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Side Arms (side + arm)
Selected AbstractsChemInform Abstract: New Diazadi(and tri)thia-21-crown-7 Ethers Containing 8-Hydroxyquinoline Side ArmsCHEMINFORM, Issue 14 2002Hua-Can Song Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Synthesis, DNA-Binding, Cleavage, and Cytotoxic Activity of New 1,7-Dioxa-4,10-diazacyclododecane Artificial Receptors Containing Bisguanidinoethyl or Diaminoethyl Double Side ArmsCHEMISTRY - A EUROPEAN JOURNAL, Issue 34 2007Xin Sheng Abstract Novel 1,7-dioxa-4,10-diazacyclododecane artificial receptors with two pendant aminoethyl (3) or guanidinoethyl (4) side arms have been synthesized. Spectroscopy, including fluorescence and CD spectroscopy, of the interactions of 3, 4, and their copper(II) complexes with calf thymus DNA indicated that the DNA binding affinity of these compounds follows the order Cu2+,4>Cu2+,3>4>3, and the binding constants of Cu2+,3 are Cu2+,4 are 7.2×104 and 8.7×104,M,1, respectively. Assessment by agarose gel electrophoresis of the plasmid pUC,19 DNA cleavage activity in the presence of the receptors showed that the complexes Cu2+,3 and Cu2+,4 exhibit powerful supercoiled DNA cleavage efficiency. Kinetic data of DNA cleavage promoted by Cu2+,3 and Cu2+,4 under physiological conditions fit to a saturation kinetic profile with kmax values of 0.865 and 0.596,h,1, respectively, which give about 108 -fold rate acceleration over uncatalyzed supercoiled DNA. This acceleration is due to efficient cooperative catalysis of the copper(II) center and the functional (diamino or bisguanidinium) groups. In-vitro cytotoxic activities toward murine melanoma B16 cells and human leukemia HL-60 cells were also examined: Cu2+,4 shows the highest activity with IC50 values of 1.62×10,4 and 1.19×10,5,M, respectively. [source] Mono(aryloxido)Titanium(IV) Complexes and Their Application in the Selective Dimerization of EthyleneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2009Jean-Benoit Cazaux Abstract We report on the synthesis of mono(aryloxido)titanium(IV) complexes of general formula {Ti[O(o -R)Ar]X3}, with X = OiPr, ArO = 2- tert -butyl-4-methylphenoxy and R = CMe3 (2a), CMe2Ph (2b) and CH2NMe2 (2c). Attempts to reach pure mono(aryloxido) complexes when R = CH2NMe(CH2Ph) (2d) or CH2N(CH2Ph)2 (2e) were unsuccessful. When R = CH2OMe, the analogous mononuclear complex was not obtained, and instead, a dinuclear complex [(2- tert -butyl-4-methyl-6-methoxymethylphenoxy) TiCl(OiPr)(,2 -OiPr)2TiCl(OiPr)2] (3) was formed. Complexes 2b and 3 were characterized by single-crystal X-ray diffraction. The former contains a tetrahedrally coordinated TiIV centre, whereas in the latter the aryloxido ligand behaves as a chelating,bridging ligand between the two, chemically very different metal centres that form two face-sharing octahedra. Different synthetic approaches starting from [Ti(OiPr)4] or [TiCl(OiPr)3] were evaluated and are discussed. The hemilabile behaviour of the aryloxido ligand resulting from reversible coordination of its side arm was studied by variable-temperature 1H NMR spectroscopy for 2c (R = CH2NMe2). Complexes 2a,d were contacted with ethylene and AlEt3 as cocatalyst. When activated with AlEt3 (3 equiv.) at 20 bar and 60 °C, complex 2c exhibits interesting activity (2100 g/gTi/h) for the selective dimerization of ethylene to 1-butene (92,% C4=; 99+% C4=1). Noticeable differences in catalyst activity were observed when the R group was modified. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Mono- and Dinuclear CuII and ZnII Complexes of Cyclen-Based Bis(macrocycles) Containing Two Aminoalkyl Pendant Arms of Different LengthsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2005Carmen Anda Abstract The basicity and coordination properties towards CuII and ZnII of the bis(macrocycles) L1, L2 and L3 have been investigated by means of potentiometric, 1H NMR and UV/Vis spectroscopic titrations in aqueous solutions. The synthesis of L1 and L3 is also described. The three ligands are composed of two [12]aneN4 units separated by a p- phenylene spacer and differ in the length of the aminoalkyl pendant arms