540 Chemie und zugeordnete Wissenschaften
Refine
Departments, institutes and facilities
- Fachbereich Angewandte Naturwissenschaften (142)
- Institut für Technik, Ressourcenschonung und Energieeffizienz (TREE) (54)
- Fachbereich Ingenieurwissenschaften und Kommunikation (18)
- Fachbereich Informatik (17)
- Graduierteninstitut (8)
- Institut für Sicherheitsforschung (ISF) (8)
- Institut für Detektionstechnologien (IDT) (5)
- Institut für funktionale Gen-Analytik (IFGA) (5)
- Institute of Visual Computing (IVC) (2)
- Internationales Zentrum für Nachhaltige Entwicklung (IZNE) (1)
Document Type
- Article (139)
- Conference Object (32)
- Part of a Book (15)
- Book (monograph, edited volume) (10)
- Doctoral Thesis (10)
- Bachelor Thesis (4)
- Master's Thesis (4)
- Contribution to a Periodical (3)
- Patent (3)
- Conference Proceedings (2)
Year of publication
Keywords
- GC/MS (9)
- Lignin (7)
- Chemie (5)
- Analytical pyrolysis (4)
- Biomass (4)
- Corrosion inhibitors (3)
- Failure analysis (3)
- Lehrbuch (3)
- lignin (3)
- Antimicrobial activity (2)
Lignin ist ein aromatisches Biopolymer, das in den Zellwänden von Pflanzen vorkommt. Es ist hauptsächlich aus drei sogenannten Monolignolen (p-Hydroxyphenyl (H), Guajakol (G) und Syringol (S)) aufgebaut, die über verschiedene Bindungen miteinander verknüpft sein können, und enthält eine Vielzahl an funktionellen Gruppen. Interessant für die Verwendung von Lignin sind dabei insbesondere die vielen phenolischen Hydroxygruppen, die als Ausgangsstoff bei der Synthese neuer Produkte dienen können, daneben aber auch für seine antioxidativen Eigenschaften verantwortlich sind. Da Struktur und Eigenschaften von vielen Faktoren wie Biomasse und Aufschlussprozess abhängen, ist eine detaillierte Charakterisierung der Lignine nötig, um Struktur-Eigenschafts-Beziehungen aufzuklären und so einen Schritt näher an eine mögliche stoffliche Nutzung zu kommen. Mit dieser Arbeit soll der Einfluss der Biomasse inklusive der verwendeten Partikelgröße sowie des Organosolv-Aufschlussprozesses auf die Monomerzusammensetzung, das Molekulargewicht und die Antioxidanz der isolierten Lignine untersucht werden.
Als Rohstoffe zur Ligningewinnung dienen die drei mehrjährigen lignocellulosereichen Low-Input-Pflanzen Miscanthus x giganteus, Silphium perfoliatum und Paulownia tomentosa, die momentan hauptsächlich zur Energiegewinnung genutzt werden. Im Rahmen der Bioökonomiestrategie der Europäischen Union soll der Schwerpunkt zukünftiger Bioraffinerien jedoch auf eine ganzheitliche Nutzung von Biomassen gelegt und so auch die stoffliche Nutzung fokussiert werden. Zusätzlich zu diesen drei Pflanzen werden auch Organosolv-Lignine aus den in der Literatur bereits gut beschriebenen Biomassen Weizenstroh und Buchenholz isoliert, und zwei Nadelholz-Kraft-Lignine als Vergleich herangezogen. Die Ergebnisse zeigen, dass die Art der Biomasse hauptsächlich die Monomerzusammensetzung beeinflusst: Gräser bestehen aus allen drei Monolignolen, Laubhölzer mehrheitlich aus S- und G-Einheiten, während Nadelhölzer nur aus G-Einheiten aufgebaut sind. Die Holzlignine besitzen zudem höhere Molekulargewichte sowie bessere antioxidative Eigenschaften als die Gras- und Krautlignine. Mit der feineren Vermahlung der Biomasse kann die Monomerzusammensetzung beeinflusst werden: der Einsatz kleinerer Partikelgrößen führt zu Ligninen mit einem höheren Gehalt an H-Einheiten, sowohl für Miscanthus als auch für Paulownia. Außerdem kann bei Paulownia die Ausbeute gesteigert und eine Zunahme des Molekulargewichtes beobachtet werden, wenn die kleinste Siebfraktion für den Organosolv-Aufschluss verwendet wird. Einen größeren Einfluss als der Mahlgrad der Biomasse haben die Autohydrolyse sowie der Organosolv-Aufschlussprozess selbst. Die Monomerzusammensetzung ändert sich aufgrund derselben Biomasse zwar kaum, die Bindungstypen zwischen den Monolignolen dagegen schon. Mit höherer Prozessstärke (Zeit, Temperatur, Ethanol-Konzentration) werden Etherbindungen gespalten, was den Anteil an phenolischen Hydroxygruppen und somit die Antioxidanz erhöht. Neben dieser Depolymerisation werden partiell auch Rekondensationsreaktionen beobachtet.
