Alternating carbazole−quinoline and phenothiazine−quinoline donor−acceptor conjugated copolymers and a corresponding oligomer were synthesized, and their solution and solid-state photophysics were investigated. The new copolymers, poly(2,2‘-9-methyl-3,6-carbazolylene-6,6‘-bis(4-phenylquinoline)) and poly(2,2‘-10-methyl-3,7-phenothiazylene-6,6‘-bis(4-phenylquinoline)), had intrinsic viscosities of 11.2−22.0 dL/g, indicating very high molecular weights. The optical band gaps of the new copolymers were 2.35−2.64 eV, which are significantly smaller than the corresponding homopolymers. The absorption and emission spectra of the related donor−acceptor oligomers, 3,6-[bis(4-phenyl-2-quinolyl)]-9-methylcarbazole and 3,7-[bis(4-phenyl-2-quinolyl)]-10-methylphenothiazine, in solvents of varying polarity showed positive solvatochromism. An unusual dual fluorescence, with a blue emission band at 454 nm and an orange emission band at 584 nm, was observed in solid films of the carbazole-linked oligomer and related to intramolecular excitons and intermolecular excimers. Solid-state emission from the phenothiazine oligomer and copolymer was from intramolecular excitons with strong charge-transfer character. The red solid-state emission from the carbazole copolymer originated from intermolecular excimers with dominant fluorescence lifetimes of 2−10 ns. The observed intramolecular charge-transfer effects on photophysics and properties were larger in the phenothiazine-containing oligomer and copolymer than the corresponding carbazole-containing materials, reflecting the fact that phenothiazine is a stronger electron-donating unit. Preliminary results suggest that the oligomers and copolymers are useful for light-emitting and photovoltaic devices.

This ''Applications'' article focuses on superquenching of the fluorescence of conjugated polyelectrolytes and related fluorescent polyelectrolytes and its applications to biosensing. Superquenching can occur for both aqueous solutions of these polymers as well as for various supported formats. For biosensing the supported formats are generally most practical. Three practical sensing applications are reviewed: nucleic acids, protease enzyme activity assays and kinase/phosphatase assays based on metal-ion-mediated superquenching.

Herein we describe studies that indicate a cationic conjugated polyelectrolyte shows biocidal activity against gram-negative bacteria (Escherichia coli, E. coli, BL21, with plasmids for Azurin and ampicillin resistance) and gram-positive bacterial spores (Bacillus anthracis, Sterne, B. anthracis, Sterne). These studies were carried out with aqueous suspensions of the conjugated polyelectrolyte, with the polyelectrolyte in supported formats and with samples in which the conjugated polyelectrolyte was coated on the bacteria. The results are interesting in that the biocidal activity is light-induced and appears effective due to the ability of the conjugated polyelectrolyte to form a surface coating on both types of bacteria. The effects observed here should be general and suggest that a range of conjugated polyelectrolytes in different formulations may provide a useful new class of biocides for both dark and light-activated applications.

Approaches using metabolic engineering and synthetic biology to overproduce terpenoids, such as the precursors of taxol and artemisinin, in microbial systems have achieved initial success. However, due to the lack of steady-state kinetic information and incomplete understanding of the terpenoid biosynthetic pathway, it has been difficult to build a highly efficient, universal system. Here, we reconstituted the mevalonate pathway to produce farnesene (a precursor of new jet fuel) in vitro using purified protein components. The information from this in vitro reconstituted system guided us to rationally optimize farnesene production in E. coli by quantitatively overexpressing each component. Targeted proteomic assays and intermediate assays were used to determine the metabolic status of each mutant. Through targeted engineering, farnesene production could be increased predictably step by step, up to 1.1 g/L (∼ 2,000 fold) 96 h after induction at the shake-flask scale. The strategy developed to release the potential of the mevalonate pathway for terpenoid overproduction should also work in other multistep synthetic pathways.