linked to each macrocyclic unit. L1,L3 form mono- and dinuclear complexes in aqueous solutions; in the dinuclear species each metal ion is coordinated by one of the two identical [12]aneN4 ligand moieties, as shown by the crystal structures of the complexes [Cu2L1]Cl4·8H2O, [Zn2L2](ClO4)4 and [Zn2L3](ClO4)4·H2O. In all structures the metal ion is pentacoordinate, and is bound to the four nitrogen donors of the cyclic unit and to the amine group of the side arm. The stability of both the [ML]2+ and [M2L]4+ complexes in aqueous solution decreases in the order L1 > L2 > L3. At the same time, both the [Cu2L]4+ and [Zn2L]4+ complexes show a different ability in proton binding among the three ligands, with the [M2L1]4+ complexes displaying the highest basicity. These results are explained in terms of the decreasing number of nitrogen donors involved in CuII or ZnII binding on passing from L1 to L3; in other words, while in the L1 dinuclear complexes each metal ion is coordinated to the four amine groups of a [12]aneN4 moiety and to the amine group of the side arm, in the L3 ones the metal cations are bound only to the four donor atoms of a cyclic moiety, the aminobutyl group not being coordinated. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] A Chemoenzymatic Approach for the Synthesis of Unnatural Disaccharides Containing D -Galacto- or D -FucofuranosidesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2005Ronan Euzen Abstract Unusual diglycosides composed of D -hexofuranosyl entities were prepared by a chemoenzymatic route using the ,- L -arabinofuranosidase, AbfD3. The required, unprotected monosaccharidic donors were first prepared according to multi-step syntheses. Since one goal of this study was the investigation of donor ,1 subsite in the active site of the enzyme, we focused on D -fucofuranosyl and 6-deoxy-6-fluoro- D -galactofuranosyl derivatives which present stereochemical similarities with L -arabinose series, but also structural variations on the side arm. These substrates were then used in AbfD3-catalysed hydrolyses to determine the parameters Km and kcat and in AbfD3-catalysed transglycosylation to evaluate their ability to serve as donor/acceptor. Four disaccharides were thus isolated and characterised, two resulting from ,-(1,2) connection along with two ,-(1,3)-regioisomers. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Phase separation of liquid-liquid two-phase flow at a T-junctionAICHE JOURNAL, Issue 1 2006L. Yang Abstract The phase separation of liquid-liquid two-phase flow at a T-junction has been studied using kerosene and deionized water as working fluids and a T-junction with a horizontal main pipe and a vertically upward side arm. Separation data are evaluated by a new criterion: separation efficiency. The results show that the T-junction is highly efficient at separating two immiscible liquids when the flows approaching the T-junction are stratified and when the fractional mass take offs close to the inlet kerosene mass fraction. A new model has been proposed for the phase separation. Comparison between the model and the experimental data shows that the data is well represented by the model. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] Spatial differences in acquisition of soil phosphate between two arbuscular mycorrhizal fungi in symbiosis with Medicago truncatulaNEW PHYTOLOGIST, Issue 2 2000F. A. SMITH Responses of Medicago truncatula to colonization by two arbuscular mycorrhizal fungi, Scutellospora calospora isolate WUM 12(2) and Glomus caledonium isolate RIS 42, were compared in the light of previous findings that the former fungus can be ineffective as a beneficial microsymbiont with some host plants. The plants were grown individually in two-compartment systems in which a lateral side arm containing soil labelled with 33P was separated from the main soil compartment by a nylon mesh that prevented penetration by roots but not fungal hyphae. Fungal inoculum was applied as a root,soil mixture in a band opposite the side arm. Nonmycorrhizal controls were set up similarly, without inoculum. There were harvests at 28, 35, 42 and 49 d. Both sets of mycorrhizal