Determination of the amino acid tryptophan in protein fibres

Tryptophan can be used as an indicator amino acid for the photostability of proteins. The analysis of tryptophan and its degradation products is hampered by their instability in oxidative or strongly acidic media, or light. Various methods were employed to quantify tryptophan in wool and other protein fibres such as silk and human hair. Acid, alkaline and enzymatic methods were used to hydrolyse protein fibres. The amino acid tryptophan in wool and other protein fibres was determined by a colorimetric method, by amino acid analysis and by reversed-phase HPLC. The different analytical methods were compared with regard to their results. The colorimetric method (p-dimethylamino-benzaldehyde) proved to give reliable results for the tryptophan content in wool and unpigmented protein fibres. This method can be used also for wool dyed with acid, metal complex or reactive dyes or for pigmented keratin fibres after correction for a blank sample. Interference between dye and colorimetric reagent also have to be evaluated.     

Safety Assessment of Fresh and Processed Seafood Products by MALDI-TOF Mass Fingerprinting

Foodborne intoxications caused by the consumption of fish and other products of marine origin contaminated with bacterial pathogens are an ever-present threat, either due to bacteria and/or its metabolites. In addition, the rapid spoilage of seafood due to microbial activity, results in high economic losses. The development of the microbiota in seafood products depends on the microbiological ambience of capture, processing and storage, and the applied preservation method. Thus, pathogenic and spoilage bacterial species in seafood may come from the indigenous microbiota of the aquatic ambience or are introduced by contamination during processing. Rapid and accurate bacterial species identification is essential for an effective control program to ensure safety and quality of either processed or minimally processed seafood. In the present work, matrix-assisted laser desorption ionization-time of flight mass spectrometry was successfully applied to identify 26 bacterial strains isolated from fresh fish and processed seafood samples. The approach was based on the comparison of unknown spectra to a reference spectral library and demonstrated to be a fast and accurate technique for bacterial species differentiation, which can be used for the rapid identification of foodborne pathogens and spoilage bacteria potentially present in products of marine origin.     

Towards an aggregate architecture: designed granular systems as programmable matter in architecture

Aggregate architectures are full-scale spatial formations made from loose granular matter. Especially if the individual grain is custom-designed, the range of behaviours can be calibrated to match a wide range of architectural and structural performance criteria. The aggregate becomes programmable matter. The relevance of loose granular systems for architecture is on the one hand their rapid re-configurability, allowing for a system not to be destroyed but rather to be recycled. On the other hand aggregates per se can be functionally graded either within one and the same particle type or through mixing different particle geometries. This enables the variation of architectural properties throughout one and the same material system, which is one of the core postulates of current architectural design research. However, very few examples of designed granular matter in architecture exist. The results presented here are thus one of the first coherent bodies of comprehensive research in this field compiled over a period of five years. Methodologically aggregate systems challenge conventional architectural design principles: whereas an architect generally precisely defines local and global geometry of a structure, in a designed granular system he can only calibrate the particle geometry in order to tune the overall behaviour of the aggregate formation. Thus new design methods have been developed throughout the research projects, which are informed by the related fields of granular physics and behaviour-based robotics. In this context the article provides an introduction to both designed particle systems and suitable fabrication approaches in an architectural context. Case study projects serve to verify the applicability of the concepts introduced. The research findings are discussed with regards to their practical, methodological and design theoretical contributions. To conclude, further directions of research are highlighted.     

Impact of the chain extension of poly(ethylene terephthalate) with 1,3‐phenylene‐bis‐oxazoline and N,N′‐carbonylbiscaprolactam by reactive extrusion on its properties

In this article, the material properties of chain extended poly(ethylene terephthalate) (PET) by application of the chain extenders, 1,3‐phenylene‐bis‐oxazoline (1,3‐PBO), N,N′‐carbonylbiscaprolactam (CBC), and combinations thereof are investigated aiming at an application during fiber production from postconsumer PET. The chain extension is performed in one step by a reactive extrusion process. The chain extenders are linearly linked to the COOH and/or OH terminal groups of PET. The influence of the chain extension on the properties of PET is analyzed by measurement of the inherent viscosity, size exclusion chromatography, and carboxyl end‐group titration. Furthermore, the impact of the chain extension on the thermal and rheological properties of PET is studied in detail by differential scanning calorimetry and rheology. The results demonstrate that chain extenders have impact on the properties of PET in dependence on their chemical composition and concentration. The improvement of the molecular weight of the obtained compounds is achieved in an effective and economical approach by the addition of small concentrations of chain extenders (0.2 wt% 1,3‐PBO or 0.3 wt% CBC) without significant negative impact on the properties of PET. POLYM. ENG. SCI., 59:284–294, 2019. © 2018 Society of Plastics Engineers     