Die erzielten Ergebnisse liefern einen Beitrag zum Verständnis des Zusammenhangs zwischen Ligninquelle und -gewinnung mit der daraus resultierenden Ligninstruktur und Antioxidanz und bieten damit eine Grundlage für den Wandel von der energetischen hin zu einer nachhaltigen stofflichen Nutzung dieses nachwachsenden Biopolymers. Gerade über die Wahl der Aufschlussparameter können Struktur und Antioxidanz gezielt beeinflusst werden, was in zukünftigen Studien weiter fokussiert werden sollte.
Microorganisms not only contribute to the spoilage of food but can also cause illnesses through consumption. Consumer concerns and doubts about the shelf life of the products and the resulting enormous amounts of food waste have led to a demand for a rapid, robust, and non-destructive method for the detection of microorganisms, especially in the food sector. Therefore, a rapid and simple sampling method for the Raman- and infrared (IR)-microspectroscopic study of microorganisms associated with spoilage processes was developed. For subsequent evaluation pre-processing routines, as well as chemometric models for classification of spoilage microorganisms were developed. The microbiological samples are taken using a disinfectable sampling stamp and measured by microspectroscopy without the usual pre-treatments such as purification separation, washing, and centrifugation. The resulting complex multivariate data sets were pre-processed, reduced by principal component analysis, and classified by discriminant analysis. Classification of independent unlabeled test data showed that microorganisms could be classified at genus, species, and strain levels with an accuracy of 96.5 % (Raman) and 94.5 % (IR), respectively, despite large biological differences and novel sampling strategies. As bacteria are exposed to constantly changing conditions and their adaptation mechanisms may make them inaccessible to conventional measurement methods, the methods and models developed were investigated for their suitability for microorganisms exposed to stress. Compared to normal growth conditions, spectral changes in lipids, polysaccharides, nucleic acids, and proteins were observed in microorganisms exposed to stress. Models were developed to discriminate microorganisms, independent of the involvement of various stress factors and storage times. Classification of the investigated bacteria yielded accuracies of 97.6 % (Raman) and 96.6 % (IR), respectively, and a robust and meaningful model was developed to discriminate different microorganisms at the genus, species, and strain levels. The obtained results are very promising and show that the methods and models developed for the discrimination of microorganisms as well as the investigation of stress factors on microorganisms by means of Raman- and IR-microspectroscopy have the potential to be used, for example, in the food sector for the rapid determination of surface contamination.
Pyrolysis–Gas Chromatography
(2022)
The methodology of analytical pyrolysis-GC/MS has been known for several years, but is seldom used in research laboratories and process control in the chemical industry. This is due to the relative difficulty of interpreting the identified pyrolysis products as well as the variety of them. This book contains full identification of several classes of polymers/copolymers and biopolymers that can be very helpful to the user. In addition, the practical applications can encourage analytical chemists and engineers to use the techniques explored in this volume.
The Potential of Sustainable Antimicrobial Additives for Food Packaging from Native Plants in Benin
(2019)
This work presents an open source database with suitable retention parameters for prediction and simulation of GC separations and gives a short introduction to three common retention models. Useful computer simulations play an important role to save resources and time in method development in GC. Thermodynamic retention parameters for the ABC model and the K-centric model are determined by isothermal measurements. This standardized procedure of measurements and calculations, presented in this work, have a useful benefit for all chromatographers, analytical chemists, and method developers because it can be used in their own laboratories to simplify the method development. The main benefits as simulations of temperature-programed GC separations are demonstrated and compared to measurements. The observed deviations of predicted retention times are in most cases less than 1%. The database includes more than 900 entries with a large range of compounds such as VOCs, PAHs, FAMEs, PCBs, or allergenic fragrances over 20 different GC columns.
