- Carbazole as Linker for Dinuclear Gadolinium-Based MRI Contrast Agents
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Ligands able to complex two gadolinium ions have been synthesized and characterized in view of the ability of the complexes to increase the spin relaxation of water protons. All ligands are based on the heptadentate diethylenetriaminetetraacetic acid (DTTA) chelator and carbazole as a rigid linker. Depending on the derivatization on the nitrogen atom of the five-membered ring, the compounds form small aggregates in aqueous solution, self-assemble to form micelles or bind to human serum albumin. In all cases, this leads to a marked increase in 1H relaxivity at nuclear Larmor frequencies between 20 and 60 MHz. Water exchange on the gadolinium ions as measured by 17O NMR relaxation is fast enough not to limit relaxivity. 1H nuclear magnetic relaxation dispersion profiles were also measured and analyzed using Solomon–Bloembergen–Morgan theory including Lipari–Szabo treatment to include internal motion or anisotropic rotation.
- Mousavi, Bibimaryam,Chauvin, Anne-Sophie,Moriggi, Lo?ck,Helm, Lothar
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p. 5403 - 5412
(2017/12/18)
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- Synthesis and fluorescence properties of 3,6-diaminocarbazole-modified pyrrolidinyl peptide nucleic acid
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This work aims to explore a new clickable carbazole-based fluorescent label, its incorporation into pyrrolidinyl peptide nucleic acid (acpcPNA), and the interactions between the labeled PNA probe and DNA by fluorescence spectrophotometry and molecular dynamics simulation. A carbazole derivative, namely 3,6-diaminocarbazole (DAC), was synthesized and incorporated into the internal and terminal positions of azide-modified acpcPNA via a sequential reductive alkylation and click reaction previously developed by our group. The DAC-modified acpcPNA can form a stable hybrid with complementary DNA with somewhat lower stability compared to unmodified acpcPNA. Most importantly, the DAC-modified acpcPNA exhibits a remarkable fluorescence increase in the presence of DNA (up to 35.5 fold with complementary DNA). Non-complementary as well as single mismatched DNA targets gave a smaller fluorescence increase (1.1 to 18.6 fold), and the discrimination could be further improved by increasing the temperature to dissociate the mismatched hybrids. Molecular dynamic simulations revealed that the DAC interacts with adjacent nucleobases in single stranded PNA, resulting in quenching of the fluorescence signal. When the PNA formed a hybrid with DNA, the DAC was pushed away from the duplex, resulting in a fluorescence increase. Thus, the DAC-labeled acpcPNA is a potential candidate as a self-reporting probe for determination of DNA sequences.
- Dangsopon, Aukkrapon,Poomsuk, Nattawee,Siriwong, Khatcharin,Vilaivan, Tirayut,Suparpprom, Chaturong
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p. 74314 - 74322
(2016/08/24)
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- Liquid-crystalline functional carbazole and naphthalene platforms
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Two novel families of highly functionalized molecules consisting of a central carbazole or naphthalene core carrying actionable acid functions and linked to gallate platforms equipped with three long alkoxy chains have been rationally designed. The presence of amide tethers and chelating rigid fragments generate a new class of luminescent mesomorphic materials. Platforms bearing long paraffin chains (n = 12 and 16) self-organize into columnar liquid crystalline phases in which the columns are arranged according to a 2D oblique, rectangular or hexagonal lattice symmetry as deduced from powder XRD experiments. FT-IR studies confirm that the common driving force for aggregation and micro-segregation in the mesophase is due to the occurrence of a tight intermolecular H-bonded network. Spectroscopic measurements show that these platforms are luminescent in solution and in the solid state. Due to the synthetic availability of carbazole and naphthalene rigid cores and the simplicity by which these platforms can be graphed, this methodology represents a practical alternative to the production of fluorescent and mesomorphic materials.
- Camerel, Franck,Donnio, Bertrand,Ziessel, Raymond
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scheme or table
p. 412 - 428
(2012/01/06)
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- Photoresponsive synthetic receptors: binding properties and photocontrol of catalytic activity
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The photoresponsive ditopic receptors 1a,b bearing two adenine binding sites linked by an azobenzene moiety were prepared.Photochromism, binding of mono- and bis-adenine derivatives and template effects on the coupling reaction of aminoadenosine 2 and the adenosine-derived active ester 3 were studied.Photoswitching of the azobenzene linker from the extended E to the folded Z isomer enhances the catalytic activity of the template 1a by a factor of 50.The binding studies provide evidence for the formation of termolecular complexes 1*2*3 and allow for mechanistic considerations.The influence of various adenine derivatives on the rate of the thermal Z-->E isomerization of (Z)-1a,b was evaluated and a significant stabilization of the Z isomers by the bis-adenine guest 4 was observed.
- Wuerthner, Frank,Rebek, Julius
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p. 1727 - 1734
(2007/10/02)
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- Photoschaltbare Katalyse mit synthetischen Rezeptoren
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Stichworte: Isomerisierungen.Photochemie.Templatsynthesen
- Wuerthner, Frank,Rebek, Julius
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p. 503 - 505
(2007/10/02)
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