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Kinds of Linker Terms modified by Linker Selected AbstractsOligonucleotide Duplexes with Tethered Photoreactive Ruthenium(II) Complexes: Influence of the Ligands and Their Linker on the Photoinduced Electron Transfer and Crosslinking Processes of the Two StrandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2009Stéphanie Deroo Abstract The photoreactivity of new RuII -oligonucleotide conjugates is investigated in the presence of their complementary strands. The goal is to determine the origins of different effects of parameters that control the photocrosslinking process of the two strands. Therefore, two RuII compounds, either [Ru(tap)3]2+or [Ru(tap)2phen]2+ (tap = 1,4,5,8-tetraazaphenanthrene, phen = 1,10-phenanthroline) with different oxidation powers, were tethered with different linkers to either the 5,- or 3,-phosphate end of the probe strand before hybridization with the complementary strand. These systems were studied by time-resolved emission spectroscopy, UV/Vis absorption experiments, PAGE and MS (ESI) analyses. The best yields of photocrosslinking (45,%) obtained with [Ru(tap)3]2+ tethered to the 3,-position are due to (i) a higher oxidation power of the complex and (ii) its attachment at the 3,-position. Indeed, this tethering favours the interaction of the Ru compound with the duplex and, therefore, inhibits its photodechelation. This work allows better design of sequence-specific DNA photodamaging agents prior to biological applications.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Optimization of the Azobenzene Scaffold for Reductive Cleavage by Dithionite; Development of an Azobenzene Cleavable Linker for Proteomic ApplicationsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2010Geoffray Leriche Abstract In this paper we conducted an extensive reactivity study to determine the key structural features that favour the dithionite-triggered reductive cleavage of the azo,arene group. Our stepwise investigation allowed identification of a highly reactive azo,arene structure 25 bearing a carboxylic acid at the ortho position of the electron-poor arene and an ortho - O -alkyl-resorcinol as the electron-rich arene. Based on this 2-(2,-alkoxy-4,-hydroxyphenylazo)benzoic acid (HAZA) scaffold, the orthogonally protected difunctional azo,arene cleavable linker 26 was designed and synthesized. Selective linker deprotection and derivatization was performed by introducing an alkyne reactive group and a biotin affinity tag. This optimized azo,arene cleavable linker led to a total cleavage in less than 10 s with only 1 mM dithionite. Similar results were obtained in biological media. [source] A New and Simply Available Class of Hydrosoluble Bioconjugates by Coupling Paclitaxel to Hyaluronic Acid through a 4-Hydroxybutanoic Acid Derived LinkerHELVETICA CHIMICA ACTA, Issue 1 2005Francesca Leonelli A simple preparation of a new hydrosoluble paclitaxel bioconjugate 8, representing a new class of paclitaxel derivatives, is described. Bioconjugate 8 was obtained by coupling hyaluronic acid (2) to paclitaxel (1) by means of a 4-hydroxybutanoic acid derived linker (Scheme,2). [source] A novel class of chemically modified iodo-containing resins: design, synthesis and application to mass spectrometry-based proteome analysisJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2004Li Zhang Abstract A novel class of chemically modified iodo-containing resins with isotope-labeled tagging for mass spectrometry-based proteome analysis is described. This iodo-containing resin contains a thiol-reactive group that is used to capture the cysteine (Cys)-containing peptides from peptide mixtures, one ,tag' amino acid, and an aminomethyl polystyrene resin with Rink Amide Linker. The ,tag' amino acid is synthesized in both heavy and light isotope-coded forms and therefore permits the direct relative quantification of peptides/proteins through mass spectrometric analysis. In the iodo-containing resin strategy, the Cys-containing peptides of two samples covalently captured by either light or heavy iodo-containing resin were mixed and washed extensively under stringent conditions. Then the Cys-containing peptides were retrieved by acid-catalyzed elution. Finally, the eluted peptides were directly analyzed by micro liquid chromatography/mass spectrometry for identification and relative quantification. The iodo-containing resins were synthesized by a simple but effective method. Their abilities