AT‐Specific DNA Binding of Binuclear Ruthenium Complexes at the Border of Threading Intercalation

The binuclear ruthenium complex [μ‐bidppz(phen)₄Ru₂]⁴⁺ has been extensively studied since the discovery of its unusual threading intercalation interaction with DNA, a binding mode with extremely slow binding and dissociation kinetics. The complex has been shown to be selective towards long stretches of alternating AT base pairs, which makes it interesting, for example, as a model compound for anti‐malaria drugs due to the high AT content of the genome of the malaria parasite P. falciparum. We have investigated the effect of bridging ligand structure on threading intercalation ability and found that length and rigidity as well as the size of the intercalated ring system are all factors that affect the rate and selectivity of the threading intercalation. In particular, we discovered a new DNA‐threading compound, [μ‐dppzip(phen)₄Ru₂]⁴⁺, which appears to be just at the border of being capable of threading intercalation and displays even greater selectivity for AT‐DNA than the parent compound, [μ‐bidppz(phen)₄Ru₂]⁴⁺.     

Development of a headspace-gas chromatography (HS-GC-PID-FID) method for the determination of VOCs in environmental aqueous matrices: Optimization, verification and elimination of matrix effect and VOC distribution on the Fortaleza Coast, Brazil

An analytical protocol combining a headspace technique with gas chromatography and detection by photoionization detector and flame ionization detector (HS-GC-PID-FID) was developed. This procedure was used to measure volatile organic compounds (VOCs) in environmental aqueous matrices and was applied in determination of VOCs on the coast of Fortaleza, Brazil. At optimum operating conditions, analytical figures of merit such as linearity (R ranged from 0.9983 to 0.9993), repeatability (5.62 to 9.63% and 0.02 to 0.19% for the quantitative and qualitative analyses, respectively), detection limits (0.22 to 7.48 μg L⁻¹) and sensibility were estimated. This protocol favors a fast sampling/sample preparation (in situ), minimizes the use of laboratory material, eliminates the matrix effect from environmental samples, and can be applied to river, estuarine and oceanic waters. The advantage of detectors in series is that a low sensitivity in detection in one is compensated by the other. Toluene was the most abundant VOC in the studied area, with an average concentration of 1.63 μg L⁻¹. It was followed by o-xylene (1.15 μg L⁻¹), trichloroethene (1.08 μg L⁻¹), benzene (0.86 μg L⁻¹), ethylbenzene (0.74 μg L⁻¹), carbon tetrachloride (0.55 μg L⁻¹), m/p-xylene (0.48 μg L⁻¹) and tetrachloroethene (0.46 μg L⁻¹), compounds which are very commonly detected in urban runoff from most cities. The results of the VOC distribution showed that port activity was not the main source of VOCs along the Fortaleza Coast, but that the contribution from urban runoff seemed more significant.     

Total synthesis of polycavernoside A, a lethal toxin of the red alga Polycavernosa tsudai

[structure: see text] Two approaches to the synthesis of the aglycon 120 of polycavernoside A (1) were developed, only one of which was completed. The successful "second-generation" route assembled the aglycon seco acids 102 and 106 via Nozaki-Hiyama-Kishi coupling of aldehyde 70, prepared from methyl (S)-3-hydroxy-2-methylpropionate (72) and (S)-pantolactone (73), with vinyl bromide 71. The latter was obtained from a sequence which commenced from the silyl ether 24 of 3-hydroxypropionaldehyde and entailed cyclization of (Z)-zeta-hydroxy-alpha,beta-unsaturated ester 82. Regioselective Yamaguchi lactonization of trihydroxycarboxylic acids 102 and 106 and subsequent functional-group adjustments led to macrolactone 120, to which the fucopyranosylxylopyranoside moiety was attached. Stille coupling of the glycosidated aglycon 128 with dienylstannane 129 furnished polycavernoside A in a synthesis for which the longest linear sequence was 25 steps. The overall yield to lactone 120 was 4.7%.     

Solvent effects on the intramolecular charge transfer character of N,N-diaryl dihydrophenazine catalysts for organocatalyzed atom transfer radical polymerization

The nature of intramolecular charge transfer (CT) of N,N-diaryl dihydrophenazine photocatalysts (PCs) in different solvents is explored in context of their performance in organocatalyzed atom transfer radical polymerization (O-ATRP). PCs having a computationally predicted lowest energy excited state exhibiting CT character can operate a highly controlled O-ATRP in a wide range of solvent polarities, from non-polar hexanes to highly polar N,N-dimethylacetamide. For PCs having a computationally predicted lowest energy excited state not possessing CT character, their ability to operate a controlled O-ATRP is decreased. This study confirms the importance of CT character in the excited state for N,N-diaryl dihydrophenazine PCs, and a deeper understanding of the activity of CT PCs has enabled the synthesis of polymers of low dispersity (<1.10) in a controlled fashion. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3017–3027     

Synthesis and antimicrobial activity of some novel benzofuran based 1,2,3-triazoles

In the present study, a series of novel {6-[(1H-1,2,3-triazol-4-yl)methoxy]-3-methylbenzofuran-2-yl}(phenyl)methanones (7a–7o) have been synthesized using click chemistry approach. The structures of all newly synthesized compounds were characterized by FT-IR, ¹H and ¹³C NMR, and MASS spectral data. Most of products demonstrated high antimicrobial activity.

     

Large deviation analysis for layered percolation problems on the complete graph

We analyze the large deviation properties for the (multitype) version of percolation on the complete graph – the simplest substitutive generalization of the Erd&0151;s‐Rènyi random graph that was treated in article by Bollobás et al. (Random Structures Algorithms 31 (2007), 3–122). Here the vertices of the graph are divided into a fixed finite number of sets (called layers) the probability of {u,v} being in our edge set depends on the respective layers of u and v. We determine the exponential rate function for the probability that a giant component occupies a fixed fraction of the graph, while all other components are small. We also determine the exponential rate function for the probability that a particular exploration process on the random graph will discover a certain fraction of vertices in each layer, without encountering a giant component.© 2011 Wiley Periodicals, Inc. Random Struct. Alg., 40, 460–492, 2012     

Testing the Weinberg-Salam model in polarized ed and ep deep inelastic scattering

Three independent tests of the Weinberg-Salam model in polarized ed and ep deep inelastic scattering are discussed for which the theoretical predictions depend only weakly on parton-model assumptions.     

Molecular reactors and machines: applications, potential, and limitations

Molecular reactors are miniature vessels for the assembly of reactants at the molecular level, in order to change the nature of chemical transformations. It seems probable that those that will find most immediate applications are those that change product ratios or give products which would not readily form in the absence of the reactors, and thereby afford easy access to materials that are otherwise difficult to obtain. Molecular machines consist of interrelated parts with separate functions and perform some kind of work, at the molecular level. Practical examples are likely to be relatively uncomplicated and not based on individual functions of single-molecule devices. Instead they will probably rely on extensive redundancy of the molecular components and their interactions and reactions, as well as of the machines themselves.