plants grew better than nonmycorrhizal plants and initially had higher concentrations of P in shoots and roots. Plants grown with S. calospora grew better than plants grown with G. caledonium, and this was associated with somewhat greater fungal colonization in terms of intraradical hyphae and numbers of arbuscules. Scutellospora calospora formed denser hyphae at root surfaces than G. caledonium. By 28 d there were extensive hyphae of both fungi in the side arms, and after 35 d S. calospora produced denser hyphae there than G. caledonium. Nevertheless, there was very little transfer of 33P via S. calospora to the plant at 28 d, and thereafter its transfer increased at a rate only c. 33% of that via G. caledonium. The results showed that plants colonized by S. calospora preferentially obtained P from sites in the main soil chamber relatively close to the roots, compared with plants colonized by G. caledonium. Hence formation of a highly beneficial arbuscular mycorrhizal symbiosis does not necessarily depend on development of hyphae at a distance from the roots or on large-scale translocation of P from distant sites. The results are discussed in relation to previous studies with compartmented systems that have involved the same fungi. Possible causes of the variable effects of S. calospora in symbiosis with different host plants are briefly assessed. Differences in spatial abilities of individual arbuscular mycorrhizal fungi to acquire P might have strong ecological implications for plant growth in soils low in P. [source] Dithioether ligands containing a 2,6-disubstituted pyridine linker with two thioether-heterocycle armsACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2010Archimede Rotondo The structure of 2,6-bis(2-pyridyltsulfanylmethyl)pyridine (pytmp), (I), C17H15N3S2, presents a twisted conformation, with the three planar moieties almost perpendicular to each other. The structures of two related derivatives, namely 2,6-bis(6-methyl-2-pyridylsulfanylmethyl)pyridine (mpytmp), (II), C19H19N3S2, and 2,6-bis(4-methyl-2-pyrimidylsulfanylmethyl)pyridine (mprtmp) n- pentane hemisolvate, (III), C17H17N5S2·0.5C5H12, present extended planar fragments with just one quasi-perpendicular arylsulfanylmethyl side arm, such that the molecules are folded in an L-shaped conformation. All three conformations appear different from those adopted by similar compounds, demonstrating the great flexibility of such species, although such differences in conformational behaviour might drive specific coordination modes. [source] Versatile Self-Complexing Compounds Based on Covalently Linked Donor,Acceptor CyclophanesCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2005Yi Liu Dr. Abstract A range of covalently linked donor,acceptor compounds which contain 1) a hydroquinone (HQ) unit, 2) a 1,5-dioxynaphthalene (DNP) ring system, or 3) a tetrathiafulvalene (TTF) unit as the ,-donor, and 4) cyclobis(paraquat- p -phenylene) (CBPQT4+) as the ,-accepting tetracationic cyclophane were prepared and shown to operate as simple molecular machines. The ,-donating arms can be included inside the cyclophane in an intramolecular fashion by virtue of stabilizing noncovalent bonding interactions. What amounts to self-complexing/decomplexing equilibria were shown to be highly temperature dependent when the ,-donating arm contains either an HQ or DNP moiety. The thermodynamic parameters associated with the equilibria have been unraveled by using variable-temperature 1H NMR spectroscopy. The negative ,H° and ,S° values account for the fact that the "uncomplexed" conformation becomes the dominant species, since the entropy gain associated with the decomplexation process overcomes the enthalpy loss resulting from the breaking of the donor,acceptor interactions. The arm's in-and-out movements with respect to the linked cyclophanes can be arrested by installing a bulky substituent at the end of the arm. In the case of compounds carrying a DNP ring system in their side arm, two diastereoisomeric, self-complexing conformations are observed below 272 K in hexadeuterioacetone. By contrast, control over the TTF-containing arm's movement is more