to identify and quantify the Cys-containing part in two samples were proved by the analysis of mixtures of amino acids, peptides and proteins. Copyright © 2004 John Wiley & Sons, Ltd. [source] Molecular-Sieve Membrane with Hydrogen Permselectivity: ZIF-22 in LTA Topology Prepared with 3-Aminopropyltriethoxysilane as Covalent Linker,ANGEWANDTE CHEMIE, Issue 29 2010Aisheng Huang Dr. Hohe Wasserstoffselektivität und thermische Stabilität zeichnen eine Membran des zeolithischen Imidazolats ZIF-22 aus, die mithilfe des kovalenten Linkers 3-Aminopropyltriethoxysilan (APTES) auf porösen keramischen Trägern abgeschieden wurde (siehe Bild). Bei 323,K wurden eine H2/CO2 -Selektivität von 7.2 und eine H2 -Durchlässigkeit von 1.6×10,7,mol,m,2,s,1,Pa,1 erreicht. [source] Development of a Building Block Strategy To Access Gigantic Nanoscale Heteropolyoxotungstates by Using SeO32, as a Template Linker,ANGEWANDTE CHEMIE, Issue 24 2010Jun Yan Heteroatome kontrollieren den Aufbau nanoskaliger Heteropolyoxowolframate: Namentlich SeO32, führte zur Bildung von [H2W43Se3O148]24,{W43Se3}, [H4W77Se5O265]44, {W77Se5}, [H6W63Se6O221]34, {W63Se6} und [H8W100Se16O364]56, {W101Se16}. Alle diese Clusteranionen leiten sich von einem gemeinsamen {W22Se2}-Baustein ab und entstehen ohne Einsatz verbrückender Heterometallbausteine; die drei kleineren Cluster enthalten pentagonale W(W4)-Einheiten. [source] Orienting Zeolite,L Microcrystals with a Functional Linker,ANGEWANDTE CHEMIE, Issue 8 2010Yu Wang Farbenfroh: Durch Anordnen von Zeolith-L-Kristallen zu lumineszierenden makroskopischen Strukturen entstehen dichte und homogene funktionelle Monoschichten, die stabil und hochgradig organisiert sind (siehe Bild). Die Farbe der Lumineszenz kann eingestellt werden, indem man Zahl und Art der Lanthanoidionen in der Verbindungseinheit variiert, die Gastspezies in den Kanälen des Zeoliths austauscht oder die Anregungswellenlänge wechselt. [source] Polystyrolsulfonylchlorid , ein hochorthogonales Linkerharz für die Synthese von Stickstoffheterocyclen,ANGEWANDTE CHEMIE, Issue 32 2009Matthias Mentel Dr. Ein Linker, breite Anwendung: Ein einfacher Sulfonamidlinker für primäre und sekundäre Amine wurde zum Aufbau von kleinen Bibliotheken privilegierter Indol- und Chinolonstrukturen an der festen Phase verwendet. Die Produkte können nach der Synthese ,spurlos" unter milden Elektronentransferbedingungen oder nach einem ,Safety-catch"-Prinzip freigesetzt werden. [source] Inhibitors of Human Histone Deacetylase: Synthesis and Enzyme Assay of Hydroxamates with Piperazine LinkerARCHIV DER PHARMAZIE, Issue 3 2010Shubhashis Chakrabarty Abstract The histone deacetylase (HDAC) enzyme plays an important role in gene transcription. Inhibitors of histone deacetylases induce cell differentiation and suppress cell proliferation in tumor cells. Hydroxamates with rigid linker have displayed better inhibition profiles than those with linear and flexible aliphatic linkers. We have designed and synthesized several potential histone deacetylase inhibitors with a piperazine moiety in the linker region to test the effect of reduced linker flexibility. Inhibitors were evaluated for their inhibitory action on human HDAC3/NCoR2 and HDAC8. N -Hydroxycarboxamide derivatives (compounds 4a,d) were found to be better than N -hydroxyacetamide derivatives (compounds 6a,d) against HDAC8. Amongst the synthesized compounds, 4a (HDAC8, IC50: 3.15 ,M) with no substitution in the aryl cap was the most active and promising lead for further investigations. [source] ChemInform Abstract: Development of a Building Block Strategy to Access Gigantic Nanoscale Heteropolyoxotungstates by Using SeO2- 3 as a Template Linker.CHEMINFORM, Issue 34 2010Jun Yan Abstract Gigantic heteropolyoxotungstates are synthesized using the SeO32- group as both heterotemplate and linker. [source] ChemInform Abstract: A Fluorous-Tagged Linker from Which Small Molecules Are Released by Ring-Closing Metathesis.CHEMINFORM, Issue 31 2008Stuart G. Leach Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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] Creation of Concave-Shaped Conformation in Crystal Structures Using an Iminodicarbonyl Linker.CHEMINFORM, Issue 42 2005An Application to Solid-State Intramolecular [4 + 4] Photocycloaddition Reactions of 2-Pyridone Derivatives. No abstract is available for this article. [source] ChemInform Abstract: Practical Synthesis of a New Analytical Construct: Thiopyrimidine Safety-Catch Linker for Facile