejo volcánico Coranzuli (Puna Argentina-Andes Centrales

Directory of Open Access Journals (Sweden)

Martí, J.

1987-12-01

Full Text Available The Coranzulí is a large Upper Miocene volcanic complex located on a NE-SW and NW-SE regional faults intersection, at 66º 15' W 23º S, in the Northwest of Argentina in Jujuy province. It corresponds to one of four large volcanic complexes which represent the end of Transversal Volcanic Chaines in La Puna Argentina in the Central Andes. The volcanic activity was characterized by at least four separate ignimbrite eruptions which produced four different ignimbrite sheets. These are well welded, very crystal-rich, lithie poor ignimbrites and have a moderate to high pumice content. The total volume of the Coranzuli ignimbrites exeededs 650 Km3. Preliminary data indicate that the eruption oeeurred from a homogeneous magmatic chamber without zoning. The emplacement characteristics of the ignimbrites and the lack of basal or interbedded plinian fall deposits suggest that the eruptions developed quickly to massive proportions.El Coranzuli es uno de los grandes complejos volcánicos que representan el remate final de las Cadenas Volcánicas Transversales de la Puna Argentina, en los Andes Centrales. Se trata de un complejo volcánico del Mioceno superior situado a los 66º 15' W 23º S en el NW de Argentina en la provincia de Jujuy, en la intersección entre dos fallas regionales de dirección NE-SW y NW-SE, respectivamente. La actividad eruptiva se caracterizó por la existencia de, al menos, cuatro erupciones ignimbríticas que produjeron cuatro diferentes mantos ignimbríticos. Se trata de ignimbritas bien soldadas, muy ricas en cristales, pobre en fragmentos líticos y que presentan un contenido en fragmentos pumíticos de moderado a alto. El volumen total que representan estas ignimbritas supera los 650 km3. Los datos preliminares indican que el magma juvenil deriva de una cámara magmática homogénea no zonada. Las características de emplazamiento de estas ignimbritas, así como la falta de depósitos plinianos de caída en la base o

Ligand photo-isomerization triggers conformational changes in iGluR2 ligand binding domain.

Directory of Open Access Journals (Sweden)

Tino Wolter

Full Text Available Neurological glutamate receptors bind a variety of artificial ligands, both agonistic and antagonistic, in addition to glutamate. Studying their small molecule binding properties increases our understanding of the central nervous system and a variety of associated pathologies. The large, oligomeric multidomain membrane protein contains a large and flexible ligand binding domains which undergoes large conformational changes upon binding different ligands. A recent application of glutamate receptors is their activation or inhibition via photo-switchable ligands, making them key systems in the emerging field of optochemical genetics. In this work, we present a theoretical study on the binding mode and complex stability of a novel photo-switchable ligand, ATA-3, which reversibly binds to glutamate receptors ligand binding domains (LBDs. We propose two possible binding modes for this ligand based on flexible ligand docking calculations and show one of them to be analogues to the binding mode of a similar ligand, 2-BnTetAMPA. In long MD simulations, it was observed that transitions between both binding poses involve breaking and reforming the T686-E402 protein hydrogen bond. Simulating the ligand photo-isomerization process shows that the two possible configurations of the ligand azo-group have markedly different complex stabilities and equilibrium binding modes. A strong but slow protein response is observed after ligand configuration changes. This provides a microscopic foundation for the observed difference in ligand activity upon light-switching.

Crowns and Crypts

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education; Volume 6; Issue 6. Crowns and Crypts - A Fascinating Group of Multidentate Macrocyclic Ligands. Debasis Bandyopadhyay. General Article Volume 6 Issue 6 June 2001 pp 71-79. Fulltext. Click here to view fulltext PDF. Permanent link:

Intervención de conservación de emergencia en el complejo arqueológico Aypate

OpenAIRE

Huisa Palomino, Lorenzo; Ministerio de Cultura

2014-01-01

En el marco del Proyecto de Investigación Arqueológica Aypate, con fines de diagnóstico para su puesta en uso social, se están desarrollando labores como la elaboración del diagnóstico del estado de conservación de los sectores y edificaciones, la identificación y mapeo de zonas de riesgo, factores y agentes de deterioro y el nivel de vulnerabilidad que presenta cada uno de los componentes arquitectónicos del Complejo Arqueológico Aypate; así como el monitoreo constante del nivel de debilidad...

Prevalencia de traumatismos dentoalveolares en pacientes infantiles del complejo asistencial Dr. Sótero del Río

OpenAIRE

Castro Brezzo, P.F.; Dreyer Arroyo, E.

2012-01-01

En el presente estudio descriptivo de incidencia, 604 niños menores de 15 años fueron examinados y atendidos en la Clínica de Odontopediatría del Complejo Asistencial Dr. Sotero del Río, con diagnóstico de Traumatismo Dentoalveolar (TDA), desde Enero a Diciembre del 2010. El propósito de este estudio fue caracterizar los TDA de acuerdo a la clasificación de Andreasen y Andreasen, determinar su frecuencia y distribución estacional, tipo y número de dientes afectados, distribución de género y e...

Insights into an original pocket-ligand pair classification: a promising tool for ligand profile prediction.

Directory of Open Access Journals (Sweden)

Stéphanie Pérot

Full Text Available Pockets are today at the cornerstones of modern drug discovery projects and at the crossroad of several research fields, from structural biology to mathematical modeling. Being able to predict if a small molecule could bind to one or more protein targets or if a protein could bind to some given ligands is very useful for drug discovery endeavors, anticipation of binding to off- and anti-targets. To date, several studies explore such questions from chemogenomic approach to reverse docking methods. Most of these studies have been performed either from the viewpoint of ligands or targets. However it seems valuable to use information from both ligands and target binding pockets. Hence, we present a multivariate approach relating ligand properties with protein pocket properties from the analysis of known ligand-protein interactions. We explored and optimized the pocket-ligand pair space by combining pocket and ligand descriptors using Principal Component Analysis and developed a classification engine on this paired space, revealing five main clusters of pocket-ligand pairs sharing specific and similar structural or physico-chemical properties. These pocket-ligand pair clusters highlight correspondences between pocket and ligand topological and physico-chemical properties and capture relevant information with respect to protein-ligand interactions. Based on these pocket-ligand correspondences, a protocol of prediction of clusters sharing similarity in terms of recognition characteristics is developed for a given pocket-ligand complex and gives high performances. It is then extended to cluster prediction for a given pocket in order to acquire knowledge about its expected ligand profile or to cluster prediction for a given ligand in order to acquire knowledge about its expected pocket profile. This prediction approach shows promising results and could contribute to predict some ligand properties critical for binding to a given pocket, and conversely

Insights into an original pocket-ligand pair classification: a promising tool for ligand profile prediction.

Science.gov (United States)

Pérot, Stéphanie; Regad, Leslie; Reynès, Christelle; Spérandio, Olivier; Miteva, Maria A; Villoutreix, Bruno O; Camproux, Anne-Claude

2013-01-01

Pockets are today at the cornerstones of modern drug discovery projects and at the crossroad of several research fields, from structural biology to mathematical modeling. Being able to predict if a small molecule could bind to one or more protein targets or if a protein could bind to some given ligands is very useful for drug discovery endeavors, anticipation of binding to off- and anti-targets. To date, several studies explore such questions from chemogenomic approach to reverse docking methods. Most of these studies have been performed either from the viewpoint of ligands or targets. However it seems valuable to use information from both ligands and target binding pockets. Hence, we present a multivariate approach relating ligand properties with protein pocket properties from the analysis of known ligand-protein interactions. We explored and optimized the pocket-ligand pair space by combining pocket and ligand descriptors using Principal Component Analysis and developed a classification engine on this paired space, revealing five main clusters of pocket-ligand pairs sharing specific and similar structural or physico-chemical properties. These pocket-ligand pair clusters highlight correspondences between pocket and ligand topological and physico-chemical properties and capture relevant information with respect to protein-ligand interactions. Based on these pocket-ligand correspondences, a protocol of prediction of clusters sharing similarity in terms of recognition characteristics is developed for a given pocket-ligand complex and gives high performances. It is then extended to cluster prediction for a given pocket in order to acquire knowledge about its expected ligand profile or to cluster prediction for a given ligand in order to acquire knowledge about its expected pocket profile. This prediction approach shows promising results and could contribute to predict some ligand properties critical for binding to a given pocket, and conversely, some key pocket

Role of ligand-ligand vs. core-core interactions in gold nanoclusters.

Science.gov (United States)

Milowska, Karolina Z; Stolarczyk, Jacek K

2016-05-14

The controlled assembly of ligand-coated gold nanoclusters (NCs) into larger structures paves the way for new applications ranging from electronics to nanomedicine. Here, we demonstrate through rigorous density functional theory (DFT) calculations employing novel functionals accounting for van der Waals forces that the ligand-ligand interactions determine whether stable assemblies can be formed. The study of NCs with different core sizes, symmetry forms, ligand lengths, mutual crystal orientations, and in the presence of a solvent suggests that core-to-core van der Waals interactions play a lesser role in the assembly. The dominant interactions originate from combination of steric effects, augmented by ligand bundling on NC facets, and related to them changes in electronic properties induced by neighbouring NCs. We also show that, in contrast to standard colloidal theory approach, DFT correctly reproduces the surprising experimental trends in the strength of the inter-particle interaction observed when varying the length of the ligands. The results underpin the importance of understanding NC interactions in designing gold NCs for a specific function.

Caracterización del complejo mayor de histocompatibilidad clase II en primates del género Aotus

OpenAIRE

Suárez Martínez, Carlos Fernando

2017-01-01

El presente trabajo tiene como propósito contribuir al conocimiento del complejo mayor de histocompatibilidad clase II (CMH-II) de los monos Aotus, contribuyendo a la validación de este primate como modelo experimental, y aumentando el conocimiento en la evolución de los genes del CMH en primates. Además, se profundizó en el análisis de convergencia y polimorfismo de los genes del CMH-DR en primates. Se implementaron metodologías de modelación computacional de la unión CMH-péptido, como ...

60Co γ-irradiation effects on electrical properties of a rectifying diode based on a novel macrocyclic Zn octaamide complex

International Nuclear Information System (INIS)

Ocak, Y.S.; Kilicoglu, T.; Topal, G.; Baskan, M.H.

2010-01-01

C 36 H 28 N 12 O 8 ZnCl 2 .9/2H 2 O, Zn-octaamide (ZnOA) macrocyclic compound was synthesized to be used in the fabrication of electronic and photoelectronic devices. The structure of new compound was identified by using 1 H NMR, 13 C NMR, IR, UV-vis and LC-MS spectroscopic methods. The Sn/ZnOA/n-Si/Au structure was engineered by forming a thin macrocyclic organic compound layer on n-Si inorganic substrate and then by evaporating Sn metal on the organic layer. It was seen that the device had a good rectifying behaviour and showed Schottky diode properties. The diode was irradiated under 60 Co γ-source at room temperature. Characteristic parameters of the diode were determined from its current-voltage (I-V) and capacitance voltage (C-V) measurements before and after irradiation. It was observed that γ-irradiation had clear effects on I-V and C-V properties. Also, it was seen that the barrier height, the ideality factor and the series resistance values decreased after the applied radiation, while the saturation current value increased.

Predicción del riesgo individual de alto coste sanitario para la identificación de pacientes crónicos complejos

Directory of Open Access Journals (Sweden)

Jordi Coderch

2014-07-01

Conclusiones: El consumo sanitario elevado se relaciona con la morbilidad crónica compleja. Un modelo basado en la edad, la morbilidad y la utilización previa es válido para predecir el riesgo de alto consumo, y así identificar la población diana de estrategias de atención proactiva para pacientes crónicos complejos.

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....

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.

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.

Final Technical Report: Targeting DOE-Relevant Ions with Supramolecular Strategies, DE-SC0010555

Energy Technology Data Exchange (ETDEWEB)

Bowman-James, Kristin [Univ. of Kansas, Lawrence, KS (United States). Dept. of Chemistry

2017-04-13

The effectiveness of three popular supramolecular strategies to selectively target negatively charged ions (anions) was evaluated. Ions of interest included oxo anions, particularly sulfate, that hamper nuclear waste remediation. Three objectives were pursued using a simple building block strategies and by strategically placing anion-binding sites at appropriate positions on organic host molecules. The goal of the first objective was to assess the influence of secondary, tertiary and quaternized amines on binding tetrahedral anions using mixed amide/amine macrocyclic and urea/amine hosts containing aromatic or heteroaromatic spacers. Objective 2 focused on the design of ion pair hosts, using mixed macrocyclic anion hosts joined through polyether linkages. Objective 3 was to explore the synthesis of new metal-linked extended macrocyclic frameworks to leverage anion binding. Key findings were that smaller 24-membered macrocycles provided the most complementary binding for sulfate ion and mixed urea/amine chelates showed enhanced binding over amide corollaries in addition to being highly selective for SO₄^2- in the presence of small quantities of water. In addition to obtaining prototype metal-linked macrocyclic anion hosts, a new dipincer ligand was designed that can be used to link macrocyclic or other supramolecular hosts in extended frameworks. When the tetraamide-based pincers are bound to two metal ions, an interesting phenomenon occurs. Upon deprotonation of the amides, two new protons appear between adjacent carbonyl pairs on the ligand, which may modify the chemistry, and metal-metal interactions in the complexes. Gel formation occurred for some of these extended hosts, and the physical properties are currently under investigation. The new tetracarboxamide-based pincers can also provide basic frameworks for double macrocycles capable of binding ion pairs as well as for binding metal ions and exploring intermetallic interactions through

Microscale Synthesis, Reactions, and (Super 1)H NMR Spectroscopic Investigations of Square Planar Macrocyclic, Tetramido-N Co(III) Complexes Relevant to Green Chemistry

Science.gov (United States)

Watson, Tanya T.; Uffelman, Erich S.; Lee, Daniel W., III; Doherty, Jonathan R.; Schulze, Carl; Burke, Amy L.; Bonnema, Kristen, R.

2004-01-01

The microscale preparation, characterization, and reactivity of a square planar Co(III) complex that has grown out of a program to introduce experiments of relevance to green chemistry into the undergraduate curriculum is presented. The given experiments illustrate the remarkable redox and aqueous acid-base stability that make the macrocycles very…

LigandRFs: random forest ensemble to identify ligand-binding residues from sequence information alone

KAUST Repository

Chen, Peng

2014-12-03

Background Protein-ligand binding is important for some proteins to perform their functions. Protein-ligand binding sites are the residues of proteins that physically bind to ligands. Despite of the recent advances in computational prediction for protein-ligand binding sites, the state-of-the-art methods search for similar, known structures of the query and predict the binding sites based on the solved structures. However, such structural information is not commonly available. Results In this paper, we propose a sequence-based approach to identify protein-ligand binding residues. We propose a combination technique to reduce the effects of different sliding residue windows in the process of encoding input feature vectors. Moreover, due to the highly imbalanced samples between the ligand-binding sites and non ligand-binding sites, we construct several balanced data sets, for each of which a random forest (RF)-based classifier is trained. The ensemble of these RF classifiers forms a sequence-based protein-ligand binding site predictor. Conclusions Experimental results on CASP9 and CASP8 data sets demonstrate that our method compares favorably with the state-of-the-art protein-ligand binding site prediction methods.

Crystallization of protein–ligand complexes

International Nuclear Information System (INIS)

Hassell, Anne M.; An, Gang; Bledsoe, Randy K.; Bynum, Jane M.; Carter, H. Luke III; Deng, Su-Jun J.; Gampe, Robert T.; Grisard, Tamara E.; Madauss, Kevin P.; Nolte, Robert T.; Rocque, Warren J.; Wang, Liping; Weaver, Kurt L.; Williams, Shawn P.; Wisely, G. Bruce; Xu, Robert; Shewchuk, Lisa M.

2007-01-01

Methods presented for growing protein–ligand complexes fall into the categories of co-expression of the protein with the ligands of interest, use of the ligands during protein purification, cocrystallization and soaking the ligands into existing crystals. Obtaining diffraction-quality crystals has long been a bottleneck in solving the three-dimensional structures of proteins. Often proteins may be stabilized when they are complexed with a substrate, nucleic acid, cofactor or small molecule. These ligands, on the other hand, have the potential to induce significant conformational changes to the protein and ab initio screening may be required to find a new crystal form. This paper presents an overview of strategies in the following areas for obtaining crystals of protein–ligand complexes: (i) co-expression of the protein with the ligands of interest, (ii) use of the ligands during protein purification, (iii) cocrystallization and (iv) soaks

Metal ion sequestration: An exciting dimension for molecularly ...

African Journals Online (AJOL)

The use of a tight binding macrocyclic ligand to complex a metal ion so that this serves as receptee on the Molecularly Imprinted Polymer (MIP) receptor as described here affords a sequestration route for a targeted metal ion, with potential for environmental remediation and restoration applications. Ethylene glycol ...

Antecedentes históricos sobre el Complejo Forestal y Maderero Panguipulli, provincia de Valdivia, Centro-sur de Chile

OpenAIRE

Barrena Ruiz, José; Hernando Arrese, Maite; Rojas Marchini, Fernanda

2016-01-01

El Complejo Forestal y Maderero Panguipulli, empresa surgida en 1971 en la provincia de Valdivia, administró un área superior a 400.000 ha y empleó a más de 3.000 trabajadores bajo un esquema de comanejo entre obreros y Estado. El objetivo fue indagar en los procesos sociales que influyeron en la conformación de esta empresa. Se desarrolló una revisión bibliográfica que incluyó artículos científicos, trabajos de tesis, informes y libros. Adicionalmente, se realizaron dos entrevistas en profun...

Sistemas de ayuda a la decisión clínica en enfermedades de diagnóstico complejo

OpenAIRE

Monsalve Torra, Ana

2017-01-01

El trabajo de investigación presentado en esta tesis doctoral aborda el uso de algoritmos de inteligencia artificial y su aplicación en los sistemas de ayuda para la toma de decisiones en enfermedades de diagnóstico complejo. La dificultad en la gestión clínica de dichas enfermedades requiere un trabajo en conjunto (área de salud e ingeniería informática) y un intercambio de conocimientos, experiencias e información que permita obtener mejores resultados en el proceso de atención de los enfer...

La enseñanza y el aprendizaje de los números complejos: un estudio en el nivel universitario

OpenAIRE

Pardo, Tomás; Gómez, Bernardo

2007-01-01

Presentamos algunos de los resultados más relevantes de un estudio sobre la problemática de la enseñanza y el aprendizaje de los números complejos. El estudio se ha dirigido a recabar información para sustentar sugerencias de intervención en las pautas educativas en relación con esta temática. We present some of the most relevant results of a study concerning the teaching and learning of complex numbers. The study is focused on collecting data to s...

Catalytic hydrogenation of carbon monoxide

Energy Technology Data Exchange (ETDEWEB)

Wayland, B.B.

1992-12-01

This project is focused on developing strategies to accomplish the reduction and hydrogenation of carbon monoxide to produce organic oxygenates at mild conditions. Our approaches to this issue are based on the recognition that rhodium macrocycles have unusually favorable thermodynamic values for producing a series of intermediate implicated in the catalytic hydrogenation of CO. Observations of metalloformyl complexes produced by reactions of H{sub 2} and CO, and reductive coupling of CO to form metallo {alpha}-diketone species have suggested a multiplicity of routes to organic oxygenates that utilize these species as intermediates. Thermodynamic and kinetic-mechanistic studies are used in constructing energy profiles for a variety of potential pathways, and these schemes are used in guiding the design of new metallospecies to improve the thermodynamic and kinetic factors for individual steps in the overall process. Variation of the electronic and steric effects associated with the ligand arrays along with the influences of the reaction medium provide the chemical tools for tuning these factors. Emerging knowledge of the factors that contribute to M-H, M-C and M-O bond enthalpies is directing the search for ligand arrays that will expand the range of metal species that have favorable thermodynamic parameters to produce the primary intermediates for CO hydrogenation. Studies of rhodium complexes are being extended to non-macrocyclic ligand complexes that emulate the favorable thermodynamic features associated with rhodium macrocycles, but that also manifest improved reaction kinetics. Multifunctional catalyst systems designed to couple the ability of rhodium complexes to produce formyl and diketone intermediates with a second catalyst that hydrogenates these imtermediates are promising approaches to accomplish CO hydrogenation at mild conditions.

Catalytic hydrogenation of carbon monoxide. Progress report, December 15, 1991--December 14, 1992

Energy Technology Data Exchange (ETDEWEB)

Wayland, B.B.

1992-12-01

This project is focused on developing strategies to accomplish the reduction and hydrogenation of carbon monoxide to produce organic oxygenates at mild conditions. Our approaches to this issue are based on the recognition that rhodium macrocycles have unusually favorable thermodynamic values for producing a series of intermediate implicated in the catalytic hydrogenation of CO. Observations of metalloformyl complexes produced by reactions of H{sub 2} and CO, and reductive coupling of CO to form metallo {alpha}-diketone species have suggested a multiplicity of routes to organic oxygenates that utilize these species as intermediates. Thermodynamic and kinetic-mechanistic studies are used in constructing energy profiles for a variety of potential pathways, and these schemes are used in guiding the design of new metallospecies to improve the thermodynamic and kinetic factors for individual steps in the overall process. Variation of the electronic and steric effects associated with the ligand arrays along with the influences of the reaction medium provide the chemical tools for tuning these factors. Emerging knowledge of the factors that contribute to M-H, M-C and M-O bond enthalpies is directing the search for ligand arrays that will expand the range of metal species that have favorable thermodynamic parameters to produce the primary intermediates for CO hydrogenation. Studies of rhodium complexes are being extended to non-macrocyclic ligand complexes that emulate the favorable thermodynamic features associated with rhodium macrocycles, but that also manifest improved reaction kinetics. Multifunctional catalyst systems designed to couple the ability of rhodium complexes to produce formyl and diketone intermediates with a second catalyst that hydrogenates these imtermediates are promising approaches to accomplish CO hydrogenation at mild conditions.

Strong Ligand-Protein Interactions Derived from Diffuse Ligand Interactions with Loose Binding Sites.

Science.gov (United States)

Marsh, Lorraine

2015-01-01

Many systems in biology rely on binding of ligands to target proteins in a single high-affinity conformation with a favorable ΔG. Alternatively, interactions of ligands with protein regions that allow diffuse binding, distributed over multiple sites and conformations, can exhibit favorable ΔG because of their higher entropy. Diffuse binding may be biologically important for multidrug transporters and carrier proteins. A fine-grained computational method for numerical integration of total binding ΔG arising from diffuse regional interaction of a ligand in multiple conformations using a Markov Chain Monte Carlo (MCMC) approach is presented. This method yields a metric that quantifies the influence on overall ligand affinity of ligand binding to multiple, distinct sites within a protein binding region. This metric is essentially a measure of dispersion in equilibrium ligand binding and depends on both the number of potential sites of interaction and the distribution of their individual predicted affinities. Analysis of test cases indicates that, for some ligand/protein pairs involving transporters and carrier proteins, diffuse binding contributes greatly to total affinity, whereas in other cases the influence is modest. This approach may be useful for studying situations where "nonspecific" interactions contribute to biological function.

