The photodecomposition products of Ru(bpy)3(2+) in water, in aqueous buffered solutions and encapsulated in zeolite-Y have been analyzed by chromatography and UV-visible spectroscopy. The chromatographic method is found to be capable of separating species with the same charge but slightly different ligands as well as geometrical isomers. In all the systems investigated, photodecomposition proce...

The self-assembly and solid-state semiconducting properties of single crystals of a trisradical tricationic complex composed of the diradical dicationic cyclobis(paraquat-p-phenylene) (CBPQT(2(•+))) ring and methyl viologen radical cation (MV(•+)) are reported. An organic field effect transistor incorporating single crystals of the CBPQT(2(•+))⊂MV(•+) complex was constructed using lithographic ...

Environmental exposure to the oxidant-producing herbicide, paraquat (PQ) (1,1'-dimethyl-4,4'-bipyridinium dichloride) has long been implicated as a risk factor in Parkinson's disease (PD). PQ-induced oxidative stress has been exploited as a model to screen putative neuroprotective compounds employing Drosophila. In the present study, we investigated the prophylactic efficacy of Bacopa monnieri ...

Sepiapterin reductase (SPR) catalyzes the reduction of sepiapterin to dihydrobiopterin (BH2), the precursor for tetrahydrobiopterin (BH4), a cofactor critical for nitric oxide biosynthesis and alkylglycerol and aromatic amino acid metabolism. SPR also mediates chemical redox cycling, catalyzing one-electron reduction of redox-active chemicals, including quinones and bipyridinium herbicides (e.g...

Oxygen reduction by chloroplast lamellae is catalyzed by low potential redox dyes with E'0 values between -0 .38 V and -0 .6 V. Compounds of E'0 values o f -0 .67 V and lower are inactive. In subchloroplast particles with an active photosystem I but devoid of photosynthetic electron transport between the two photosystems, the active redox compounds enhance chlorophyll bleaching, superoxide form...

Enterobacter cloacae NAD(P)H:nitroreductase (NR; EC 1.6.99.7) catalyzes two-electron reduction of a series of quinoidal compounds according to a "ping-pong" scheme, with marked substrate inhibition by quinones. The steady-state catalytic constants (k(cat)) range from 0.1 to 1600s(-1), and bimolecular rate constants (k(cat)/K(m)) range from 10(3) to 10(8)M(-1)s(-1). Quinones, nitroaromatic compo...

The development of a simple approach to studying self-assembly processes in the chemical laboratory began with an investigation of the donor/acceptor complexes formed between (a) crown ethers, like bisparaphenylene-34crown10, and 4,4 '-bipyridinium dications, such as paraquat, and (b) tetracationic cyclophanes, like cyclobis(paraquat-p-phenylene), and neutral substrates, such as 1.4dimethoxyben...

We report the synthesis of a series of homologous oligoviologens in which different numbers of 4,4'-bipyridinium (BIPY(2+)) subunits are linked by p-xylylene bridges, as a prelude to investigating how their radical cationic forms self-assemble both in solution and in the solid state. The strong radical-radical interactions between the radical cationic forms of the BIPY(2+) units-namely, BIPY(•+...

Cells in the nervous system (NS) are exposed to a strong and constant production of reactive oxygen and nitrogen species (RS) because of their highly demanding metabolism. This oxidative load is tightly regulated to sustainable limits by an effective array of antioxidant proteins and compounds. However, physiological aging and a number of genetic and environmentally-induced degenerative disease...

By incorporating the concepts of structural preorganisation and complementarity in concert with non-covalent donor-acceptor [ππ] and hydrophobic interactions, a duo of π-electron deficient bipyridinium-based linear and gemini amphiphiles capable of responding to molecular templation have been designed and synthesised. When combined with π-electron rich di(ethylene glycol)-disubstituted 1,5-dihy...