Several species of (poly)saccharides and organic acids can be found often simultaneously in various biological matrices, e.g., fruits, plant materials, and biological fluids. The analysis of such matrices sometimes represents a challenging task. Using Aloe vera (A. vera) plant materials as an example, the performance of several spectroscopic methods (80 MHz benchtop NMR, NIR, ATR-FTIR and UV-Vis) for the simultaneous analysis of quality parameters of this plant material was compared. The determined parameters include (poly)saccharides such as aloverose, fructose and glucose as well as organic acids (malic, lactic, citric, isocitric, acetic, fumaric, benzoic and sorbic acids). 500 MHz NMR and high-performance liquid chromatography (HPLC) were used as the reference methods.
UV-VIS data can be used only for identification of added preservatives (benzoic and sorbic acids) and drying agent (maltodextrin) and semiquantitative analysis of malic acid. NIR and MIR spectroscopies combined with multivariate regression can deliver more informative overview of A. vera extracts being able to additionally quantify glucose, aloverose, citric, isocitric, malic, lactic acids and fructose. Low-field NMR measurements can be used for the quantification of aloverose, glucose, malic, lactic, acetic, and benzoic acids. The benchtop NMR method was successfully validated in terms of robustness, stability, precision, reproducibility and limit of detection (LOD) and quantification (LOQ), respectively.
All spectroscopic techniques are useful for the screening of (poly)saccharides and organic acids in plant extracts and should be applied according to its availability as well as information and confidence required for the specific analytical goal. Benchtop NMR spectroscopy seems to be the most feasible solution for quality control of A. vera products.
Im Rahmen dieser Arbeit wurden zunächst neuartige ionische Agarosederivate synthetisiert und anschließend umfassend charakterisiert. Anionische Agarosesulfate mit einer regioselektiven Derivatisierung in Position G6 wurden durch homogene Umsetzung in ionischer Flüssigkeit erhalten. Kationische Agarosecarbamate mit einstellbarem Funktionalisierungsgrad waren durch einen zweistufigen Syntheseansatz zugänglich. Hierzu wurden zunächst Agarosephenylcarbonate in einer homogenen Synthese hergestellt, im Anschluss folgte eine Aminolyse zu den gewünschten funktionalen Agarosederivaten. Die ionischen Agarosederivate waren bereits bei geringen Funktionalisierungsgraden vollständig löslich in Wasser. Damit war es möglich, Alginatmikrokapseln polyelektrolytisch zu beschichten und diese als Träger für eine kontrollierte Wirkstofffreisetzung zu verwenden. Ebenfalls konnten Kompositgele aus Agarose, Hydroxyapatit und Agarosederivaten hergestellt und charakterisiert werden. Im zweiten Teil wurden sowohl die Kompositträgermaterialien als auch die Alginatmikrokapseln mit vier verschiedenen Modellwirkstoffen (ATP, Suramin, Methylenblau und A740003) beladen und die Wirkstofffreisetzung über einen Zeitraum von zwei Wochen untersucht. Für die ionischen Modellwirkstoffe erwiesen sich Kompositträgermaterialien mit ionischem Agarosederivat, die beschichteten Mikrokapseln sowie die Kombination aus Komposit und Kapseln als effektiv, um die Freisetzung auf bis zu 40% zu verlangsamen. Für die schlecht wasserlösliche Substanz A740003, ein Rezeptorligand für die osteogene Differenzierung von Stammzellen, wurde eine stark verzögerte Freisetzung aus Polyelektrolytemikrokapseln festgestellt. Mithilfe von literaturbekannten und neu entwickelten Anpassungsmodellen gelang es, die Diffusion als Hauptmechanismus der Wirkstofffreisetzung zu identifizieren und die Freisetzungskurven mathematisch akkurat zu beschreiben und daraus Rückschlüsse über die einzelnen Phasen der Freisetzung zu ziehen.
