Using a Fragment‐Based Approach To Target Protein–Protein Interactions

The ability to identify inhibitors of protein–protein interactions represents a major challenge in modern drug discovery and in the development of tools for chemical biology. In recent years, fragment‐based approaches have emerged as a new methodology in drug discovery; however, few examples of small molecules that are active against chemotherapeutic targets have been published. Herein, we describe the fragment‐based approach of targeting the interaction between the tumour suppressor BRCA2 and the recombination enzyme RAD51; it makes use of a screening pipeline of biophysical techniques that we expect to be more generally applicable to similar targets. Disruption of this interaction in vivo is hypothesised to give rise to cellular hypersensitivity to radiation and genotoxic drugs. We have used protein engineering to create a monomeric form of RAD51 by humanising a thermostable archaeal orthologue, RadA, and used this protein for fragment screening. The initial fragment hits were thoroughly validated biophysically by isothermal titration calorimetry (ITC) and NMR techniques and observed by X‐ray crystallography to bind in a shallow surface pocket that is occupied in the native complex by the side chain of a phenylalanine from the conserved FxxA interaction motif found in BRCA2. This represents the first report of fragments or any small molecule binding at this protein–protein interaction site.     

High‐Temperature Creep Behavior of Dense SiOC‐Based Ceramic Nanocomposites: Microstructural and Phase Composition Effects

In this work, dense monolithic polymer‐derived ceramic nanocomposites (SiOC, SiZrOC, and SiHfOC) were synthesized via hot‐pressing techniques and were evaluated with respect to their compression creep behavior at temperatures beyond 1000°C. The creep rates, stress exponents as well as activation energies were determined. The high‐temperature creep in all materials has been shown to rely on viscous flow. In the quaternary materials (i.e., SiZrOC and SiHfOC), higher creep rates and activation energies were determined as compared to those of monolithic SiOC. The increase in the creep rates upon modification of SiOC with Zr/Hf relies on the significant decrease in the volume fraction of segregated carbon; whereas the increase of the activation energies corresponds to an increase of the size of the silica nanodomains upon Zr/Hf modification. Within this context, a model is proposed, which correlates the phase composition as well as network architecture of the investigated samples with their creep behavior and agrees well with the experimentally determined data.     

Probability distributions of gas hydrate formation

Induction time distributions for gas hydrate formation were measured for gas mixtures of methane + propane at pressures up to 11.3 MPa using a high‐pressure automated lag time apparatus (HP‐ALTA). Measurements were made at subcooling temperatures between 4.3 and 13.5 K and, while isothermal induction times between 0 and 15,000 s were observed, the median isothermal induction times for the distributions ranged from 100 to 4000 s. A hyperbolic relationship between median induction time and subcooling was used to correlate the data. A graphical interpretation is presented that relates the two types of data that can be acquired by using the HP‐ALTA in one of two modes to study hydrate formation: induction time distributions at constant subcooling and formation temperature distributions observed during linear cooling ramps. The equivalence of these two modes provides a robust method for studying the variation of formation phenomena in different hydrate systems. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2640–2646, 2013     

Effect of formulation and processing conditions on light shielding efficiency of thermotropic systems with fixed domains based on UV curing acrylate resins

Within this study relationships between material formulation and processing parameters and the morphology (vacuole formation) of thermotropic systems with fixed domains (TSFD) for overheating protection purposes were investigated. Main aim was on improving light shielding efficiency of TSFD based on UV curable acrylate resins by optimization of selected key parameters including photo‐initiator type and content, type of reactive diluent, radiation intensity/dose, and thermal treatment of layers during manufacturing. Variations of type of reactive diluent and thermal treatment had a minor effect on overheating protection performance. Utilization of photo‐bleaching photo‐initiator of acylphospine oxide type instead of a blend of conventional Type I (α‐hydroxy ketone type) and Type II (benzophenone) photo‐initiators enabled reduction of radiation dose to achieve properly cured layers. The results revealed that a significant reduction of radiation intensity/dose prevented formation of vacuoles. Consequently, light shielding efficiency of TSFD was enhanced significantly. Nevertheless, obtained scattering domain size was inappropriate for optimum light shielding efficiency and requires further optimization strategies. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3299–3310, 2013     