Filogeografía del complejo Caesalpinia hintonii: (Leguminosae: Caesalpinioideae: Poincianella Phylogeography of the Caesalpinia hintonii complex (Leguminosae: Caesalpinioideae: Poincianella

Directory of Open Access Journals (Sweden)

Solange Sotuyo

2010-12-01

Full Text Available A pesar del crecido número de estudios que se ha realizado para explorar la estructura genética y filogeográfica en especies mexicanas, hay carencia de estudios para especies de selva baja, zonas con alto grado de endemismo. Para un mejor entendimiento de dichas áreas se realizó un estudio filogeográfico y el fechamiento de las especies del complejo Caesalpinia hintonii distribuido en la depresión del río Balsas y el valle de Tehuacán-Cuicatlán. Se determinó la estructura filogeográfica del complejo analizando las secuencias de 4 regiones de plastidio (intrón trnL, espaciador trnL-F, espaciador psbA-trnH y espaciador accD-psaI en todas las poblaciones disponibles. Se estimó la fecha del origen del complejo mediante un método no paramétrico (NPRS. Las diversidades haplotídicas (0.64-1 y las diferencias nucleotídicas (3.8-11.52 en todas las especies fueron altas respecto a valores registrados para otras plantas. Las poblaciones de C. oyamae, morfológicamente indistintas están genéticamente estructuradas y presentan 3 haplogrupos donde el flujo génico entre ellos es bajo y se consideraron entidades crípticas. Las poblaciones de C. hintonii son un grupo genéticamente homogéneo a pesar de ser morfológicamente distintas. Las poblaciones de C. macvaughii forman 2 linajes divergentes entre los que existe flujo génico (Nm=1.41. Los eventos de divergencia en 2 grandes linajes al este y oeste del río Balsas pueden explicarse por eventos geológicos. Los resultados indican que el complejo se encuentra bajo divergencia y en algunos casos radiación morfostática.Although many phylogeographic studies have been conducted to analyze the genetic and phylogeographic structure of Mexican species, such studies are nearly absent for plants of dry seasonal forest, precincts with high level of endemism. To better understand this areas, we undertook a phylogeographic study and dating were carried out on the Caesalpinia hintonii complex

LigandRFs: random forest ensemble to identify ligand-binding residues from sequence information alone

KAUST Repository

Chen, Peng; Huang, Jianhua Z; Gao, Xin

2014-01-01

Protein-ligand binding is important for some proteins to perform their functions. Protein-ligand binding sites are the residues of proteins that physically bind to ligands. Despite of the recent advances in computational prediction

A new class of PN3-pincer ligands for metal–ligand cooperative catalysis

KAUST Repository

Li, Huaifeng

2014-12-01

Work on a new class of PN3-pincer ligands for metal-ligand cooperative catalysis is reviewed. While the field of the pyridine-based PN3-transition metal pincer complexes is still relatively young, many important applications of these complexes have already emerged. In several cases, the PN3-pincer complexes for metal-ligand cooperative catalysis result in significantly improved or unprecedented activities. The synthesis and coordination chemistry of PN3-pincer ligands are briefly summarized first to cover the synthetic routes for their preparation, followed by a focus review on their applications in catalysis. A specific emphasis is placed on the later section about the role of PN3-pincer ligands\\' dearomatization-rearomatization steps during the catalytic cycles. The mechanistic insights from density functional theory (DFT) calculations are also discussed.

A new class of PN3-pincer ligands for metal–ligand cooperative catalysis

KAUST Repository

Li, Huaifeng; Zheng, Bin; Huang, Kuo-Wei

2014-01-01

Work on a new class of PN3-pincer ligands for metal-ligand cooperative catalysis is reviewed. While the field of the pyridine-based PN3-transition metal pincer complexes is still relatively young, many important applications of these complexes have already emerged. In several cases, the PN3-pincer complexes for metal-ligand cooperative catalysis result in significantly improved or unprecedented activities. The synthesis and coordination chemistry of PN3-pincer ligands are briefly summarized first to cover the synthetic routes for their preparation, followed by a focus review on their applications in catalysis. A specific emphasis is placed on the later section about the role of PN3-pincer ligands' dearomatization-rearomatization steps during the catalytic cycles. The mechanistic insights from density functional theory (DFT) calculations are also discussed.

Magneto-electroluminescence effects in the single-layer organic light-emitting devices with macrocyclic aromatic hydrocarbons

Directory of Open Access Journals (Sweden)

S.-T. Pham

2018-02-01

Full Text Available Magneto-electroluminescence (MEL effects are observed in single-layer organic light-emitting devices (OLEDs comprising only macrocyclic aromatic hydrocarbons (MAHs. The fluorescence devices were prepared using synthesized MAHs, namely, [n]cyclo-meta-phenylene ([n]CMP, n = 5, 6. The MEL ratio of the resulting OLED is 1%–2% in the spectral wavelength range of 400-500 nm, whereas it becomes negative (−1.5% to −2% in the range from 650 to 700 nm. The possible physical origins of the sign change in the MEL are discussed. This wavelength-dependent sign change in the MEL ratio could be a unique function for future single-layer OLEDs capable of magnetic-field-induced color changes.

Magneto-electroluminescence effects in the single-layer organic light-emitting devices with macrocyclic aromatic hydrocarbons

Science.gov (United States)

Pham, S.-T.; Ikemoto, K.; Suzuki, K. Z.; Izumi, T.; Taka, H.; Kita, H.; Sato, S.; Isobe, H.; Mizukami, S.

2018-02-01

Magneto-electroluminescence (MEL) effects are observed in single-layer organic light-emitting devices (OLEDs) comprising only macrocyclic aromatic hydrocarbons (MAHs). The fluorescence devices were prepared using synthesized MAHs, namely, [n]cyclo-meta-phenylene ([n]CMP, n = 5, 6). The MEL ratio of the resulting OLED is 1%-2% in the spectral wavelength range of 400-500 nm, whereas it becomes negative (-1.5% to -2%) in the range from 650 to 700 nm. The possible physical origins of the sign change in the MEL are discussed. This wavelength-dependent sign change in the MEL ratio could be a unique function for future single-layer OLEDs capable of magnetic-field-induced color changes.

Genotipificación de aislamientos clínicos del complejo Cryptococcus neoformans/Cryptococcus gattii obtenidos en el Hospital «Dr. Julio C. Perrando», de la ciudad de Resistencia (Chaco, Argentina

Directory of Open Access Journals (Sweden)

Maria E Cattana

Full Text Available La criptococosis es una infección fúngica causada por levaduras del género Cryptococcus, particularmente las del complejo Cryptococcus neoformans/Cryptococcus gattii. El conocimiento sobre la casuística de la criptococosis en el nordeste argentino es exiguo y no se tiene información sobre los tipos moleculares circulantes. El objetivo de este estudio fue realizar la caracterización genética de los aislamientos pertenecientes al complejo C. neoformans/C. gattii obtenidos en el Hospital «Dr. Julio C. Perrando» de la ciudad de Resistencia (Chaco, Argentina, con el fin de determinar especie, variedad y genotipo. Durante dos años y un mes se estudiaron 26 aislamientos clínicos. Mediante métodos convencionales y moleculares, un aislamiento fue identificado como C. gattii genotipo VGI y los 25 restantes como C. neoformans var.grubii, 23 de los cuales correspondieron al genotipo VNI y dos al genotipo VNII. Estos datos son una contribución al conocimiento de la epidemiología de la criptococosis en la Argentina y el primer informe sobre genotipos del complejo C. neoformans/C. gattii de origen clínico en el nordeste argentino.

Poynting's theorem for complex fields; El teorema de Poynting para campos complejos

Energy Technology Data Exchange (ETDEWEB)

Fernandez Guasti, M. [Universidad Autonoma Metropolitana-Unidad Iztapalapa, Mexico, D.F (Mexico)

2001-04-01

Poynting's theorem is derived for complex electromagnetic fields without invoking the harmonic dependence of the fields. This reformulation yields the functional form of a continuity equation. The definition of poynting's vector for complex fields reduces to its traditional definition for real fields without involving an extra factor of 1/2. [Spanish] Se presenta la derivacion del teorema de Poynting utilizando una representacion compleja de los campos electromagneticos. En esta reformulacion se obtiene cabalmente la forma funcional de una ecuacion de continuidad. Este resultado no requiere que los campos armonicos sean trenes de onda infinitos, de manera que con este formalismo es posible abordar el caso de pulsos electromagneticos. La definicion del vector Poynting para campos complejos se reduce a la definicion convencional si los campos son reales sin involucrar un factor de 1/2 adicional.

Ammonia formation by metal-ligand cooperative hydrogenolysis of a nitrido ligand

Science.gov (United States)

Askevold, Bjorn; Nieto, Jorge Torres; Tussupbayev, Samat; Diefenbach, Martin; Herdtweck, Eberhardt; Holthausen, Max C.; Schneider, Sven

2011-07-01

Bioinspired hydrogenation of N2 to ammonia at ambient conditions by stepwise nitrogen protonation/reduction with metal complexes in solution has experienced remarkable progress. In contrast, the highly desirable direct hydrogenation with H2 remains difficult. In analogy to the heterogeneously catalysed Haber-Bosch process, such a reaction is conceivable via metal-centred N2 splitting and unprecedented hydrogenolysis of the nitrido ligands to ammonia. We report the synthesis of a ruthenium(IV) nitrido complex. The high nucleophilicity of the nitrido ligand is demonstrated by unusual N-C coupling with π-acidic CO. Furthermore, the terminal nitrido ligand undergoes facile hydrogenolysis with H2 at ambient conditions to produce ammonia in high yield. Kinetic and quantum chemical examinations of this reaction suggest cooperative behaviour of a phosphorus-nitrogen-phosphorus pincer ligand in rate-determining heterolytic hydrogen splitting.

Reduction of dinitrogen ligands

International Nuclear Information System (INIS)

Richards, R.L.

1983-01-01

Processes of dinitrogen ligand reduction in complexes of transition metals are considered. The basic character of the dinitrogen ligand is underlined. Data on X-ray photoelectronic spectroscopy and intensities of bands ν (N 2 ) in IR-spectra of nitrogen complexes are given. The mechanism of protonation of an edge dinitrogen ligand is discussed. Model systems and mechanism of nitrogenogenase are compared

Introducción a un modelo complejo de los softwares multimediales educativos

Directory of Open Access Journals (Sweden)

Luis R. Lara

2004-01-01

Full Text Available El diseño de softwares multimediales educativos como materiales para educación a distancia, ha llevado a que éstos sean realizados basados en principios de desarrollos empíricos. Este artículo, desde una nueva perspectiva teórica interdisciplinaria, enfoca la cuestión del desarrollo de estos materiales interactivos, considerándolos como Sistemas Interactivos Multimediales (SIM, relacionándolos con principios de disciplinas y conceptos tan diversos como la termodinámica, entropía, constructivismo y teoría general de sistemas. De esta manera, se orienta el proceso de diseño de los SIMs como un sistema complejo aceptando, desde una perspectiva constructivista, que el alumno toma el rol protagónico en el proceso de aprendizaje, entonces, un nuevo modelo de software multimedial educativo debería implicar al alumno no sólo en el tramo final como usuario, sino que tendría que intervenir durante toda la etapa en que se va realizando el proceso de aprendizaje.

Estudio de la adición de estabilizantes y vitamina B12 al complejo inyectable de hierro dextrana

OpenAIRE

Georgina Michelena; Antonio Bell; Graciela Cerutti; Emilia Carrera; Mónica Coronel; Gracia Rivas Monte

2007-01-01

Se realizó el estudio de adición de estabilizantes al complejo hierro dextrana mediante un diseño experimental 33 tipo mezcla con el objetivo de aumentar la fijación del hierro en el proceso de síntesis y disminuir su viscosidad, lo que incide favorablemente en la tecnología al obtener un producto de mayor filtrabilidad y con alto contenido de hierro. Los mejores resultados se alcanzaron con la variante de adición en iguales relaciones de ácido cítrico y sorbitol y tres veces la cantidad en d...

Histology and Gadolinium Distribution in the Rodent Brain After the Administration of Cumulative High Doses of Linear and Macrocyclic Gadolinium-Based Contrast Agents.

Science.gov (United States)

Lohrke, Jessica; Frisk, Anna-Lena; Frenzel, Thomas; Schöckel, Laura; Rosenbruch, Martin; Jost, Gregor; Lenhard, Diana Constanze; Sieber, Martin A; Nischwitz, Volker; Küppers, Astrid; Pietsch, Hubertus

2017-06-01

Retrospective studies in patients with primary brain tumors or other central nervous system pathologies as well as postmortem studies have suggested that gadolinium (Gd) deposition occurs in the dentate nucleus (DN) and globus pallidus (GP) after multiple administrations of primarily linear Gd-based contrast agents (GBCAs). However, this deposition has not been associated with any adverse effects or histopathological alterations. The aim of this preclinical study was to systematically examine differences between linear and macrocyclic GBCAs in their potential to induce changes in brain and skin histology including Gd distribution in high spatial resolution. Fifty male Wistar-Han rats were randomly allocated into control (saline, n = 10 rats) and 4 GBCA groups (linear GBCAs: gadodiamide and gadopentetate dimeglumine, macrocyclic GBCAs: gadobutrol and gadoteridol; n = 10 rats per group). The animals received 20 daily intravenous injections at a dose of 2.5 mmol Gd/kg body weight. Eight weeks after the last GBCA administration, the animals were killed, and the brain and skin samples were histopathologically assessed (hematoxylin and eosin; cresyl violet [Nissl]) and by immunohistochemistry. The Gd concentration in the skin, bone, brain, and skeletal muscle samples were analyzed using inductively coupled plasma mass spectroscopy (ICP-MS, n = 4). The spatial Gd distribution in the brain and skin samples was analyzed in cryosections using laser ablation coupled with ICP-MS (LA-ICP-MS, n = 3). For the ultra-high resolution of Gd distribution, brain sections of rats injected with gadodiamide or saline (n = 1) were assessed by scanning electron microscopy coupled to energy dispersive x-ray spectroscopy and transmission electron microscopy, respectively. No histological changes were observed in the brain. In contrast, 4 of 10 animals in the gadodiamide group but none of the animals in other groups showed macroscopic and histological nephrogenic systemic fibrosis-like skin

Exodoncia de diente supernumerario, canino en transposición y enucleación de odontoma complejo: Reporte de Caso

OpenAIRE

Perea Paz, Miguel; Aliaga Del Castillo, Rosalinda; Aliaga Del Castillo, Arón

2014-01-01

Las anomalías dentarias más frecuentes e importantes que afectan a los niños son la presencia de piezas supernumerarias, piezas retenidas y odontomas. Algunos dientes retenidos se pueden encontrar en  transposición. Reportamos el caso de una paciente de sexo femenino de 11 años de edad con presencia de diente supernumerario, canino en transposición y odontoma complejo situados en la hemiarcada derecha del maxilar superior. El motivo de consulta fue por la presencia de dientes anteriores sobre...

Ligand modeling and design

Energy Technology Data Exchange (ETDEWEB)

Hay, B.P. [Pacific Northwest National Lab., Richland, WA (United States)

1997-10-01

The purpose of this work is to develop and implement a molecular design basis for selecting organic ligands that would be used in the cost-effective removal of specific radionuclides from nuclear waste streams. Organic ligands with metal ion specificity are critical components in the development of solvent extraction and ion exchange processes that are highly selective for targeted radionuclides. The traditional approach to the development of such ligands involves lengthy programs of organic synthesis and testing, which in the absence of reliable methods for screening compounds before synthesis, results in wasted research effort. The author`s approach breaks down and simplifies this costly process with the aid of computer-based molecular modeling techniques. Commercial software for organic molecular modeling is being configured to examine the interactions between organic ligands and metal ions, yielding an inexpensive, commercially or readily available computational tool that can be used to predict the structures and energies of ligand-metal complexes. Users will be able to correlate the large body of existing experimental data on structure, solution binding affinity, and metal ion selectivity to develop structural design criteria. These criteria will provide a basis for selecting ligands that can be implemented in separations technologies through collaboration with other DOE national laboratories and private industry. The initial focus will be to select ether-based ligands that can be applied to the recovery and concentration of the alkali and alkaline earth metal ions including cesium, strontium, and radium.

Hybrid macrocycle formation and spiro annulation on cis-syn-cis-tricyclo[6.3.0.02,6]undeca-3,11-dione and its congeners via ring-closing metathesis

Directory of Open Access Journals (Sweden)

Sambasivarao Kotha

2015-07-01

Full Text Available We have developed a simple methodology to transform cis-syn-cis-triquinane derivative 2 into the diindole based macrocycle 6 involving Fischer indolization and ring-closing metathesis (RCM. Various spiro-polyquinane derivatives have been assembled via RCM as a key step.

Ligand identification using electron-density map correlations

International Nuclear Information System (INIS)

Terwilliger, Thomas C.; Adams, Paul D.; Moriarty, Nigel W.; Cohn, Judith D.

2007-01-01

An automated ligand-fitting procedure is applied to (F o − F c )exp(iϕ c ) difference density for 200 commonly found ligands from macromolecular structures in the Protein Data Bank to identify ligands from density maps. A procedure for the identification of ligands bound in crystal structures of macromolecules is described. Two characteristics of the density corresponding to a ligand are used in the identification procedure. One is the correlation of the ligand density with each of a set of test ligands after optimization of the fit of that ligand to the density. The other is the correlation of a fingerprint of the density with the fingerprint of model density for each possible ligand. The fingerprints consist of an ordered list of correlations of each the test ligands with the density. The two characteristics are scored using a Z-score approach in which the correlations are normalized to the mean and standard deviation of correlations found for a variety of mismatched ligand-density pairs, so that the Z scores are related to the probability of observing a particular value of the correlation by chance. The procedure was tested with a set of 200 of the most commonly found ligands in the Protein Data Bank, collectively representing 57% of all ligands in the Protein Data Bank. Using a combination of these two characteristics of ligand density, ranked lists of ligand identifications were made for representative (F o − F c )exp(iϕ c ) difference density from entries in the Protein Data Bank. In 48% of the 200 cases, the correct ligand was at the top of the ranked list of ligands. This approach may be useful in identification of unknown ligands in new macromolecular structures as well as in the identification of which ligands in a mixture have bound to a macromolecule

Structure-based drug design of a highly potent CDK1,2,4,6 inhibitor with novel macrocyclic quinoxalin-2-one structure.

Science.gov (United States)

Kawanishi, Nobuhiko; Sugimoto, Tetsuya; Shibata, Jun; Nakamura, Kaori; Masutani, Kouta; Ikuta, Mari; Hirai, Hiroshi

2006-10-01

The design of a novel series of cyclin-dependent kinase (CDK) inhibitors containing a macrocyclic quinoxaline-2-one is reported. Structure-based drug design and optimization from the starting point of diarylurea 2, which we previously reported as a moderate CDK1,2,4,6 inhibitor [J. Biol.Chem.2001, 276, 27548], led to the discovery of potent CDK1,2,4,6 inhibitor that were suitable for iv administration for in vivo study.

Dark and Photoinduced Cytotoxic Activity of the New Chlorophyll-a Derivatives with Oligoethylene Glycol Substituents on the Periphery of Their Macrocycles

OpenAIRE

Yana I. Pylina; Dmitry M. Shadrin; Oksana G. Shevchenko; Olga M. Startseva; Igor O. Velegzhaninov; Dmitry V. Belykh; Ilya O. Velegzhaninov

2017-01-01

In the present work, we investigated the dark and photoinduced cytotoxic activity of the new chlorophyll-a derivatives which contain the substituents of oligoethylene glycol on the periphery of their macrocycles. These compounds were tested using human cell lines to estimate their potential as photosensitizers for photodynamic therapy of cancer. It was shown that all the tested compounds have expressed photoinduced cytotoxic activity in vitro. Detailed study of the biological activity of one ...

Schiff base ligand

Indian Academy of Sciences (India)

Unknown

Low-temperature stoichiometric Schiff base reaction in air in 3 : 1 mole ratio between benz- aldehyde and triethylenetetramine (trien) in methanol yields a novel tetraaza µ-bis(bidentate) acyclic ligand L. It was .... electrochemical work was performed as reported in ..... change in ligand shape through change in oxidation.

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.

Evaluando y fomentando el desarrollo cognitivo y el aprendizaje complejo

Directory of Open Access Journals (Sweden)

Sandra Castañeda Figueiras

2004-01-01

Full Text Available Se abordan los desarrollos investigativos originales que han traducido premisas teóricas acerca de la cognición humana a marcos de trabajo y herramientas tecnológicas aplicables al campo educativo. Los artefactos han sido diseñados para abrir la caja negra del qué, del cómo y del hasta dónde de la oferta generada en los niveles educativos medio superior y superior en México. Marcos y herramientas se fundan en la actividad cognitiva constructiva autorregulada, apoyan la medición y el fomento de resultados del aprendizaje complejo y de sus habilidades asociadas. La asunción subyacente considera que la aplicación de premisas cognitivas al diseño de herramientas educativas es central y que, en este contexto, es fundamental asegurar la estrecha relación entre la investigación y la práctica educativa ordinaria, a fin de apoyar los cambios deseados. En este trabajo se argumentan fundamentos teóricos, se aportan evidencias en apoyo a los desarrollos generados y se enfatiza la necesidad de extender investigación que identifique mecanismos responsables del aprendizaje efectivo en escenarios reales, con el fin de lograr su comprensión cabal y generar alternativas ecológicamente válidas y útiles.

Study of water role during the complexing of uranyl aquanitrate compounds with cyclic polyethers

International Nuclear Information System (INIS)

Belomestnykh, V.I.; Sveshnikova, L.B.; Shabel'nik, K.S.

1990-01-01

By the method of vibrational spectroscopy and thermogravimetry the determining role of water molecules during complexing of uranyl aquonitrate compounds with macrocyclic polyethers is confirmed. It is ascertained that in the synthesized complexes of the composition UO 2 (NO 3 ) 2 (H 2 O) 2 ·mH 2 O·nL (m=0,1,2; L-18-crown-6, 15-crown-5, dibenzo-18-crown-6; n=1,2) molecules of macrocyclic ligand are joined at the expense of strong hydrogen bonds with participation of protons of crystallographically nonequivalent water molecules. In the compounds hydrogen bonds of water-water and water-nitrato group type are also realized. Energies of the above-mentioned bonds are calculated

ProBiS-ligands: a web server for prediction of ligands by examination of protein binding sites.

Science.gov (United States)

Konc, Janez; Janežič, Dušanka

2014-07-01

The ProBiS-ligands web server predicts binding of ligands to a protein structure. Starting with a protein structure or binding site, ProBiS-ligands first identifies template proteins in the Protein Data Bank that share similar binding sites. Based on the superimpositions of the query protein and the similar binding sites found, the server then transposes the ligand structures from those sites to the query protein. Such ligand prediction supports many activities, e.g. drug repurposing. The ProBiS-ligands web server, an extension of the ProBiS web server, is open and free to all users at http://probis.cmm.ki.si/ligands. © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.

Interaction of calreticulin with CD40 ligand, TRAIL and Fas ligand

DEFF Research Database (Denmark)

Duus, K; Pagh, R T; Holmskov, U

2007-01-01

is utilized by many other functionally diverse molecules and in this work the interaction of calreticulin with C1q and structurally similar molecules was investigated. In addition to C1q and MBL, CD40 ligand (CD40L), tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) and Fas ligand (FasL) were...... found to bind calreticulin strongly. A low level or no binding was observed for adiponectin, tumour necrosis factor-alpha (TNF-alpha), CD30L, surfactant protein-A and -D and collagen VIII. The interaction with calreticulin required a conformational change in CD40L, TRAIL and FasL and showed the same...