While many proteins are known clients of heat shock protein 90 (Hsp90), it is unclear whether the transcription factor, thyroid hormone receptor beta (TRb), interacts with Hsp90 to control hormonal perception and signaling. Higher Hsp90 expression in mouse fibroblasts was elicited by the addition of triiodothyronine (T3). T3 bound to Hsp90 and enhanced adenosine triphosphate (ATP) binding of Hsp90 due to a specific binding site for T3, as identified by molecular docking experiments. The binding of TRb to Hsp90 was prevented by T3 or by the thyroid mimetic sobetirome. Purified recombinant TRb trapped Hsp90 from cell lysate or purified Hsp90 in pull-down experiments. The affinity of Hsp90 for TRb was 124 nM. Furthermore, T3 induced the release of bound TRb from Hsp90, which was shown by streptavidin-conjugated quantum dot (SAv-QD) masking assay. The data indicate that the T3 interaction with TRb and Hsp90 may be an amplifier of the cellular stress response by blocking Hsp90 activity.
Nanomedicine strategies were first adapted and successfully translated to clinical application for diseases, such as cancer and diabetes. These strategies would no doubt benefit unmet diseases needs as in the case of leishmaniasis. The latter causes skin sores in the cutaneous form and affects internal organs in the visceral form. Treatment of cutaneous leishmaniasis (CL) aims at accelerating wound healing, reducing scarring and cosmetic morbidity, preventing parasite transmission and relapse. Unfortunately, available treatments show only suboptimal effectiveness and none of them were designed specifically for this disease condition. Tissue regeneration using nano-based devices coupled with drug delivery are currently being used in clinic to address diabetic wounds. Thus, in this review, we analyse the current treatment options and attempt to critically analyse the use of nanomedicine-based strategies to address CL wounds in view of achieving scarless wound healing, targeting secondary bacterial infection and lowering drug toxicity.
Process-induced changes in the morphology of biodegradable polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA) blends modified with various multifunctional chainextending cross-linkers (CECLs) are presented. The morphology of unmodified and modified films produced with blown film extrusion is examined in an extrusion direction (ED) and a transverse direction (TD). While FTIR analysis showed only small peak shifts indicating that the CECLs modify the molecular weight of the PBAT/PLA blend, SEM investigations of the fracture surfaces of blown extrusion films revealed their significant effect on the morphology formed during the processing. Due to the combined shear and elongation deformation during blown film extrusion, rather spherical PLA islands were partly transformed into long fibrils, which tended to decay to chains of elliptical islands if cooled slowly. The CECL introduction into the blend changed the thickness of the PLA fibrils, modified the interface adhesion, and altered the deformation behavior of the PBAT matrix from brittle to ductile. The results proved that CECLs react selectively with PBAT, PLA, and their interface. Furthermore, the reactions of CECLs with PBAT/PLA induced by the processing depended on the deformation directions (ED and TD), thus resulting in further non-uniformities of blown extrusion films.
Cathepsin K (CatK) is a target for the treatment of osteoporosis, arthritis, and bone metastasis. Peptidomimetics with a cyanohydrazide warhead represent a new class of highly potent CatK inhibitors; however, their binding mechanism is unknown. We investigated two model cyanohydrazide inhibitors with differently positioned warheads: an azadipeptide nitrile Gü1303 and a 3-cyano-3-aza-β-amino acid Gü2602. Crystal structures of their covalent complexes were determined with mature CatK as well as a zymogen-like activation intermediate of CatK. Binding mode analysis, together with quantum chemical calculations, revealed that the extraordinary picomolar potency of Gü2602 is entropically favoured by its conformational flexibility at the nonprimed-primed subsites boundary. Furthermore, we demonstrated by live cell imaging that cyanohydrazides effectively target mature CatK in osteosarcoma cells. Cyanohydrazides also suppressed the maturation of CatK by inhibiting the autoactivation of the CatK zymogen. Our results provide structural insights for the rational design of cyanohydrazide inhibitors of CatK as potential drugs.
