Isolated β‐Turn Model Systems Investigated by Combined IR/UV Spectroscopy

The functionality of bioactive molecules sensitively depends on their structure. For the investigation of intrinsic structural properties, molecular beam experiments combined with laser spectroscopy have proven to be a suitable tool. Herein we present an analysis of the two isolated tripeptide model systems Ac‐Phe‐Tyr(Me)‐NHMe and Boc‐Phe‐Tyr(Me)‐NHMe. For this purpose, mass‐selective combined IR/UV spectroscopy is applied to both substances in a molecular beam experiment. The comparison of the experimental data with DFT calculations, including different functionals as well as dispersion corrections, allows an assignment of both tripeptide models to β‐turns formed independently from the protection groups and supported by the interaction of the two aromatic chromophores.     

The Application of HEXS and HERFD XANES for Accurate Structural Characterisation of Actinide Nanomaterials: The Case of ThO2

The structural characterisation of actinide nanoparticles (NPs) is of primary importance and hard to achieve, especially for non-homogeneous samples with NPs less than 3 nm. By combining high-energy X-ray scattering (HEXS) and high-energy-resolution fluorescence-detected X-ray absorption near-edge structure (HERFD XANES) analysis, we have characterised for the first time both the short- and medium-range order of ThO₂ NPs obtained by chemical precipitation. By using this methodology, a novel insight into the structures of NPs at different stages of their formation has been achieved. The pair distribution function revealed a high concentration of ThO₂ small units similar to thorium hexamer clusters mixed with 1 nm ThO₂ NPs in the initial steps of formation. Drying the precipitates at around 150 °C promoted the recrystallisation of the smallest units into more thermodynamically stable ThO₂ NPs. HERFD XANES analysis at the thorium M₄ edge, a direct probe for f states, showed variations that we have correlated with the breakdown of the local symmetry around the thorium atoms, which most likely concerns surface atoms. Together, HEXS and HERFD XANES are a powerful methodology for investigating actinide NPs and their formation mechanism.     

Katalysatoren für die Produktion von Biokunststoffen

Bioplastics represent an important possibility to reduce environmental pollution by non‐degradable plastics and open up new resources for plastics production. To promote wide application of bioplastics, new catalysts are urgently needed. This article summarises recent developments of robust lactide polymerisation catalysts as well as the embedding of the produced PLA into the life cycle of bioplastics.     

On the hydrogen atom beyond the Born–Oppenheimer approximation

Recently a new formulation of quantum mechanics has been suggested which is based on the concept of signed particles, that is, classical objects provided with a position, a momentum and a sign simultaneously. In this article, we comment on the plausibility of simulating atomic systems beyond the Born–Oppenheimer approximation by means of the signed particle formulation of quantum mechanics. First, to show the new perspective offered by this new formalism, we provide an example studying quantum tunnelling through a simple Gaussian barrier in terms of the signed particle formulation. Then, we perform a direct simulation of the hydrogen atom as a full quantum two‐body system, showing that the formalism can be a very promising tool for first‐principle‐only quantum chemistry.     

Thermal and colour properties of leuco dye-based thermochromic composite with dodecanol solvent

Leuco dye–developer–solvent composites with thermochromic properties were studied. The applied 1-dodecanol solvent shows β crystalline, α solid (rotator) and liquid phases. The inclusion of the crystal violet lactone dye increases transition temperatures of all phases and strengthens the α phase. The benzyl 4-hydroxybenzoate developer causes opposite effects and prevents the appearance of the α phase. These consequences combine in ternary composites, where lower transition temperatures were obtained as in the solvent, but the α phase is formed more likely as expected due to the presence of the developer. The hydration of the composite strengthens its crystalline network, but makes α phase more unstable. The thermal properties were related to the temperature-dependent colour. Composites with well-resolved α and β phases at cooling show a typical colour hysteresis. If only weak α phase or none at all was found in DSC curves, the colour hysteresis has an unusual shape with heating and cooling curves crossing each other. The hydration of the composite changes the colorimetric properties in accordance with the relation found for anhydrous composite. More conclusions and interrelations between the two properties require application of other analytical methods.     

The role of mean maximum pressure in specifying cross-country mobility for armoured fighting vehicle design

This paper examines the relationship between a military vehicle's mobility and its survivability. The theoretical model governing this relationship is based on a series of steps, each of which is critically examined. The tactical role of the vehicle is translated into a mobility requirement stated in terms of the percentage of ground to be trafficable in specified areas. The assessment of soil strength is achieved using the cone index, the statistical handling of which is described. The link between Vehicle Cone Index and Rowland's Mean Maximum Pressure (MMP) is discussed, as is its role as an indicator of vehicle mobility. Vehicle and armour weight follow directly from Rowland's MMP, leading to an assessment of survivability. Examples are given of the effects of varying the mobility requirement, the threat level and the armour type on the ultimate survivability of the vehicle.     

Medium-high resolution electrochemical genotyping of HLA-DQ2/DQ8 for detection of predisposition to coeliac disease

Coeliac disease is a small intestinal disorder, induced by ingestion of gluten in genetically predisposed individuals. Coeliac disease has been strongly linked to human leukocyte antigens (HLA) located on chromosome 6, with almost 100 % of coeliac disease sufferers carrying either a HLA-DQ2 or HLA-DQ8 heterodimer, with the majority carrying HLA-DQ2 encoded by the DQA1*05:01/05:05, DQB1*02:01/02:02 alleles, whereas the remaining carry the HLA-DQ8 encoded by the DQA1*03:01, DQB1*03:02 alleles. In this work, we present the development of a multiplex electrochemical genosensor array of 36 electrodes, housed within a dedicated microfluidic platform and using a total of 10 sequence-specific probes for rapid medium-high resolution HLA-DQ2/DQ8 genotyping. An evaluation of the selectivity of the designed probes was carried out with the target sequences and 44 potentially interfering alleles, including single base mismatch differentiations; good selectivity was demonstrated. The performance of the electrochemical genosensor array was validated, analyzing real human samples for the presence of HLA-DQ2/DQ8 alleles, and compared with those obtained using laboratory-based HLA typing, and an excellent correlation was obtained.

Chemical interactions between silver nanoparticles and thiols: a comparison of mercaptohexanol against cysteine

The interaction between citrate capped silver nanoparticles and two different thiols, mercaptohexanol(MH) and cysteine, was investigated. The thiols interacted with silver nanoparticles in a significantly contrasting manner. With MH, a sparingly soluble silver(I) thiolate complex AgSRm(Rm = –(CH2)6OH) was formed on the silver nanoparticle surface. Cyclic voltammograms and UV-vis spectra were used to infer that the AgSRm complex on the nanoparticle surface undergoes a phase transition to give a mixture of AgSRm and Ag2S-like complexes. In contrast, when silver nanoparticles were exposed to cysteine, the citrate capping agent on the silver nanoparticles was replaced by cysteine to give cysteine capped nanoparticles. As cysteine capped nanoparticles form, the electrochemical data displayed a decrease in oxidative peak charge but the UV-vis spectra showed a constant signal. Therefore, cysteine capped nanoparticles were suggested to have either inactivated the silver surface or else promoted detachment from the electrode surface.