Propiedades insecticidas de la ceniza del complejo volcánico Puyehue-Cordón Caulle y su posible impacto ambiental

Directory of Open Access Journals (Sweden)

Micaela BUTELER

2011-01-01

Full Text Available Se examina el efecto insecticida de las cenizas volcánicas en general y sus efectos ambientales, con especial énfasis en las cenizas acumuladas como consecuencia de la erupción del complejo volcánico Puyehue-Cordón Caulle, que actualmente afecta un área de más de 7,5 millones de hectáreas en la Patagonia Argentina. Se determinó la composición química de las cenizas provenientes del complejo Puyehue- Cordón Caulle por EDS, y se comprobó que los componentes mayoritarios son el O, Si, Al, Fe, Na y K. A través de bioensayos de laboratorio, utilizando dos especies de insectos como modelo biológico, se determinó que las cenizas se adhieren profusamente a la superficie corporal y resultan tóxicas para ambas especies cuando se mezclan con el sustrato en baja concentración. La susceptibilidad a las cenizas difirió entre ambas especies en bioensayos de siete días de exposición continua [CL99(Oryzaephilus surinamensis L. = 10.25 mg.g-1; CL99((Tribolium castaneum (Herbst = 4.96 mg.g-1]. De estos resultados, se desprende que el impacto de la ceniza del complejo Puyehue- Cordón Caulle sobre la comunidad de artrópodos puede ser radical en la fase aguda de la deposición, y que sus efectos podrían ser substancialmente cualitativos en la fase crónica de la exposición. Así también, la recuperación de las poblaciones afectadas por la ceniza en las zonas con clima desértico, donde persiste la ceniza seca, será más lenta, hecho que tendrá consecuencias tangibles a largo plazo para las plantas hospederas de insectos, para la polinización y sobre el desarrollo de las poblaciones de vertebrados insectívoros. En contraste, en las regiones húmedas, la presencia de cenizas representa un cambio manifiesto en el ecosistema debido al aporte de nutrientes, que en combinación con la retención de agua por las cenizas, llevará a la recuperación cuali y cuantitativa de las poblaciones bajo condiciones favorables.

Complejo industrial, en Sparanise, Italia

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Figini, Luigi

1966-02-01

Full Text Available In the neighbourhood of Saranise an industrial group of buildings has been built, which affects four distinct types of industries, and occupies a ground area of 850.000 m2 close to the national Appia roadway. This industrial complex is served by roads, water, light and fuel supplies, garages, workshops, offices, etc. The project was initiated by Pozi Ceramic Manufacturers. Care has been taken that the general architectural style for all the buildings shall be the same, and that the project as a whole shall exhibit a unity of pattern. Although the structure of the buildings is very similar, since all involve prestressed beams for the roofs, details vary in each particular case, depending on the spans to be covered. A special feature is the roofing of the varnishes factory, which is covered with precast, V shaped units, made in a nearby workshop. These large units have been handled by a travelling crane, which has lifted them to their final emplacement. The units weigh between 13 and 14 tons each. A specialised firm made a study of the ground, and calculated the maximum permissible loadings. They then decided on the most suitable type of foundations in each case.En las inmediaciones de Sparanise se ha construido un complejo fabril, constituido por cuatro grupos de industrias diferentes, cuyos edificios ocupan un solar de 850.000 m2, inmediato a la carretera nacional Appia, dotado de todos los servicios, redes de viales, de agua, luz y combustibles, garaje, talleres, oficinas, etc. La empresa iniciadora es la Manufactura Cerámica Pozzi. Se ha cuidado de que la línea general arquitectónica para los distintos edificios que componen cada grupo sea homogénea, y de que el conjunto tenga un tratamiento semejante que le dé la debida unidad. Aunque las estructuras son muy similares, pues todas ellas se componen de vigas pretensadas para los forjados de cubierta, aquéllas varían de una a otra nave, en cada grupo, de acuerdo con las luces previstas

Variación genética en el complejo infraespecífico de chayote evaluada mediante sistemas isoenzimáticos

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Carlos Hugo Avendaño-Arrazate

2012-02-01

Full Text Available El objetivo de este trabajo fue estimar el grado de variación genética dentro del complejo infraespecífico de Sechium mediante el uso de sistemas isoenzimáticos. Se analizaron 23 loci codificados por 12 sistemas isoenzimáticos, en geles de almidón, en 10 individuos de cada una de las 30 accesiones (27 cultivadas y tres silvestres. La variación genética se estimó con base en el número promedio de alelos por locus (NPAL, porcentaje de porlimorfismo (PP, heterocigosidad observada y esperada (Ho y He, índice relativo de heterocigosidad (IRH e índice de Shannon (IS. Para NPAL y PP, el promedio para las 30 accesiones fue de 2, 03 y 59, 8%, respectivamente. El análisis de Ho y He mostró variación genética en el complejo infraespecífico de Sechium, con valores promedio de 0, 05 y 0, 26, respectivamente. El IRH mostró una deficiencia de individuos heterocigotos (promedio de -0, 75. El IS mostró gran diversidad en las 30 accesiones (0, 41. Las poblaciones con mayor diversidad fueron Negrito, Verde liso, Negro xalapa, Verde espinoso y Negro cónico; con una variación intermedia fueron Castilla blanco, Caldero y Blanco pequeño; y, con poca variación, Castilla verde, Cambray y los parientes silvestres.

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.

Bitopic Ligands and Metastable Binding Sites

DEFF Research Database (Denmark)

Fronik, Philipp; Gaiser, Birgit I; Sejer Pedersen, Daniel

2017-01-01

of orthosteric binding sites. Bitopic ligands have been employed to address the selectivity problem by combining (linking) an orthosteric ligand with an allosteric modulator, theoretically leading to high-affinity subtype selective ligands. However, it remains a challenge to identify suitable allosteric binding...... that have been reported to date, this type of bitopic ligands would be composed of two identical pharmacophores. Herein, we outline the concept of bitopic ligands, review metastable binding sites, and discuss their potential as a new source of allosteric binding sites....

Resultados del tratamiento quirúrgico de los aneurismas del complejo cerebral anterior-arteria comunicante anterior

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Armando Alemán Rivera

2001-06-01

Full Text Available Se realiza un estudio de 30 pacientes con aneurismas localizados en el complejo de la arteria cerebral anterior-arteria comunicante anterior (ACoA, operados en el Servicio de Neurocirugía del Hospital Universitario "Arnaldo Milián Castro", durante un período de 7 años. Se analizan variables tales como edad, sexo, estado neurológico preoperatorio, momento quirúrgico, complicaciones y estado al egreso. La mortalidad general fue del 10 %The authors carried out a study in 30 patients with aneurysms located in the anterior communicating artery-anterior cerebral complex (ACA-ACC, that were operated on at the Neurosurgery Service of "Arnaldo Milián Castro" Teaching Hospital, during a period of 7 years. Variables such as age, sex, preoperative neurologic state, surgical moment, complications and status on discharge were analyzed. General mortality was 10 %

Summary reports of the R and D programme: recycling of non-ferrous metals (1986-1989)

International Nuclear Information System (INIS)

Donato, M.

1992-01-01

This document contains the summary reports of cost sharing research and development contracts funded under the recycling of non-ferrous metals subprogramme of the Commission of the European Communities. In particular from p.171 to 212 is described the recovery of rare earths by supported liquid membranes: synthesis and use of new selective macrocyclic and/or compartmental ligands

Cyanide Scavenging by a Cobalt Schiff-Base Macrocycle: A Cost-Effective Alternative to Corrinoids.

Science.gov (United States)

Lopez-Manzano, Elisenda; Cronican, Andrea A; Frawley, Kristin L; Peterson, Jim; Pearce, Linda L

2016-06-20

The complex of cobalt(II) with the ligand 2,12-dimethyl-3,7,11,17-tetraazabicyclo-[11.3.1]heptadeca-1(17)2,11,13,15-pentaene (CoN4[11.3.1]) has been shown to bind two molecules of cyanide in a cooperative fashion with an association constant of 2.7 (±0.2) × 10(5). In vivo, irrespective of whether it is initially administered as the Co(II) or Co(III) cation, EPR spectroscopic measurements on blood samples show that at physiological levels of reductant (principally ascorbate) CoN4[11.3.1] becomes quantitatively reduced to the Co(II) form. However, following addition of sodium cyanide, a dicyano Co(III) species is formed, both in blood and in buffered aqueous solution at neutral pH. In keeping with other cobalt-containing cyanide-scavenging macrocycles like cobinamide and cobalt(III) meso-tetra(4-N-methylpyridyl)porphine, we found that CoN4[11.3.1] exhibits rapid oxygen turnover in the presence of the physiological reductant ascorbate. This behavior could potentially render CoN4[11.3.1] cytotoxic and/or interfere with evaluations of the antidotal capability of the complex toward cyanide through respirometric measurements, particularly since cyanide rapidly inhibits this process, adding further complexity. A sublethal mouse model was used to assess the effectiveness of CoN4[11.3.1] as a potential cyanide antidote. The administration of CoN4[11.3.1] prophylactically to sodium cyanide-intoxicated mice resulted in the time required for the surviving animals to recover from "knockdown" (unconsciousness) being significantly decreased (3 ± 2 min) compared to that of the controls (22 ± 5 min). All observations are consistent with the demonstrated antidotal activity of CoN4[11.3.1] operating through a cyanide-scavenging mechanism, which is associated with a Co(II) → Co(III) oxidation of the cation. To test for postintoxication neuromuscular sequelae, the ability of mice to remain in position on a rotating cylinder (RotaRod test) was assessed during and after recovery

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.

Rosetta Ligand docking with flexible XML protocols.

Science.gov (United States)

Lemmon, Gordon; Meiler, Jens

2012-01-01

RosettaLigand is premiere software for predicting how a protein and a small molecule interact. Benchmark studies demonstrate that 70% of the top scoring RosettaLigand predicted interfaces are within 2Å RMSD from the crystal structure [1]. The latest release of Rosetta ligand software includes many new features, such as (1) docking of multiple ligands simultaneously, (2) representing ligands as fragments for greater flexibility, (3) redesign of the interface during docking, and (4) an XML script based interface that gives the user full control of the ligand docking protocol.

Ligand-receptor Interactions by NMR Spectroscopy

Directory of Open Access Journals (Sweden)

Novak. P.

2008-04-01

Full Text Available Today NMR spectroscopy is a method of choice for elucidation of interactions between biomolecules and the potential ligands. Knowledge on these interactions is an essential prerequisite for the rational drug design. The most important contribution of NMR to drug design a few years ago was the 3D structure determination of proteins. Besides delivering the 3D structures of the free proteins as a raw material for the modeling studies on ligand binding, NMR can directly yield valuable experimental data on the biologically important protein-ligand complexes. In addition to X-ray diffraction, NMR spectroscopy can provide information on the internal protein dynamics ordynamics of intermolecular interactions. Changes in NMR parameters allow us to detect ("SAR by NMR" and quantitatively determine binding affinities (titration, diffusion NMR experiments, etc. of potential ligands. Also, it is possible to determine the binding site and conformations of ligands, receptors and receptor-ligand complexes with the help of NMR methods such as tr-NOESY. Epitopes or functional groups responsible for binding of ligands to the receptor can be identified by employing STD or WaterLOGSY experiments. In this review are described some of the most frequent NMR methods for the characterization of the interactions between biomolecules and ligands, together with their advantages and disadvantages.

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

Turn on macrocyclic chemosensor for Al3+ ion with facile synthesis and application in live cell imaging

Science.gov (United States)

Ezhumalai, Dhineshkumar; Mathivanan, Iyappan; Chinnadurai, Anbuselvan

2018-06-01

An effort of a new Schiff base macrocyclic chemosensor, 14‑methyl‑2,6,8,12,14,18‑hexaaza‑1,7,13(1,2),4,10,16(1,4)‑hexabenzenacyclooctadecaphane‑2,5,8,11,14,17‑hexaene (me1) and 14,74‑dimethyl‑2,6,8,12,14,18‑hexaaza‑1,7,13(1,2),4,10,16(1,4)‑hexabenzenacyclooctadecadecaphane‑2,5,8,11,14,17‑hexaene (dm2), which enables selective sensing of Al3+ in aqueous DMF were synthesized by a simplistic one-step condensation reaction of macrocyclic compounds. The probe me1 and dm2 characterized by elemental analysis, FT-IR, 1H and 13C NMR, LC-MS spectral techniques. The compounds as mentioned above subjected to FE-SEM with EDS and elemental color mapping. On addition of Al3+, the fluorescent probe me1 and dm2 induces turn-on responses in both absorption and sensing spectra by a PET mechanism. The receptor me1 and dm2 serve highly selective, sensitive and turn-on detection of Al3+. Further, they did not interfere with other cations present in biological or environmental samples. The detection limit is found to be 3 μM and 5 μM. From the view of cytotoxic activity, the ability of these compounds me1 and dm2 to inhibit the growth of KB cell lines examined. The chelating functionality of compounds me1 and dm2 examined for their inhibitory properties of KB cell, live cell images. The compounds me1 and dm2 subjected to theoretical studies by DFT-B3LYP invoking the 6-31G level of theory. The energy of the HOMO and LUMO has been established.

Influencia del uso de complejos enzimáticos en la segunda centrifugación de pastas de aceitunas

Directory of Open Access Journals (Sweden)

Jackisch, Björn Oliver

2006-09-01

Full Text Available Virgin olive oil is a natural fruit juice that conserves the flavor, aroma, vitamins and all the properties of the fruit from which it comes, being, in addition, the only vegetal oil that can be consumed as “virgin” or completely unrefined. The extraction of the juice from the olive is carried out exclusively by mechanical means in the first centrifugation step, in order to obtain directly consumable virgin olive oil. The use of enzymatic complexes in the process of a second centrifugation step has been contemplated in order to obtain a greater yield of refinable virgin oil.With this work, we attempt to demonstrate an increase in the yield of oil extraction with the use of an enzymatic complex in the second centrifugation and to confirm that its use does not affect the quality of the oils obtainedEl aceite de Oliva Virgen es un zumo de fruta natural que conserva el paladar, perfume, vitaminas y todas las propiedades del fruto del que procede, siendo, además, el único aceite vegetal que puede consumirse directamente virgen y crudo. Se defiende la elaboración del zumo de aceituna por medios exclusivamente mecánicos en la primera centrifugación, para obtener aceites de oliva vírgenes directamente consumibles, pero se contempla el uso de complejos enzimáticos en los procesos de segunda centrifugación, para incrementar los rendimientos en la obtención de aceites vírgenes refinables.Pretendemos demostrar con este trabajo que el uso de un complejo enzimático en la segunda centrifugación aumenta el rendimiento del aceite y, al mismo tiempo, confirmar que su uso no tiene efecto en los parámetros de calidad de los aceites obtenidos

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

High-performance liquid chromatographic enantioseparation of 2-aminomono- and dihydroxycyclopentanecarboxylic and 2-aminodihydroxycyclohexanecarboxylic acids on macrocyclic glycopeptide-based phases.

Science.gov (United States)

Berkecz, Róbert; Ilisz, István; Benedek, Gabriella; Fülöp, Ferenc; Armstrong, Daniel W; Péter, Antal

2009-02-06

The direct separation of the enantiomers of four 2-aminomono- or dihydroxycyclopentanecarboxylic acids and four 2-aminodihydroxycyclohexanecarboxylic acids was performed on chiral stationary phases containing macrocyclic glycopeptide antibiotics such as teicoplanin (Astec Chirobiotic T and T2), teicoplanin aglycone (Chirobiotic TAG) or ristocetin A (Chirobiotic R) as chiral selectors. The effects of the nature of organic modifiers, the pH, the mobile phase composition and the structures of the analytes on the separation were investigated. Chirobiotic TAG, and in some cases Chirobiotic T, proved to be the most useful of these columns. The elution sequence was determined in most cases.

A Ferrocene-Based Catecholamide Ligand: the Consequences of Ligand Swivel for Directed Supramolecular Self-Assembly

Energy Technology Data Exchange (ETDEWEB)

Mugridge, Jeffrey; Fiedler, Dorothea; Raymond, Kenneth

2010-02-04

A ferrocene-based biscatecholamide ligand was prepared and investigated for the formation of metal-ligand supramolecular assemblies with different metals. Reaction with Ge(IV) resulted in the formation of a variety of Ge{sub n}L{sub m} coordination complexes, including [Ge{sub 2}L{sub 3}]{sup 4-} and [Ge{sub 2}L{sub 2}({mu}-OMe){sub 2}]{sup 2-}. The ligand's ability to swivel about the ferrocenyl linker and adopt different conformations accounts for formation of many different Ge{sub n}L{sub m} species. This study demonstrates why conformational ligand rigidity is essential in the rational design and directed self-assembly of supramolecular complexes.

Estudio de reacciones de oxidación catalizadas por complejos biomiméticos de Fe (II), Fe (III) y Mn (III)

OpenAIRE

Clemente Tejeda, David

2015-01-01

[ES]Se ha desarrollado una metodología económicamente asequible y medioambientalmente sostenible para la oxidación catalítica de sustratos orgánicos con interés preparativo, utilizando para ello sistemas biomiméticos de Fe(II), Fe(III) y Mn(III). En primer lugar se ha llevado a cabo la síntesis de los complejos metálicos catalizadores, optimizando los procedimientos descritos en la bibliografía precedente. Asimismo se ha llevado a cabo un análisis exhaustivo de todas las variables implicadas ...

Epitope targeting of tertiary protein structure enables target-guided synthesis of a potent in-cell inhibitor of botulinum neurotoxin.

Science.gov (United States)

Farrow, Blake; Wong, Michelle; Malette, Jacquie; Lai, Bert; Deyle, Kaycie M; Das, Samir; Nag, Arundhati; Agnew, Heather D; Heath, James R

2015-06-08

Botulinum neurotoxin (BoNT) serotype A is the most lethal known toxin and has an occluded structure, which prevents direct inhibition of its active site before it enters the cytosol. Target-guided synthesis by in situ click chemistry is combined with synthetic epitope targeting to exploit the tertiary structure of the BoNT protein as a landscape for assembling a competitive inhibitor. A substrate-mimicking peptide macrocycle is used as a direct inhibitor of BoNT. An epitope-targeting in situ click screen is utilized to identify a second peptide macrocycle ligand that binds to an epitope that, in the folded BoNT structure, is active-site-adjacent. A second in situ click screen identifies a molecular bridge between the two macrocycles. The resulting divalent inhibitor exhibits an in vitro inhibition constant of 165 pM against the BoNT/A catalytic chain. The inhibitor is carried into cells by the intact holotoxin, and demonstrates protection and rescue of BoNT intoxication in a human neuron model. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Histology and Gadolinium Distribution in the Rodent Brain After the Administration of Cumulative High Doses of Linear and Macrocyclic Gadolinium-Based Contrast Agents

Science.gov (United States)

Lohrke, Jessica; Frisk, Anna-Lena; Frenzel, Thomas; Schöckel, Laura; Rosenbruch, Martin; Jost, Gregor; Lenhard, Diana Constanze; Sieber, Martin A.; Nischwitz, Volker; Küppers, Astrid; Pietsch, Hubertus

2017-01-01

Objectives Retrospective studies in patients with primary brain tumors or other central nervous system pathologies as well as postmortem studies have suggested that gadolinium (Gd) deposition occurs in the dentate nucleus (DN) and globus pallidus (GP) after multiple administrations of primarily linear Gd-based contrast agents (GBCAs). However, this deposition has not been associated with any adverse effects or histopathological alterations. The aim of this preclinical study was to systematically examine differences between linear and macrocyclic GBCAs in their potential to induce changes in brain and skin histology including Gd distribution in high spatial resolution. Materials and Methods Fifty male Wistar-Han rats were randomly allocated into control (saline, n = 10 rats) and 4 GBCA groups (linear GBCAs: gadodiamide and gadopentetate dimeglumine, macrocyclic GBCAs: gadobutrol and gadoteridol; n = 10 rats per group). The animals received 20 daily intravenous injections at a dose of 2.5 mmol Gd/kg body weight. Eight weeks after the last GBCA administration, the animals were killed, and the brain and skin samples were histopathologically assessed (hematoxylin and eosin; cresyl violet [Nissl]) and by immunohistochemistry. The Gd concentration in the skin, bone, brain, and skeletal muscle samples were analyzed using inductively coupled plasma mass spectroscopy (ICP-MS, n = 4). The spatial Gd distribution in the brain and skin samples was analyzed in cryosections using laser ablation coupled with ICP-MS (LA-ICP-MS, n = 3). For the ultra-high resolution of Gd distribution, brain sections of rats injected with gadodiamide or saline (n = 1) were assessed by scanning electron microscopy coupled to energy dispersive x-ray spectroscopy and transmission electron microscopy, respectively. Results No histological changes were observed in the brain. In contrast, 4 of 10 animals in the gadodiamide group but none of the animals in other groups showed macroscopic and histological

Reacción de ligandos azufrados con el complejo au2pt (ch2p(Sph24,cl2

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Guillermo Garzón

2010-07-01

Full Text Available Se describe la reacción de intercambio del cloro en el complejo au2pt (ch2p(Sph24,cl2 por los ligandos SCH2Ph-,S2CN(CH2CH3,2- y SCN-. Los nuevos derivados azufrados se caracterizan por análisis químico, espectroscopia infrarroja, electrónica y resonancia magnética nuclear protónica. Los ligandos se coordinan por el azufre a los dos átomos sw oro metálico en forma simétrica. El análisis elemental concuerda con las estequiomctrías y estructuras propuestas.

Conformational diversity of flexible ligand in metal-organic frameworks controlled by size-matching mixed ligands

International Nuclear Information System (INIS)

Hua, Xiu-Ni; Qin, Lan; Yan, Xiao-Zhi; Yu, Lei; Xie, Yi-Xin; Han, Lei

2015-01-01

Hydrothermal reactions of N-auxiliary flexible exo-bidentate ligand 1,3-bis(4-pyridyl)propane (bpp) and carboxylates ligands naphthalene-2,6-dicarboxylic acid (2,6-H_2ndc) or 4,4′-(hydroxymethylene)dibenzoic acid (H_2hmdb), in the presence of cadmium(II) salts have given rise to two novel metal-organic frameworks based on flexible ligands (FL-MOFs), namely, [Cd_2(2,6-ndc)_2(bpp)(DMF)]·2DMF (1) and [Cd_3(hmdb)_3(bpp)]·2DMF·2EtOH (2) (DMF=N,N-Dimethylformamide). Single-crystal X-ray diffraction analyses revealed that compound 1 exhibits a three-dimensional self-penetrating 6-connected framework based on dinuclear cluster second building unit. Compound 2 displays an infinite three-dimensional ‘Lucky Clover’ shape (2,10)-connected network based on the trinuclear cluster and V-shaped organic linkers. The flexible bpp ligand displays different conformations in 1 and 2, which are successfully controlled by size-matching mixed ligands during the self-assembly process. - Graphical abstract: Compound 1 exhibits a 3D self-penetrating 6-connected framework based on dinuclear cluster, and 2 displays an infinite 3D ‘Lucky Clover’ shape (2,10)-connected network based on the trinuclear cluster. The flexible 1,3-bis(4-pyridyl)propane ligand displays different conformations in 1 and 2, which successfully controlled by size-matching mixed ligands during the self-assembly process.

Conformational diversity of flexible ligand in metal-organic frameworks controlled by size-matching mixed ligands

Energy Technology Data Exchange (ETDEWEB)

Hua, Xiu-Ni; Qin, Lan; Yan, Xiao-Zhi; Yu, Lei; Xie, Yi-Xin; Han, Lei, E-mail: hanlei@nbu.edu.cn

2015-12-15

Hydrothermal reactions of N-auxiliary flexible exo-bidentate ligand 1,3-bis(4-pyridyl)propane (bpp) and carboxylates ligands naphthalene-2,6-dicarboxylic acid (2,6-H{sub 2}ndc) or 4,4′-(hydroxymethylene)dibenzoic acid (H{sub 2}hmdb), in the presence of cadmium(II) salts have given rise to two novel metal-organic frameworks based on flexible ligands (FL-MOFs), namely, [Cd{sub 2}(2,6-ndc){sub 2}(bpp)(DMF)]·2DMF (1) and [Cd{sub 3}(hmdb){sub 3}(bpp)]·2DMF·2EtOH (2) (DMF=N,N-Dimethylformamide). Single-crystal X-ray diffraction analyses revealed that compound 1 exhibits a three-dimensional self-penetrating 6-connected framework based on dinuclear cluster second building unit. Compound 2 displays an infinite three-dimensional ‘Lucky Clover’ shape (2,10)-connected network based on the trinuclear cluster and V-shaped organic linkers. The flexible bpp ligand displays different conformations in 1 and 2, which are successfully controlled by size-matching mixed ligands during the self-assembly process. - Graphical abstract: Compound 1 exhibits a 3D self-penetrating 6-connected framework based on dinuclear cluster, and 2 displays an infinite 3D ‘Lucky Clover’ shape (2,10)-connected network based on the trinuclear cluster. The flexible 1,3-bis(4-pyridyl)propane ligand displays different conformations in 1 and 2, which successfully controlled by size-matching mixed ligands during the self-assembly process.