or less ineffective through the thermally sensitive equilibrium although it can be realized by chemical and electrochemical ways as a result of TTF's excellent redox properties. Such self-complexing compounds could find applications as thermo- and electroswitches. In addition, the thermochromism associated with the arm's movement could lead to some of the compounds finding uses as imaging and sensing materials. [source] Bis(terdentate) Pyrazole/Pyridine Ligands: Synthesis, Crystal Structures and Magnetic Properties of Bridged Binuclear and Tetranuclear Copper(II) ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2009Akhilesh Kumar Singh Abstract A new binucleating bis(terdentate) ligand, 3,5-[3-bis(2-pyridyl)pyrazole-1-ylmethyl]pyrazole (HL2), was synthesized. Reaction of the deprotonated ligand L2 with hydrated CuII salts gives (,-pyrazolato)(,-hydroxido)-bridged binuclear and tetranuclear complexes [L2Cu2(,-OH)(ClO4)(MeCN)](ClO4) (2), [L2Cu2(dmf)2(,3 -OH)]2(ClO4)4·4dmf (3·4dmf) and [L2L,Cu2](ClO4)2 [4; HL, = 3-(2-pyridyl)pyrazole]. In these complexes, both ,-OH and ,3 -OH bridges were observed. This contrasts the situation for a dicopper(II) complex of the related bis(terdentate) ligand 3,5-bis[6(2,2,-dipyridyl)]pyrazole (HL1), {L1Cu2(OMe)(MeOH)[,1 - O -(NO3)]}{[Cu2(NO3)2(,-OMe)2]}0.5·MeOH (1·MeOH), where the shorter and more rigid ligand side arms enforce a larger Cu···Cu separation and the formation of a MeO,HOMe moiety within the bimetallic pocket. Molecular structures of all complexes were elucidated by X-ray crystallography. Variable-temperature magnetic susceptibility measurements (295,2 K) for powdered samples of complexes 2,4 reveal strong antiferromagnetic coupling between two copper centres. The magnitude of the coupling is discussed in view of the structural features. During the preparation of complex 4, partial ligand hydrolysis was also observed, but this strongly depends on the reaction conditions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Pyrazolate-Based Dinucleating Ligands in L2M2 Scaffolds: Effects of Bulky Substituents and Coligands on Structures and M···H,C InteractionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2004Jens C. Röder Abstract A series of nickel(II) and palladium(II) complexes [L2M2]2+ have been prepared and structurally characterized, where L is a pyrazolate ligand with bulky 2,6-dimethyl- or 2,6-di(isopropyl)anilinomethyl side arms. Coordinating counter anions such as chloride can bind to axial sites of the dinickel species in a solvent-dependent process, giving rise to five-coordinate high-spin metal ions. In the case of weakly coordinating anions, the metal ions are found in roughly square-planar environments, and the structures are governed by the tendency of the bulky aryl groups to avoid each other, which forces the methyl or isopropyl substituents in the aryl 2- and 6-positions to approach the metal ions from the axial directions. This leads to drastic low-field shifts of the respective 1H NMR signals, e.g. , = 7.86 ppm for the isopropyl ,CH which comes in close proximity to the low-spin nickel(II) center. The relevance of such low-field NMR resonances of protons close to the axial sites of d8 metal ions for possible three-center four-electron M···H,C hydrogen bonds involving the filled d orbital of the metal ion is discussed. In the present case, attractive M···H interactions are assumed to be of no major significance. This was corroborated by the structure of a further [L2Ni2]2+ type complex where the anilinomethyl side arms bear only a single 2-isopropyl group, which was found rotated away from the metal. Additional spectroscopic and electrochemical properties of the various complexes are reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] External morphology of a Slovenian population of pumpkinseed Lepomis gibbosus (L.) from a habitat with extreme thermal conditionsJOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2005umer Summary The external morphology and growth variability of morphometric characters of pumpkinseed (n = 141) from an oxbow (River Sava, Slovenia) that receives thermal effluent were examined using triple regression