The 10 most recently published documents
Many industrial processes are performed using harmful chemicals. The current technical synthesis of N-acyl-amino acids relies on acyl chlorides, which are typically obtained from phosgene chemistry. A greener alternative is the application of whole cells or enzymes to carry out synthesis in an environmentally friendly manner. Aminoacylases belong to the hydrolase family and the resolution of racemic mixtures of N-acetyl-amino acids is a well-known industrial process. Several new enzymes accepting long-chain fatty acids as substrates were discovered in recent years. This article reviews the synthetic potential of aminoacylases to produce biobased N-acyl-amino acid surfactants. The focus lays on a survey of the different types of aminoacylases available for synthesis and their reaction products. The enzymes are categorized according to their protein family classification and their biochemical characteristics including substrate spectra, reaction optima and process stability, both in hydrolysis and under process conditions suitable for synthesis. Finally, the benefits and future challenges of enzymatic N-acyl-amino acid synthesis with aminoacylases will be discussed.
To respond to the increasing demand for hyaluronic acid (HA) in dietary supplements (DSs) and nutricosmetics marketed for the treatment of osteoarthritis or moistening, it is essential to have an accurate and reliable method for its analysis in the final products. The study aimed to develop and validate alternative method for the quality control of HA in DSs using low-field (LF) and high-field (HF) nuclear magnetic resonance (NMR) spectroscopy at 80 MHz and 600 MHz, respectively. Moreover, chondroitin sulphate (CH), another active ingredient in DSs, can be simultaneously quantified. The 1H-NMR methods have been successfully validated in terms of limit of detection (LOD) and limit of quantitation (LOQ), which were found to be 0.1 mg/mL and 0.2 mg/mL (80 MHz) as well as 0.2 mg/mL and 0.6 mg/mL (600 MHz). Recovery rates were estimated to be between 92 and 120% on both spectrometers; precision including sample preparation was found to be 4.2% and 8.0% for 600 MHz and 80 MHz, respectively. Quantitative results obtained by HF and LF NMR were comparable for 16 DSs with varying matrix. HF NMR experiments at 70 ℃ serve as a simple and efficient quality control tool for HA and CH in multicomponent DSs. Benchtop NMR measurements, upon preceding acid hydrolysis, offer a cost-effective and cryogen-free alternative for analyzing DSs in the absence of CH and paramagnetic matrix components.
Das Schloss Lichtenburg in Prettin, im sachsen-anhaltischen Landkreis Wittenberg gelegen, ist eine der bedeutendsten Schlossanlagen der Renaissance in Mitteldeutschland und zugleich eines der wichtigsten historischen Zeugnisse für die Entwicklungsgeschichte der frühen nationalsozialistischen Lager, die ab 1933 in Bestandsbauten eingerichtet wurden und in heutiger Zeit meist unsichtbar sind. Im Schloss Lichtenburg ist die Gedenkstätte KZ Lichtenburg Prettin als Teil der Stiftung Gedenkstätten Sachsen-Anhalt heute eine zentrale Akteurin. Zugleich steht der größte Teil der Schlossanlage leer und sucht – verwaltet durch die Bundesanstalt für Immobilienaufgaben – eine neue Nutzung. Die Frage von Angemessenheit stellt sich an diesem Ort in besonderem Maße; gleiches gilt für viele andere NS-Tatorte mit komplexer Überlagerungsgeschichte. Sie betrifft sowohl den Umgang mit den baulichen Zeugnissen, die die einzelnen Zeitschichten widerspiegeln, als auch die zukünftigen Nutzungen.