Monitoring of Solid-Phase Chemistry.CHEMINFORM, Issue 4 2001Olivier Lorthioir 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] Macrocyclic Cyclooctene-Supported AlCl,Salen Catalysts for Conjugated Addition Reactions: Effect of Linker and Support Structure on CatalysisCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2009Nandita Madhavan Dr. Abstract AlCl,salen (salen=N,N,-bis(salicylidene)ethylenediamine dianion) catalysts supported onto macrocyclic oligomeric cyclooctene through linkers of varying length and flexibility have been developed to demonstrate the importance of support architecture on catalyst activity. The role played by the support and the linkers in dictating catalyst activity was found to vary for reactions with contrasting mechanisms, such as the bimetallic cyanide and the monometallic indole addition reactions. While the flexible support significantly enhanced the cyanide addition reaction, most likely by improving salen,salen interactions in the transition state, it lowered the reaction rate for the monometallic indole reaction. For both reactions, significant increase in catalytic activity was observed for catalysts with the longest linkers. The effect of the flexible macrocyclic support on catalysis was further exemplified by the enhanced activity of the supported catalyst in comparison with its unsupported analogue for the conjugate addition of tetrazoles, which is known to be catalyzed by dimeric ,-oxo,salen catalysts. Our studies with the cyclooctene supported AlCl,salen catalysts provides significant insights for rationally designing highly efficient AlCl,salen catalysts for a diverse set of reactions. [source] Efficient Preparation of Photoswitchable Dithienylethene-Linker-Conjugates by Palladium-Catalyzed Coupling Reactions of Terminal Alkynes with Thienyl Chlorides and Other Aryl HalidesCHEMISTRY - AN ASIAN JOURNAL, Issue 5 2010Marc Zastrow Abstract Three photochromic dithienylethene-linker-conjugates with an adamantane core containing different spacer lengths and footprint areas with carboxylic anchoring groups are synthesized. The synthetic routes start either from the ethynylene-linker 5 or the iodo-substituted linker 8. Reaction conditions for the final Sonogashira coupling step between ethynylene-linker 5 with the chloro-substituted dithienylethene 4 in the presence of [PdCl2(CH3CN)2]/X-Phos and Cs2CO3 or K3PO4 are optimized using 2-chloro-5-methylthiophene (9) and triethylsilylacetylene or triisopropylsilylacetylene (10,a,b) as model compounds. Experimental conditions are found to suppress the activation of the C(sp)Si bond in TIPS-acetylene 10,b, a reaction leading to a subsequent cross-coupling reaction to form by-product 12. Furthermore, activation of the C(sp)Si bond in the presence of the fluorinated backbone of the chloro-substituted dithienylethene 4 can also be prevented. The photochromic properties of the conjugate 3 and its precursor dithienylethene 7,b are also investigated. Beschrieben wird die Synthese von drei photochromen Dithienylethen-Linker-Konjugaten, bestehend aus einer zentralen Adamantaneinheit, Carbonsäure-Ankergruppen, sowie variierenden "Spacerlängen" und unterschiedlichen Fußabdrücken. Die synthetischen Routen zu diesen Verbindungen beginnen entweder ausgehend von dem Ethinylen-Linker 5 oder von dem Iod-substituierten Linker 8. Für die finale Sonogashira-Kupplung wurden dabei Reaktionsbedingungen zwischen dem Ethinylen-Linker 5 und dem Chlor-substituierten Dithienylethen 4 in Gegenwart von [PdCl2(CH3CN)2]/X-Phos und Cs2CO3 oder K3PO4 verwendet, die anhand von Modellstudien mit 2-Chlor-5-methylthiophen (9) und Triethylsilylacetylen oder Triisopropylsilylacetylen (10,a,b) optimiert wurden. Dabei wurden experimentelle Bedingungen gefunden, um die Aktivierung der C(sp)-Si-Bindung von TIPS-Acetylen 10,b zu unterdrücken, welche ansonsten zu dem Nebenprodukt 12 führte. Darüber hinaus konnte die Aktivierung der C(sp)-Si-Bindung in Anwesenheit des fluorierten Rückgrats des chlor-substituierten Dithienylethen 4 verhindert werden. Schließlich wurden die photochromen Eigenschaften des Konjugates 3 und der Vorläuferverbindung 7,b untersucht. [source] A tethered ascorbate-norepinephrine compound, 4-UT, displays long-acting adrenergic activity on rabbit aortic smooth muscleDRUG DEVELOPMENT RESEARCH, Issue 5 2008Robert Root-Bernstein Abstract We previously demonstrated that adrenergic and histaminergic receptors have an ascorbic acid (vitamin C) binding site on the first extracellular