Gestión organizacional en entornos complejos por parte de las Mipymes del sector servicios de la ciudad de Sincelejo

OpenAIRE

Jorge Luis Del Rio Vásquez

2017-01-01

Con el propósito de determinar los modelos de gestión organizacional en entornos complejos que practican las MIPYMES del sector servicios en la ciudad de Sincelejo - Sucre - Colombia, se adelanta la presente investigación. Para ello es importante tener en cuenta su gestión actual, toda vez que estas representan en su mayoría el tejido empresarial de las economías locales y nacionales. El presente artículo pretende un análisis, a la luz de la teoría y antecedentes empíricos, que demuestre l...

Caracterización y ambiente tectónico de las rocas máficas del Complejo El Chilar: evidencias de un prisma de acreción pre-Jurásico Tardío en el centro de México

OpenAIRE

Dávila-Alcocer, Víctor M.; Centeno-García, Elena; Meriggi, Lorenzo

2013-01-01

El Complejo El Chilar aflora en el estado de Querétaro y es una unidad sedimentaria muy deformada a tal grado que forma una mezcla tectónica (mélange). Este complejo de edad pre-Jurásico Tardío, contiene bloques autóctonos de arenisca o arenisca con intercalaciones de lutita así como bloques exóticos de pedernal con horizontes de radiolaritas. El bloque exótico de mayor tamaño tiene 1.5 km de longitud y aflora en las inmediaciones del poblado El Terrero. Este bloque está cortado por diques de...

La argumentación científica escolar: contribución a la comprensión de un modelo complejo de salud y enfermedad

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Andrea Fernanda Revel Chion

2014-12-01

Full Text Available Este trabajo aborda la relación existente entre el aprendizaje de la argumentación científica escolar y la adquisición de un modelo complejo en torno a la salud y la enfermedad, más específicamente para la explicación de la emergencia o reemergencia de las enfermedades. Se asume que la argumentación científica escolar es un procedimiento cognitivo lingüístico que da lugar a la producción de un texto que explica, en el que pueden reconocerse cuatro componentes: pragmática, retórica, teórica y lógica. Se realizó un análisis histórico-epistemológico del concepto de salud y se tomó posición por un modelo complejo, que hemos denominado multicausal y multirreferencial. Se diseñó una unidad didáctica para la enseñanza de ambos contenidos con énfasis en procesos metacognitivos y autorregulatorios puestos en marcha pr medio de bases de orientación, e instancias de autoevaluación, coevaluación y heteroevaluación. El estudio realizado se alinea en un modelo de explicación ilocutivo.

A General Ligand Design for Gold Catalysis allowing Ligand-Directed Anti Nucleophilic Attack of Alkynes

Science.gov (United States)

Wang, Yanzhao; Wang, Zhixun; Li, Yuxue; Wu, Gongde; Cao, Zheng; Zhang, Liming

2014-01-01

Most homogenous gold catalyses demand ≥0.5 mol % catalyst loading. Due to the high cost of gold, these reactions are unlikely to be applicable in medium or large scale applications. Here we disclose a novel ligand design based on the privileged biphenyl-2-phosphine framework that offers a potentially general approach to dramatically lowering catalyst loading. In this design, an amide group at the 3’ position of the ligand framework directs and promotes nucleophilic attack at the ligand gold complex-activated alkyne, which is unprecedented in homogeneous gold catalysis considering the spatial challenge of using ligand to reach antiapproaching nucleophile in a linear P-Au-alkyne centroid structure. With such a ligand, the gold(I) complex becomes highly efficient in catalyzing acid addition to alkynes, with a turnover number up to 99,000. Density functional theory calculations support the role of the amide moiety in directing the attack of carboxylic acid via hydrogen bonding. PMID:24704803

Secondary ligand-directed assembly of Co(II) coordination polymers based on a pyridine carboxylate ligand

International Nuclear Information System (INIS)

Cao, Ke-Li; Zhang, Yi-Ping; Cai, Yi-Ni; Xu, Xiao-Wei; Feng, Yun-Long

2014-01-01

To investigate the influence of hydrogen bonds and secondary ligands on the structures and properties of the resulting frameworks, five new Co(II) compounds have been synthesized by the reactions of Co(II) salts and 3,5-bis(pyridin-4-ylmethoxy)benzoic acid (HL) with four rationally selected dicarboxylic acid ligands. Without secondary ligand, we got one compound [CoL 2 (H 2 O) 2 ] n ·2nH 2 O (1), which possesses a 1D chain structure. In the presence of ancillary ligands, namely, 1,3-adamantanedicarboxylic acid (H 2 adbc), terephthalic acid (H 2 tpa), thiophene-2,5-dicarboxylic acid (H 2 tdc) and 1,4-benzenedithioacetic acid (H 2 bdtc), four 3D structures [Co 2 L 2 (adbc)] n ·nH 2 O (2), [Co 2 L 2 (tpa)] n (3), [Co 2 L 2 (tdc)] n (4), [Co 2 L 2 (bdtc)(H 2 O)] n (5) were obtained, respectively. It can be observed from the architectures of 1–5 that hydrogen bonds and secondary ligands both have great effects on the spatial connective fashions, resulting in the formation of various dimensional compounds. The XRPD, TGA data of title polymers and the magnetic properties for 2 and 5 have also been investigated. - Graphical abstract: The structural differences show that the ancillary ligands have great effects on the spatial connective fashions, resulting in the formation of various dimensional compounds. - Highlights: • Five new Co(II) coordination polymers have been synthesized by solvothermal reactions based on 3,5-bis(pyridin-4-ylmethoxy)benzoic acid (HL). • The long-flexible ligand (HL) is a good candidate to produce interpenetrating architectures. • The secondary dicarboxylic acid ligands play important roles in the spatial connective fashions and the formation of various dimensional compounds. • The magnetism studies show that both 2 and 5 exhibit antiferromagnetic interactions

Diseño de complejos binucleares de cobre en estudios biomiméticos de la tirosinasa.

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Rolando Calero

2015-10-01

Full Text Available Se ha estudiado la reactividad de ciertos metaloenzimas de cobre y algunos complejos de Cobre sintéticos que presentan reactividad frente a sustratos, a través de la interacción con el oxígeno molecular, además se ha observado en las varias formas en como ocurre esta interacción y la razón por la cual  porque unos actúan con el oxigeno para ser transportadores como las Hemocianinas y otros formando aductos para mediar reacciones químicas hacia ciertos sustratos fenólicos. También se propone una revisión de los mecanismos para la hidroxilación de fenoles y la oxidación a quinonas, encontrando una dependencia atribuible a factores estéricos y redox en la unión catalizador-sustrato.

Specific ability of sulfur-ligands on removal of 203Hg-labeled organomercury from hemoglobin in comparison with nitrogen-ligands

International Nuclear Information System (INIS)

Hojo, Yasuji; Sugiura, Yukio; Tanaka, Hisashi

1975-01-01

Removal of 203 Hg-labeled organomercurials, bound to sulfhydryl groups of hemoglobin, by various chelating agents was investigated by the use of equilibrium dialysis. Organomercurials employed were chlormerodrin, methylmercury, ethylmercury and phenylmercury compounds. Higher and more specific effects of the sulfur-ligands, such as penicillamine and glutathione, on removal of organomercurial were found as compared with those of the nitrogen-ligands such as EDTA, glycine and polymethylenediamines. Linear correlation was observed between the degree of organomercury elimination from hemoglobin and the stability constant (log K 1 ) of 1:1 organomercury complex in both the sulfur- and nitrogen-ligand systems and at the same value of log K 1 , the elimination-effect of sulfur-ligands was extremely greater than that of the nitrogen-ligands. The relationship between the average percentage of removal and the Taft's polar substituent constant of organic moiety of the metal was also linear among the organomercury compounds other than chlormerodrin. The average removal percentage by sulfur-ligands increased in the order, ethylmercury>methylmercury>phenylmercury, while that of the nitrogen-ligands was not different among the organomercurials investigated. In addition, direct ligand-exchange reaction between hemoglobin-SH and the ligand coordinating-atom (S or N) against organomercurials rather than Ssub(N2) reaction via the ternary complex, hemoglobin-S-RHg-ligand, is postulated. (auth.)

ESTUDIOS DE AISLAMIENTO Y FRACCIONAMIENTO DE UN COMPLEJO GLICOPROTEICO DE PASTEURELLA MULTOCIDA

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Yolanda de Navarro

2010-07-01

Full Text Available Mediante la extracción con solución de NaCl 2.5% (p/v a 47' C, se obtuvo un complejo glicoproteíco de Pasteurella multocida que fue parcialmente purificado mediante filtración por gel usando Sephacryl S-200. Las fracciones 1, 2 y 3 presentaron líneas de precipitinas en imnunodifusión contra sueros hiperimnunes de conejos inoculados con extracto salino 2.5% (P/V a 47" C y 66' C. Por electroforesis SDS-PAGE. se determinaron bandas de proteínas con pesos moleculares entre 98.800 y 17.700 daltons. Lafracción lyel extracto salino crudo a 47" C se utilizaron como antígenos adsorbidos en gel de Al(OHj y con ellos se efectuaron ensayos de protección en ratones, teniendo como referencia la vacuna comercial contra Septicemia Hemorrágica producida por VECOL S.A. Mediante el método estadístico de Reed Muench se estableció el índice de protección y se encontró que todos los antígenos fueron considerados prolectores, siendo la fracción 1 la de mayor índice de protección con una dosis inferior.

Complejo de piscinas calentadas por energía solar Saizburgo – Austria

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Garstenauer, G.

1980-06-01

Full Text Available The main feature of this complex, located in Dorfgastein (Salzburg is to use the «greenhouse » effect to heat the water instead of the solar panels that have been used up until now in similar constructions. The chief installations of this work are: — two saunas, one for ladies, the other for gentlemen; — a solarium with swimming lanes; and — two hot water round swimming pools. Centers such as this permit the bathing season to be prolonged, which otherwise is normally limited to the summertime months, to all the year round.

La característica principal de este complejo, situado en Dorfgastein (Saizburgo, es la utilización del efecto de «invernadero » para calentar el agua en lugar de los paneles solares empleados hasta ahora en construcciones similares. Las principales instalaciones de esta obra son: — dos saunas, una para señoras y otra para caballeros; — un solario con canales de natación; y — dos piscinas circulares de agua caliente. Centros de este tipo permiten prolongar la temporada de baños, normalmente reducida a los meses de verano, a prácticamente todo el año.

Ligand cluster-based protein network and ePlatton, a multi-target ligand finder.

Science.gov (United States)

Du, Yu; Shi, Tieliu

2016-01-01

Small molecules are information carriers that make cells aware of external changes and couple internal metabolic and signalling pathway systems with each other. In some specific physiological status, natural or artificial molecules are used to interact with selective biological targets to activate or inhibit their functions to achieve expected biological and physiological output. Millions of years of evolution have optimized biological processes and pathways and now the endocrine and immune system cannot work properly without some key small molecules. In the past thousands of years, the human race has managed to find many medicines against diseases by trail-and-error experience. In the recent decades, with the deepening understanding of life and the progress of molecular biology, researchers spare no effort to design molecules targeting one or two key enzymes and receptors related to corresponding diseases. But recent studies in pharmacogenomics have shown that polypharmacology may be necessary for the effects of drugs, which challenge the paradigm, 'one drug, one target, one disease'. Nowadays, cheminformatics and structural biology can help us reasonably take advantage of the polypharmacology to design next-generation promiscuous drugs and drug combination therapies. 234,591 protein-ligand interactions were extracted from ChEMBL. By the 2D structure similarity, 13,769 ligand emerged from 156,151 distinct ligands which were recognized by 1477 proteins. Ligand cluster- and sequence-based protein networks (LCBN, SBN) were constructed, compared and analysed. For assisting compound designing, exploring polypharmacology and finding possible drug combination, we integrated the pathway, disease, drug adverse reaction and the relationship of targets and ligand clusters into the web platform, ePlatton, which is available at http://www.megabionet.org/eplatton. Although there were some disagreements between the LCBN and SBN, communities in both networks were largely the same

Signal intensity at unenhanced T1-weighted magnetic resonance in the globus pallidus and dentate nucleus after serial administrations of a macrocyclic gadolinium-based contrast agent in children

Energy Technology Data Exchange (ETDEWEB)

Rossi Espagnet, Maria Camilla; Bernardi, Bruno; Figa-Talamanca, Lorenzo [Ospedale Pediatrico Bambino Gesu, IRCCS, Neuroradiology Unit, Imaging Department, Rome (Italy); Pasquini, Luca [Ospedale Pediatrico Bambino Gesu, IRCCS, Neuroradiology Unit, Imaging Department, Rome (Italy); University Sapienza, Neuroradiology Unit, Azienda Ospedaliera Sant' Andrea, Rome (Italy); Toma, Paolo [Ospedale Pediatrico Bambino Gesu, IRCCS, Department of Imaging, Rome (Italy); Napolitano, Antonio [Ospedale Pediatrico Bambino Gesu, IRCCS, Enterprise Risk Management, Medical Physics Department, Rome (Italy)

2017-09-15

Few studies have been conducted on the relations between T1-weighted signal intensity changes in the pediatric brain following gadolinium-based contrast agent (GBCA) exposure. The purpose of this study is to investigate the effect of multiple administrations of a macrocyclic GBCA on signal intensity in the globus pallidus and dentate nucleus of the pediatric brain on unenhanced T1-weighted MR images. This retrospective study included 50 patients, mean age: 8 years (standard deviation: 4.8 years), with normal renal function exposed to ≥6 administrations of the same macrocyclic GBCA (gadoterate meglumine) and a control group of 59 age-matched GBCA-naive patients. The globus pallidus-to-thalamus signal intensity ratio and dentate nucleus-to-pons signal intensity ratio were calculated from unenhanced T1-weighted images for both patients and controls. A mixed linear model was used to evaluate the effects on signal intensity ratios of the number of GBCA administrations, the time interval between administrations, age, radiotherapy and chemotherapy. T-test analyses were performed to compare signal intensity ratio differences between successive administrations and baseline MR signal intensity ratios in patients compared to controls. P-values were considered significant if <0.05. A significant effect of the number of GBCA administrations on relative signal intensities globus pallidus-to-thalamus (F[8]=3.09; P=0.002) and dentate nucleus-to-pons (F[8]=2.36; P=0.021) was found. The relative signal intensities were higher at last MR examination than at baseline (P<0.001). Quantitative analysis evaluation of globus pallidus:thalamus and dentate nucleus:pons of the pediatric brain demonstrated an increase after serial administrations of macrocyclic GBCA. Further research is necessary to fully understand GBCA pharmacokinetic in children. (orig.)

Immobilisation of ligands by radio-derivatized polymers; Immobilisering av ligander med radioderiverte polymerer

Energy Technology Data Exchange (ETDEWEB)

Varga, J.M.; Fritsch, P.

1995-01-30

The invention relates to radio-derivatized polymers and a method of producing them by contacting non-polymerizable conjugands with radiolysable polymers in the presence of irradiation. The resulting radio-derivatized polymers can be further linked with ligand of organic or inorganic nature to immobilize such ligands. 2 figs., 5 tabs.

Petrografía, geoquímica y geocronología de rocas metamórficas aflorantes en San Francisco Putumayo y la vía Palermo-San Luis asociadas a los complejos La Cocha - Río Téllez y Aleluya

OpenAIRE

Zapata García, Gilberto; Rodríguez García, Gabriel; Mejía, María Isabel Arango

2017-01-01

El Complejo Migmatítico La Cocha - Río Téllez comprende un conjunto de rocas metamórficas: migmatitas, esquistos, neises y anfibolitas, en contacto fallado con la Cuarzomonzonita de Sombrerillo y rocas sedimentarias cretácicas. Se asume como la edad del metamorfismo del Complejo Migmatítico La Cocha-Río Téllez la edad U-Pb en circones de 163.6±4.7 Ma, obtenida en un esquisto cuarzo feldespático que aflora en el municipio de San Francisco-Putumayo, las edades de194.4±2.0 Ma, 218.8 Ma y 229.8 M...

Complejo «Australia Square», en Sidney – Australia

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Seidler, Harry

1971-02-01

Full Text Available This project has given a new style to the overcrowded centre of Sydney city. Its outstanding feature is the 50 storey, 170.70 m high tower, of circular cross section, which is a distinctive feature in the urban skyline. Most of the building is devoted to office space, but the lower floors include a commercial centre, and a theatre, which can be converted into a convention hall. At the top there is a terrace, offering a fine view of the town, and just below a rotating restaurant, with capacity for 330 guests, which turns round once every ninety minutes and enables diners to enjoy a total view of Sydney in the course of a meal. This building is also significant because of its structural design, the good space distribution, and the novelty and quality of its internal fittings.Destaca en este complejo, que ha aportado un nuevo sentido de vida al congestionado centro de Sydney, la torre de 50 plantas, 170,69 m de altura, y planta circular, que constituye un hito destacado en el centro de la ciudad. La mayor parte de sus plantas están destinadas a oficinas; las inferiores se dedican a centro comercial, y albergan un teatro convertible en sala de Juntas y Reuniones. La planta superior incluye una terraza, desde la que los visitantes pueden disfrutar de la vista de Sydney; debajo de ella hay un restaurante giratorio, con capacidad para 330 plazas, desde el cual los comensales pueden contemplar una vista panorámica completa del área metropolitana de Sydney, ya que su plataforma da una vuelta completa cada hora y media. Características de este edificio son: la bella solución estructural que presenta; máximo aprovechamiento del espacio logrado; flexibilidad en la distribución, y perfección y originalidad de sus instalaciones.

Selective extraction of lithium with a macrocyclic trinuclear complex of (1,3,5-trimethylbenzene)ruthenium(II) bridged by 2,3-dioxopyridine.

Science.gov (United States)

Katsuta, Shoichi; Imoto, Takahiro; Kudo, Yoshihiro; Takeda, Yasuyuki

2008-10-01

A macrocyclic trinuclear complex of (1,3,5-trimethylbenzene)ruthenium(II) bridged by 2,3-dioxopyridine was synthesized, and the extraction properties for lithium and sodium picrates were investigated in a dichloromethane/water system at 25 degrees C. The complex was found to have extremely high extractability and selectivity for lithium picrate; the logarithmic values of the extraction constants are 5.86 and 2.63 for Li(+) and Na(+), respectively. By using this complex as an extractant, nearly quantitative extraction and separation of Li(+) from Na(+) could be achieved by a single extraction.

Expresión de las moléculas del Complejo Mayor de Histocompatibilidad clase II y moléculas co-estimuladoras en carcinomas orales in vitro

OpenAIRE

Villarroel, Mariana; Speight, Paul M.; Barrett, A. William

2005-01-01

El descubrimiento de que el epitelio escamoso estratificado que cubre la mucosa oral podia expresar moleculas del Complejo Mayor de Histocompatibilidad clase II en varias condiciones patologicas de tipo inflamatorio abrio la posibilidad de que los queratinocitos orales sean celulas inmunologicamente activas, las cuales pueden funcionar con .celulas presentadoras de antigenos'ñ. Para una efectiva activacion de los linfocitos T, las celulas presentadoras de antigenos requie...

Reactivity of halide and pseudohalide ligands

International Nuclear Information System (INIS)

Kukushkin, Yu.N.

1987-01-01

Reactivity of halide and pseudohalide (cyanide, azide, thiocyanate, cyanate) ligands tending to form bridge bonds in transition metal (Re, Mo, W) complexes is considered. Complexes where transition metal salts are ligands of other, complex-forming ion, are described. Transformation of innerspheric pseudohalide ligands is an important way of directed synthesis of these metal coordination compounds

Metal-ligand cooperative activation of nitriles by a ruthenium complex with a de-aromatized PNN pincer ligand

NARCIS (Netherlands)

Eijsink, Linda E; Perdriau, Sébastien C P; de Vries, Johannes G; Otten, Edwin

2016-01-01

The pincer complex (PNN)RuH(CO), with a de-aromatized pyridine in the ligand backbone, is shown to react with nitriles in a metal-ligand cooperative manner. This leads to the formation of a series of complexes with new Ru-N(nitrile) and C(ligand)-C(nitrile) bonds. The initial nitrile cycloaddition

Paramagnetic epoxy resin

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E. C. Vazquez Barreiro

2017-01-01

Full Text Available This work illustrates that macrocycles can be used as crosslinking agents for curing epoxy resins, provided that they have appropriate organic functionalities. As macrocycles can complex metal ions in their structure, this curing reaction allows for the introduction of that metal ion into the resin network. As a result, some characteristic physical properties of the metallomacrocycle could be transferred to the new material. The bisphenol A diglycidyl ether (BADGE, n = 0 and hemin (a protoporphyrin IX containing the Fe(III ion, and an additional chloride ligand have been chosen. The new material has been characterized by differential scanning calorimetry (DSC, thermogravimetric analysis (TGA, Fourier Transform Infrared (FT-IR, Nuclear Magnetic Resonance (NMR, Transmission Electron Microscopy (TEM, and magnetic susceptibility measurements. Fe(III remains in the high-spin state during the curing process and, consequently, the final material exhibits the magnetic characteristics of hemin. The loss of the chlorine atom ligand during the cure of the resin allows that Fe(III can act as Lewis acid, catalyzing the crosslinking reactions. At high BADGE n = 0/hemin ratios, the formation of ether and ester bonds occurs simultaneously during the process.

El Complejo de Cambio en Suelos del Municipio de Marinilla [Antioquia] según el Método de Brown

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Galiano S. Francisco

1959-12-01

Full Text Available Se estudió el complejo de cambio en suelos aluviales recientes, terrazas medias y terrazas altas del Municipio de Marinilla por el método rápido de Brown. El grado de saturación, bajo en todos ellos, se acentúa en los suelos de las terrazas más antiguas y nos indica el bajo nivel de fertilidad de estos suelos. La extracción del hidrógeno de cambio con acetato cálcico coincide con la que efectúa el acetato amónico, excepto para los suelos más ricos en materia orgánica con los que proporciona resultados más altos la solución extractora de acetato cálcico.

Astrocitoma subependimario de células gigantes asociado a complejo de esclerosis tuberosa: recomendaciones para el diagnóstico oportuno y tratamiento.

OpenAIRE

Matilde Ruiz; Sandra Sánchez; Alejandro Rea; Roberto Sanromán; Joao García; Antonio Bravo; Infante Cantú; Hugo Ceja; Ariadna González; María del Mar Sáez

2015-01-01

RESUMEN El complejo de esclerosis tuberosa es una enfermedad genética poco frecuente, autosómica dominante con fenotipo y expresión clínica muy variables. Se caracteriza por alteraciones en la migración, diferenciación y proliferación celulares con formación de múltiples tumores benignos llamados hamartomas, las cuales afectan principalmente piel, encéfalo, riñón, ojo, corazón y pulmón. Los astrocitomas subependimarios de células gigantes son tumores benignos de crecimien...