analysis. Differences in external morphology between pumpkinseed from the oxbow and both native North American (River Otonabee, Looncall Lake, Canada) and non-native Central European populations (side arms of the River Danube, Slovakia) were evaluated. Two possible morphotypes among adults were observed, whereas the morphology of juveniles appears rather uniform across geographical location (i.e. Otonabee, Looncall, Danube). This suggests that environmental conditions, i.e. epigenetical information, seem to be responsible for most of variability in pumpkinseed morphology, which represents a function of epigenetical mechanisms. However, further investigation into epigenetical interactions, especially early development, fecundity, number of spawning acts per season, parental care, egg size and age at maturation are necessary to test this hypothesis. [source] Synthesis of dibenzo-16-crown-5 compounds with pendant ester and ether groupsJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2004David A. Babb Structurally related dibenzo-16-crown-5 lariat ethers with pendant ester and ether groups are prepared. Structural variations within the series of alkyl lariat ether esters include changes in the O-alkyl group, attachment site and nature of the lipophilic group, and length of the spacer, which connects the ester group to the polyether framework. Also synthesized are bis(crown ether) diesters with two dibenzo-16-crown-5 or two dicyclohexano-16-crown-5 units and two ester groups connected to each other by a linker of varying length. Synthetic strategies for the preparation of these lariat ethers with pendant ester- and ether-containing side arms are described. [source] Heteroarm H-shaped terpolymers through the combination of the Diels,Alder reaction and controlled/living radical polymerization techniquesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2006Hakan Durmaz Abstract Heteroarm H-shaped terpolymers (PS)(PtBA),PEO,(PtBA)(PS) and (PS)(PtBA),PPO,(PtBA)(PS) [where PS is polystyrene, PtBA is poly(tert -butyl acrylate), PEO is poly(ethylene oxide), and PPO is poly(propylene oxide)], containing PEO or PPO as a backbone and PS and PtBA as side arms, were prepared via the combination of the Diels,Alder reaction and atom transfer radical and nitroxide-mediated radical polymerization routes. Commercially available PEO or PPO containing bismaleimide end groups was reacted with a compound having an anthracene functionality, succinic acid anthracen-9-yl methyl ester 3-(2-bromo-2-methylpropionyloxy)-2-methyl-2-[2-phenyl-2-(2,2,6,6-tetramethylpiperidin-1-yloxy)ethoxycarbonyl]propyl ester, with a Diels,Alder reaction strategy. The obtained macroinitiator with tertiary bromide and 2,2,6,6-tetramethylpiperidin-1-oxy functional end groups was used subsequently in the atom transfer radical polymerization of tert -butyl acrylate and in the nitroxide-mediated free-radical polymerization of styrene to produce heteroarm H-shaped terpolymers with moderately low molecular weight distributions (<1.31). The polymers were characterized with 1H NMR, ultraviolet, gel permeation chromatography, and differential scanning calorimetry. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3947,3957, 2006 [source] Spatial differences in acquisition of soil phosphate between two arbuscular mycorrhizal fungi in symbiosis with Medicago truncatulaNEW PHYTOLOGIST, Issue 2 2000F. A. SMITH Responses of Medicago truncatula to colonization by two arbuscular mycorrhizal fungi, Scutellospora calospora isolate WUM 12(2) and Glomus caledonium isolate RIS 42, were compared in the light of previous findings that the former fungus can be ineffective as a beneficial microsymbiont with some host plants. The plants were grown individually in two-compartment systems in which a lateral side arm containing soil labelled with 33P was separated from the main soil compartment by a nylon mesh that prevented penetration by roots but not fungal hyphae. Fungal inoculum was applied as a root,soil mixture in a band opposite the side arm. Nonmycorrhizal controls were set up similarly, without inoculum. There were harvests at 28, 35, 42 and 49 d. Both sets of