loop, immediately adjacent to the aminergic binding site. Binding of ascorbate to this site strongly potentiates any sub-maximal dose of an adrenergic or histaminergic compound, significantly increasing its duration of activity. We report here the successful synthesis of a tethered compound that mimics the combined effects of a mixture of ascorbate with norepinephrine. The tethered compound uses a four-unit polyethylene linker to tether ascorbate to norepinephrine. The tethered compound is about tenfold less effective than norepinephrine in stimulating rabbit aortic smooth muscle, but has a very significantly enhanced duration of activity compared with norepinephrine alone and comparable to a mixture of norepinephrine and ascorbate. Additional ascorbate does not enhance the tethered compound's effects and we demonstrate that the compound binds to a synthetic peptide spanning the ascorbate binding site of the receptor. These experiments strongly suggest that the compound binds to both the adrenergic binding site and the ascorbate binding site simultaneously. Tethered compounds with linkers of other lengths did not have these properties. We believe that the synthesis of enhanced adrenergic and histaminergic drugs by tethering them to potentiators such as ascorbate will permit a new class of potential drugs to be created with high specificity and long duration of activity. Drug Dev Res 69:242,250, 2008. © 2008 Wiley-Liss, Inc. [source] Comparison of Different Strategies on DNA Chip Fabrication and DNA-Sensing: Optical and Electrochemical ApproachesELECTROANALYSIS, Issue 22 2005Sabine Szunerits Abstract New strategies for the construction of DNA chips and the detection of DNA hybridization will be discussed in this review. The focus will be on the use of polypyrrole as a linker between a substrate and oligonucleotide probes. The modification step is based on the electrochemical copolymerization of pyrrole and oligonucleotides bearing a pyrrole group on its 5, end. This strategy was employed for the immobilization of oligonucleotides on millimeter-sized electrodes, microelectrode arrays, as well as for the local structuring of homogeneous gold surfaces. Our approaches for the localized patterning of gold surfaces will be also discussed. Localized immobilization was achieved by using an electrospotting technique, where a micropipette served as an electrochemical cell where spot sizes with 800,,m diameters were fabricated. The use of a microcell using a Teflon covered metal needle with a cavity of 100,,m resulted in immobilized probe spots of 300,,m. Scanning electrochemical microscopy (SECM) was also used, and surface modifications of 100,,m were obtained depending on the experimental conditions. Different detection methods were employed for the reading of the hybridization event: fluorescence imaging, surface plasmon resonance imaging (SPRI), photocurrent measurements, and voltamperometric measurements using intercalators. Their advantages concerning the various immobilization strategies will also be discussed. [source] A Rapid Method for the Pre-Enrichment and Detection of Salmonella Typhimurium by Immunomagnetic Separation and Subsequent Fluorescence Microscopical TechniquesENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 3 2005J. Steingroewer Abstract Detection of food-borne pathogens is of great importance in order to minimize the risk of infection for customers. These analyses should be as fast as possible. Any detection method requires enrichment and quantitative analysis of the enriched microbes. Conventional enrichment methods, which take several days, need to be replaced by faster techniques such as immunomagnetic separation (IMS). This technique is based on the use of paramagnetic microspheres coated with antibodies as ligands that have specific affinity to the microbes that have to be detected. In the studies reported here, a rapid method for the detection of Salmonella enterica serovar Typhimurium (Salmonella Typhimurium), combining IMS and Direct Epifluorescence Filter Technique (DEFT), was developed. It was focused on releasing the target cells from the magnetic beads after IMS, because this is a premise for combining IMS, as an alternative pre-enrichment, with DEFT. Otherwise, the high number of beads form a layer on the filter membrane that makes the following microscopic analysis for the detection of the contaminants impossible. The CELLectionTM Dynabeads® used in this study, are coated with recombinant streptavidin (rSA) via a DNA linker. The rSA binds biotinylated antibodies that are able to capture target cells. The DNA linker provides the cleavable site, so that the beads can be removed from the captured cells after isolation. In this study a releasing procedure was developed. This procedure allows for an average 74,% ± 4,% of the bead-bound Salmonella Typhimurium cells to be released from the beads after IMS, so that the detection of the separated cells by DEFT will be possible. [source] Both Fc,RIV and Fc,RIII are essential receptors mediating type II and type III autoimmune responses via FcR,-LAT-dependent generation of C5aEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 12 2009Shahzad N. Syed Abstract Fc,RIV is a relatively new IgG Fc receptor (Fc,R) that is reported to contribute to the pathogenesis of autoimmune diseases, although its specific role in relation to Fc,RIII, complement and IgG2 subclasses remains uncertain. Here we define Fc,RIV on macrophages as a receptor for soluble IgG2a/b complexes but not for cellular bound IgG2a and show that simultaneous activation of Fc,RIV and Fc,RIII is critical to mediate certain type II/III autoimmune responses. Fc,RIII-deficient mice display compensatory enhanced Fc,RIV expression, are protected from lung inflammation after deposition of IgG complexes, and show reduced sensitivity to IgG2a/b-mediated hemolytic anemia, indicating that increased Fc,RIV alone is not sufficient to trigger these diseases in the absence of Fc,RIII. Importantly, however, blockade of Fc,RIV is also effective in inhibiting phagocytosis and cytokine production in IgG2b-induced anemia and acute lung injury, processes that display a further dependence on C5a anaphylatoxin receptor. Using gene deletion and functional inhibition studies, we found that Fc,RIII and Fc,RIV are each essential to trigger an FcR,-linker for activation of T-cell-dependent signal that drives C5a production in the Arthus reaction. Together, the results demonstrate a combined requirement for Fc,RIII and Fc,RIV in autoimmune injury, and identify the linker for activation of T cells adaptor as an integral component of linked Fc,R and C5a anaphylatoxin receptor activation to generate inflammation. [source] A new function for LAT and CD8 during CD8-mediated apoptosis that is independent of TCR signal transductionEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 6 2009Raedun L. Clarke Abstract The majority (>95%) of thymocytes undergo apoptosis during selection in the thymus. Several mechanisms have been proposed to explain how apoptosis of thymocytes that are not positively selected occurs; however, it is unknown whether thymocytes die purely by "neglect" or whether signaling through a cell-surface receptor initiates an apoptotic pathway. We have previously demonstrated that on double positive thymocytes the ligation of CD8 in the absence of TCR engagement results in apoptosis and have postulated this is a mechanism to remove thymocytes that have failed positive selection. On mature single positive T cells CD8 acts as a co-receptor to augment signaling through the TCR that is dependent on the phosphorylation of the adaptor protein, linker for activation of T cells (LAT). Here, we show that during CD8-mediated apoptosis of double positive thymocytes there is an increase in the association of CD8 with LAT and an increase in LAT tyrosine phosphorylation. Decreasing LAT expression and mutation of tyrosine residues of LAT reduced apoptosis upon crosslinking of CD8. Our results identify novel functions for both CD8 and LAT that are independent of TCR signal transduction and suggest a mechanism for signal transduction leading to apoptosis upon CD8 crosslinking. [source] A female-specific pentraxin, CrOctin, bridges pattern recognition receptors to bacterial phosphoethanolamineEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 12 2007Yue Li Abstract Pathogen recognition and binding are crucial functions of innate immunity. It has been observed that the short pentraxin superfamily including C-reactive protein (CRP) and serum amyloid,P component are pathogen pattern recognition receptors (PRR) in the plasma. We isolated and characterized a novel and distinctive pentraxin from the plasma of horseshoe crab, Carcinoscorpius rotundicauda, henceforth named CrOctin, which binds to bacteria via phosphoethanolamine (PE), a chemical component present on lipid,A and core polysaccharide moieties of bacterial lipopolysaccharide (LPS). Infection enhances the