Ausführungsbeispiele schaffen eine Vorrichtung zur Desinfektion oder Sanitisierung zumindest eines Gegenstands. Die Vorrichtung umfasst einen Ozongenerator, der ausgebildet ist, um Ozon zu erzeugen und in einem Volumen freizusetzen. Ferner umfasst die Vorrichtung einen Ozonsensor, der ausgebildet ist, um eine Ozonkonzentration in dem Volumen zu messen. Ferner umfasst die Vorrichtung eine Steuereinrichtung, die konfiguriert ist, um den Ozongenerator anzusteuern Ozon zu erzeugen, so dass eine gemessene Ozonkonzentration für einen vorgegebenen Zeitraum bei einer vorgegebenen Ozonkonzentration oder innerhalb eines vorgegebenen Ozonkonzentrationsbereichs liegt, um in dem Volumen befindliche Gegenstände zu desinfizieren oder sanitisieren.
Vorrichtung (1) zur Bestimmung eines TOC-Gehalts in einer wässrigen Lösung, die folgendes aufweist:- zumindest eine Ozonquelle (8) zur Erzeugung von Ozon in der wässrigen Lösung;- zumindest eine Strahlungsquelle (9) zur Bestrahlung der wässrigen Lösung mit UV-Strahlung;- eine Einrichtung (15) zur Bestimmung der elektrischen Leitfähigkeit der ozonierten und bestrahlten wässrigen Lösung.
Hydrophilic surface-enhanced Raman spectroscopy (SERS) substrates were prepared by a combination of TiO2-coatings of aluminium plates through a direct titanium tetraisopropoxide (TTIP) coating and drop coated by synthesised gold nanoparticles (AuNPs). Differences between the wettability of the untreated substrates, the slowly dried Ti(OH)4 substrates and calcinated as well as plasma treated TiO2 substrates were analysed by water contact angle (WCA) measurements. The hydrophilic behaviour of the developed substrates helped to improve the distribution of the AuNPs, which reflects in overall higher lateral SERS enhancement. Surface enhancement of the substrates was tested with target molecule rhodamine 6G (R6G) and a fibre-coupled 638 nm Raman spectrometer. Additionally, the morphology of the substrates was characterised using scanning electron microscopy (SEM) and Raman microscopy. The studies showed a reduced influence of the coffee ring effect on the particle distribution, resulting in a more broadly distributed edge region, which increased the spatial reproducibility of the measured SERS signal in the surface-enhanced Raman mapping measurements on mm scale.
Cathepsin K (CatK) is a target for the treatment of osteoporosis, arthritis, and bone metastasis. Peptidomimetics with a cyanohydrazide warhead represent a new class of highly potent CatK inhibitors; however, their binding mechanism is unknown. We investigated two model cyanohydrazide inhibitors with differently positioned warheads: an azadipeptide nitrile Gü1303 and a 3-cyano-3-aza-β-amino acid Gü2602. Crystal structures of their covalent complexes were determined with mature CatK as well as a zymogen-like activation intermediate of CatK. Binding mode analysis, together with quantum chemical calculations, revealed that the extraordinary picomolar potency of Gü2602 is entropically favoured by its conformational flexibility at the nonprimed-primed subsites boundary. Furthermore, we demonstrated by live cell imaging that cyanohydrazides effectively target mature CatK in osteosarcoma cells. Cyanohydrazides also suppressed the maturation of CatK by inhibiting the autoactivation of the CatK zymogen. Our results provide structural insights for the rational design of cyanohydrazide inhibitors of CatK as potential drugs.
The white ground crater by the Phiale Painter (450–440 BC) exhibited in the “Pietro Griffo” Archaeological Museum in Agrigento (Italy) depicts two scenes from Perseus myth. The vase is of utmost importance to archaeologists because the figures are drawn on a white background with remarkable daintiness and attention to detail. Notwithstanding the white ground ceramics being well documented from an archaeological and historical point of view, doubts concerning the compositions of pigments and binders and the production technique are still unsolved. This kind of vase is a valuable rarity, the use of which is documented in elitist funeral rituals. The study aims to investigate the constituent materials and the execution technique of this magnificent crater. The investigation was carried out using non-destructive and non-invasive techniques in situ. Portable X-ray fluorescence and Fourier-transform total reflection infrared spectroscopy complemented the use of visible and ultraviolet light photography to get an overview and specific information on the vase. The XRF data were used to produce false colour maps showing the location of the various elements detected, using the program SmART_scan. The use of gypsum as the material for the white ground is an important result that deserves to be further investigated in similar vases.
