The design, synthesis, and characterization of the first cavitand-based de novo hetero-template-assembled synthetic proteins (Hetero-TASPs)

The design, synthesis, and characterization of novel cavitand-based hetero-TASPs, TASPs having different peptide sequences within one bundle, are described. Three families of hetero-TASPs were designed: the LG3/LG2 family (different linker lengths), LG3/AG3 family (altering helix hydrophobicity), and the LG3/LG2C family (anti-parallel caviteins). These first generation hetero-TASPs were found to be alpha-helical, stable towards guanidine hydrochloride, and monomeric in solution. The LG3/LG2 caviteins exhibited primarily native-like properties. The remaining hetero-TASP families were found to exhibit less dispersion and broader signals in the amide regions of their (1)H NMR spectra than their respective reference caviteins. The success in the design of the LG3/LG2 hetero-TASPs suggests that subsequent hetero-TASPs may have potential to manifest superior native-like structure compared with homo-TASPs, and refinement of the linker and peptide sequences may accomplish this goal.     

Fabrication of graphene-based porous materials: traditional and emerging approaches

The anisotropic nature of ‘graphenic’ nanosheets enables them to form stable three-dimensional porous materials. The use of these porous structures has been explored in several applications including electronics and batteries, environmental remediation, energy storage, sensors, catalysis, tissue engineering, and many more. As method of fabrication greatly influences the final pore architecture, and chemical and mechanical characteristics and performance of these porous materials, it is essential to identify and address the correlation between property and function. In this review, we report detailed analyses of the different methods of fabricating porous graphene-based structures – with a focus on graphene oxide as the base material – and relate these with the resultant morphologies, mechanical responses, and common applications of use. We discuss the feasibility of the synthesis approaches and relate the GO concentrations used in each methodology against their corresponding pore sizes to identify the areas not explored to date.

Due to their anisotropic nature, graphene nanosheets can be used to form 3-dimensional porous materials using template-free and template-directed methodologies. These fabrication strategies are found to influence the properties of the final structure.     

Detection of Bisphenol A and Four Analogues in Atmospheric Emissions in Petrochemical Complexes Producing Polypropylene in South America

Because of its toxicity and impacts on the environment and human health, bisphenol A (BPA) has been controlled in numerous industrialized nations, increasing demand for bisphenol analogues (BP) for its replacement. However, the consequences of these chemicals on the environment and the health of persons exposed to their emissions are still being researched. The emissions from polypropylene manufacturing facilities in Colombia and Brazil were evaluated in this study, and the presence of bisphenol A and four BPs was detected among the gaseous compounds released, with total concentrations of BPs (∑BP) between 92 and 1565 ng g⁻¹. As the melt flow index (MFI) of the polymer rises, so does the quantity of volatiles in its matrix that are eliminated during deodorization, indicating that the MFI and the amount of bisphenol released have a directly proportional connection.     

Synthesis of new o-alkyl substituted arylalkylphosphanes: study of their molecular structure and influence on rhodium-catalyzed propene and 1-hexene hydroformylation

A set of new phosphane ligands designed to increase the branched-to-normal ratio of the hydroformylation reaction were prepared in the same way as the previously reported ortho-alkyl substituted arylphosphanes, which have shown increased i/n ratios in the hydroformylation of propene and 1-hexene. In order to determine the relationship between the catalytic behavior and stereoelectronic properties of the ligands, various functional alkyl groups (methyl, isopropyl, cyclohexyl) were placed on the phosphorus atom directly and in the ortho position of the phenyl ring connected to phosphorus. In the hydroformylation reaction of propene and 1-hexene a higher i/n ratio resulted with nearly all the ligands compared with that of triphenylphosphane. Additionally as the ortho-alkyl-substituent became larger, it had a favorable effect on the i-selectivity. Characterization of the ligands was carried out by NMR spectroscopy (mainly ¹H, ³¹P{¹H}, ¹³C{¹H}, HSQC/HETCOR and COSY-90). Properties of the ligands were also studied by quantum mechanical calculations and by synthesizing three Rh(acac)(CO)(PR₃) derivatives. The o-alkyl-substituent was orientated outside the ligands’ cone angle in the X-ray crystal structures of (2-cyclohexylphenyl)dicyclohexylphosphane and (2,5-dimethylphenyl)bis(4-pyridyl)phosphane, and Rh(acac)(CO)(PR₃) complex of (2-methylphenyl)dicyclohexylphosphane.     

Facile synthesis of aliphatic isothiocyanates and thioureas on solid phase using peptide coupling reagents

Peptide coupling reagents can be used as versatile reagents for the formation of aliphatic isothiocyanates and thioureas on solid phase from the corresponding solid-phase anchored aliphatic primary amines. The formation of the thioureas is fast and highly chemoselective, and proceeds via formation of the intermediate isothiocyanate. The isothiocyanate and subsequent thiourea formation take place under standard peptide coupling conditions using carbon disulfide as the ‘amino acid’. The thioureas are released from the resin and isolated in moderate to high yields.     