formation of the PRR interactome constituting CrOctin, CRP and galactose-binding protein. In particular, infection increases the affinity of CRP to CrOctin by 1000-fold. Furthermore, we observed that by binding to PE, CrOctin acts as a linker that bridges the PRR interactome to the inner core of LPS. On the other hand, under normal physiological conditions, binding of CrOctin to PE appears to obscure other PRR from interacting directly with PE. Interestingly, the cluster of "CrOctin-interactive PRR" is sex specific. We report, for the first time, the change in PRR protein profiles with a distinctive gender difference during Pseudomonas infection. [source] In vivo disruption of T cell development by expression of a dominant-negative polypeptide designed to abolish the SLP-76/Gads interactionEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 10 2007Martha Abstract Multi-molecular complexes nucleated by adaptor proteins play a central role in signal transduction. In T cells, one central axis consists of the assembly of several signaling proteins linked together by the adaptors linker of activated T cells (LAT), Src homology,2 domain-containing leukocyte-specific phosphoprotein of 76,kDa (SLP-76), and Grb2-related adaptor downstream of Shc (Gads). Each of these adaptors has been shown to be important for normal T cell development, and their proper sub-cellular localization is critical for optimal function in cell lines. We previously demonstrated in Jurkat T cells and a rat basophilic leukemic cell line that expression of a 50-amino acid polypeptide identical to the site on SLP-76 that binds to Gads blocks proper localization of SLP-76 and SLP-76-dependent signaling events. Here we extend these studies to investigate the ability of this polypeptide to inhibit TCR-induced integrin activity in Jurkat cells and to inhibit in vivo thymocyte development and primary T cell function. These data provide evidence for the in vivo function of a dominant-negative peptide based upon the biology of SLP-76 action and suggest the possibility of therapeutic potential of targeting the SLP-76/Gads interaction. [source] Systematic Hydrothermal Investigation of Metal Phosphonatobenzenesulfonates by High-Throughput MethodsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2010Palanikumar Maniam Abstract A high-throughput (HT) investigation using the rigid bifunctional ligand 4-phosphonobenzenesulfonic acid, H2O3P-C6H4 -SO3H (H3L), generated five new phosphonatobenzenesulfonates with copper(II) or lead(II) ions. A comprehensive HT study comprising the screenings of different metal ions, metal salt types and the synthesis optimization were conducted whereby the influence of pH and molar ratios M2+/H3L were investigated. The HT-study led to five new compounds Pb2[(O3P-C6H4 -SO3)(OH)] (1), Cu1.5[(O3P-C6H4 -SO3)(H2O)] (2), NaCu(O3P-C6H4 -SO3)(H2O)3 (3), Cu2[(O3P-C6H4 -SO3)(OH)(H2O)] (4) and Cu3[(O3P-C6H4 -SO3)2(H2O)2] (5). Metal ion screening showed lead(II) and copper(II) to be suitable metal ions. The utilization of discovery and focused arrays allowed to determine the optimal formation fields of the respective compounds. The crystal structures were determined from single-crystal X-ray diffraction and revealed the presence of various MOx polyhedra that form clusters, chains or layers which are connected through the organic linker. IR spectra, thermogravimetric studies, magnetic susceptibility measurements and elemental analyses were conducted to further characterize the compounds 1, 3, 4 and 5. [source] Base-Induced Formation of Two Magnesium Metal-Organic Framework Compounds with a Bifunctional Tetratopic LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2008Pascal D. C. Dietzel Abstract Two coordination polymers constructed from magnesium and the tetratopic organic linker 2,5-dihydroxyterephthalic acid are reported, denominated CPO-26-Mg and CPO-27-Mg. The organic component carries two different types of protic functional groups. The degree of deprotonation of the organic component can be regulated by the amount of sodium hydroxide employed in the synthesis, thus determining which of the compounds forms. In CPO-26-Mg, only the carboxylic acid groups of the linker are deprotonated and take part in the construction of the three-dimensional framework. The structure is non-porous, and its topology is based on the PtS net. In CPO-27-Mg, both the carboxylic acid and the hydroxy groups are deprotonated and involved in the construction of a microporous