Biomedical subjects
Publications and source records attributed to V M Rotello.
Polymer 4 and its monomeric counterpart 3 exhibit electrochemically tuneable interactions with anthracene polymer 2 and a structurally similar monomer 1 and seen by the variation of the oxidation waves of TTF groups and the fluorescence of the anthracene.
The first example of a redox controlled hydrogen bonded three-pole switch is described, which exploits both electrochemical oxidation and reduction of the host-guest dyad to modulate the intermolecular recognition properties.
Efficient recognition of DNA is a prerequisite for the development of biological effectors, including transcription and translation regulators, transfection vectors, and DNA sensors. To provide an effective scaffold for multivalent interactions with DNA, we have fabricated mixed monolayer protected gold clusters (MMPCs) functionalized with tetraalkylammonium ligands that can interact with the DNA backbone via charge complementarity. Binding studies indicate that the MMPCs and DNA form a charge-neutralized, nonaggregated assembly. The interactions controlling these assemblies are highly efficient, completely inhibiting transcription by T7 RNA polymerase in vitro.
We report the use of the electron-donating 4,5-dipentyl-4'-methyl-TTF (TTF = tetrathiafulvalene) moiety in combination with the electron acceptor 11,11,12,12-tetracyanoanthraquinodimethane (TCNAQ) unit in the novel D-sigma-A diad molecules 11, 17, and 18. These compounds display a weak, broad, low-energy intramolecular charge-transfer (ICT) band in the UV-vis spectra (lambda(max) 430-450 nm). Cyclic voltammetric studies show two reversible one-electron oxidation processes for the R(3)TTF moiety, and a reversible two-electron reduction process for the TCNAQ moiety. The electron affinity of TCNAQ is significantly enhanced by the electron-withdrawing sulfonamide and sulfonic ester groups (compounds 17 and 18, respectively). Simultaneous electrochemistry and EPR (SEEPR) experiments show no significant intramolecular interaction between the R(3)TTF and TCNAQ moieties in compounds 11 and 18. X-ray crystallographic data are presented for 5, 11, and 20. The structure of 5 reveals hydrogen-bonded dimers. In molecule 11 the bond lengths and conformations of both donor and acceptor moieties are typical for neutral species. Compound 20 is an unusual calcium complex of TCNAQ derivative obtained by dicyanomethylation of anthraquinone-2-carboxylic acid.
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[structure: see text] A model system has been used to study the interactions of dipole-containing aromatic systems with oxidized and reduced flavin. Ab initio computational and experimental studies show that dipole orientation within the host is a critical determinant for recognition and redox behavior of the flavin guest.
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Numerous model studies of organic redox cofactor activity have appeared in the latter half of 1998 and the first half of 1999. These investigations include the use of solution models to explore flavin-dependent, quinone-dependent and pyrroloquinone-dependent redox processes, the exploration of flavin and quinone redox events using organized interfaces, and the application of computational methods to increase the understanding of flavin-catalyzed, nicotinamide-catalyzed and quinone-catalyzed redox processes.
We have developed a family of receptors designed to bind flavin derivatives using specific hydrogen bond interactions. These synthetic host molecules provide a model for specific flavoenzyme-cofactor interactions, allowing isolation and observation of the effects of hydrogen bonding on flavin NMR. We describe here the use of one of these receptors to study the effects of hydrogen bonding to O(2), N(3), and O(4) on flavin 1H and 13C NMR.