The synthesis and characterization of a new class of 1,2,4-oxadiazolylpyridinium as a cationic scaffold for fluorinated ionic liquid crystals is herein described. A series of 12 fluorinated heterocyclic salts based on a 1,2,4-oxadiazole moiety, connected through its C(5) or C(3) to an N-alkylpyridinium unit and a perfluoroheptyl chain, differing in the length of the alkyl chain and counterions, has been synthesized. As counterions iodide, bromide and bis(trifluoromethane)sulfonimide have been considered. The synthesis, structure, and liquid crystalline properties of these compounds are discussed on the basis of the tuned structural variables. The thermotropic properties of this series of salts have been investigated by differential scanning calorimetry and polarized optical microscopy. The results showed the existence of an enantiotropic mesomorphic smectic liquid crystalline phase for six bis(trifluoromethane)sulfonimide salts.
The molecular weight properties of lignins are one of the key elements that need to be analyzed for a successful industrial application of these promising biopolymers. In this study, the use of 1H NMR as well as diffusion-ordered spectroscopy (DOSY NMR), combined with multivariate regression methods, was investigated for the determination of the molecular weight (Mw and Mn) and the polydispersity of organosolv lignins (n = 53, Miscanthus x giganteus, Paulownia tomentosa, and Silphium perfoliatum). The suitability of the models was demonstrated by cross validation (CV) as well as by an independent validation set of samples from different biomass origins (beech wood and wheat straw). CV errors of ca. 7–9 and 14–16% were achieved for all parameters with the models from the 1H NMR spectra and the DOSY NMR data, respectively. The prediction errors for the validation samples were in a similar range for the partial least squares model from the 1H NMR data and for a multiple linear regression using the DOSY NMR data. The results indicate the usefulness of NMR measurements combined with multivariate regression methods as a potential alternative to more time-consuming methods such as gel permeation chromatography.
Recent experimental evidence suggest that mebendazole, a popular antiparasitic drug, binds to heat shock protein 90 (Hsp90) and inhibit acute myeloid leukemia cell growth. In this study we use quantum mechanics (QM), molecular similarity and molecular dynamics (MD) calculations to predict possible binding poses of mebendazole to the adenosine triphosphate (ATP) binding site of Hsp90. Extensive conformational searches and minimization of the five tautomers of mebendazole using MP2/aug-cc-pVTZ theory level resulting in 152 minima being identified. Mebendazole-Hsp90 complex models were created using the QM optimized conformations and protein coordinates obtained from experimental crystal structures that were chosen through similarity calculations. Nine different poses were identified from a total of 600 ns of explicit solvent, all-atom MD simulations using two different force fields. All simulations support the hypothesis that mebendazole is able to bind to the ATP binding site of Hsp90.
This study investigates the effects of four multifunctional chain-extending cross-linkers (CECL) on the processability, mechanical performance, and structure of polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA) blends produced using film blowing technology. The newly developed reference compound (M·VERA® B5029) and the CECL modified blends are characterized with respect to the initial properties and the corresponding properties after aging at 50 °C for 1 and 2 months. The tensile strength, seal strength, and melt volume rate (MVR) are markedly changed after thermal aging, whereas the storage modulus, elongation at the break, and tear resistance remain constant. The degradation of the polymer chains and crosslinking with increased and decreased MVR, respectively, is examined thoroughly with differential scanning calorimetry (DSC), with the results indicating that the CECL-modified blends do not generally endure thermo-oxidation over time. Further, DSC measurements of 25 µm and 100 µm films reveal that film blowing pronouncedly changes the structures of the compounds. These findings are also confirmed by dynamic mechanical analysis, with the conclusion that tris(2,4-di-tert-butylphenyl)phosphite barely affects the glass transition temperature, while with the other changes in CECL are seen. Cross-linking is found for aromatic polycarbodiimide and poly(4,4-dicyclohexylmethanecarbodiimide) CECL after melting of granules and films, although overall the most synergetic effect of the CECL is shown by 1,3-phenylenebisoxazoline.
Simultaneous determination of selected catechins and pyrogallol in deer intoxications by HPLC-MS/MS
(2021)