Bacterial Catabolism of Biphenyls: Synthesis and Evaluation of Analogues

A series of alkylated 2,3‐dihydroxybiphenyls has been prepared on the gram scale by using an effective Directed ortho Metalation–Suzuki–Miyaura cross‐coupling strategy. These compounds have been used to investigate the substrate specificity of the meta‐cleavage dioxygenase BphC, a key enzyme in the microbial catabolism of biphenyl. Isolation and characterization of the meta‐cleavage products will allow further study of related processes, including the catabolism of lignin‐derived biphenyls.     

Study of Lewis acid catalyzed chemical bromination and bromoalkylation of multi-walled carbon nanotubes

Chemical functionalization of carbon nanotubes (CNT) with nucleophiles requires introduction of electrophilic reactive sites on the CNTs. This can, for instance, be accomplished by the chemical bromination procedure with elemental bromine and a set of Lewis acids (BBr₃, BF₃ × Et₂O, AlBr₃, FeBr₃, ZnBr₂, TiBr₄, SiBr₄, SnBr₄, VBr₃) or a radical starter like dibenzoylperoxide (DBPO) in appropriate solvents at varied temperature. The present approach to electrophilic sites relies on the well-known electrophilic aromatic substitution or addition of bromine with aromatic structural units. In addition to the use of bromine, the introduction of haloalkyl groups was also investigated here using bis-electrophiles or haloalcohols and Brønsted acids. The advantages and drawbacks of the studied reaction conditions, the obtained degree of bromination as analyzed by X-ray photoelectron spectroscopy (XPS) and the amount of introduced bromine that can be substituted by a nucleophile are presented and discussed.     

Interaction of 1-allyl-3-methyl-imidazolium chloride and carbon black and its influence on carbon black filled rubbers

The interactions of the ionic liquid 1-allyl-3-methyl-imidazolium chloride (AMIMCl) with different grades of carbon black have been investigated using rheological measurements, differential scanning calorimetry and Raman spectroscopy. We could prove strong attractive interactions of AMIMCl with the carbon black surface, which result, for example, in the formation of an AMIMCl–carbon black–bucky gel and in an increased glass transition temperature of the ionic liquid in the presence of carbon black. Raman spectroscopy revealed that the AMIMCl is preferably attached to the edges of graphitic crystals at the carbon black surface, which have the highest adsorption energies. A surface treatment of different grades of carbon black with AMIMCl led to significant changes of the mechanical and electrical properties of different rubber compounds filled with carbon black, which can be attributed to a decreased filler–polymer interaction and a local plasticising effect of the AMIMCl at the carbon black surface.     

Dielectric relaxation of polar aromatics in unoriented and oriented linear low‐density polyethylene

The dielectric behavior of some polar aromatics dissolved in nonpolar unoriented and stretched linear low‐density polyethylene was investigated within the temperature region between 150 and 350 K. The measurements were carried out in the frequency range 1 kHz to 10 MHz. The maximum temperatures and the half widths of the loss tangent peaks depend upon the shape and the polar structure of guest molecules. Stretching the samples induced a shift of the loss tangent to higher temperatures, decreased the height, and increased the width of tan δ peak. The activation energy is also influenced by the type of guest molecules and orientation of polymer matrix. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1278–1282, 2001     

Influence of a modified fatty acid profile of egg yolk fat on technological properties of hen's eggs

A feeding experiment with brown layers was carried out to find effects of graded levels of rapeseed (without, 15% and 30%) in layer diets on the fatty acid composition of egg yolk and related functional properties of such modified eggs. A considerable increase of the content of essential n-3 fatty acids in egg yolk fat was noticed by including graded levels of rapeseed in layer diets. The destruction force of a gel prepared from whole egg was improved by the highest rapeseed level (30%) and emulsifying capacity by medium inclusion of rapeseed in layer diets (15%). The thermal stability of an emulsion prepared from whole egg was not influenced by rape feeding. Viscosity of mayonnaise prepared from egg yolk and whole egg yolk was decreased by increased rapeseed levels in the diets. In tendency, organoleptic evaluation of sponge cake prepared from whole egg revealed better results for the control group. The baking height of sponge cake was improved by rapeseed inclusion in layer diets. It may be assumed that all these changes caused by rapeseed feeding are closely related to the mentioned changes in the fatty acid profile.     