Der globale Nachrichtenkonsum hat sich seit der Jahrtausendwende in ungeahnter Form und Geschwindigkeit verändert und fortentwickelt. Jahrzehnte lang waren Printzeitung, Radio und Fernsehen die drei vorherrschenden Informationsmedien. Der in seiner stets an den Stand technischer Neuerungen gebundene Pressemarkt blieb seinen etablierten und erfolgreichen Kommunikationswegen treu. Erst mit Aufkommen des World Wide Webs taten sich neue ungeahnte Möglichkeiten für Journalist*innen auf. Plötzlich war es möglich, die eigenen Inhalte über die Grenzen des Einzugsgebietes der Zeitung und über die Reichweite der Radiofrequenz oder des TV-Signals hinaus zu verbreiten. Es ergaben sich erstmalig ganz neue Zielgruppen, Kooperationen und Konkurrenzen. Diese Entwicklungen haben die Nachrichtenwelt in vielerlei Hinsicht in neue Sphären gehievt. Mitte der Nullerjahre wurde die Presselandschaft erneut mit einem technologischen Einschnitt konfrontiert, der ihr Schaffen von Grund auf beeinflussen sollte. Das Smartphone ermöglichte plötzlich, die Zeitung stets in der Hosentasche zu tragen; die aktuellsten Nachrichten sofort in der Hand halten; unmittelbar und unabhängig auf jegliche Information zugreifen. Die zweite große Entwicklung dieses Jahrtausends folgte gleich wenige Jahre später, die ersten sozialen Netzwerke entstanden. Der kometenhafte Aufstieg von Facebook und Co. stellte die Presse, und stellt sie immer noch, vor existentielle Fragen über die Natur des allgemeinen Nachrichtenkonsums. Vor wenigen Jahren hat sich nun eine dritte große Innovation dieses Jahrtausends ins Rampenlicht der Welt gedrängt und fließt stetig mehr und mehr in alle Bereiche der Alltagsrealität ein - die künstliche Intelligenz. Diese hat das Potential dazu, für unseren Nachrichtenkonsum die folgenschwerste aller zu sein - sowohl in den Chancen die durch sie entstehen als auch in den Problematiken, die sie aufwirft. Die kommenden Jahre versprechen, eine zukunftsweisende Zeit für die Presselandschaft zu werden. Wenn es gelingt, sich den modernen Gegebenheiten entsprechend zu entwickeln, und innovative Wege zu finden, Nachrichten zu produzieren und zu verbreiten, kann der Journalismus stärker denn je aus diesen entscheidenden Jahren hervorkommen. Vor diesem Kontext recherchieren, Lösungsansätze definieren und konkrete Umsetzungen erarbeiten, ist Ziel dieser Arbeit. The Presser ist ein Nachrichtenportal, das innovative journalistische Formate präsentiert und disruptive Lösungswege in gestalterischer und konzeptueller Form des Newskonsums darlegt
Magnetic nanoparticles (MNP) are widely investigated for biomedical applications in diagnostics (e.g. imaging), therapeutics (e.g. hyperthermia) and general biosensing. For all these applications, the MNPs’ unique magnetic relaxation mechanism in an alternating magnetic field (AFM) is stimulated to induce desired effects. Whereas magnetic fluid hyperthermia (MFH) and magnetic particle imaging (MPI) are the most prominent examples for biomedical application, we investigate the relatively new biosensing application of frequency mixing magnetic detection (FMMD) from a fundamental perspective. Generally, we ask how specific MNP parameters (core size, magnetic anisotropy) influence the signal, specifically we predict the most effective MNP core size for signal generation. In FMMD, simultaneously two AFM are applied: a low-frequency magnetic driving field, driving MNP close to saturation, and a high-frequency excitation field that probes MNP susceptibility: . Resulting from the nonlinear magnetization of the MNP, harmonics of both individual incident frequencies as well as intermodulation products of these frequencies are generated. In this work, we present numerical Monte-Carlo(MC)-based simulations of the MNP relaxation process, solving the Landau-Lifshitz-Gilbert (LLG) equation to predict FMMD signals: As Figure 1 shows for the first four intermodulation signals , with , we can clearly see that larger core sizes generally increase the signal intensity. Same trend is predicted by a simple Langevin-function based thermal equilibrium model. Both predictions include a lognormal size distribution. The effect of core size distribution presumably dominates the effect of magnetic anisotropy. The findings are supported by comparison with experimental data and help to identify which MNP are best suited for magnetic biosensing applications using FMMD.