Towards ligand docking including explicit interface water molecules.

Directory of Open Access Journals (Sweden)

Gordon Lemmon

Full Text Available Small molecule docking predicts the interaction of a small molecule ligand with a protein at atomic-detail accuracy including position and conformation the ligand but also conformational changes of the protein upon ligand binding. While successful in the majority of cases, docking algorithms including RosettaLigand fail in some cases to predict the correct protein/ligand complex structure. In this study we show that simultaneous docking of explicit interface water molecules greatly improves Rosetta's ability to distinguish correct from incorrect ligand poses. This result holds true for both protein-centric water docking wherein waters are located relative to the protein binding site and ligand-centric water docking wherein waters move with the ligand during docking. Protein-centric docking is used to model 99 HIV-1 protease/protease inhibitor structures. We find protease inhibitor placement improving at a ratio of 9:1 when one critical interface water molecule is included in the docking simulation. Ligand-centric docking is applied to 341 structures from the CSAR benchmark of diverse protein/ligand complexes [1]. Across this diverse dataset we see up to 56% recovery of failed docking studies, when waters are included in the docking simulation.

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

Crystallization of bi-functional ligand protein complexes.

Science.gov (United States)

Antoni, Claudia; Vera, Laura; Devel, Laurent; Catalani, Maria Pia; Czarny, Bertrand; Cassar-Lajeunesse, Evelyn; Nuti, Elisa; Rossello, Armando; Dive, Vincent; Stura, Enrico Adriano

2013-06-01

Homodimerization is important in signal transduction and can play a crucial role in many other biological systems. To obtaining structural information for the design of molecules able to control the signalization pathways, the proteins involved will have to be crystallized in complex with ligands that induce dimerization. Bi-functional drugs have been generated by linking two ligands together chemically and the relative crystallizability of complexes with mono-functional and bi-functional ligands has been evaluated. There are problems associated with crystallization with such ligands, but overall, the advantages appear to be greater than the drawbacks. The study involves two matrix metalloproteinases, MMP-12 and MMP-9. Using flexible and rigid linkers we show that it is possible to control the crystal packing and that by changing the ligand-enzyme stoichiometric ratio, one can toggle between having one bi-functional ligand binding to two enzymes and having the same ligand bound to each enzyme. The nature of linker and its point of attachment on the ligand can be varied to aid crystallization, and such variations can also provide valuable structural information about the interactions made by the linker with the protein. We report here the crystallization and structure determination of seven ligand-dimerized complexes. These results suggest that the use of bi-functional drugs can be extended beyond the realm of protein dimerization to include all drug design projects. Copyright © 2013 Elsevier Inc. All rights reserved.

Theoretical studies on the possible sensitizers of DSSC: Nanocomposites of graphene quantum dot hybrid phthalocyanine/tetrabenzoporphyrin/tetrabenzotriazaporphyrins/cis-tetrabenzodiazaporphyrins/tetrabenzomonoazaporphyrins and their Cu-metallated macrocycles

Science.gov (United States)

Gao, Feng; Yang, Chuan-Lu; Wang, Mei-Shan; Ma, Xiao-Guang; Liu, Wen-Wang

2018-04-01

The feasibility of nanocomposites of cir-coronene graphene quantum dot (GQD) with phthalocyanine, tetrabenzoporphyrin, tetrabenzotriazaporphyrins, cis-tetrabenzodiazaporphyrins, tetrabenzomonoazaporphyrins and their Cu-metallated macrocycles as a sensitizer of dye-sensitized solar cells (DSSC) are investigated. Based on the first principles density functional theory (DFT), the geometrical structures of the separate GQD and 10 macrocycles, and their hybridized nanocomposites are fully optimized. The energy stabilities of the obtained structures are confirmed by harmonic frequency analysis. The optical absorptions of the optimized structures are calculated with time-dependent DFT. The feasibility of the nanocomposites as the sensitizer of DSSC is examined by the charge spatial separation, the electron transfer, the molecular orbital energy levels of the nanocomposites and the electrolyte, and the conduction band minimum of TiO2 electrode. The results demonstrate that all the nanocomposites have enhanced absorptions in the visible light range, and their molecular orbital energies satisfy the requirement of sensitizers. However, only two of the ten considered nanocomposites demonstrate significantly charge spatial separation. The GQD-Cu-TBP is identified as the most favorable candidate sensitizer of DSSC by the most enhanced in optical absorption, obvious charge spatial separation, suitable LUMO energy levels and driving force for electron transfer, and low recombination rate of electron and hole.

Autocrine signal transmission with extracellular ligand degradation

Science.gov (United States)

Muratov, C B; Posta, F; Shvartsman, S Y

2009-03-01

Traveling waves of cell signaling in epithelial layers orchestrate a number of important processes in developing and adult tissues. These waves can be mediated by positive feedback autocrine loops, a mode of cell signaling where binding of a diffusible extracellular ligand to a cell surface receptor can lead to further ligand release. We formulate and analyze a biophysical model that accounts for ligand-induced ligand release, extracellular ligand diffusion and ligand-receptor interaction. We focus on the case when the main mode for ligand degradation is extracellular and analyze the problem with the sharp threshold positive feedback nonlinearity. We derive expressions that link the speed of propagation and other characteristics of traveling waves to the parameters of the biophysical processes, such as diffusion rates, receptor expression level, etc. Analyzing the derived expressions we found that traveling waves in such systems can exhibit a number of unusual properties, e.g. non-monotonic dependence of the speed of propagation on ligand diffusivity. Our results for the fully developed traveling fronts can be used to analyze wave initiation from localized perturbations, a scenario that frequently arises in the in vitro models of epithelial wound healing, and guide future modeling studies of cell communication in epithelial layers.

Cell-specific targeting by heterobivalent ligands.

Science.gov (United States)

Josan, Jatinder S; Handl, Heather L; Sankaranarayanan, Rajesh; Xu, Liping; Lynch, Ronald M; Vagner, Josef; Mash, Eugene A; Hruby, Victor J; Gillies, Robert J

2011-07-20

Current cancer therapies exploit either differential metabolism or targeting to specific individual gene products that are overexpressed in aberrant cells. The work described herein proposes an alternative approach--to specifically target combinations of cell-surface receptors using heteromultivalent ligands ("receptor combination approach"). As a proof-of-concept that functionally unrelated receptors can be noncovalently cross-linked with high avidity and specificity, a series of heterobivalent ligands (htBVLs) were constructed from analogues of the melanocortin peptide ligand ([Nle(4), dPhe(7)]-α-MSH) and the cholecystokinin peptide ligand (CCK-8). Binding of these ligands to cells expressing the human Melanocortin-4 receptor and the Cholecystokinin-2 receptor was analyzed. The MSH(7) and CCK(6) were tethered with linkers of varying rigidity and length, constructed from natural and/or synthetic building blocks. Modeling data suggest that a linker length of 20-50 Å is needed to simultaneously bind these two different G-protein coupled receptors (GPCRs). These ligands exhibited up to 24-fold enhancement in binding affinity to cells that expressed both (bivalent binding), compared to cells with only one (monovalent binding) of the cognate receptors. The htBVLs had up to 50-fold higher affinity than that of a monomeric CCK ligand, i.e., Ac-CCK(6)-NH(2). Cell-surface targeting of these two cell types with labeled heteromultivalent ligand demonstrated high avidity and specificity, thereby validating the receptor combination approach. This ability to noncovalently cross-link heterologous receptors and target individual cells using a receptor combination approach opens up new possibilities for specific cell targeting in vivo for therapy or imaging.

Geomorfología y sedimentología de los ambientes depositacionales recientes del complejo estuarino de los ríos Hueque y Curarí, Estado Falcón, Venezuela

Directory of Open Access Journals (Sweden)

Scarlet Cartaya

2012-02-01

Full Text Available En este trabajo se presentan los resultados de la caracterización geomorfológica y sedimentológica del complejo estuarino de la desembocadura de los ríos Hueque y Curarí, localizada en la costa nororiental del Estado Falcón (Venezuela. La investigación se desarrolló en tres fases. En la fase de campo se recolectaron muestras de sedimentos y se realizaron mediciones morfométricas de los ambientes depositacionales. En la fase de laboratorio se ejecutaron análisis sedimentológicos de textura, carbonatos, materia orgánica, minerales pesados y mineralogía por difracción de rayos X. La fase de gabinete se basó en la interpretación y análisis espacial de los ambientes depositacionales con apoyo en fotografías aéreas y mapas topográficos a escala 1:25 000; en la confección de los mapas y perfiles del área, y en la elaboración del modelo sedimentológico. La desembocadura de los ríos Hueque y Curarí se encuentra en un borde costero de clima semi-árido, con una cuenca de baja densidad de drenaje y dinámica litoral de rango micromareal, marea mixta, con oleaje de alta energía y corriente litoral favorable. Se identificaron dos grandes conjuntos sedimentológicos: Complejo Cordón Litoral (infraplaya, mesoplaya, supraplaya, dunas playeras, contrabarrera y barra, de litofacies arenosas y el Complejo Pantanoso (cauces de los ríos Hueque y Curarí, canal de marea y caño de marea, de litofacies arcillo-limosa. Los canales fluviales se comportan como estuarios hipersalinos.

EPR studies on binuclear copper(II) complexes with N,N',N'',N'''-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraaza-cyclotetradecane in solutions

International Nuclear Information System (INIS)

Jezierska, J.; Ozarowski, A.; Vuckovic, G.

1997-01-01

Binuclear copper(II) complexes of macrocyclic ligand TMPC (tetraazamacrocycle with four pendant 2-pirydylmethyl groups attached to the ring nitrogen atoms) with various anions forming bridge between copper ions, or coordinating to copper(II) ions at the apex, were prepared and their frozen solutions in DMF and NMF were investigated by EPR. The spectroscopic results have been interpreted in terms of molecular structure of investigated complexes

Modular assembly of metal-organic super-containers incorporating calixarenes

Science.gov (United States)

Wang, Zhenqiang; Dai, Feng-Rong

2018-01-16

A new strategy to design container molecules is presented. Sulfonylcalix[4]arenes, which are synthetic macrocyclic containers, are used as building blocks that are combined with various metal ions and tricarboxylate ligands to construct metal-organic `super-containers` (MOSCs). These MOSCs possess both endo and exo cavities and thus mimic the structure of viruses. The synthesis of MOSCs is highly modular, robust, and predictable.

Calixarenes and cations: a time-lapse photography of the big-bang.

Science.gov (United States)

Casnati, Alessandro

2013-08-07

The outstanding cation complexation properties emerging from the pioneering studies on calixarene ligands during a five-year period in the early 1980s triggered a big-bang burst of publications on such macrocycles that is still lasting at a distance of more than 30 years. A time-lapse photography of this timeframe is proposed which allows the readers to pinpoint the contributions of the different research groups.

Acid-base and coordination properties of Meso-substituted porphyrins in nonaqueous solutions

Science.gov (United States)

Pukhovskaya, S. G.; Nam, Dao Tkhe; Fien, Chan Ding; Domanina, E. N.; Ivanova, Yu. B.; Semeikin, A. S.

2017-09-01

Acid-base and coordination properties of alkyl and aryl meso-substituted porphyrins are studied spectrophotometrically in nonaqueous solutions. It is found that the nature of the substituent greatly affects the basicity of ligands for porphyrins characterized by a flat structure of macrocycle. The electronic effects of substituents have a much weaker influence on the kinetics of complexing. These effects could be due to the opposite orientation of some factors: an increase in the basicity and stability of the N-H bonds of porphyrin reaction centers. Dissociation constants p K b of the cationic forms of meso-substituted derivatives of porphyrin are measured. The values of p K b are in good agreement with classic concepts of the nature of substituents, particularly those indirectly included in the macrocycle through phenyl buffer rings.

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.

Mixed-ligand Pt(II) dithione-dithiolato complexes: influence of the dicyanobenzodithiolato ligand on the second-order NLO properties.

Science.gov (United States)

Espa, Davide; Pilia, Luca; Marchiò, Luciano; Artizzu, Flavia; Serpe, Angela; Mercuri, Maria Laura; Simão, Dulce; Almeida, Manuel; Pizzotti, Maddalena; Tessore, Francesca; Deplano, Paola

2012-03-28

The mixed-ligand dithiolene complex [Pt(Bz(2)pipdt)(dcbdt)] (1) bearing the two ligands Bz(2)pipdt = 1,4-dibenzyl-piperazine-3,2-dithione and dcbdt = dicyanobenzodithiolato, has been synthesized, characterized and studied to evaluate its second-order optical nonlinearity. The dithione/dithiolato character of the two ligands gives rise to an asymmetric distribution of the charge in the molecule. This is reflected by structural data showing that in the C(2)S(2)PtS(2)C(2) dithiolene core the four sulfur atoms define a square-planar coordination environment of the metal where the Pt-S bond distances involving the two ligands are similar, while the C-S bond distances in the C(2)S(2) units exhibit a significant difference in Bz(2)pipdt (dithione) and dcbdt (dithiolato). 1 shows a moderately strong absorption peak in the visible region, which can be related to a HOMO-LUMO transition, where the dcbdt ligand (dithiolato) contributes mostly to the HOMO, and the Bz(2)pipdt one (dithione) mostly to the LUMO. Thus this transition has ligand-to-ligand charge transfer (CT) character with some contribution of the metal and undergoes negative solvatochromism and molecular quadratic optical nonlinearity (μβ(0) = -1296 × 10(-48) esu), which was determined by the EFISH (electric-field-induced second-harmonic generation) technique and compared with the values of similar complexes on varying the dithiolato ligand (mnt = maleonitriledithiolato, dmit = 2-thioxo-1,3-dithiole-4,5-dithiolato). Theoretical calculations help to elucidate the role of the dithiolato ligands in affecting the molecular quadratic optical nonlinearity of these complexes.

Role of ligands in permanganate oxidation of organics.

Science.gov (United States)

Jiang, Jin; Pang, Su-Yan; Ma, Jun

2010-06-01

We previously demonstrated that several ligands such as phosphate, pyrophosphate, EDTA, and humic acid could significantly enhance permanganate oxidation of triclosan (one phenolic biocide), which was explained by the contribution of ligand-stabilized reactive manganese intermediates in situ formed upon permanganate reduction. To further understand the underlying mechanism, we comparatively investigated the influence of ligands on permanganate oxidation of bisphenol A (BPA, one phenolic endocrine-disrupting chemical), carbamazepine (CBZ, a pharmaceutical containing the olefinic group), and methyl p-tolyl sulfoxide (TMSO, a typical oxygen-atom acceptor). Selected ligands exerted oxidation enhancement for BPA but had negligible influence for CBZ and TMSO. This was mainly attributed to the effects of identified Mn(III) complexes, which would otherwise disproportionate spontaneously in the absence of ligands. The one-electron oxidant Mn(III) species exhibited no reactivity toward CBZ and TMSO for which the two-electron oxygen donation may be the primary oxidation mechanism but readily oxidized BPA. The latter case was a function of pH, the complexing ligand, and the molar [Mn(III)]:[ligand] ratio, generally consistent with the patterns of ligand-affected permanganate oxidation. Moreover, the combination of the one-electron reduction of Mn(III) (Mn(III) + e(-) -->Mn(II)) and the Mn(VII)/Mn(II) reaction in excess ligands (Mn(VII) + 4Mn(II) ----> (ligands) 5Mn(III)) suggested a catalytic role of the Mn(III)/Mn(II) pair in permanganate oxidation of some phenolics in the presence of ligands.

Determination of ligand binding modes in weak protein–ligand complexes using sparse NMR data

Energy Technology Data Exchange (ETDEWEB)

Mohanty, Biswaranjan; Williams, Martin L.; Doak, Bradley C.; Vazirani, Mansha; Ilyichova, Olga [Monash University, Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences (Australia); Wang, Geqing [La Trobe University, La Trobe Institute for Molecular Bioscience (Australia); Bermel, Wolfgang [Bruker Biospin GmbH (Germany); Simpson, Jamie S.; Chalmers, David K. [Monash University, Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences (Australia); King, Glenn F. [The University of Queensland, Institute for Molecular Bioscience (Australia); Mobli, Mehdi, E-mail: m.mobli@uq.edu.au [The University of Queensland, Centre for Advanced Imaging (Australia); Scanlon, Martin J., E-mail: martin.scanlon@monash.edu [Monash University, Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences (Australia)

2016-11-15

We describe a general approach to determine the binding pose of small molecules in weakly bound protein–ligand complexes by deriving distance constraints between the ligand and methyl groups from all methyl-containing residues of the protein. We demonstrate that using a single sample, which can be prepared without the use of expensive precursors, it is possible to generate high-resolution data rapidly and obtain the resonance assignments of Ile, Leu, Val, Ala and Thr methyl groups using triple resonance scalar correlation data. The same sample may be used to obtain Met {sup ε}CH{sub 3} assignments using NOESY-based methods, although the superior sensitivity of NOESY using [U-{sup 13}C,{sup 15}N]-labeled protein makes the use of this second sample more efficient. We describe a structural model for a weakly binding ligand bound to its target protein, DsbA, derived from intermolecular methyl-to-ligand nuclear Overhauser enhancements, and demonstrate that the ability to assign all methyl resonances in the spectrum is essential to derive an accurate model of the structure. Once the methyl assignments have been obtained, this approach provides a rapid means to generate structural models for weakly bound protein–ligand complexes. Such weak complexes are often found at the beginning of programs of fragment based drug design and can be challenging to characterize using X-ray crystallography.

Radiation induced ligand loss from cobalt complexes

International Nuclear Information System (INIS)

Funston, A. M.; McFadyen, W.D.; Tregloan, P.A.

2000-01-01

Full text: Due to the rapid nature of ligand dissociation from cobalt(II) complexes the study of the rate of ligand dissociation necessitates the use of a technique such as pulse radiolysis. This allows the rapid reduction of the corresponding cobalt(III) complex by a reducing radical, such as the aquated electron, to form the cobalt(II) complex. However, to date, no systematic study of either the mechanism of reduction or the influence of the electronic structure on the rate of ligand dissociation has been carried out. In order to understand these processes more fully the mechanism of reduction of a range of related cobalt(III) complexes by the aquated electron and the subsequent rate of ligand dissociation from the resulting cobalt(II) complexes is being investigated. It has been found that a number of processes are observed following the initial rapid reaction of the cobalt(III) complex with the aquated electron. Ultimately ligand loss is observed. Depending upon the complex, the initial processes observed may include the formation of coordinated radicals and electron transfer within the complex. For complexes containing aromatic ligands such as 2,2'-bipyridine, 1,10-phenanthroline and dipyrido[3,2-a:2',3'-c]phenazine the formation of a coordinated radical is observed as the initial reduction step. The kinetics of ligand dissociation of these complexes has been determined. The loss of monodentate ligands is fast and has been indistinguishable from the reduction processes when aromatic ligands are also present in the complex. However, for diamine chelates and diimine chelates spectra of the transient species can be resolved

Regulation mechanisms of the FLT3-ligand after irradiation; Mecanismes de regulation du FLT3-ligand apres irradiation

Energy Technology Data Exchange (ETDEWEB)

Prat-Lepesant, M

2005-06-15

The hematopoietic compartment is one of the most severely damaged after chemotherapy, radiotherapy or accidental irradiations. Whatever its origin, the resulting damage to the bone marrow remains difficult to evaluate. Thus, it would be of great interest to get a biological indicator of residual hematopoiesis in order to adapt the treatment to each clinical situation. Recent results indicated that the plasma Flt3 ligand concentration was increased in patients suffering from either acquired or induced aplasia, suggesting that Flt3 ligand might be useful as a biological indicator of bone marrow status. We thus followed in a mouse model as well as in several clinical situations the variations in plasma Flt3 ligand concentration, after either homogeneous or heterogeneous irradiations. These variations were correlated to the number of hematopoietic progenitors and to other parameters such as duration and depth of pancytopenia. The results indicated that the concentration of Flt3 ligand in the blood reflects the bone marrow status, and that the follow-up of plasma Flt3 ligand concentration could give predictive information about the bone marrow function and the duration and severity of pancytopenia and thrombocytopenia. Nevertheless, the clinical use of Flt3 ligand as a biological indicator of bone marrow damage require the knowledge of the mechanisms regulating the variations in plasma Flt3 ligand concentration. We thus developed a study in the mouse model. The results indicated that the variations in plasma Flt3 ligand variations were not solely due to a balance between its production by lymphoid cells and its consumption by hematopoietic cells. Moreover, we showed that T lymphocytes are not the main regulator of plasma Flt3 ligand concentration as previously suggested, and that other cell types, possibly including bone marrow stromal cells, might be strongly implicated. These results also suggest that the Flt3 ligand is a main systemic regulator of hematopoiesis

Synthesis and characterization of mixed ligand chiral nanoclusters

KAUST Repository

Guven, Zekiye P.; Ustbas, Burcin; Harkness, Kellen M.; Coskun, Hikmet; Joshi, Chakra Prasad; Besong, Tabot M.D.; Stellacci, Francesco; Bakr, Osman; Akbulut, Ozge

2016-01-01

Chiral mixed ligand silver nanoclusters were synthesized in the presence of a chiral and an achiral ligand. While the chiral ligand led mostly to the formation of nanoparticles, the presence of the achiral ligand drastically increased the yield of nanoclusters with enhanced chiral properties. © 2016 The Royal Society of Chemistry.

Synthesis and characterization of mixed ligand chiral nanoclusters

KAUST Repository

Guven, Zekiye P.

2016-06-22

Chiral mixed ligand silver nanoclusters were synthesized in the presence of a chiral and an achiral ligand. While the chiral ligand led mostly to the formation of nanoparticles, the presence of the achiral ligand drastically increased the yield of nanoclusters with enhanced chiral properties. © 2016 The Royal Society of Chemistry.

Identifying Marine Copper-Binding Ligands in Seawater

Science.gov (United States)

Whitby, H.; Hollibaugh, J. T.; Maldonado, M. T.; Ouchi, S.; van den Berg, S. M.

2016-02-01

Complexation reactions are important because they affect the bioavailability of trace metals such as copper and iron. For example, organic complexation can determine whether copper is a limiting or a toxic micronutrient at natural levels. Copper competes with iron for complexing ligands, and when iron is limiting, copper can also substitute for iron in some metabolic pathways. The speciation of copper can be measured using complexing capacity titrations, which provide the concentration of individual ligand classes (L1, L2 etc.) and the complex stabilities (log K). Using methods recently developed in our laboratory, we show that the ligands within these classes can be measured independently of titrations, thus confirming the titration method and simultaneously identifying the ligands within each class. Thiols were identified as the L1 ligand class and humic compounds as the weaker L2 class in samples from coastal Georgia, USA, collected monthly from April to December. Log K values of the ligand complexes were consistent with values expected for thiols and humic substances. Recent results from culture studies and from samples collected along Line P, a coastal - oceanic transect in the HNLC region of the NE subarctic Pacific, will be presented in comparison to the estuarine results. This comparison will help to broaden our perspective on copper complexation and the ligands responsible, furthering our understanding of ligand sources and life cycles.