NMR Spectroscopic Characterization of Isocyano‐ and 1, 1′‐Diisocyanoferrocene. The Molecular Structure of Isocyanoferrocene

Isocyanoferrocene ( 1 ) and 1, 1′‐diisocyanoferrocene ( 2 ) were prepared and studied by ¹H, ¹³C, ¹⁴N and ⁵⁷Fe NMR spectroscopy in order to gain a more complete data set. The NMR data of 1 (chemical shifts and coupling constants) were calculated by DFT methods [B3LYP/6‐311+G(d, p)] and compare favourably with experimental data. The molecular structure of 1 was determined by X‐ray structural analysis, and an almost undistorted ferrocene‐like geometry was found.     

Transfer and propagation reactions in free-radical copolymerization

The contribution of entropic factors to the penultimate unit effect in free-radical copolymerizations is discussed and exemplified. In addition, significant penultimate unit effects on radical selectivity in transfer reactions are demonstrated and are shown to have a significant polar component. Further, ring-opening copolymerization studies are presented and describe surprising results that seem to originate from strong solvent effects in copolymerization. These results could not have been predicted with current knowledge, prior to the experiment. The present contribution demonstrates in detail that radical reactions are highly complex and there are significant dangers and drawbacks in employing simplified kinetic models when in search of fundamental understanding.     

Disproof of the neighborhood conjecture with implications to SAT

We study a special class of binary trees. Our results have implications on Maker/Breaker games and SAT: We disprove a conjecture of Beck on positional games and construct an unsatisfiable k-CNF formula with few occurrences per variable, thereby improving a previous result by Hoory and Szeider and showing that the bound obtained from the Lovász Local Lemma is tight up to a constant factor. A (k, s)-CNF formula is a boolean formula in conjunctive normal form where every clause contains exactly k distinct literals and every variable occurs in at most s clauses. The (k, s)-SAT problem is the satisfiability problem restricted to (k, s)-CNF formulas. Kratochvíl, Savický and Tuza showed that for every k≥3 there is an integer f(k) such that every (k, f(k))-CNF formula is satisfiable, but (k, f(k) + 1)-SAT is already NP-complete (it is not known whether f(k) is computable). Kratochvíl, Savický and Tuza also gave the best known lower bound $f(k) = \Omega \left( {\tfrac{{2^k }} {k}} \right)$ , which is a consequence of the Lovász Local Lemma. We prove that, in fact, $f(k) = \Theta \left( {\tfrac{{2^k }} {k}} \right)$ , improving upon the best known upper bound $O\left( {(\log k) \cdot \tfrac{{2^k }} {k}} \right)$ by Hoory and Szeider. Finally we establish a connection between the class of trees we consider and a certain family of positional games. The Maker/Breaker game we study is as follows. Maker and Breaker take turns in choosing vertices from a given n-uniform hypergraph $\mathcal{F}$ , with Maker going first. Maker’s goal is to completely occupy a hyperedge and Breaker tries to prevent this. The maximum neighborhood size of a hypergraph $\mathcal{F}$ is the maximal s such that some hyperedge of $\mathcal{F}$ intersects exactly s other hyperedges. Beck conjectures that if the maximum neighborhood size of $\mathcal{F}$ is smaller than 2 ^n?1 ? 1 then Breaker has a winning strategy. We disprove this conjecture by establishing, for every n≥3, the existence of an n-uniform hypergraph with maximum neighborhood size 3·2 ^n?3 where Maker has a winning strategy. Moreover, we show how to construct, for every n, an n-uniform hypergraph with maximum degree at most $\frac{{2^{n + 2} }} {n}$ where Maker has a winning strategy. In addition we show that each n-uniform hypergraph with maximum degree at most $\frac{{2^{n - 2} }} {{en}}$ has a proper halving 2-coloring, which solves another open problem posed by Beck related to the Neighborhood Conjecture.     

Chemistry and morphology of dried‐up pollen suspension residues

Pollen grains are covered with lots of different biochemical compounds, like proteins, saccharides and lipids, which are only loosely attached to the pollen. Therefore, they can be separated from the pollen by suspending them in water. Since these compounds play a key role in many atmospheric processes (e.g. cloud condensation nucleation, ice nucleation, aerial allergen exposure), their separation and analyzing are of interest. The chemical composition of whole pollen grains is compared by both Raman and infrared spectroscopy with material that could be extracted from pollen with water. The dominant signals in the pollen grain Raman spectra are those from sporopollenin and carotenoids. These bands decrease in the washing water spectra, since sporopollenin is high molecular and thus is not extractable. The released material shows in turn a chemical composition that differs significantly between species, what is quite expected, since they differ even in the optical properties of their aqueous suspensions. The FTIR spectra show some additional bands to appear in comparison to the Raman spectra. Furthermore, we investigated the pollen rupturing and material release in the aqueous suspensions by drying them up and picturing the residues with a scanning electron microscope. We saw that corn pollen ejected loads of micrometer‐sized organelles, which are most likely starch granules. The more the pollen disrupted, the more the measured samples were covered with an amorphous film, which consists of the extracted pollen material, like lipids, sugars, and proteins – the same substances we detected by spectroscopy. Copyright © 2013 John Wiley & Sons, Ltd.