A series of poly (3,4-alkylenedioxypyrrole)s are reported as a new class of electronically conducting polymers exhibiting especially low oxidation potentials from ca. -0.6 to -0.4 V vs Fc/Fc + (equivalent to -0.15 to +0.05 V vs SCE) as desired for ambient stability of the doped and conducting states. These polymers exhibit unique combinations of multicolor electrochromism, switching from a red or orange neutral state to a light blue/gray doped state, passing through a darker intermediate state (brown), as examined by in situ colorimetry. High spectral contrast ratios have been measured throughout the visible region with a maximum ∆%T ) 76% at 534 nm for poly[3,4-(2,2-dimethylpropylenedioxy)pyrrole) (PProDOP-(CH3)2). PProDOP-(CH3)2 exhibits outstanding redox switching stability, being able to undergo 40 000 deep double-potential switches between its doped and neutral states (1 s, ∆%Tmax ) 76%) while retaining more than 90% of its electroactivity. A high level of stability to overoxidation has also been observed as these materials show limited degradation of their electroactivity at potentials 2 V above their half-wave potential. Triflate-doped free-standing films of PEDOP and PProDOP, having high electrical conductivities of 83 and 95 S/cm, respectively, have been obtained by galvanostatic deposition at low temperature (-7 °C).

A family of six donor-acceptor-donor monomers was synthesized using combinations of thiophene, 3,4-ethylenedioxythiophene and 3,4-ethylenedioxypyrrole as donor moieties, and cyanovinylene as the acceptor moiety, to understand the effects of modified donor ability on the optoelectronic and redox properties of the resulting electropolymerized materials. Spectroelectrochemistry, differential pulse voltammetry, and cyclic voltammetry results indicate band gaps ranging from 1.1 to 1.6 eV and suggest that these polymers can be both p-type and n-type doped at accessible potentials. In situ conductivity results indicate that the n-type conductivity magnitude is modest, and the conductivity profile indicates a redox conductivity mechanism as opposed to a delocalized electronic band mechanism as observed for p-type doping.

sulting mixture was stirred at room temperature for 12 h. From this mixture, polymer 7 was obtained as a bright yellow solid (1.20 g, 99 %) by suction filtration, followed by washing with a large volume of methanol and drying under vacuum at 50 C for 8 h. Anal. (calcd. Br± (C 17 Polymer 8: To a solution of polymer 7 (500 mg) in freshly distilled THF (50 mL) benzeneboronic acid (120 mg) was added and argon was bubbled through the mixture for 10 min. Pd(PPh 3 ) 4 (40 mg) and 1 M Na 2 CO 3 solution (2 mL) were added sequentially. The mixture was stirred and refluxed under argon for 90 h. THF was removed under vacuum and water (100 mL) was added to the flask. Suction filtration and washing with a large volume of water gave a light gray solid. The solid was dissolved in chloroform then filtered through Celite. The filtrate was precipitated in methanol followed by stirring for 24 h. Polymer 11: By analogy with the preparation and purification of polymer 7, 2,5-dibromo-4-hexylpyridine 6 (1.219 g, 3.797 mmol) and 2,5-dimethoxy-1,4-benzenediboronic acid 9 (0.857 g, 3.797 mmol) were polymerized to yield polymer 11 as a bright yellow solid (1.20 g, 90 % (m, 6 H, ±OMe); the aromatic proton signals have similar shapes to those of polymer 7, with five peaks at d 6.9, 7.3, 7.6, 8.0, and 8.6, with a total integral of 4.5 H.Polymer 12: By analogy with the preparation and purification of polymer 8, polymer 11 was treated with benzeneboronic acid (11.3 mg), Pd(PPh 3 ) 4 (2 mg), and 1 M Na 2 CO 3 solution (1 mL) in THF (10 mL) to yield polymer 12 as a light gray solid (85 mg Polymer 13: By analogy with the preparation of polymer 7, 2,5-dimethoxy-1,4-benzenediboronic acid 9 (0.565 g, 2.50 mmol) and 2,5-dibromopyridine (0.592 g, 2.50 mmol) were polymerized to yield polymer 13 (0.50 g, 94 %). Due to the low solubility of the polymer in ordinary organic solvents, further purification was not possible, apart from washing the solid with large volumes of water and methanol. Anal. (calcd. Br±(C 13 H 11 NO 2 ) 5 ± Br) C 63.03 (63.77), H 4.41 (4.53), N 4.67 (5.72), Br 11.17 (12.90). The polymer was essentially insoluble in standard NMR solvents, so no NMR data were recorded.Polymer 16: By analogy with the preparation of polymer 7, 1,4-benzenediboronic acid (0.416 g, 2.509 mmol) and the ditriflate 15 (1.150 g, 2.509 mmol) were polymerized to yield polymer 16 as a pale brown solid (0.41 g, 69 %). Attempted purification of the polymer involved dissolving the crude solid in hot o-dichlorobenzene and filtering through Celite under vacuum, then precipitating the polymer with ethanol, followed by suction filtration and washing the precipitate with a large volume of ethanol, and drying for 8 h at 50 C under vacuum.

No abstract

No abstract

No abstract

Hydrophobic amino acids of the group Leu, Ile, Val, Phe, and Met (LIVFM) are distributed in favored or suppressed patterns within protein sequences. The frequencies of all five-position combinations of * = LIVFM and C = non-LIVFM residues were analyzed in 48 proteins of known crystallographic structure. Some motifs were strongly preferred or suppressed; e.g., >**CC was favored (z = 3.5),

The ability of pore-forming proteins to interact with various analytes has found vast applicability in single molecule sensing and characterization. In spite of their abundance in organisms from all kingdoms of life, only a few pore-forming proteins have been successfully reconstituted in artificial membrane systems for sensing purposes. Lysenin, a pore-forming toxin extracted from the earthworm E. fetida, inserts large conductance nanopores in lipid membranes containing sphingomyelin. Here we show that single lysenin channels may function as stochastic nanosensors by allowing the short cationic peptide angiotensin II to be electrophoretically driven through the conducting pathway. Long-term translocation experiments performed using large populations of lysenin channels allowed unequivocal identification of the unmodified analyte by Liquid Chromatography-Mass Spectrometry. However, application of reverse voltages or irreversible blockage of the macroscopic conductance of lysenin channels by chitosan addition prevented analyte translocation. This investigation demonstrates that lysenin channels have the potential to function as nano-sensing devices capable of single peptide molecule identification and characterization, which may be further extended to other macromolecular analytes.