A Review on the Toxicity and Non-Target Effects of Macrocyclic Lactones in Terrestrial and Aquatic Environments

Science.gov (United States)

Lumaret, Jean-Pierre; Errouissi, Faiek; Floate, Kevin; Römbke, Jörg; Wardhaugh, Keith

2012-01-01

The avermectins, milbemycins and spinosyns are collectively referred to as macrocyclic lactones (MLs) which comprise several classes of chemicals derived from cultures of soil micro-organisms. These compounds are extensively and increasingly used in veterinary medicine and agriculture. Due to their potential effects on non-target organisms, large amounts of information on their impact in the environment has been compiled in recent years, mainly caused by legal requirements related to their marketing authorization or registration. The main objective of this paper is to critically review the present knowledge about the acute and chronic ecotoxicological effects of MLs on organisms, mainly invertebrates, in the terrestrial and aquatic environment. Detailed information is presented on the mode-of-action as well as the ecotoxicity of the most important compounds representing the three groups of MLs. This information, based on more than 360 references, is mainly provided in nine tables, presenting the effects of abamectin, ivermectin, eprinomectin, doramectin, emamectin, moxidectin, and spinosad on individual species of terrestrial and aquatic invertebrates as well as plants and algae. Since dung dwelling organisms are particularly important non-targets, as they are exposed via dung from treated animals over their whole life-cycle, the information on the effects of MLs on dung communities is compiled in an additional table. The results of this review clearly demonstrate that regarding environmental impacts many macrocyclic lactones are substances of high concern particularly with larval instars of invertebrates. Recent studies have also shown that susceptibility varies with life cycle stage and impacts can be mitigated by using MLs when these stages are not present. However information on the environmental impact of the MLs is scattered across a wide range of specialised scientific journals with research focusing mainly on ivermectin and to a lesser extent on abamectin

Substrate coated with receptor and labelled ligand for assays

International Nuclear Information System (INIS)

1980-01-01

Improvements in the procedures for assaying ligands are described. The assay consists of a polystyrene tube on which receptors are present for both the ligand to be assayed and a radioactively labelled form of the ligand. The receptors on the bottom portion of the tube are also coated with labelled ligands, thus eliminating the necessity for separate addition of the labelled ligand and sample during an assay. Examples of ligands to which this method is applicable include polypeptides, nucleotides, nucleosides and proteins. Specific examples are given in which the ligand to be assayed is digoxin, the labelled form of the ligand is 3-0-succinyl digoxyigenin tyrosine ( 125 I) and the receptor is digoxin antibody. (U.K.)

Parallel β-sheet vibrational couplings revealed by 2D IR spectroscopy of an isotopically labeled macrocycle: quantitative benchmark for the interpretation of amyloid and protein infrared spectra.

Science.gov (United States)

Woys, Ann Marie; Almeida, Aaron M; Wang, Lu; Chiu, Chi-Cheng; McGovern, Michael; de Pablo, Juan J; Skinner, James L; Gellman, Samuel H; Zanni, Martin T

2012-11-21

Infrared spectroscopy is playing an important role in the elucidation of amyloid fiber formation, but the coupling models that link spectra to structure are not well tested for parallel β-sheets. Using a synthetic macrocycle that enforces a two stranded parallel β-sheet conformation, we measured the lifetimes and frequency for six combinations of doubly (13)C═(18)O labeled amide I modes using 2D IR spectroscopy. The average vibrational lifetime of the isotope labeled residues was 550 fs. The frequencies of the labels ranged from 1585 to 1595 cm(-1), with the largest frequency shift occurring for in-register amino acids. The 2D IR spectra of the coupled isotope labels were calculated from molecular dynamics simulations of a series of macrocycle structures generated from replica exchange dynamics to fully sample the conformational distribution. The models used to simulate the spectra include through-space coupling, through-bond coupling, and local frequency shifts caused by environment electrostatics and hydrogen bonding. The calculated spectra predict the line widths and frequencies nearly quantitatively. Historically, the characteristic features of β-sheet infrared spectra have been attributed to through-space couplings such as transition dipole coupling. We find that frequency shifts of the local carbonyl groups due to nearest neighbor couplings and environmental factors are more important, while the through-space couplings dictate the spectral intensities. As a result, the characteristic absorption spectra empirically used for decades to assign parallel β-sheet secondary structure arises because of a redistribution of oscillator strength, but the through-space couplings do not themselves dramatically alter the frequency distribution of eigenstates much more than already exists in random coil structures. Moreover, solvent exposed residues have amide I bands with >20 cm(-1) line width. Narrower line widths indicate that the amide I backbone is solvent

Correcting binding parameters for interacting ligand-lattice systems

Science.gov (United States)

Hervy, Jordan; Bicout, Dominique J.

2017-07-01

Binding of ligands to macromolecules is central to many functional and regulatory biological processes. Key parameters characterizing ligand-macromolecule interactions are the stoichiometry, inducing the number of ligands per macromolecule binding site, and the dissociation constant, quantifying the ligand-binding site affinity. Both these parameters can be obtained from analyses of classical saturation experiments using the standard binding equation that offers the great advantage of mathematical simplicity but becomes an approximation for situations of interest when a ligand binds and covers more than one single binding site on the macromolecule. Using the framework of car-parking problem with latticelike macromolecules where each ligand can cover simultaneously several consecutive binding sites, we showed that employing the standard analysis leads to underestimation of binding parameters, i.e., ligands appear larger than they actually are and their affinity is also greater than it is. Therefore, we have derived expressions allowing to determine the ligand size and true binding parameters (stoichiometry and dissociation constant) as a function of apparent binding parameters retrieved from standard saturation experiments.

THERMODYNAMICS OF PROTEIN-LIGAND INTERACTIONS AND THEIR ANALYSIS

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Rummi Devi Saini

2017-11-01

Full Text Available Physiological processes are controlled mainly by intermolecular recognition mechanisms which involve protein–protein and protein–ligand interactions with a high specificity and affinity to form a specific complex. Proteins being an important class of macromolecules in biological systems, it is important to understand their actions through binding to other molecules of proteins or ligands. In fact, the binding of low molecular weight ligands to proteins plays a significant role in regulating biological processes such as cellular metabolism and signal transmission. Therefore knowledge of the protein–ligand interactions and the knowledge of the mechanisms involved in the protein-ligand recognition and binding are key in understanding biology at molecular level which will facilitate the discovery, design, and development of drugs. In this review, the mechanisms involved in protein–ligand binding, the binding kinetics, thermodynamic concepts and binding driving forces are discussed. Thermodynamic mechanisms involved in a few important protein-ligand binding are described. Various spectroscopic, non-spectroscopic and computational method for analysis of protein–ligand binding are also discussed.

Development of immobilized ligands for actinide separations

International Nuclear Information System (INIS)

Paine, R.T.

1994-01-01

Primary goals during this grant period were to (1) synthesize new bifunctional chelating ligands, (2) characterize the structural features of the Ln and An coordination complexes formed by these ligands, (3) use structural data to iteratively design new classes of multifunctional ligands, and (4) explore additional routes for attachment of key ligands to solid supports that could be useful for chromatographic separations. Some highlights of recently published work as well as a summary of submitted, unpublished and/or still in progress research are outlined

Entangled zinc-ditetrazolate frameworks involving in situ ligand synthesis and topological modulation by various secondary N-donor ligands

International Nuclear Information System (INIS)

Li Yunwu; Chen Weilin; Wang Yonghui; Li Yangguang; Wang Enbo

2009-01-01

The introduction of various secondary N-donor ligands into an in situ ditetrazolate-ligand synthesis system of terephthalonitrile, NaN 3 and ZnCl 2 led to the formation of three new entangled frameworks Zn(pdtz)(4,4'-bipy).3H 2 O (1), [Zn(pdtz)(bpp)] 2 .3H 2 O (2) and Zn(pdtz) 0.5 (N 3 )(2,2'-bipy) (3) (4,4'-bipy=4,4'-bipyridine; bpp=1,3-bis(4-pyridyl)propane; 2,2'-bipy=2,2'-bipyridine; H 2 pdtz=5,5'-1,4-phenylene-ditetrazole). The formation of pdtz 2- ligand involves the Sharpless [2+3] cycloaddition reaction between terephthalonitrile and NaN 3 in the presence of Zn 2+ ion as a Lewis-acid catalyst under hydrothermal conditions. Compound 1 exhibits a fivefold interpenetrating 3D framework based on the diamondoid topology. Compound 2 displays a twofold parallel interpenetrating framework based on the wavelike individual network. Compound 3 possesses a 2D puckered network. These new Zn-ditetrazolate frameworks are highly dependent on the modulation of different secondary N-donor ligands. Their luminescent properties were investigated. - Graphical abstract: Three new entangled frameworks were prepared by an in situ ditetrazolate-ligand synthesis system assisted with various auxiliary N-donor ligands. The entangled structures can be modulated by different secondary ligands.

Selective extraction of trivalent actinides with hard-soft mixed donor ligands: role of intra-ligand synergism

International Nuclear Information System (INIS)

Ghanty, Tapan K.

2016-01-01

In recent years, considerable attention has been given to understand the coordination chemistry of trivalent lanthanide (Ln) and actinide (An) with various ligands because of its close link with the nuclear waste management processes. It is well known that lanthanide-actinide separation is a challenging and difficult task because of very similar chemical properties of these two series of ions, which are associated with similar ionic radii and coordination numbers. Recently, we have introduced a new concept, 'intra-ligand synergism', where hard donor atom, such as, oxygen preferentially binds to trivalent actinides (An(III)) as compared to the valence iso-electronic trivalent lanthanides (Ln(III)) in presence of another soft donor centre. In the present work, the conventional concept of selective complexation of actinides with soft donor ligands (either S or N donor) has been modified through exploiting this concept, and thereby the higher selectivity of 1,10-phenanthroline-2,9-dicarboxylamide (PDAM) based ligands, namely PDAM and its isobutyl and decyl derivatives towards Am(III) ion has been predicted theoretically through density functional calculations. Subsequently, several such amide derivatives have been synthesized to optimize the solubility of the ligands in organic phase. Finally, solvent extraction experiments have been carried out to validate the theoretical prediction on the selectivity of oxygen donor ligands towards Am(III) as compared to Eu(III), and a maximum separation factor of about 51 has been achieved experimentally using 2,9-bis(N-decylaminocarbonyl)-1,10-phenanthroline ligand. The separation factor is increased with the decrease in pH, which is very interesting since extraction of the Am 3+ ion is considered to be important under highly acidic conditions from the nuclear waste management point of view. (author)

Comparison of MRI properties between derivatized DTPA and DOTA gadolinium-dendrimer conjugates.

Science.gov (United States)

Nwe, K; Bernardo, M; Regino, C A S; Williams, M; Brechbiel, M W

2010-08-15

In this report we directly compare the in vivo and in vitro MRI properties of gadolinium-dendrimer conjugates of derivatized acyclic diethylenetriamine-N,N',N',N'',N''-pentaacetic acid (1B4M-DTPA) and macrocyclic 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (C-DOTA). The metal-ligand chelates were pre-formed in alcohol prior to conjugation to the generation 4 PAMAM dendrimer (G4D), and the dendrimer-based agents were purified by Sephadex(R) G-25 column. The analysis and SE-HPLC data indicated chelate to dendrimer ratios of 30:1 and 28:1, respectively. Molar relaxivity measured at pH 7.4, 22 degrees C, and 3T are comparable (29.5 vs 26.9 mM(-1)s(-1)), and both conjugates are equally viable as MRI contrast agents based on the images obtained. The macrocyclic agent however exhibits a faster rate of clearance in vivo (t(1/2)=16 vs 29 min). Our conclusion is that the macrocyclic-based agent is the more suitable agent for in vivo use for these reasons combined with kinetic inertness associated with the Gd(III) DOTA complex stability properties. Published by Elsevier Ltd.

Synthesis, spectral, thermal and biological studies of mixed ligand complexes with newly prepared Schiff base and 1,10-phenanthroline ligands

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Abd El-Halim, Hanan F.; Mohamed, Gehad G.; Khalil, Eman A. M.

2017-10-01

A series of mixed ligand complexes were prepared from the Schiff base (L1) as a primary ligand, prepared by condensation of oxamide and furan-2-carbaldehyde, and 1,10-phenanthroline (1,10-phen) as a secondary ligand. The Schiff base ligand and its mixed ligand chelates were characterized based on elemental analysis, IR, 1H NMR, thermal analysis, UV-Visible, mass, molar conductance, magnetic moment. X-ray diffraction, solid reflectance and ESR also have been studied. The mixed ligand complexes were found to have the formulae of [M(L1) (1,10-phen)]Clm.nH2O (M = Cr(III) and Fe(III) (m = 3) (n = 0); M = Mn(II), Cu(II) and Cd(II) (m = 2) (n = 0); and M = Co(II) (m = 2) (n = 1), Ni(II) (m = 2) (n = 2) and Zn(II) (m = 2) (n = 3)) and that the geometrical structure of the complexes were octahedral. The parameters of thermodynamic using Coats-Redfern and Horowitz-Metzger equations were calculated. The synthesized Schiff base ligand, 1,10-phenanthroline ligand and Their mixed ligand complexes were also investigated for their antibacterial and antifungal activity against bacterial species (Gram-Ve bacteria: Pseudomonas aeruginosa and Escherichia coli) and (Gram + Ve bacteria: Bacillus subtilis and Streptococcus pneumonia) and fungi (Aspergillus fumigates and Candida albicans). The anticancer activity of the new compounds had been tested against breast (MFC7) and colon (HCT-116) cell lines. The results showed high activity for the synthesized compounds.

Autocrine signal transmission with extracellular ligand degradation

International Nuclear Information System (INIS)

Muratov, C B; Posta, F; Shvartsman, S Y

2009-01-01

Traveling waves of cell signaling in epithelial layers orchestrate a number of important processes in developing and adult tissues. These waves can be mediated by positive feedback autocrine loops, a mode of cell signaling where binding of a diffusible extracellular ligand to a cell surface receptor can lead to further ligand release. We formulate and analyze a biophysical model that accounts for ligand-induced ligand release, extracellular ligand diffusion and ligand–receptor interaction. We focus on the case when the main mode for ligand degradation is extracellular and analyze the problem with the sharp threshold positive feedback nonlinearity. We derive expressions that link the speed of propagation and other characteristics of traveling waves to the parameters of the biophysical processes, such as diffusion rates, receptor expression level, etc. Analyzing the derived expressions we found that traveling waves in such systems can exhibit a number of unusual properties, e.g. non-monotonic dependence of the speed of propagation on ligand diffusivity. Our results for the fully developed traveling fronts can be used to analyze wave initiation from localized perturbations, a scenario that frequently arises in the in vitro models of epithelial wound healing, and guide future modeling studies of cell communication in epithelial layers

Dockomatic - automated ligand creation and docking.

Science.gov (United States)

Bullock, Casey W; Jacob, Reed B; McDougal, Owen M; Hampikian, Greg; Andersen, Tim

2010-11-08

The application of computational modeling to rationally design drugs and characterize macro biomolecular receptors has proven increasingly useful due to the accessibility of computing clusters and clouds. AutoDock is a well-known and powerful software program used to model ligand to receptor binding interactions. In its current version, AutoDock requires significant amounts of user time to setup and run jobs, and collect results. This paper presents DockoMatic, a user friendly Graphical User Interface (GUI) application that eases and automates the creation and management of AutoDock jobs for high throughput screening of ligand to receptor interactions. DockoMatic allows the user to invoke and manage AutoDock jobs on a single computer or cluster, including jobs for evaluating secondary ligand interactions. It also automates the process of collecting, summarizing, and viewing results. In addition, DockoMatic automates creation of peptide ligand .pdb files from strings of single-letter amino acid abbreviations. DockoMatic significantly reduces the complexity of managing multiple AutoDock jobs by facilitating ligand and AutoDock job creation and management.

Dockomatic - automated ligand creation and docking

Directory of Open Access Journals (Sweden)

Hampikian Greg

2010-11-01

Full Text Available Abstract Background The application of computational modeling to rationally design drugs and characterize macro biomolecular receptors has proven increasingly useful due to the accessibility of computing clusters and clouds. AutoDock is a well-known and powerful software program used to model ligand to receptor binding interactions. In its current version, AutoDock requires significant amounts of user time to setup and run jobs, and collect results. This paper presents DockoMatic, a user friendly Graphical User Interface (GUI application that eases and automates the creation and management of AutoDock jobs for high throughput screening of ligand to receptor interactions. Results DockoMatic allows the user to invoke and manage AutoDock jobs on a single computer or cluster, including jobs for evaluating secondary ligand interactions. It also automates the process of collecting, summarizing, and viewing results. In addition, DockoMatic automates creation of peptide ligand .pdb files from strings of single-letter amino acid abbreviations. Conclusions DockoMatic significantly reduces the complexity of managing multiple AutoDock jobs by facilitating ligand and AutoDock job creation and management.

Synthesis in aqueous medium and organic praseodymium complexes with ligands derived from Schiff base quinolinic. Characterization and physicochemical study; Sintesis en medio acuoso y organico de complejos de praseodimio con ligantes derivados de base de Schiff quinolicos. Caracterizacion y estudio fisicoquimico

Energy Technology Data Exchange (ETDEWEB)

Garcia G, A.

2015-07-01

It was investigated the coordination ability of the quinolinic Schiff base organic tetradentate quinolinic ligand (Q Schiff-(OH){sub 2}) towards the trivalent praseodymium by UV/Vis spectrophotometric titration (St). By St, was studied the formed species between the Q Schiff-(OH){sub 2} ligand and the praseodymium nitrate salt in equimolar concentrations (5.86 x 10{sup -4} M: 5.22 x 10{sup -4} M) in methanol. The statistical analysis of the experimental results suggested three complexed species with 1Pr:3L, 1Pr:2L y 1Pr:1L stoichiometries. The predominant stoichiometries were the second and the latter. Based on these results and data from the scientific literature, the methodology for the syntheses of the complexes Q Schiff-(OH){sub 2}-Pr in aqueous-organic and organic media was established and a molar ratio M:L= 1:2 of praseodymium nitrate and the ligand was used. The new complexes were characterized by UV/Vis, Infrared, X-ray Photoelectron Spectroscopy (XP S), Diffuse Reflectance (Dr) and Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC). Elemental analysis of C, N, O and Pr by XP S suggested 1Pr:2L:1Na (PrC{sub 32}H{sub 20}N{sub 4}O{sub 4}Na) stoichiometry of the complex synthesized by the aqueous-organic medium while for the complex synthesized by the organic medium it was 1Pr:3L (PrC{sub 48}H{sub 33}N{sub 6}O{sub 6}). In the first case, the praseodymium ion charge was neutralized by the anionic ligands whose remaining charge was compensated by the sodium ion. In the second case, the ion charge was neutralized by the ligands. The minimum formula was Pr(Q Schiff){sub 2}Na for the pure coordination compound from the aqueous-organic medium and the minimum formula Pr(Q Schiff){sub 3} for that from the organic medium. XP S also indicated that the oxidation state of praseodymium ion was maintained. Both complexes were stable in methanol, ethanol and acetonitrile at least for 5 days. The photophysical properties of the studied complexes were

Bis(μ-bis{[4-(2-pyridylpyrimidin-2-yl]sulfanyl}methanedisilver(I bis(perchlorate

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Hai-Bin Zhu

2010-12-01

Full Text Available In the macrocyclic centrosymmetric dinuclear complex, [Ag2(C19H14N6S22](ClO42, the AgI atom, bis{[4-(2-pyridylpyrimidin-2-yl]sulfanyl}methane (2-bppt ligand and perchlorate anion each lie on a twofold rotation axis. The 2-bppt ligand chelates two four-coordinated AgI atoms through its two bipyridine-like arms. The O atoms of the perchlorate anion are disordered each over two positions of equal occupancy. Adjacent complex molecules are linked by π–π interactions between the pyridine and pyrimidine rings [centroid–centroid distance = 3.663 (8 Å].

NMR study of heteroligand lanthanide complexes. Structure and stoichiometry of chelates of cerium subgroup with 18-member polyethers

International Nuclear Information System (INIS)

Bajbalov, S.P.; Kriger, Yu.G.

1993-01-01

Different ligand complexes of lanthanides were studied by the method of 1 H NMR, the results being presented. The literature data on the study of complexes of the class in solution were generalized. Detection of lanthanide-induced splitting of group CH 2 diastereotopic proton signals of macrocyclic polyethers in the complexes is enough to identify kinetically stable complexes, having inclusive type structure. 16 refs., 2 figs., 2 tabs

The Effect of the Equatorial Environment on Oxo-Group Silylation of the Uranyl Dication: A Computational Study

International Nuclear Information System (INIS)

Yahia, A.; Maron, L.; Yahia, A.; Arnold, P.L.; Love, J.B.

2010-01-01

A theoretical investigation of the reductive oxo-group silylation reaction of the uranyl dication held in a Pacman macrocyclic environment has been carried out. The effect of the modeling of the Pacman ligand on the reaction profiles is found to be important, with the dipotassiation of a single oxo group identified as a key component in promoting the reaction between the Si-X and uranium-oxo bonds. This reductive silylation reaction is also proposed to occur in an aqueous environment but was found not to operate on bare ions; in this latter case, substitution of a ligand in the equatorial plane was the most likely reaction. These results demonstrate the importance of the presence but not the identity of the equatorial ligands upon the silylation of the uranyl U-O bond. (authors)

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.

Synthesis of novel '4+1' Tc(III)/Re(III) mixed-ligand complexes with dendritically modified ligands

International Nuclear Information System (INIS)

Gniazdowska, E.; Kuenstler, J.U.; Stephan, H.; Pietzsch, H.J.

2006-01-01

Coordination chemistry of technetium and rhenium attracts a considerable interest due to the nuclear medicine applications of their radionuclides. Inert, so-called '3+1' or '4+1' technetium/rhenium mixed-ligand complexes open a new way to application of 99 mTc/ 188 Re labeled compounds in tumor diagnosis and therapy. In the presented paper, authors describe the synthesis and study of novel 99 mTc/ 188 Re complexes with dendritically functionalized tetradentate (tripodal chelator 2,2',2''-nitrilotris(ethanethiol), NS 3 and carboxyl group-bearing ligand, NS 3 (COOH) 3 ) and monodentate (dendritically modified isocyanide, CN-R(COOMe) 3 and isocyanide-modified peptide, CN-GGY) ligands. To verify the identity of the prepared n.c.a. complexes, non-radioactive analogous '4+1' Re compounds were synthesized. The experimental data show that a dendritic modification of the tetradentate/monodentate ligands changes the complex lipophilicity and does not influence its stability

La Política Social en el Estado de Bienestar: el desafío de los sistemas complejos

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PIERPAOLO DONATI

1987-01-01

Full Text Available Es incorrecto asumir que la actual crisis en los medios del estado de bienestar supone también una crisis estructural en la política social; la política social en la sociedad postindustrial debe ser distinguida, estructural y culturalmente, del estado de bienestar. Así, se discuten la naturaleza de la ciudadanía y de los valores en la sociedad post-industrial. Los sistemas sociales post-industriales se caracterizan por la complejidad y la diferenciación social. Las tendencias actuales van hacia la desregulación, la descentralización, y la privatización. Se hace necesario entender un nuevo marco conceptual para estos procesos sociales complejos; el articulo hace una tentativa para definir ese marco basándose en el interaccionismo simbólico Talcott Parsons y Niklas Luhmann.

Bexarotene ligand pharmaceuticals.