mycorrhizal plants grew better than nonmycorrhizal plants and initially had higher concentrations of P in shoots and roots. Plants grown with S. calospora grew better than plants grown with G. caledonium, and this was associated with somewhat greater fungal colonization in terms of intraradical hyphae and numbers of arbuscules. Scutellospora calospora formed denser hyphae at root surfaces than G. caledonium. By 28 d there were extensive hyphae of both fungi in the side arms, and after 35 d S. calospora produced denser hyphae there than G. caledonium. Nevertheless, there was very little transfer of 33P via S. calospora to the plant at 28 d, and thereafter its transfer increased at a rate only c. 33% of that via G. caledonium. The results showed that plants colonized by S. calospora preferentially obtained P from sites in the main soil chamber relatively close to the roots, compared with plants colonized by G. caledonium. Hence formation of a highly beneficial arbuscular mycorrhizal symbiosis does not necessarily depend on development of hyphae at a distance from the roots or on large-scale translocation of P from distant sites. The results are discussed in relation to previous studies with compartmented systems that have involved the same fungi. Possible causes of the variable effects of S. calospora in symbiosis with different host plants are briefly assessed. Differences in spatial abilities of individual arbuscular mycorrhizal fungi to acquire P might have strong ecological implications for plant growth in soils low in P. [source] Synthesis, DNA-Binding, Cleavage, and Cytotoxic Activity of New 1,7-Dioxa-4,10-diazacyclododecane Artificial Receptors Containing Bisguanidinoethyl or Diaminoethyl Double Side ArmsCHEMISTRY - A EUROPEAN JOURNAL, Issue 34 2007Xin Sheng Abstract Novel 1,7-dioxa-4,10-diazacyclododecane artificial receptors with two pendant aminoethyl (3) or guanidinoethyl (4) side arms have been synthesized. Spectroscopy, including fluorescence and CD spectroscopy, of the interactions of 3, 4, and their copper(II) complexes with calf thymus DNA indicated that the DNA binding affinity of these compounds follows the order Cu2+,4>Cu2+,3>4>3, and the binding constants of Cu2+,3 are Cu2+,4 are 7.2×104 and 8.7×104,M,1, respectively. Assessment by agarose gel electrophoresis of the plasmid pUC,19 DNA cleavage activity in the presence of the receptors showed that the complexes Cu2+,3 and Cu2+,4 exhibit powerful supercoiled DNA cleavage efficiency. Kinetic data of DNA cleavage promoted by Cu2+,3 and Cu2+,4 under physiological conditions fit to a saturation kinetic profile with kmax values of 0.865 and 0.596,h,1, respectively, which give about 108 -fold rate acceleration over uncatalyzed supercoiled DNA. This acceleration is due to efficient cooperative catalysis of the copper(II) center and the functional (diamino or bisguanidinium) groups. In-vitro cytotoxic activities toward murine melanoma B16 cells and human leukemia HL-60 cells were also examined: Cu2+,4 shows the highest activity with IC50 values of 1.62×10,4 and 1.19×10,5,M, respectively. [source] Synthesis, Characterization, and Folding Behavior of ,-Amino Acid Derived PolyisocyanidesCHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2006Sander J. Wezenberg Abstract Helical polymers of isocyanopeptides derived from ,-amino acids have been synthesized and their architectures have been studied in detail. Similar to their ,-amino acid analogues, the helical conformation in these macromolecules is stabilized by internal hydrogen-bonding arrays along the polymeric backbone. Unexpectedly, the flexibility of the ,-peptide side arms results in a rearrangement of the initial macromolecular architecture, leading to a more stable helical structure possessing a better defined hydrogen-bonding pattern, as was concluded from IR and temperature-dependent circular dichroism studies. Based on these results we propose a dynamic helical model for the ,-amino acid derived polyisocyanopeptides; this model is in contrast to the kinetically stable helical macromolecules that are formed upon polymerization of ,-amino acid based isocyanopeptides. [source] | ||||||||||