three-dimensional framework which is based on a honeycomb motif containing large solvent-filled channels. The metal atoms are arranged in chiral chains along the intersection of the honeycomb and contain one water molecule in their coordination sphere, which allows for the creation of coordinatively unsaturated metal sites upon dehydration. CPO-27-Mg is a potentially useful lightweight adsorbent with a pore volume of 60,% of the total volume of the structure and an apparent Langmuir surface area of up to 1030 m2,g,1. Its thermal stability was investigated by thermogravimetry and variable-temperature powder X-ray diffraction, which shows framework degradation to commence at 160 °C in air, at 235 °C under nitrogen, and at 430 °C in a dynamic vacuum. Thermogravimetric dehydration and re-hydration experiments at miscellaneous temperatures indicate that it is possible to obtain open metal sites in CPO-27-Mg, but the water is more tightly bound in this material than in the previously reported isostructural nickel compound.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Synthesis, Upconversion Luminescence and Magnetic Properties of New Lanthanide,Organic Frameworks with (43)2(46,66,83) TopologyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2007Danfeng Weng Abstract The synthesis and crystal structures of three new lanthanide,organic frameworks [Ln(pza)(OH)(H2O)]n (Ln = Y(1), Er(2), Yb(3); H2pza = 2,3-pyrazinedicarboxylic acid) with helical chains and novel 2D (43)2(46,66,83) topology are reported. The topology is obtained by simplifying the dinuclear metal core as a six-connected node and the ligand as a three-connected linker. The upconversion property measurement gives green and red emissions coming from two-photon excitation of Y: Er, Yb codoped coordination polymer and arising from ErIII transitions of 4S3/2/2H11/2,4I15/2 and 4F9/2,4I15/2. The magnetic properties of complexes 2 and 3 are also studied.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis and Transition Metal Complexes of Novel N,N,O Scorpionate Ligands Suitable for Solid Phase ImmobilisationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2006Eike Hübner Abstract Introduction of an allyl or a hydroxymethyl group to bis(3,5-dimethylpyrazol-1-yl)acetic acid (1) at the bridging carbon atom leads to the new tripodal N,N,O ligands 2,2-bis(3,5-dimethylpyrazol-1-yl)pent-4-enoic acid (Hbdmpzpen) (2) and 2,2-bis(3,5-dimethylpyrazol-1-yl)-3-hydroxypropionic acid (Hbdmpzhp) (3). These ligands exhibit similar chemical behaviour to that of 1, but they have the additional possibility to be immobilised to a solid phase. Esterification of the hydroxymethyl linker of 3 yields 2,2-bis(3,5-dimethylpyrazol-1-yl)-3-acetatopropionic acid (Hbdmpzap) (4). The molecular structures of 2, 3 and 4 all exhibit intramolecular hydrogen bridges. Introduction of a hydroxymethyl group to methyl bis(3,5-dimethylpyrazol-1-yl)acetate (5) yields methyl2,2-bis(3,5-dimethylpyrazol-1-yl)-3-hydroxypropionate(Mebdmpzhp) (6), which can be immobilised on Merrifield polymer to yield modified resin P - 6. To investigate the reactivity of these new ligands, manganese and rhenium complexes of 2, 3 and 4 have been studied. The molecular structures of the two manganese complexes [Mn(bdmpzpen)(CO)3] (7) and [Mn(bdmpzap)(CO)3] (8) have been confirmed by single-crystal X-ray structure determination. Saponification of polymer resin P - 6 and subsequent reaction with [ReBr(CO)5] yields rhenium tricarbonyl complexes anchored on Merrifield polymer (P -Re). Solid phase immobilisation of the [Mn(bdmpzpen)(CO)3] (7) and [Re(bdmpzpen)(CO)3] (9) complexes on 3-mercaptopropyl functionalised silica is initialised by AIBN. The tripodal coordination of manganese and rhenium in these functionalised Merrifield resins (P -Re) and silica (S -Mn, S -Re) is proven by a single A1 and two E signals in the IR spectra that are typical for unsymmetrical "piano stool" type carbonyl complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Optimization of the Azobenzene Scaffold for Reductive Cleavage by Dithionite; Development of an Azobenzene Cleavable Linker for Proteomic ApplicationsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2010Geoffray Leriche Abstract In this paper we conducted an extensive reactivity study to determine the key structural features that favour the dithionite-triggered reductive cleavage of the azo,arene group. Our stepwise investigation allowed identification of a highly reactive azo,arene structure 25 bearing