Science.gov (United States)

Hurst, R E

2000-12-01

Bexarotene (LGD-1069), from Ligand, was the first retinoid X receptor (RXR)-selective, antitumor retinoid to enter clinical trials. The company launched the drug for the treatment of cutaneous T-cell lymphoma (CTCL), as Targretin capsules, in the US in January 2000 [359023]. The company filed an NDA for Targretin capsules in June 1999, and for topical gel in December 1999 [329011], [349982] specifically for once-daily oral administration for the treatment of patients with early-stage CTCL who have not tolerated other therapies, patients with refractory or persistent early stage CTCL and patients with refractory advanced stage CTCL. The FDA approved Targretin capsules at the end of December 1999 for once-daily oral treatment of all stages of CTCL in patients refractory to at least one prior systemic therapy, at an initial dose of 300 mg/m2/day. After an NDA was submitted in December 1999 for Targretin gel, the drug received Priority Review status for use as a treatment of cutaneous lesions in patients with stage IA, IB or IIA CTCL [354836]. The FDA issued an approvable letter in June 2000, and granted marketing clearance for CTCL in the same month [370687], [372768], [372769], [373279]. Ligand had received Orphan Drug designation for this indication [329011]. At the request of the FDA, Ligand agreed to carry out certain post-approval phase IV and pharmacokinetic studies [351604]. The company filed an MAA with the EMEA for Targretin Capsules to treat lymphoma in November 1999 [348944]. The NDA for Targretin gel is based on a multicenter phase III trial that was conducted in the US, Canada, Europe and Australia involving 50 patients and a multicenter phase I/II clinical program involving 67 patients. Targretin gel was evaluated for the treatment of patients with early stage CTCL (IA-IIA) who were refractory to, intolerant to, or reached a response plateau for at least 6 months on at least two prior therapies. Efficacy results exceeded the protocol-defined response

LASSO-ligand activity by surface similarity order: a new tool for ligand based virtual screening.

Science.gov (United States)

Reid, Darryl; Sadjad, Bashir S; Zsoldos, Zsolt; Simon, Aniko

2008-01-01

Virtual Ligand Screening (VLS) has become an integral part of the drug discovery process for many pharmaceutical companies. Ligand similarity searches provide a very powerful method of screening large databases of ligands to identify possible hits. If these hits belong to new chemotypes the method is deemed even more successful. eHiTS LASSO uses a new interacting surface point types (ISPT) molecular descriptor that is generated from the 3D structure of the ligand, but unlike most 3D descriptors it is conformation independent. Combined with a neural network machine learning technique, LASSO screens molecular databases at an ultra fast speed of 1 million structures in under 1 min on a standard PC. The results obtained from eHiTS LASSO trained on relatively small training sets of just 2, 4 or 8 actives are presented using the diverse directory of useful decoys (DUD) dataset. It is shown that over a wide range of receptor families, eHiTS LASSO is consistently able to enrich screened databases and provides scaffold hopping ability.

LASSO—ligand activity by surface similarity order: a new tool for ligand based virtual screening

Science.gov (United States)

Reid, Darryl; Sadjad, Bashir S.; Zsoldos, Zsolt; Simon, Aniko

2008-06-01

Virtual Ligand Screening (VLS) has become an integral part of the drug discovery process for many pharmaceutical companies. Ligand similarity searches provide a very powerful method of screening large databases of ligands to identify possible hits. If these hits belong to new chemotypes the method is deemed even more successful. eHiTS LASSO uses a new interacting surface point types (ISPT) molecular descriptor that is generated from the 3D structure of the ligand, but unlike most 3D descriptors it is conformation independent. Combined with a neural network machine learning technique, LASSO screens molecular databases at an ultra fast speed of 1 million structures in under 1 min on a standard PC. The results obtained from eHiTS LASSO trained on relatively small training sets of just 2, 4 or 8 actives are presented using the diverse directory of useful decoys (DUD) dataset. It is shown that over a wide range of receptor families, eHiTS LASSO is consistently able to enrich screened databases and provides scaffold hopping ability.

"Síndrome complejo de malnutrición e inflamación" en la hemodiálisis crónica

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Pablo Young

2011-02-01

Full Text Available La malnutrición calórico-proteica y la inflamación suelen ser condiciones comunes y concurrentes en pacientes con hemodiálisis crónica, asociándose ambas a mal pronóstico. La hiporexia y el hipercatabolismo son características comunes y frecuentes. Se ha sugerido que la primera es secundaria a la inflamación. Si bien la evidencia no es concluyente, se ha acuñado el término síndrome complejo de malnutrición e inflamación para englobar esta situación clínica, independientemente de la causa originaria. Posibles causas de este síndrome incluyen diferentes comorbilidades, estrés oxidativo, pérdida de nutrientes a través de la diálisis, hiporexia, toxinas urémicas, elevación de citoquinas inflamatorias, sobrecarga de volumen, hiperfosfatemia, subdiálisis, entre otros. Se cree que en este síndrome la resistencia a la eritropoyetina, promueve la enfermedad aterosclerótica, disminuyendo la calidad de vida e incrementando el tiempo de internación y la mortalidad. Este síndrome origina un bajo índice de masa corporal, hipocolesterolemia, sarcopenia e hipocreatininemia, e hipohomocisteinemia, paradójicamente incrementando el riesgo cardiovascular. A este fenómeno se lo ha denominado "epidemiología reversa". Por lo tanto, y dentro de ciertos límites, la obesidad, la hipercolesterolemia, el incremento de la creatinina y de la homocisteína jugarían un rol protector, asociándose a mejor pronóstico. No existe consenso sobre cómo determinar la gravedad del síndrome complejo de malnutrición e inflamación, su abordaje y su tratamiento. En este trabajo se discuten varias herramientas diagnósticas y modalidades de tratamiento. El correcto manejo de este cuadro podría disminuir en última instancia la enfermedad cardiovascular, principal causa de óbito en esta población.

Copper(II)-catalyzed amidations of alkynyl bromides as a general synthesis of ynamides and Z-enamides. An intramolecular amidation for the synthesis of macrocyclic ynamides.

Science.gov (United States)

Zhang, Xuejun; Zhang, Yanshi; Huang, Jian; Hsung, Richard P; Kurtz, Kimberly C M; Oppenheimer, Jossian; Petersen, Matthew E; Sagamanova, Irina K; Shen, Lichun; Tracey, Michael R

2006-05-26

A general and efficient method for the coupling of a wide range of amides with alkynyl bromides is described here. This novel amidation reaction involves a catalytic protocol using copper(II) sulfate-pentahydrate and 1,10-phenanthroline to direct the sp-C-N bond formation, leading to a structurally diverse array of ynamides including macrocyclic ynamides via an intramolecular amidation. Given the surging interest in ynamide chemistry, this atom economical synthesis of ynamides should invoke further attention from the synthetic organic community.

Synthesis and characterization β-ketoamine ligands

Science.gov (United States)

Zaid, Nurzati Amani Mohamed; Hassan, Nur Hasyareeda; Karim, Nurul Huda Abd

2018-04-01

β-ketoamine ligands are important members of heterodonor ligand because of their ease of preparation and modification of both steric and/or electronic effects. Complexes with β-ketoamine has received much less attention and there has been no study about this complex with β-ketoamine in ionic liquid reported. Two type of β-ketoamine ligands which are 4-amino-3-pentene-2-onato (A) and 3-amino-2-butenoic acid methyl ester (B) have been synthesized in this work. The resulting compound formed was characterized using standard spectroscopic and structural techniques which includes 1H and 13C, NMR spectroscopy and FTIR spectroscopy. The 1H and 13C NMR spectrum displayed all the expected signals with correct integration and multiplicity. And it is proved that there are some differences between two ligands as observed in NMR and FTIR spectrum.

Designer TGFβ superfamily ligands with diversified functionality.

Directory of Open Access Journals (Sweden)

George P Allendorph

Full Text Available Transforming Growth Factor--beta (TGFβ superfamily ligands, including Activins, Growth and Differentiation Factors (GDFs, and Bone Morphogenetic Proteins (BMPs, are excellent targets for protein-based therapeutics because of their pervasiveness in numerous developmental and cellular processes. We developed a strategy termed RASCH (Random Assembly of Segmental Chimera and Heteromer, to engineer chemically-refoldable TGFβ superfamily ligands with unique signaling properties. One of these engineered ligands, AB208, created from Activin-βA and BMP-2 sequences, exhibits the refolding characteristics of BMP-2 while possessing Activin-like signaling attributes. Further, we find several additional ligands, AB204, AB211, and AB215, which initiate the intracellular Smad1-mediated signaling pathways more strongly than BMP-2 but show no sensitivity to the natural BMP antagonist Noggin unlike natural BMP-2. In another design, incorporation of a short N-terminal segment from BMP-2 was sufficient to enable chemical refolding of BMP-9, without which was never produced nor refolded. Our studies show that the RASCH strategy enables us to expand the functional repertoire of TGFβ superfamily ligands through development of novel chimeric TGFβ ligands with diverse biological and clinical values.

El impacto del cambio climático en los glaciares del complejo volcánico Nevado Coropuna, (Cordillera Occidental de los Andes Centrales)

OpenAIRE

Ubeda Palenque, José

2010-01-01

El objetivo de la investigación ha sido evaluar el impacto del cambio climático en los glaciares del Nevado Coropuna, que en la actualidad recubren el área de cumbres de ese complejo de edificios volcánicos alcanzando una superficie de casi medio centenar de km2. El interés del trabajo de investigación se debe a tres razones principales: 1) De esas masas de hielo depende el abastecimiento de varias decenas de miles de personas; 2) El escenario de riesgo que se deduce de la localización vulner...

Prediction of GPCR-Ligand Binding Using Machine Learning Algorithms

Directory of Open Access Journals (Sweden)

Sangmin Seo

2018-01-01

Full Text Available We propose a novel method that predicts binding of G-protein coupled receptors (GPCRs and ligands. The proposed method uses hub and cycle structures of ligands and amino acid motif sequences of GPCRs, rather than the 3D structure of a receptor or similarity of receptors or ligands. The experimental results show that these new features can be effective in predicting GPCR-ligand binding (average area under the curve [AUC] of 0.944, because they are thought to include hidden properties of good ligand-receptor binding. Using the proposed method, we were able to identify novel ligand-GPCR bindings, some of which are supported by several studies.

New pinene-derived pyridines as bidentate chiral ligands

Czech Academy of Sciences Publication Activity Database

Malkov, A. V.; Stewart-Liddon, A.; Teplý, Filip; Kobr, L.; Muir, K. W.; Haigh, D.; Kočovský, P.

2008-01-01

Roč. 64, č. 18 (2008), s. 4011-4025 ISSN 0040-4020 Institutional research plan: CEZ:AV0Z40550506 Keywords : chiral ligands * transition metal catalysis * asymmetric catalysis * pyridine ligands * oxazoline ligands Subject RIV: CC - Organic Chemistry Impact factor: 2.897, year: 2008

A new oxomolybdate component extracted from the "virtual dynamic library" yielding the macrocyclic anion [(Mo(VI)(8)O(28))(4)(Mo(V)(2)O(2)S(2))(4)](24-).

Science.gov (United States)

Korenev, Vladimir S; Boulay, Antoine G; Dolbecq, Anne; Sokolov, Maxim N; Hijazi, Akram; Floquet, Sébastien; Fedin, Vladimir P; Cadot, Emmanuel

2010-11-01

A rare isomer of the {Mo(8)O(28)}(8-) anion has been trapped from an acidified aqueous solution of molybdate by using the {Mo(2)O(2)S(2)}(2+) oxothio cation as the linker and isolated as a part of a unique macrocyclic anion, which consists of four isopolyoxomolybdate fragments {Mo(8)O(28)} bridged by four {Mo(2)O(2)S(2)} units.

Glucagon-like peptide-1 receptor ligand interactions: structural cross talk between ligands and the extracellular domain.

Directory of Open Access Journals (Sweden)

Graham M West

Full Text Available Activation of the glucagon-like peptide-1 receptor (GLP-1R in pancreatic β-cells potentiates insulin production and is a current therapeutic target for the treatment of type 2 diabetes mellitus (T2DM. Like other class B G protein-coupled receptors (GPCRs, the GLP-1R contains an N-terminal extracellular ligand binding domain. N-terminal truncations on the peptide agonist generate antagonists capable of binding to the extracellular domain, but not capable of activating full length receptor. The main objective of this study was to use Hydrogen/deuterium exchange (HDX to identify how the amide hydrogen bonding network of peptide ligands and the extracellular domain of GLP-1R (nGLP-1R were altered by binding interactions and to then use this platform to validate direct binding events for putative GLP-1R small molecule ligands. The HDX studies presented here for two glucagon-like peptide-1 receptor (GLP-1R peptide ligands indicates that the antagonist exendin-4[9-39] is significantly destabilized in the presence of nonionic detergents as compared to the agonist exendin-4. Furthermore, HDX can detect stabilization of exendin-4 and exendin-4[9-39] hydrogen bonding networks at the N-terminal helix [Val19 to Lys27] upon binding to the N-terminal extracellular domain of GLP-1R (nGLP-1R. In addition we show hydrogen bonding network stabilization on nGLP-1R in response to ligand binding, and validate direct binding events with the extracellular domain of the receptor for putative GLP-1R small molecule ligands.

EXAFS Studies of Some Copper(II) Mixed-Ligand Complexes

International Nuclear Information System (INIS)

Joshi, S. K.; Katare, R. K.; Shrivastava, B. D.

2007-01-01

X-ray K-absorption spectroscopic studies have been carried out on copper (II) mixed-ligand complexes with glutamic acid and aspartic acid as the primary ligands, where as water, pyridine, imidazole and benz-imidazole have been used as secondary ligands. Chemical shifts obtained from the X-ray absorption data have indicated that the glutamic acid complexes are more ionic as compared to their corresponding aspartic acid complexes having similar secondary ligands. Further, we have estimated the average metal-ligand bond distances from the from structure data. For the different complexes studied under the present investigation, the studies reveal that the bonding parameter α1 decreases with the increase in the percentage covalency of the metal-ligand bond. Thus, the bonding parameter α1 may be used for the estimation of percentage covalency of the metal-ligand bond in other similar complexes

Interactions between alkaline earth cations and oxo ligands. DFT study of the affinity of the Mg²+ cation for phosphoryl ligands.

Science.gov (United States)

da Costa, Leonardo Moreira; de Mesquita Carneiro, José Walkimar; Paes, Lilian Weitzel Coelho

2011-08-01

DFT (B3LYP/6-31+G(d)) calculations of Mg(2+) affinities for a set of phosphoryl ligands were performed. Two types of ligands were studied: a set of trivalent [O = P(R)] and a set of pentavalent phosphoryl ligands [O = P(R)(3)] (R = H, F, Cl, Br, OH, OCH(3), CH(3), CN, NH(2) and NO(2)), with R either bound directly to the phosphorus atom or to the para position of a phenyl ring. The affinity of the Mg(2+) cation for the ligands was quantified by means of the enthalpy for the substitution of one water molecule in the [Mg(H(2)O)(6)](2+) complex for a ligand. The enthalpy of substitution was correlated with electronic and geometric parameters. Electron-donor groups increase the interaction between the cation and the ligand, while electron-acceptor groups decrease the interaction enthalpy.

Semiconductor Quantum Dots with Photoresponsive Ligands.

Science.gov (United States)

Sansalone, Lorenzo; Tang, Sicheng; Zhang, Yang; Thapaliya, Ek Raj; Raymo, Françisco M; Garcia-Amorós, Jaume

2016-10-01

Photochromic or photocaged ligands can be anchored to the outer shell of semiconductor quantum dots in order to control the photophysical properties of these inorganic nanocrystals with optical stimulations. One of the two interconvertible states of the photoresponsive ligands can be designed to accept either an electron or energy from the excited quantum dots and quench their luminescence. Under these conditions, the reversible transformations of photochromic ligands or the irreversible cleavage of photocaged counterparts translates into the possibility to switch luminescence with external control. As an alternative to regulating the photophysics of a quantum dot via the photochemistry of its ligands, the photochemistry of the latter can be controlled by relying on the photophysics of the former. The transfer of excitation energy from a quantum dot to a photocaged ligand populates the excited state of the species adsorbed on the nanocrystal to induce a photochemical reaction. This mechanism, in conjunction with the large two-photon absorption cross section of quantum dots, can be exploited to release nitric oxide or to generate singlet oxygen under near-infrared irradiation. Thus, the combination of semiconductor quantum dots and photoresponsive ligands offers the opportunity to assemble nanostructured constructs with specific functions on the basis of electron or energy transfer processes. The photoswitchable luminescence and ability to photoinduce the release of reactive chemicals, associated with the resulting systems, can be particularly valuable in biomedical research and can, ultimately, lead to the realization of imaging probes for diagnostic applications as well as to therapeutic agents for the treatment of cancer.

EL TURISMO SUSTENTABLE EN EL ESTADO DE TAMAULIPAS, MÉXICO COMPLEJO TURISTICO SUSTENTABLE

Directory of Open Access Journals (Sweden)

Ma. de Lourdes Arias Gómez

2013-06-01

Full Text Available El turismo sustentable es de gran importancia, tanto para la economía del país como para la persona que gusta del eco turismo. Asimismo, el turismo sustentable considera el cuidado del medio ambiente y la mejora de la población. El sur del estado de Tamaulipas cuenta con un sinnúmero de recursos naturales, tiene mar, playa, ríos, lagunas, manantiales, cenotes, montañas, flora, fauna, por ende, el turista podrá practicar surf, jetski, velero, rapel, ciclismo de montaña, buceo, espeleología, caminata, caza, pesca, observar aves, fotografía, entre muchas otras actividades. Por ese motivo, presentamos la propuesta de un complejo turístico sustentable “El sur mágico de Tamaulipas”, el cual cubre el circuito turístico del sur del estado, se propone la construcción de ocho cedes, distribuidos en los municipios del sur del estado. Los visitantes podrán hospedarse en dos o más cedes todo por un mismo precio. Por ser Tamaulipas parte de la huasteca, proponemos a los turistas la oportunidad de conocer las cuatro huastecas tamaulipeca, veracruzana, potosina e hidalguense. Consideramos que Tampico debe ser el centro del circuito, porque todos los lugares que seleccionamos están a no más de tres horas de distancia por carretera.

Discovering protein-ligand chalcogen bonding in the protein data bank using endocyclic sulfur-containing heterocycles as ligand search subsets.

Science.gov (United States)

Mitchell, Miguel O

2017-09-24

The chalcogen bond, the noncovalent, electrostatic attraction between covalently bonded atoms in group 16 and Lewis bases, is present in protein-ligand interactions based on X-ray structures deposited in the Protein Data Bank (PDB). Discovering protein-ligand chalcogen bonding in the PDB employed a strategy that focused on searching the database for protein complexes of five-membered, heterocyclic ligands containing endocyclic sulfur with endo electron-withdrawing groups (isothiazoles; thiazoles; 1,2,3-, 1,2.4-, 1,2,5-, 1,3,4-thiadiazoles) and thiophenes with exo electron-withdrawing groups, e.g., 2-chloro, 2-bromo, 2-amino, 2-alkylthio. Out of 930 ligands investigated, 33 or 3.5% have protein-ligand S---O interactions of which 31 are chalcogen bonds and two appear to be S---HO hydrogen bonds. The bond angles for some of the chalcogen bonds found in the PDB are less than 90°, and an electrostatic model is proposed to explain this phenomenon.

Nuclease-like activity of some Cu(II) complexes

International Nuclear Information System (INIS)

Durackova, Z.; Fenikova, L.; Svorenova, L.; Labudova, O.; Kollarova, M.; Labuda, J.

1995-01-01

The nuclease reaction of a copper complex with the macrocyclic Schiff base ligand tetrabenzo[b,f,j,n][a,3,9,13]tetraaza cyclohexadecine (TAAB) at the cleavage of DNA in aerobic conditions and the presence of ascorbic acid has been investigated and compared with that of the copper phenanthroline complex. The AT specifity of the Cu(TAAB) 2+ for both single-stranded and double-stranded DNA templates was observed. (authors), 4 figs., 6 refs

A tandem regression-outlier analysis of a ligand cellular system for key structural modifications around ligand binding.

Science.gov (United States)

Lin, Ying-Ting

2013-04-30

A tandem technique of hard equipment is often used for the chemical analysis of a single cell to first isolate and then detect the wanted identities. The first part is the separation of wanted chemicals from the bulk of a cell; the second part is the actual detection of the important identities. To identify the key structural modifications around ligand binding, the present study aims to develop a counterpart of tandem technique for cheminformatics. A statistical regression and its outliers act as a computational technique for separation. A PPARγ (peroxisome proliferator-activated receptor gamma) agonist cellular system was subjected to such an investigation. Results show that this tandem regression-outlier analysis, or the prioritization of the context equations tagged with features of the outliers, is an effective regression technique of cheminformatics to detect key structural modifications, as well as their tendency of impact to ligand binding. The key structural modifications around ligand binding are effectively extracted or characterized out of cellular reactions. This is because molecular binding is the paramount factor in such ligand cellular system and key structural modifications around ligand binding are expected to create outliers. Therefore, such outliers can be captured by this tandem regression-outlier analysis.

-Pincer Ligand Family through Ligand Post-Modification

KAUST Repository

Huang, Mei-Hui; Hu, Jinsong; Huang, Kuo-Wei

2017-01-01

A series of air-stable nickel complexes containing triazine-based PN3P-pincer ligands were synthesized and fully characterized. Complex 3 contains a de-aromatized central triazine ring from the deprotonation of one of the N–H arms. With a post-modification strategy, the Me-PN3P*NiCl complex (3) could be converted into a new class of diimine–traizine PN3P-pincer nickel complexes.

-Pincer Ligand Family through Ligand Post-Modification

KAUST Repository

Huang, Mei-Hui

2017-10-02

A series of air-stable nickel complexes containing triazine-based PN3P-pincer ligands were synthesized and fully characterized. Complex 3 contains a de-aromatized central triazine ring from the deprotonation of one of the N–H arms. With a post-modification strategy, the Me-PN3P*NiCl complex (3) could be converted into a new class of diimine–traizine PN3P-pincer nickel complexes.

Simultaneous biosynthesis of putrebactin, avaroferrin and bisucaberin by Shewanella putrefaciens and characterisation of complexes with iron(III), molybdenum(VI) or chromium(V).

Science.gov (United States)

Soe, Cho Zin; Telfer, Thomas J; Levina, Aviva; Lay, Peter A; Codd, Rachel

2016-09-01

Cultures of Shewanella putrefaciens grown in medium containing 10mM 1,4-diamino-2-butanone (DBO) as an inhibitor of ornithine decarboxylase and 10mM 1,5-diaminopentane (cadaverine) showed the simultaneous biosynthesis of the macrocyclic dihydroxamic acids: putrebactin (pbH 2 ), avaroferrin (avH 2 ) and bisucaberin (bsH 2 ). The level of DBO did not completely repress the production of endogenous 1,4-diaminobutane (putrescine) as the native diamine substrate of pbH 2 . The relative concentration of pbH 2 :avH 2 :bsH 2 was 1:2:1, which correlated with the substrate selection of putrescine:cadaverine in a ratio of 1:1. The macrocycles were characterised using LC-MS as free ligands and as 1:1 complexes with Fe(III) of the form [Fe(pb)] + , [Fe(av)] + or [Fe(bs)] + , with labile ancillary ligands in six-coordinate complexes displaced during ESI-MS acquisition; or with Mo(VI) of the form [Mo(O) 2 (pb)], [Mo(O) 2 (av)] or [Mo(O) 2 (bs)]. Chromium(V) complexes of the form [CrO(pb)] + were detected from solutions of Cr(VI) and pbH 2 in DMF using X-band EPR spectroscopy. Supplementation of S. putrefaciens medium with DBO and 1,3-diaminopropane, 1,6-diaminohexane or 1,4-diamino-2(Z)-butene (Z-DBE) resulted only in the biosynthesis of pbH 2 . The work has identified a native system for the simultaneous biosynthesis of a suite of three macrocyclic dihydroxamic acid siderophores and highlights both the utility of precursor-directed biosynthesis for expanding the structural diversity of siderophores, and the breadth of their coordination chemistry. Copyright © 2015 Elsevier Inc. All rights reserved.

