In situ growth of interdigitated electrodes made of polypyrrole for active fiber composites

Active fiber composites are electromechanical actuators based on piezo-ceramic fibers, which are embedded in a polymer matrix. The fibers are electrically contacted through so-called interdigitated electrodes (IDEs). State-of-the-art metallic IDEs only contact the fibers at two small sections of their circumference at the top and bottom of the composite ply, respectively. This paper presents an original technique to manufacture IDEs made of a conducting polymer (polypyrrole/p-toluene sulfonic acid), where the polymer electrodes contact the fibers around their whole circumference. The necessary process steps are discussed, namely design of the master electrodes and electrochemical polymer growth with and without fibers. Processing issues are discussed and solutions are suggested. Copyright © 2007 John Wiley & Sons, Ltd.     

Mapping protein pockets through their potential small-molecule binding volumes: QSCD applied to biological protein structures

Previously we demonstrated a method, Quantized Surface Complementarity Diversity (QSCD), of defining molecular diversity by measuring shape and functional complementarity of molecules to a basis set of theoretical target surfaces [Wintner E.A. and Moallemi C.C., J. Med. Chem., 43 (2000) 1993]. In this paper we demonstrate a method of mapping actual protein pockets to the same basis set of theoretical target surfaces, thereby allowing categorization of protein pockets by their properties of shape and functionality. The key step in the mapping is a `dissection' algorithm that breaks any protein pocket into a set of potential small molecule binding volumes. It is these binding volumes that are mapped to the basis set of theoretical target surfaces, thus measuring a protein pocket not as a single surface but as a collection of molecular recognition environments.     

The interaction of highly helical structural mutants with the NOP receptor discloses the role of the address domain of nociceptin/orphanin FQ

Nociceptin is a heptadecapeptide whose sequence is similar to that of Dynorphin A, sharing a message domain characterized by two glycines and two aromatic residues, and a highly basic C-terminal address domain but, in spite of these similarities, displays no opioid activity. Establishing the relative importance of the message and address domains of nociceptin has so far been hampered by its extreme conformational flexibility. Here we show that mutants of this peptide, designed to increase the helical content in the address domain, can be employed to explain the mode of interaction with the NOP receptor. Nociceptin analogues in which Ala residues are substituted with aminoisobutyric acid (Aib) show a substantial increment of activity in their interaction with the NOP receptor. The increment of biological activity was attributed to the well-documented ability of Aib to induce helicity. Here we have verified this working hypothesis by a conformational investigation extended to new analogues in which the role of Aib is taken up by Leu. The NMR conformational analysis confirms that all Ala/Aib peptides as well as [Leu(7,11)]-N/OFQ-amide and [Leu(11,15)]-N/OFQ-amide mutants (N/OFQ=nociceptin/orphanin FQ) have comparable helix content in helix-promoting media. We show that the helical address domain of nociceptin can place key basic residues at an optimal distance from complementary acidic groups of the EL(2) loop of the receptor. Our structural data are used to rationalize pharmacological data which show that although [Leu(11,15)]-N/OFQ-amide has an activity comparable to those of Ala/Aib peptides, [Leu(7,11)]-N/OFQ-amide is less active than N/OFQ-amide. We hypothesize that bulky residues cannot be hosted in or near the hinge region (Thr(5)-Gly(6)-Ala(7)) without severe steric clash with the receptor. This hypothesis is also consistent with previous data on this hinge region obtained by systematic substitution of Thr, Gly, and Ala with Pro.     

Synthesis, Characterization, and Catalytic Activity of Rh(I) Complexes with (S)-BINAPO, an Axially Chiral Inducer Capable of Hemilabile P,O-Heterobidentate Coordination

Summary.  The reaction of dinuclear rhodium(I) derivatives of the formula [Rh(DIOL)X]₂ with the axially chiral phosphinyl phosphane 2-(diphenylphosphinyl)-2′-(diphenylphosphanyl)-1,1′-binaphthalene ((S)-BINAPO, 1) leads to the formation of cationic complexes [(BINAPO)Rh(DIOL)]⁺ where the ligand (S)-BINAPO consistently displays a P,O-chelate coordination which is mantained even in solvents of fair polarity. The mononuclear rhodium(I) complexes (S)-2-diphenylphosphanyl-2′-diphenylphosphinyl-1,1′-binaphthalene-(1,5-cyclooctadiene) rhodium tetrafluoroborate (3b) and (S)-2-diphenylphosphanyl-2′-diphenylphosphinyl-1,1′-binaphthalene-(1,4-norbornadiene) rhodium tetrafluoroborate (3c) with 1,5-cyclooctadiene (COD) and 2,5-norbornadiene (NBD) as the diolefin were isolated and characterized. Both show a fluxional behaviour in solution which is due to the mobility of the diolefin rather than to a displacement-recombination of the oxygenated arm of the ligand. The mobility of the 1,4-norbornadiene ligand in 3c is extremely pronounced and the coordinated diolefin flexibility could be frozen only at about 200 K. These complexes are active but poorly stereoselective catalysts for the hydrogenation, hydroboration, and hydroformylation of alkenes. Received June 16, 2000. Accepted (revised) July 24, 2000     

Palladium-Nanoparticle-Catalysed Ullmann Reactions in Ionic Liquids with Aldehydes as the Reductants: Scope and Mechanism

An efficient Ullmann-type reductive homocoupling of aryl, vinyl and heteroaryl halides can be promoted by an aldehyde in tetraalkylammonium ionic liquids under very mild reaction conditions. This simple procedure generates symmetrical biaryls under relatively mild conditions. The ionic liquid is crucial for this process because it behaves simultaneously as a base, ligand and reaction medium. The role of the aldehyde is also discussed and a general mechanism for this unusual reaction is proposed. These results open the way to a new efficient method of Pd-catalysed dehydrogenation of carbonyl compounds.