a carboxylic acid at the ortho position of the electron-poor arene and an ortho - O -alkyl-resorcinol as the electron-rich arene. Based on this 2-(2,-alkoxy-4,-hydroxyphenylazo)benzoic acid (HAZA) scaffold, the orthogonally protected difunctional azo,arene cleavable linker 26 was designed and synthesized. Selective linker deprotection and derivatization was performed by introducing an alkyne reactive group and a biotin affinity tag. This optimized azo,arene cleavable linker led to a total cleavage in less than 10 s with only 1 mM dithionite. Similar results were obtained in biological media. [source] Indole in DNA: Comparison of a Nucleosidic with a Non-Nucleosidic DNA Base SubstitutionEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2009Janez Barbaric Abstract The synthetic incorporation of indole as an artificial DNA base into oligonucleotides by two different structural approaches is described. For both types of modification, the indole moiety is attached through the C-3 position to the oligonucleotides. As a mimic of natural nucleosides, the indole nucleoside of ,-2,-deoxyribofuranoside (In) was synthesized. The corresponding In-modified duplexes were compared with duplexes that contained the indole group connected through (S)-3-amino-1,2-propanediol as an acyclic linker between the phosphodiester bridges of the oligonucleotides. This linker was tethered to the C-3 position of the indole heterocycle either directly (In,) or by a carbamate function (In,). The melting temperatures of the corresponding indole-modified DNA duplexes were measured and compared. Interestingly, not only the In, and In, modifications but also the natural-like In base surrogate destabilize the DNA duplex strongly. This result supports our approach to apply the acyclic glycol linker to incorporate aromatic molecules as artificial DNA base substitutions. The major advantage of acyclic glycol linkers [such as the applied (S)-3-amino-1,2-propanediol] is that the corresponding modifications are synthetically more easily and readily accessible, as it avoids the preparation of the nucleosidic bond and the separation and purification of the ,- and ,-anomers. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Chiral Concave Imidazolinium Salts as Precursors to Chiral Concave N -Heterocyclic Carbenes,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2007Ole Winkelmann Abstract Imidazolinium moieties have been incorporated into bimacrocycles to generate precursors for concave N -heterocyclic carbenes (NHCs). By using one symmetrically substituted benzene bridgehead and one naphthalene bridgehead devoid of local C2 -symmetry, axially chiral concave imidazolinium ions have been obtained. Starting from 2,7-dihydroxy-1-nitronaphthalene (7), the phenol groups have been transformed to 4-pentenyl ethers 8, and the nitro group was then reduced to the corresponding amine 9. Next, 9 and a 2,6-bis(alkenyloxy)aniline 10 were connected by an oxalic acid linker. After reduction of the diamide 13 to diamine 14, a bridge was installed with triethyl orthoformate to give a tetraalkenyl-substituted imidazolinium salt 15. Ring-closing metathesis of 15 followed by hydrogenation of the products 16 yielded the bimacrocyclic salts 17 in 9,18,% overall yield (based on 7), giving amounts up to >300 mg. The configurational stability of 17 was investigated by NMR using chiral enantiopure anions TRISPHAT 18 and BINPHAT 19 as stereodynamic probes.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] An Expeditious Synthesis of N -Acetylneuraminic Acid ,- C -Glycosyl Derivatives (",- C -Glycosides") from the Anomeric AcetatesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2007Adeline Malapelle Abstract The reductive metallation of the readily available peracetylated derivatives of methyl N -acetylneuraminate 3a and 3b by samarium diiodide without any additive generates the corresponding anomeric samarium(III) organometallics. These intermediates react efficiently with carbonyl compounds under Barbier conditions, providing a fast synthesis of C -ketosides. The ,- and ,-acetates are equally effective, and excellent yields are obtained for coupling with cyclic ketones. The procedure has been conveniently applied to the synthesis of a C -ketoside of N -acetylneuraminic acid with an attached linker, ready to use as a building block in the elaboration of multivalent biological probes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] | |||||||||||||||||||||||||||||||||||||||||||||||||