Frequency mixing magneticdetection(FMMD) has been widely utilized as a measurement technique in magnetic immunoassays. It can also be used for characterization[1]and distinction[2](also known as “colorization”) ofdifferent types of magnetic nanoparticlesaccording totheircore sizes.It is well known that the large particles contribute most of the FMMD signal. Typically, 90% of the signal stems from the largest 10% of the particles [1]. This leads to ambiguities in core size fitting since thecontribution of thesmall sized particles is almostundetectable among the strong responses from the large ones. In this work, we report on how this ambiguity can be overcome. Magnetic nanoparticle samples from Micromod (Rostock, Germany) were prepared in liquid and filterbound state. Their FMMD response at mixing frequencies f1 ± nf2 to magnetic excitation H(t)=H0+H1sin(2 f1t)+H2sin(2 f2t),with H1=1.3mT/μ0 at f1=40.5kHzandH2=16mT/μ0 at f2=63Hz,was measured as a function ofoffset field strength H0= (0,…,24) mT/μ0.The signal calculated fromLangevin model in thermodynamic equilibrium[1]with a lognormal core size distribution fL(dc,d0, ,A) = Aexp(–ln²(dc/d0)/(2 ²))/(dc (2 )1/2)was fitted to the experimental data. For each choice of median diameter d0, pairs of parameters ( ,A) are found which yield excellent fit results with R²>0.99.All the lognormal core size distributions shown in Figure (a) are compatible with the measurements because their large-size tails are almost equal. However, all distributions have different number of particles and different total iron content. We determined the samples’ total iron mass with inductively coupled plasma optical emission spectrometry(ICP-OES) and, out of all possible lognormal distributions, determined the one with the same amount of iron. With this additional externally measured parameter, we resolved the ambiguity in core size distribution and determined the parameters (d0, ,A).
Hyperthermia with the use of magnetic nanoparticles (MNP) is a challenging but most promising approach for cancer therapy. After being magnetically trapped at the tumor site, MNP are heated in alternating magnetic fields (AMF) to approx. 43 °C, which causes tumor cell apoptosis. For an effective and controllable hyperthermia application, two parameters are most important: the amount of internalized MNP in tumor cells and their heating characteristics in AMF. In this study, we evaluated if a sufficient temperature could be achieved by cell internalized MNP heated up in AMF and if cell death could be induced in this way. The heating of pancreatic tumor cell lines MiaPaCa-2 and BxPC-3 loaded with different amounts of selfsynthesized magnetoliposomes nanoparticles (MLs) was measured with a custom-built setup. The MLs consisted of a fluorescent bi-layer of phospholipids and multiple magnetite (Fe3O4) cores with a diameter of (10.0 ± 0.5) nm each. The hydrodynamic diameter of the MLs was (90 ± 5) nm. Cell loading was performed by incubation of tumor cells for up to 24 h at 37 °C in a DMEM cell medium with MLs, which had an iron concentration of 150 μg/mL. Transmission electron microscopy and fluorescence microscopy were used to depict the uptake of MLs into the tumor cells (see Figure). The internalized iron-content per cell was determined with a magnetic particle spectrometer (MPS). After application of AMF for approx. 30 min, cell viability was assessed by clonogenic assay. The cellular uptake of MLs was time-dependent, cell line-specific and saturated: For both MiaPaCa-2 and BxPC-3 cell lines, the MLs cell internalization followed an exponential growth function which saturated after about 24 h cell incubation time at an iron load of (110 ± 6) pg/cell and (30 ± 2) pg/cell, respectively. The time constants of the exponential growth were (7.2 ± 1.4) h and (4.0 ± 0.6) h, respectively. In AMF, cells with the saturated MLs loading reached temperatures of approx. 44 °C and 43.5 °C, which caused the cell survival fraction to drop to approx. one third compared to untreated tumor cells for both MiaPaCa-2 and BxPC-3 cell lines. These results demonstrate the feasibility of hyperthermia in pancreatic cancer treatment by confirming cell death of pancreatic tumor cells at temperatures of approx. 43 °C. Further investigations are planned, which aim for the optimization of MNP dosage in targeting experiments as well as the assessment of incubation times and AMF parameters needed for a successful hyperthermic therapy.