Development of low‐shrinkage composites based on novel crosslinking vinylcyclopropanes

Polymerization shrinkage of methacrylate‐based dental composites remains a major concern in restorative dentistry. Cyclic monomers that undergo ring‐opening polymerization are known to exhibit reduced polymerization shrinkage compared to methacrylates. In this article, the synthesis of four crosslinking 1,1‐disubstituted 2‐vinylcyclopropanes bearing rigid spacers is described. These monomers were synthesized by esterification of 1‐ethoxycarbonyl‐2‐vinylcyclopropane‐1‐carboxylic acid with the corresponding diols. The photopolymerization kinetics of these monomers was investigated by photo‐differential scanning calorimeter using bis(4‐methoxybenzoyl)diethylgermane as the photoinitiator. The synthesized vinylcyclopropanes (VCPs) were shown to be more reactive than the frequently used reactive diluent triethylene glycol dimethacrylate. Composites based on these VCPs showed good mechanical properties and exhibited a significantly reduced volumetric shrinkage and shrinkage stress compared to a corresponding dimethacrylate‐based restorative material. This work highlights the excellent potential of VCPs as alternatives to methacrylates in the development of low‐shrinkage dental composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45577.     

Design of S‐Allylcysteine in Situ Production and Incorporation Based on a Novel Pyrrolysyl‐tRNA Synthetase Variant

The noncanonical amino acid S‐allyl cysteine (Sac) is one of the major compounds of garlic extract and exhibits a range of biological activities. It is also a small bioorthogonal alkene tag capable of undergoing controlled chemical modifications, such as photoinduced thiol‐ene coupling or Pd‐mediated deprotection. Its small size guarantees minimal interference with protein structure and function. Here, we report a simple protocol efficiently to couple in‐situ semisynthetic biosynthesis of Sac and its incorporation into proteins in response to amber (UAG) stop codons. We exploited the exceptional malleability of pyrrolysyl‐tRNA synthetase (PylRS) and evolved an S‐allylcysteinyl‐tRNA synthetase (SacRS) capable of specifically accepting the small, polar amino acid instead of its long and bulky aliphatic natural substrate. We succeeded in generating a novel and inexpensive strategy for the incorporation of a functionally versatile amino acid. This will help in the conversion of orthogonal translation from a standard technique in academic research to industrial biotechnology.     

Biocatalytic Asymmetric Phosphorylation Catalyzed by Recombinant Glycerate‐2‐Kinase

The efficient synthesis of pure d ‐glycerate‐2‐phosphate is of great interest due to its importance as an enzyme substrate and metabolite. Therefore, we investigated a straightforward one‐step biocatalytic phosphorylation of glyceric acid. Glycerate‐2‐kinase from Thermotoga maritima was expressed in Escherichia coli, allowing easy purification. The selective glycerate‐2‐kinase‐catalyzed phosphorylation was followed by ³¹P NMR and showed excellent enantioselectivity towards phosphorylation of the d ‐enantiomer of glyceric acid. This straightforward phosphorylation reaction and subsequent product isolation enabled the preparation of enantiomerically pure d ‐glycerate 2‐phosphate. This phosphorylation reaction, using recombinant glycerate‐2‐kinase, yielded d ‐glycerate 2‐phosphate in fewer reaction steps and with higher purity than chemical routes.     

Rational Structure-Based Design of Fluorescent Probes for Amyloid Folds

Amyloid fibrils are pathological hallmarks of various human diseases, including Parkinson's, Alzheimer's, amyotrophic lateral sclerosis (ALS or motor neurone disease), and prion diseases. Treatment of the amyloid diseases are hindered, among other factors, by timely detection and therefore, early detection of the amyloid fibrils would be beneficial for treatment against these disorders. Here, a small molecular fluorescent probe is reported that selectively recognize the fibrillar form of amyloid beta(1–42), α-synuclein, and HET-s(218–289) protein over their monomeric conformation. The rational design of the reporters relies on the well-known cross-β-sheet repetition motif, the key structural feature of amyloids.