Database of ligand-induced domain movements in enzymes

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Hayward Steven

2009-03-01

Full Text Available Abstract Background Conformational change induced by the binding of a substrate or coenzyme is a poorly understood stage in the process of enzyme catalysed reactions. For enzymes that exhibit a domain movement, the conformational change can be clearly characterized and therefore the opportunity exists to gain an understanding of the mechanisms involved. The development of the non-redundant database of protein domain movements contains examples of ligand-induced domain movements in enzymes, but this valuable data has remained unexploited. Description The domain movements in the non-redundant database of protein domain movements are those found by applying the DynDom program to pairs of crystallographic structures contained in Protein Data Bank files. For each pair of structures cross-checking ligands in their Protein Data Bank files with the KEGG-LIGAND database and using methods that search for ligands that contact the enzyme in one conformation but not the other, the non-redundant database of protein domain movements was refined down to a set of 203 enzymes where a domain movement is apparently triggered by the binding of a functional ligand. For these cases, ligand binding information, including hydrogen bonds and salt-bridges between the ligand and specific residues on the enzyme is presented in the context of dynamical information such as the regions that form the dynamic domains, the hinge bending residues, and the hinge axes. Conclusion The presentation at a single website of data on interactions between a ligand and specific residues on the enzyme alongside data on the movement that these interactions induce, should lead to new insights into the mechanisms of these enzymes in particular, and help in trying to understand the general process of ligand-induced domain closure in enzymes. The website can be found at: http://www.cmp.uea.ac.uk/dyndom/enzymeList.do

Receptor-ligand binding sites and virtual screening.

Science.gov (United States)

Hattotuwagama, Channa K; Davies, Matthew N; Flower, Darren R

2006-01-01

Within the pharmaceutical industry, the ultimate source of continuing profitability is the unremitting process of drug discovery. To be profitable, drugs must be marketable: legally novel, safe and relatively free of side effects, efficacious, and ideally inexpensive to produce. While drug discovery was once typified by a haphazard and empirical process, it is now increasingly driven by both knowledge of the receptor-mediated basis of disease and how drug molecules interact with receptors and the wider physiome. Medicinal chemistry postulates that to understand a congeneric ligand series, or set thereof, is to understand the nature and requirements of a ligand binding site. Likewise, structural molecular biology posits that to understand a binding site is to understand the nature of ligands bound therein. Reality sits somewhere between these extremes, yet subsumes them both. Complementary to rules of ligand design, arising through decades of medicinal chemistry, structural biology and computational chemistry are able to elucidate the nature of binding site-ligand interactions, facilitating, at both pragmatic and conceptual levels, the drug discovery process.

The affinity plutonium(IV) for nitrogen donor ligands

International Nuclear Information System (INIS)

Jarvis, N.V.; Hancock, R.D.

1994-01-01

Established ligand design principles are used to predict the solution chemistry of Pu(IV) with nitrogen donor ligands which do not contain carboxylate donors. pK a 's of the nitrogen donors are lowered by addition of hydroxyalkyl groups causing Pu(IV) to have a greater affinity for these ligands than for hydroxide. Potentiometric studies using the ligands N,N,N'N',N''-pentakis(2-hydroxypropyl)-1,4,7-triazaheptane; N,N,N',N',N''-pentakis(2-hydroxyethyl)-1,4,7-triazaheptane; N,N,N',N',N'-tetrakis(2-hydroxyethyl)-1,2-diaminoethane; N,N,N',N'-tetrakis(2-hydroxyethyl)-trans-1,2-diaminocyclohexane; 1,4,8,11-tetrakis(2-hydroxyethyl)-1,4,8,11-tetraazacyclotetradecane and N,N-bis(2-hydroxyethyl)glycine with Pu(IV) showed that Pu(IV) has a considerable aqueous solution chemistry with these ligands. Data were processed by the ESTA library of programs and stability constants for all the systems are reported. Implications for selective ligand design for Pu(IV) are discussed. (orig.)

Predicting Nanocrystal Shape through Consideration of Surface-Ligand Interactions

KAUST Repository

Bealing, Clive R.

2012-03-27

Density functional calculations for the binding energy of oleic acid-based ligands on Pb-rich {100} and {111} facets of PbSe nanocrystals determine the surface energies as a function of ligand coverage. Oleic acid is expected to bind to the nanocrystal surface in the form of lead oleate. The Wulff construction predicts the thermodynamic equilibrium shape of the PbSe nanocrystals. The equilibrium shape is a function of the ligand surface coverage, which can be controlled by changing the concentration of oleic acid during synthesis. The different binding energy of the ligand on the {100} and {111} facets results in different equilibrium ligand coverages on the facets, and a transition in the equilibrium shape from octahedral to cubic is predicted when increasing the ligand concentration during synthesis. © 2012 American Chemical Society.

Mixed ligand chelates of rare earths in aqueous solution

International Nuclear Information System (INIS)

Lakhani, S.U.; Thakur, G.S.; Sangal, S.P.

1981-01-01

Mixed ligand chelates of the 1:1 trivalent lanthanoids-EDTA, HEDTA and NTA chelates-1, 2-Dihydroxybenzene (Pyrocatechol) have been investigated at 35degC and 0.2 M ionic strength maintained by NaC10 4 . The formation of mixed ligand chelates has been found in all cases. The formation of mixed ligand chelates with EDTA shows the coordination number of lanthanoids to be eight, while the mixed ligand chelates with HEDTA and NTA shows the coordination number to be seven and six respectively. The stability constants of mixed ligand chelates are smaller than the binary complexes. The order of stability constants with respect to primary ligands follows the order NTA>HEDTA>EDTA. With respect to metal ions the stability constants increases with the decrease in ionic radii such as Gd< Er< Yb. (author)

Calculating the mean time to capture for tethered ligands and its effect on the chemical equilibrium of bound ligand pairs.

Science.gov (United States)

Shen, Lu; Decker, Caitlin G; Maynard, Heather D; Levine, Alex J

2016-09-01

We present here the calculation of the mean time to capture of a tethered ligand to the receptor. This calculation is then used to determine the shift in the partitioning between (1) free, (2) singly bound, and (3) doubly bound ligands in chemical equilibrium as a function of the length of the tether. These calculations are used in the research article Fibroblast Growth Factor 2 Dimer with Superagonist in vitro Activity Improves Granulation Tissue Formation During Wound Healing (Decker et al., in press [1]) to explain quantitatively how changes in polymeric linker length in the ligand dimers modifies the efficacy of these molecules relative to that of free ligands.

Importance of the pharmacological profile of the bound ligand in enrichment on nuclear receptors: toward the use of experimentally validated decoy ligands.

Science.gov (United States)

Lagarde, Nathalie; Zagury, Jean-François; Montes, Matthieu

2014-10-27

The evaluation of virtual ligand screening methods is of major importance to ensure their reliability. Taking into account the agonist/antagonist pharmacological profile should improve the quality of the benchmarking data sets since ligand binding can induce conformational changes in the nuclear receptor structure and such changes may vary according to the agonist/antagonist ligand profile. We indeed found that splitting the agonist and antagonist ligands into two separate data sets for a given nuclear receptor target significantly enhances the quality of the evaluation. The pharmacological profile of the ligand bound in the binding site of the target structure was also found to be an additional critical parameter. We also illustrate that active compound data sets for a given pharmacological activity can be used as a set of experimentally validated decoy ligands for another pharmacological activity to ensure a reliable and challenging evaluation of virtual screening methods.

Diammine{N-[2-(hydroxyiminopropionyl]-N′-[2-(oxidoiminopropionyl]propane-1,3-diaminido-κ4N,N′,N′′,N′′′}iron(III

Directory of Open Access Journals (Sweden)

Stefania Tomyn

2012-12-01

Full Text Available In the title compound, [Fe(C9H13N4O4(NH32], the FeIII atom, lying on a mirror plane, is coordinated by four N atoms of a triply deprotonated tetradentate N-[2-(hydroxyiminopropionyl]-N′-[2-(oxidoiminopropionyl]propane-1,3-diaminide ligand in the equatorial plane and two N atoms of two ammonia molecules at the axial positions in a distorted octahedral geometry. A short intramolecular O—H...O hydrogen bond between the cis-disposed oxime O atoms stabilizes the pseudo-macrocyclic configuration of the ligand. In the crystal, molecules are linked by N—H...O hydrogen bonds into a three-dimensional network. The ligand has a mirror-plane symmetry. One of the methylene groups of the propane bridge is disordered over two sets of sites with equal occupancy factors.

Expression of nociceptive ligands in canine osteosarcoma.

Science.gov (United States)

Shor, S; Fadl-Alla, B A; Pondenis, H C; Zhang, X; Wycislo, K L; Lezmi, S; Fan, T M

2015-01-01

Canine osteosarcoma (OS) is associated with localized pain as a result of tissue injury from tumor infiltration and peritumoral inflammation. Malignant bone pain is caused by stimulation of peripheral pain receptors, termed nociceptors, which reside in the localized tumor microenvironment, including the periosteal and intramedullary bone cavities. Several nociceptive ligands have been determined to participate directly or indirectly in generating bone pain associated with diverse skeletal abnormalities. Canine OS cells actively produce nociceptive ligands with the capacity to directly or indirectly activate peripheral pain receptors residing in the bone tumor microenvironment. Ten dogs with appendicular OS. Expression of nerve growth factor, endothelin-1, and microsomal prostaglandin E synthase-1 was characterized in OS cell lines and naturally occurring OS samples. In 10 dogs with OS, circulating concentrations of nociceptive ligands were quantified and correlated with subjective pain scores and tumor volume in patients treated with standardized palliative therapies. Canine OS cells express and secrete nerve growth factor, endothelin-1, and prostaglandin E2. Naturally occurring OS samples uniformly express nociceptive ligands. In a subset of OS-bearing dogs, circulating nociceptive ligand concentrations were detectable but failed to correlate with pain status. Localized foci of nerve terminal proliferation were identified in a minority of primary bone tumor samples. Canine OS cells express nociceptive ligands, potentially permitting active participation of OS cells in the generation of malignant bone pain. Specific inhibitors of nociceptive ligand signaling pathways might improve pain control in dogs with OS. Copyright © 2015 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of American College of Veterinary Internal Medicine.

Potential of 57Ni/57Co generator system for radiolabelling proteins for imaging

International Nuclear Information System (INIS)

Du, T.; Smith, S.V.; Baker, T.

1998-01-01

Full text: There is increasing interest in the use of inert metal complexes for radiolabelling proteins. The present study involves an investigation into the use to the parent/daughter system 57 Ni/ 57 Co for PET and SPECT imaging. In order to assess the potential of the system for such applications it is important to examine whether the ligand chosen complexes with both 57 Ni and 57 Co. A selection of ligands with varying number of donor groups and open-chain and macrocyclic ligands were chosen; ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), 1,4,8,11 - tetraazocyclotetradecane-1 4,8,11-tetraacetic acid (TETA) and diaminohydroxyaryl - diethylenetriaminepentaacetic acid, (DAHA-EDTA). Complexation behaviour over a range of pH and temperatures was investigated. Results show that the ligands have strong complexation for 57 Ni however once 57 Ni decayed to 57 Co evidence ol chemical instability was noted. The DAHA-EDTA ligand (developed in house) was observed to be the most stable under conditions studied. lt was selected for use in radiolabelling B72.3 antibody and preliminary radiolabelling conditions were established

A Versatile Dinucleating Ligand Containing Sulfonamide Groups

DEFF Research Database (Denmark)

Sundberg, Jonas; Witt, Hannes; Cameron, Lisa

2014-01-01

ligand can be prepared in aqueous solutions using only divalent metal ions. Two of the copper(II) complexes, [Cu2(psmp)(OH)] and [Cu2(psmp)(OAc)2]-, demonstrate the anticipated 1:2 ligand/metal stoichiometry and show that the dimetallic binding site created for exogenous ligands possesses high inherent...... of antiferromagnetic coupling. This is corroborated computationally by broken-symmetry density functional theory, which for isotropic modeling of the coupling predicts an antiferromagnetic coupling strength of J = 70.5 cm-1....

Implicit ligand theory for relative binding free energies

Science.gov (United States)

Nguyen, Trung Hai; Minh, David D. L.

2018-03-01

Implicit ligand theory enables noncovalent binding free energies to be calculated based on an exponential average of the binding potential of mean force (BPMF)—the binding free energy between a flexible ligand and rigid receptor—over a precomputed ensemble of receptor configurations. In the original formalism, receptor configurations were drawn from or reweighted to the apo ensemble. Here we show that BPMFs averaged over a holo ensemble yield binding free energies relative to the reference ligand that specifies the ensemble. When using receptor snapshots from an alchemical simulation with a single ligand, the new statistical estimator outperforms the original.

Example of uranium(IV) insertion within a macrocyclic crown ether with coexistence of the metal in two oxidation states

Energy Technology Data Exchange (ETDEWEB)

Bombieri, G; De Paoli, G [Consiglio Nazionale delle Ricerche, Padua (Italy). Lab. di Chimica e Tecnologia dei Radioelementi; Immirzi, A

1978-01-01

Reaction of UCl/sub 4/ with 18-crown-6 in tetrahydrofuran yields (UCl/sub 4/)/sub 3/ (18-crown-6)/sub 2/ which on recrystallization in nitromethane, gives a partially oxidized and hydrolyzed product whose structure has been investigated by X-ray diffraction. The compound crystallizes in the orthorhombic system. The cell contains eight UCl/sub 3//sup +/ cations each inserted within a crown molecule and four (UO/sub 2/Cl/sub 3/(OH)(H/sub 2/O))/sup 2 -/anions having a pentagonal bipyramidal structure. Four solvated nitromethane molecules are also present. The compound represents one of the very few examples in which uranium exists in two oxidation states, and the first example in which its insertion within a crown macrocycle has been proved by an X-ray diffraction study.

Use of macrocycle- or hemisepulcrand-type poly(oxygen) compounds in nuclear hydrometallurgy. Study of the diluent effect: supra-molecular approach

International Nuclear Information System (INIS)

Bethmont, Valerie

1997-01-01

Liquid/liquid extraction has been used for many years to obtain high purity nuclear fuels (uranium salts and plutonium salts), notably with the Purex process which allows 99 per cent of uranium and plutonium contained by spent nuclear fuels to be recovered. This research thesis deals with the search for new and steadier extracting agents, and focuses on macro-cycle or hemisepulcrand type poly(oxygenated) compounds which have excellent properties in nuclear hydrometallurgy. The author thus first discusses the synthesis of oxygenated tripodands (bibliographical study and development of a catalytic method to synthesise ethers). Then, she reports the use of poly(oxygenated) compounds in liquid/liquid extraction, and the experimental study of the effect of the diluting agent by using a supramolecular approach [fr

Superior serum half life of albumin tagged TNF ligands

International Nuclear Information System (INIS)

Mueller, Nicole; Schneider, Britta; Pfizenmaier, Klaus; Wajant, Harald

2010-01-01

Due to their immune stimulating and apoptosis inducing properties, ligands of the TNF family attract increasing interest as therapeutic proteins. A general limitation of in vivo applications of recombinant soluble TNF ligands is their notoriously rapid clearance from circulation. To improve the serum half life of the TNF family members TNF, TWEAK and TRAIL, we genetically fused soluble variants of these molecules to human serum albumin (HSA). The serum albumin-TNF ligand fusion proteins were found to be of similar bioactivity as the corresponding HSA-less counterparts. Upon intravenous injection (i.v.), serum half life of HSA-TNF ligand fusion proteins, as determined by ELISA, was around 15 h as compared to approximately 1 h for all of the recombinant control TNF ligands without HSA domain. Moreover, serum samples collected 6 or 24 h after i.v. injection still contained high TNF ligand bioactivity, demonstrating that there is only limited degradation/inactivation of circulating HSA-TNF ligand fusion proteins in vivo. In a xenotransplantation model, significantly less of the HSA-TRAIL fusion protein compared to the respective control TRAIL protein was required to achieve inhibition of tumor growth indicating that the increased half life of HSA-TNF ligand fusion proteins translates into better therapeutic action in vivo. In conclusion, our data suggest that genetic fusion to serum albumin is a powerful and generally applicable mean to improve bioavailability and in vivo activity of TNF ligands.

Quantitative chemogenomics: machine-learning models of protein-ligand interaction.

Science.gov (United States)

Andersson, Claes R; Gustafsson, Mats G; Strömbergsson, Helena

2011-01-01

Chemogenomics is an emerging interdisciplinary field that lies in the interface of biology, chemistry, and informatics. Most of the currently used drugs are small molecules that interact with proteins. Understanding protein-ligand interaction is therefore central to drug discovery and design. In the subfield of chemogenomics known as proteochemometrics, protein-ligand-interaction models are induced from data matrices that consist of both protein and ligand information along with some experimentally measured variable. The two general aims of this quantitative multi-structure-property-relationship modeling (QMSPR) approach are to exploit sparse/incomplete information sources and to obtain more general models covering larger parts of the protein-ligand space, than traditional approaches that focuses mainly on specific targets or ligands. The data matrices, usually obtained from multiple sparse/incomplete sources, typically contain series of proteins and ligands together with quantitative information about their interactions. A useful model should ideally be easy to interpret and generalize well to new unseen protein-ligand combinations. Resolving this requires sophisticated machine-learning methods for model induction, combined with adequate validation. This review is intended to provide a guide to methods and data sources suitable for this kind of protein-ligand-interaction modeling. An overview of the modeling process is presented including data collection, protein and ligand descriptor computation, data preprocessing, machine-learning-model induction and validation. Concerns and issues specific for each step in this kind of data-driven modeling will be discussed. © 2011 Bentham Science Publishers

Effects of electrostatic interactions on ligand dissociation kinetics

Science.gov (United States)

Erbaş, Aykut; de la Cruz, Monica Olvera; Marko, John F.

2018-02-01

We study unbinding of multivalent cationic ligands from oppositely charged polymeric binding sites sparsely grafted on a flat neutral substrate. Our molecular dynamics simulations are suggested by single-molecule studies of protein-DNA interactions. We consider univalent salt concentrations spanning roughly a 1000-fold range, together with various concentrations of excess ligands in solution. To reveal the ionic effects on unbinding kinetics of spontaneous and facilitated dissociation mechanisms, we treat electrostatic interactions both at a Debye-Hückel (DH) (or implicit ions, i.e., use of an electrostatic potential with a prescribed decay length) level and by the more precise approach of considering all ionic species explicitly in the simulations. We find that the DH approach systematically overestimates unbinding rates, relative to the calculations where all ion pairs are present explicitly in solution, although many aspects of the two types of calculation are qualitatively similar. For facilitated dissociation (FD) (acceleration of unbinding by free ligands in solution) explicit-ion simulations lead to unbinding at lower free-ligand concentrations. Our simulations predict a variety of FD regimes as a function of free-ligand and ion concentrations; a particularly interesting regime is at intermediate concentrations of ligands where nonelectrostatic binding strength controls FD. We conclude that explicit-ion electrostatic modeling is an essential component to quantitatively tackle problems in molecular ligand dissociation, including nucleic-acid-binding proteins.

[Supercomputer investigation of the protein-ligand system low-energy minima].

Science.gov (United States)

Oferkin, I V; Sulimov, A V; Katkova, E V; Kutov, D K; Grigoriev, F V; Kondakova, O A; Sulimov, V B

2015-01-01

The accuracy of the protein-ligand binding energy calculations and ligand positioning is strongly influenced by the choice of the docking target function. This work demonstrates the evaluation of the five different target functions used in docking: functions based on MMFF94 force field and functions based on PM7 quantum-chemical method accounting or without accounting the implicit solvent model (PCM, COSMO or SGB). For these purposes the ligand positions corresponding to the minima of the target function and the experimentally known ligand positions in the protein active site (crystal ligand positions) were compared. Each function was examined on the same test-set of 16 protein-ligand complexes. The new parallelized docking program FLM based on Monte Carlo search algorithm was developed to perform the comprehensive low-energy minima search and to calculate the protein-ligand binding energy. This study demonstrates that the docking target function based on the MMFF94 force field can be used to detect the crystal or near crystal positions of the ligand by the finding the low-energy local minima spectrum of the target function. The importance of solvent accounting in the docking process for the accurate ligand positioning is also shown. The accuracy of the ligand positioning as well as the correlation between the calculated and experimentally determined protein-ligand binding energies are improved when the MMFF94 force field is substituted by the new PM7 method with implicit solvent accounting.

ESTUDIO DEL EFECTO DE ISOTÓPO DE HIDRÓGENO EN LOS COMPLEJOS M–H•••H–F (M=Li, Na

Directory of Open Access Journals (Sweden)

Andrés Reyes

2009-06-01

Full Text Available Se estudió teóricamente el efecto de isotópo de hidrógeno sobre la geometría, la distribución de carga electrónica, la estabilidad relativa y la energía de formación de complejos lineales tipo M–X···Y–F y todos sus isotopólogos de hidrógeno (M=Li, Na; X, Y= H, D, T. Estos estudios fueron realizados con el paquete computacional APMO a un nivel de teoría Hartree-Fock electrónico y nuclear. Los resultados obtenidos están de acuerdo con resultados reportados por otros autores que usan métodos de estructura electrónica convencional.  

Statistical Estimation of the Protein-Ligand Binding Free Energy Based On Direct Protein-Ligand Interaction Obtained by Molecular Dynamics Simulation

Directory of Open Access Journals (Sweden)

Haruki Nakamura

2012-09-01

Full Text Available We have developed a method for estimating protein-ligand binding free energy (DG based on the direct protein-ligand interaction obtained by a molecular dynamics simulation. Using this method, we estimated the DG value statistically by the average values of the van der Waals and electrostatic interactions between each amino acid of the target protein and the ligand molecule. In addition, we introduced fluctuations in the accessible surface area (ASA and dihedral angles of the protein-ligand complex system as the entropy terms of the DG estimation. The present method included the fluctuation term of structural change of the protein and the effective dielectric constant. We applied this method to 34 protein-ligand complex structures. As a result, the correlation coefficient between the experimental and calculated DG values was 0.81, and the average error of DG was 1.2 kcal/mol with the use of the fixed parameters. These results were obtained from a 2 nsec molecular dynamics simulation.

Rational Ligand Design for U(VI) and Pu(IV)

International Nuclear Information System (INIS)

Szigethy, Geza

2009-01-01

Nuclear power is an attractive alternative to hydrocarbon-based energy production at a time when moving away from carbon-producing processes is widely accepted as a significant developmental need. Hence, the radioactive actinide power sources for this industry are necessarily becoming more widespread, which is accompanied by the increased risk of exposure to both biological and environmental systems. This, in turn, requires the development of technology designed to remove such radioactive threats efficiently and selectively from contaminated material, whether that be contained nuclear waste streams or the human body. Raymond and coworkers (University of California, Berkeley) have for decades investigated the interaction of biologically-inspired, hard Lewis-base ligands with high-valent, early-actinide cations. It has been established that such ligands bind strongly to the hard Lewis-acidic early actinides, and many poly-bidentate ligands have been developed and shown to be effective chelators of actinide contaminants in vivo. Work reported herein explores the effect of ligand geometry on the linear U(IV) dioxo dication (uranyl, UO 2 2+ ). The goal is to utilize rational ligand design to develop ligands that exhibit shape selectivity towards linear dioxo cations and provides thermodynamically favorable binding interactions. The uranyl complexes with a series of tetradentate 3-hydroxy-pyridin-2-one (3,2-HOPO) ligands were studied in both the crystalline state as well as in solution. Despite significant geometric differences, the uranyl affinities of these ligands vary only slightly but are better than DTPA, the only FDA-approved chelation therapy for actinide contamination. The terepthalamide (TAM) moiety was combined into tris-beidentate ligands with 1,2- and 3,2-HOPO moieties were combined into hexadentate ligands whose structural preferences and solution thermodynamics were measured with the uranyl cation. In addition to achieving coordinative saturation, these