Thermal degradation of anthocyanins and its impact on color and in vitro antioxidant capacity

The aim of the current study was to thoroughly investigate the structural changes of anthocyanins at pH 3.5 in purified fractions from black carrot, elderberry and strawberry heated over 6 h at 95 degrees C. Degradation products were monitored by HPLC-DAD-MS(3 )to elucidate the prevailing degradation pathways. In addition, alterations of color and antioxidant properties observed upon heating were scrutinized. Most interestingly, the degradation pathways at pH 3.5 were found to differ from those at pH 1. Among others, chalcone glycosides were detected at 320 nm in heat-treated elderberry and strawberry pigment isolates, and opening of the pyrylium ring initiated anthocyanin degradation. In the case of acylated anthocyanins, acyl-glycoside moieties were split off from the flavylium backbone, first. Finally, for all pigment isolates, phenolic acids and phloroglucinaldehyde were the terminal degradation products as remainders of the B- and A-ring, respectively. Maximum and minimum antioxidant stabilizing capacities were found in black carrot and strawberry, respectively, which was explained by the high degree of acylation in the former. After heating, decline of trolox equivalent antioxidant capacity (TEAC) was observed in all samples, which was attributed to both anthocyanins and their colorless degradation products following thermal exposure. As deduced from the ratio of TEAC value and anthocyanin content, the loss of anthocyanin bioactivity could not be compensated by the antioxidant capacity of newly formed colorless phenolics upon heating.     

Velocity navigator for motion compensated thermometry

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Proton resonance frequency shift thermometry is sensitive to breathing motion that leads to incorrect phase differences. In this work, a novel velocity-sensitive navigator technique for triggering MR thermometry image acquisition is presented.     

Application of thermography for thermoplastic waveguide fabrication

The production of short polymer optical fibers from small material batches is valuable for materials research, especially in the investigation of copolymers. A two‐step fiber drawing process is usually used for this purpose. The drawing temperature of the individual materials is an important parameter in the process. Temperature measurements using contactless methods are preferred because they enable online monitoring and do not affect the drawing process. Such measurements can be carried out with a pyrometer, which allows the measurement of a wide range of temperatures but requires a precise adjustment of the spot to the core of the preform. To circumvent this limitation, a thermographic camera with a resolution of 134 µm per pixel in the heating zone is used. The measurement range 0–250 °C is suitable for the usual drawing conditions. The device is installed outside the resistive heating furnace. The absolute temperature is obtained by calibrating the sensor to the beam path and the material emission properties. Different materials, shapes and thicknesses lead to variations in these parameters. In this work, an analysis of the temperature calibration for poly(methyl methacrylate), poly(styrene) and the copolymers poly[styrene‐co‐(isobornyl methacrylate)] and poly[(methyl methacrylate)‐co‐(isobornyl methacrylate)] is presented. These are all thermoplastic polymers and may be used for the fabrication of polymer optical fibers. © 2018 Society of Chemical Industry     

Shared-memory parallelization of a local correlation multi-reference CI program

We present a shared-memory parallelization of our open-source, local correlation multi-reference framework, TigerCI. Benchmarks of the total parallel speedup show a reasonable scaling for typical modern computing system setups. The efficient use of available computing resources will extend simulations on this high level of theory into a new size regime. We demonstrate our framework using local-correlation multireference computations of alkyl-substituted dioxirane and solvated methyl nitrene as examples.     

Recent Advances in Experimental Techniques for Flow and Mass Transfer Analyses in Thermal Separation Systems

Modelling flow and mass transfer of thermal separation equipment constitutes one of the most challenging tasks in fluids process engineering. The difficulty of this task comes from the multiscale multiphase flow phenomena in rather complex geometries. Both analysis of flow and mass transfer on different scales as well as validation of models and simulation results require advanced experimental and measurement techniques. As a follow-up to intensive discussions during the 2019 Tutzing Symposium “Separation Units 4.0” a wide set of available modern experimental technologies is presented.     

Selenoimidazolium Salts as Supramolecular Reagents for Protein Alkylation

Se-benzyl selenoimidazolium salts are characterized by remarkable alkyl-transfer potential under physiological conditions. Structure-activity relationship studies show that selective monoalkylation of primary amines depends on supramolecular interactions between the selenoimidazole leaving group and the target nucleophile. We demonstrate that these reagents can be used for site-selective and nearly quantitative modification of the model protein lysozyme on Lys13, bypassing the higher intrinsic reactivities of Lys1 and Lys33. These observations introduce selenoimidazolium salts as novel class of electrophiles for selective N-alkylation of native proteins.     

Investigation of a New Type I Baeyer–Villiger Monooxygenase from Amycolatopsis thermoflava Revealed High Thermodynamic but Limited Kinetic Stability

Baeyer–Villiger monooxygenases (BVMOs) are remarkable biocatalysts, but, due to their low stability, their application in industry is hampered. Thus, there is a high demand to expand on the diversity and increase the stability of this class of enzyme. Starting from a known thermostable BVMO sequence from Thermocrispum municipale (TmCHMO), a novel BVMO from Amycolaptosis thermoflava (BVMO_Flava), which was successfully expressed in Escherichia coli BL21(DE3), was identified. The activity and stability of the purified enzyme was investigated and the substrate profile for structurally different cyclohexanones and cyclobutanones was assigned. The enzyme showed a lower activity than that of cyclohexanone monooxygenase (CHMO_Acineto) from Acinetobacter sp., as the prototype BVMO, but indicated higher kinetic stability by showing a twofold longer half-life at 30 °C. The thermodynamic stability, as represented by the melting temperature, resulted in a T_m value of 53.1 °C for BVMO_Flava, which was comparable to the T_m of TmCHMO (ΔT_m=1 °C) and significantly higher than the T_m value for CHMO_Acineto ((ΔT_m=14.6 °C)). A strong deviation between the thermodynamic and kinetic stabilities of BVMO_Flava was observed; this might have a major impact on future enzyme discovery for BVMOs and their synthetic applications.     

Optimisation of SrBi2(Nb,Ta)2O9 Aurivillius phase for lead-free electrocaloric cooling

The influence of different substitutional mechanisms on the electrocaloric effect of a lead-free SrBi₂(Nb_0.2Ta_0.8)₂O₉ Aurivillius phase was studied for application in electrocaloric cooling systems. The A-site substitution with barium efficiently reduced the temperature of maximum permittivity from about 300?°C to 100?°C. The A-site substitution induced phenomena that are typical of strong relaxor ferroelectrics such as significant broadening of the permittivity peak and an increase in its frequency dispersion and with a depolarization temperature below room temperature. These features directly influenced the electrocaloric effect. A direct measurement system, based on a modified-differential scanning calorimeter, was used to analyze the EC effect of the dense (Sr_0.5Ba_0.5)Bi₂(Nb_0.2Ta_0.8)₂O₉ ceramics. In accordance with the relaxor characteristics, the EC effect was found to increase continuously over a broad temperature range above the room temperature. This was attributed to the alignment of field induced polar nanodomains. Directions for optimization towards a high-performing EC ceramic were identified.     

Large unsaturated room temperature negative magnetoresistance in graphene foam composite for wearable and flexible magnetoelectronics

Nano Research - Room temperature positive magnetoresistance (PMR) in graphene is a conventional phenomenon but we observed large negative magnetoresistance (NMR) in GF/polydimethylsiloxane...