Novel building blocks for oligonuclear copper complexes derived from β‐ketoenamines of histidine

Condensation products of L‐histidine with the 3‐oxoenolethers diethyl‐ethoxymethylene‐malonate ( 1 ) and ethyl‐ethoxymethylene‐cyanoacetate ( 2 ) react with copper(II) as di‐anionic ligands to give neutral 1:1 complexes Cu‐ His1 and Cu‐ His2 . Both complexes crystallize as oligonuclear units, even from strongly donating solvents like N‐methylimidazole (Meim) (Cu‐ His1 ) and pyridine (Cu‐ His2 ). X‐ray structure analyses show supramolecular structures, formed of two (Cu‐ His1 ) or four (Cu‐ His2 ) formula units of the complex, which arrange to macrocycles by means of intermolecular coordination of the imidazole‐N. Strong H‐bridges result in a face‐to‐face orientation of the hydrophilic sites of two great rings. ESI‐MS investigations in pyridine solution give evidence for the existence of dimeric, tetrameric and – in case of Cu‐ His2 – trimeric units, besides the monomeric adducts with one pyridine. In contrast to the dimeric or tetrameric (“cubane‐like”) copper(II) complexes of amino alcohols and their β‐ketoenamines, the complexes Cu‐ His1 and Cu‐ His2 show no significant spin coupling from room temperature down to 4 K. The complexes Cu‐ His1 and Cu‐ His2 give no electrochemically reversible Cu^II/I reduction in pyridine. However, the isolation of a stable diamagnetic copper(I) complex of the methylester derivative, Cu^I‐ HisMe1 , supports the assumption, that similar histidine‐derived copper complexes should display reversible redox behaviour and catalytic activity in reactions with O₂.     

Titannitrid als gasabgabereduzierende Schicht auf Edelstahl

TiN films were deposited on stainless steel samples using a new coating procedure, the so-called modified pulse arc process. The influence of titanium nitride films on the outgassing rate was studied and the obtained results were discussed. Measurements of the outgassing rate carried out with untreated stainless steel samples and with stainless steel samples coated with titanium nitride by DC arc process are compared with the results obtained from the samples coated with the modified pulse arc process in order to get information about the influence of the coating procedure on the outgassing rate.     

Ultrasound evaluation of heart disease, with special reference to congenital and acquired lesions (author's transl)

Time position monitoring of numerous cardiac structures can be obtained by single element echocardiography with high time resolution. This method offers an important way to measure cardiac dimensions and to prove the anatomical relation different cardiac structures. Technological problems are briefly discussed and normal values are given. Cardiac lesions diagnosed by echocardiography are reviewed.     

Granular Morphologies: Programming Material Behaviour with Designed Aggregates

What if designers were to become more than specifiers of materials, and actually defined the composition of the matter they work with? Granular materials, or rather ‘designed aggregates’, as introduced here by Karola Dierichs , architect and researcher at the Institute for Computational Design (ICD), and Guest-Editor Achim Menges , are one distinct group of materials that can be considered ‘designed matter’. What makes designed granular systems particularly interesting is that they do not obtain a final structure with preset properties. Instead, their elemental constituents remain unfixed, allowing them to continuously and physically recompute structural and spatial characteristics, challenging our very conception of design.     

Inhibition of quality loss in chilled megrim (Lepidorhombus whiffiagonis) by employing citric and lactic acid icing

This study focuses on the quality retention of megrim (Lepidorhombus whiffiagonis) during chilled storage. Aqueous solutions of two different concentrations of citric (CA) and lactic (LA) acids were employed as icing media (0.125% CA–0.050% LA and 0.175% CA–0.050% LA, respectively; w/v). The effects of each solution on microbial activity, lipid damage and sensory acceptance were monitored for up to 13 days of storage. Lower (P < 0.05) bacterial growth was detected according to microbiological (aerobe and psychrotroph counts) and chemical (trimethylamine‐N and pH) assessments, which led to an enhancement of sensory appreciation. Whereas control fish were determined as unacceptable at day 13, the acid‐iced fish were still acceptable at that time. Concerning lipid damage, an inhibitory effect (P < 0.05) on fluorescent compound formation was observed in the acid‐iced fish. Present results allow to conclude that the use of a CA–LA icing system can provide a profitable strategy to obtain higher quality chilled fish.