Hybrid Conjugated Organic Oligomers Consisting of Oligodiacetylene and Thiophene Units: Synthesis and Optical Properties

Novel and highly soluble hybrid conjugated organic oligomers consisting of oligodiacetylene and thiophene units have been synthesized in high purity through iterative and divergent approaches based on a sequence of Sonogashira reactions. The series of thiophene‐containing oligodiacetylenes (ThODAs) and homocoupled ThODAs (HThODAs) show—both in solution and in the solid state—a strong optical absorption, which is progressively red shifted with increasing chain length. The linear correlation of the absorption maximum (λ^A_max) with the inverse of conjugation length (CL=number of double and triple bonds) shows that the effective conjugation length of this system is extended up to at least CL=20. Furthermore, absorption measurements of dropcast thin films display not only a bathochromic shift of the absorption maxima but also a higher wavelength absorption, which is attributed to increased π–π interactions. The wavelength of the maximum fluorescence emission (λ^E_max) also increases with CL, and emission is maximal for oligomers with CL=7–12 (fluorescence quantum yield Φ_F=～0.2). Both longer and shorter oligomers display marginal emission. The calculated Stokes shifts of these planar materials are relatively large (0.4 eV) for all oligomers, and likely due to excitation to the S₂ state, thus suggesting that the presence of enyne moieties dominates the ordering of the lowest excited states. The fluorescence lifetimes (τ_F) are short (τ_F,_max=?1 ns) and closely follow the tendency obtained for the fluorescence quantum yield. The anisotropy lifetimes show a near‐linear increase with CL, in line with highly rigid oligomers.     

Synthesis of poly(arylene ether ketone)s bearing skeletal crown ether units for cation exchange membranes

Poly(arylene ether ketone)s (PAEKs) are the most commonly known high‐performance materials used for ion exchange and fuel cell membranes. Described here is the design of novel sulfonated PAEKs (SPAEKs) and nonsulfonated PAEKs containing crown ether units in the main chain, which can be used in sensing applications and ion‐selective membranes. To this end, 4,4′(5′)‐di(hydroxybenzo)‐18‐crown‐6 was synthesized and used as monomer in a step growth polymerization to form crown ether‐containing PAEKs and SPAEKs. The successful synthesis of PAEKs containing 18‐crown‐6 and sulfonate groups was confirmed by gel permeation chromatography, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. Membranes are fabricated from the sulfonated polymers. Potassium ion transport properties of the SPAEK and crown ether‐containing SPAEK membranes are assessed by diffusion dialysis. Potassium ion diffusion in the crown ether‐containing SPAEK membranes is almost four times lower than K⁺ diffusion in the native polymer membranes, without crown ether. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2786–2793     

In Vivo Effects on Photosynthesis Gene Expression of Base Pair Exchanges in the Gene Encoding the Light-responsive BLUF Domain of AppA in Rhodobacter Sphaeroides

The Rhodobacter sphaeroides protein AppA has the unique quality of sensing and transmitting light and redox signals. By acting as antirepressor to the PpsR protein, it acts as a major regulator in photosynthesis gene expression. In this study, we show that by introducing amino acid exchanges into the AppA protein, the in vivo activity as an antirepressor can be greatly altered. The tryptophan 104 to phenylalanine (W104F) base exchange greatly diminished blue-light sensitivity of the BLUF domain. From the obtained in vivo data, the difference in thermal recovery rate of the signaling state of the BLUF domain between the wild type and mutated protein was calculated, predicting an about 10-fold faster recovery in the mutant, which is consistent with in vitro data. Introduction of a tyrosine 21 to phenylalanine (Y21F) or to cysteine (Y21C) mutation led to a complete loss of AppA antirepressor activity, while additionally leading to an increase of photosynthesis gene expression after illumination with high blue-light quantities. Interestingly, this effect is not visible in a W104F/Y21F double mutant that again shows a wild-type–like behavior of the BLUF domain after blue-light illumination, thus restoring the activity of AppA.     

Use of a ruthenium-containing conjugated polymer as a photosensitizer in photovoltaic devices fabricated by a layer-by-layer deposition process

Multilayer polymer films composed of a ruthenium terpyridine complex containing poly(p-phenylenevinylene) (Ru-PPV) and sulfonated polyaniline (SPAN) were prepared by a layer-by-layer electrostatic self-assembly deposition. The deposition process was carried out from SPAN solution in water and Ru-PPV in dimethylformamide (DMF). Optical-quality multilayer thin films were obtained. The film growth process was monitored by quartz crystal microbalance, and the surface morphology of the films was studied by atomic force microscopy. It was found that the properties of the multilayer films were dependent on deposition conditions such as the pH of the SPAN solution, the presence of salt in the polymer solutions, and the post-film-forming thermal annealing process. Cross-section transmission electron microscopic images suggested that there was no stratified structure formed in the multilayer films. Photovoltaic cells were fabricated by sandwiching the multilayer films between indium-tin-oxide and aluminum electrodes. The device performances were examined by illumination with AM 1.5 simulated solar light. The power conversion efficiencies of these devices were on the order of 10(-3)%. The maximum incident photon-to-electron conversion efficiency (IPCE) of the devices was found to be approximately 2% at 510 nm, which is consistent with the absorption maximum of the ruthenium complex. This indicates that the photosensitization process is due to the electronic excitation of the ruthenium complex.     

Global test for metabolic pathway differences between conditions

In many metabolomics applications there is a need to compare metabolite levels between different conditions, e.g., case versus control. There exist many statistical methods to perform such comparisons but only few of these explicitly take into account the fact that metabolites are connected in pathways or modules. Such a priori information on pathway structure can alleviate problems in, e.g., testing on individual metabolite level. In gene-expression analysis, Goeman's global test is used to this extent to determine whether a group of genes has a different expression pattern under changed conditions. We examined if this test can be generalized to metabolomics data. The goal is to determine if the behavior of a group of metabolites, belonging to the same pathway, is significantly related to a particular outcome of interest, e.g., case/control or environmental conditions. The results show that the global test can indeed be used in such situations. This is illustrated with extensive intracellular metabolomics data from Escherichia coli and Saccharomyces cerevisiae under different environmental conditions.     

Mean Location and Sample Mean Location on Manifolds: Asymptotics, Tests, Confidence Regions

In a previous investigation we studied some asymptotic properties of the sample mean location on submanifolds of Euclidean space. The sample mean location generalizes least squares statistics to smooth compact submanifolds of Euclidean space. In this paper these properties are put into use. Tests for hypotheses about mean location are constructed and confidence regions for mean location are indicated. We study the asymptotic distribution of the test statistic. The problem of comparing mean locations for two samples is analyzed. Special attention is paid to observations on Stiefel manifolds including the orthogonal groupO(p) and spheresS^k−1, and special orthogonal groupsSO(p). The results also are illustrated with our experience with simulations.