Discovery and Mechanism of Type III Secretion System Inhibitors

The Type III Secretion System (TTSS) is indispensable for virulence of many Gram-negative pathogenic bacteria, including Escherichia coli, Salmonella spp., Yersinia spp., Vibrio spp., Chlamydia spp., Shigella spp., Pseudomonas spp., Xanthomonas spp., and Auromonas spp. Such pathogenic bacteria are responsible for diseases such as plague, shigellosis, chlamydia, cholera, pneumonia, and gastroenteritis. This review offers insights into the known inhibitors of the TTSS, their discovery, and their mode of action.     

A Novel Route to Multiphase Polymer Systems Containing Nano‐Droplets: Radical Polymerization of Vinylic Monomers in Gelled Water‐in‐Oil Miniemulsions

Summary: A new strategy for the synthesis of composite polymers with larger volume fraction of aqueous inclusions less than 1 µm in diameter is presented. A water‐in‐oil miniemulsion of aqueous droplets in a continuous, cross‐linkable monomer phase is prepared. The addition of an organo‐gelator allows the immobilization of the droplets in a solid gel, thus avoiding the usual demixing upon polymerization of the continuous phase. This pregelled system is then converted into a composite polymer by photoinitiated free radical polymerization. Such coatings may be used for an improved climate control of buildings or as a deposit for the controlled release of actives from polar nano‐droplets.

SEM image of a cross‐linked composite polymer showing controlled droplet inclusions with a maximal diameter of 500 nm.     

P450 BM3 Monooxygenase as an Efficient NAD(P)H‐Oxidase for Regeneration of Nicotinamide Cofactors in ADH‐Catalysed Preparative Scale Biotransformations

Enzymatic oxidations of primary and secondary alcohols catalysed by nicotinamide dependent alcohol dehydrogenases on the preparative scale require cofactor regeneration systems. Of critical value from an economic and ecological perspective is the application of NAD(P)H‐oxidases, which utilise molecular oxygen as a cost‐effective, atom‐efficient and environmentally benign oxidant to regenerate the cofactor NAD(P)⁺. Herein, the P450 BM3 monooxygenase from Bacillus megaterium is presented as an NAD(P)H‐oxidase for the successful regeneration of both NADP⁺ and NAD⁺ on the preparative scale. This enzyme was exemplarily applied for ADH‐catalysed oxidative kinetic resolutions of racemic secondary alcohols and the desymmetrisation of a meso‐diol leading to enantiomerically enriched secondary alcohols in both cases. Furthermore, the ADH‐catalysed oxidation of a primary alcohol targeting the corresponding aldehyde was performed. The obtained results significantly broaden the scope of feasible oxidative biotransformations, thereby increasing the number of synthetic reactions complying with key challenges of a modern and sustainable chemistry such as mild reaction conditions, environmentally benign solvents, and biodegradable non‐toxic catalysts.

     

Separation of He/N2/CH4 ternary mixtures by a triple-reflux pressure swing adsorption process

Conventional pressure swing adsorption (PSA) processes can only produce one high purity product in a single stage, whereas the state-of-art dual-reflux PSA (DR-PSA) can produce two high purity products simultaneously. However, multicomponent gas separation is often required in the industry, targeting at recovering several valued products at the same time. In this study, we propose a novel adsorption process, namely triple-reflux PSA (TR-PSA), to separate three components simultaneously. A middle product outlet and a middle reflux stream were introduced to the adsorption columns of a conventional DR-PSA process to separate ternary mixtures of nitrogen, methane, and helium. Nonisothermal dynamic models were built to investigate the impacts of operating parameters particularly the location of the middle reflux/product stream and the middle reflux flow rates. Results showed that the TR-PSA process successfully separated ternary mixtures obtaining three enriched products simultaneously in a single stage, yielding a separation performance comparable to that of the double-stage DR-PSA with significantly lower capital and energy cost.