At any given moment, information reaches us via our different sensory systems. In order to navigate this multitude of information, associated information needs to be integrated to a coherent percept. In recent years, the hypothesis that synchronous neural oscillations play a prominent role in unisensory and multisensory processing has received substantial support. Current findings further convey the idea that local oscillations and functional connectivity reflect bottom-up as well as top-down processes during multisensory integration and perception. In the current work, I review recent findings on the role of neural oscillations for conscious multisensory perception. Subsequently, I present an integrative network model for multisensory integration that describes the cortical correlates of conscious multisensory perception, the influence of fluctuations of oscillatory neural activity on subsequent perception, and the influence of cognitive processes on neural oscillations and perception. I propose that neural oscillations in distinct, coexisting frequencies reflect the various processing steps underlying multisensory perception.Weniger anzeigen
Seit der Entdeckung der RIPs und der Aufklärung der enzymatischen Aktivität dieser Proteine sind einige Reviews veröffentlicht worden. Jedoch kam es im Laufe der Zeit zu Unstimmigkeiten bezüglich der Nomenklatur und Definition mancher RIPs. Für diese Arbeit wurde eine Übersichtstabelle erstellt, die diese Unstimmigkeiten beseitigen sollte und es konnte gezeigt werden, dass aktuell 193 Typ 1 RIPs und 88 Typ 2 RIPs existieren. Daneben existieren Proteine, die den klassischen RIPs sehr ähnlich sind, aber aufgrund struktureller oder funktioneller Unterschiede nicht als solche klassifiziert werden können und dementsprechend wurde ein Vorschlag unterbreitet wie diese Proteine klassifiziert und benannt werden könnten. Durch eine Affinitätschromatographie, bei der aufgereinigte Antikörper verwendet wurden, konnte ein Protein aus Agrostemma githago isoliert werden, welches in einer Echtzeit-Untersuchung eine gewisse Toxizität zeigte, die in Kombination mit dem Saponin SO1861 verstärkt wurde. Die Aminosäuresequenzen von fünf Peptidfragmenten wurden durch MALDI-TOF-MS erhalten. Dadurch war zum einen die Produktion von anti-Peptid Antikörpern möglich, mit deren Hilfe eine größere Menge Protein isoliert werden konnte. Zum anderen konnte eine Datenbank kreiert werden, um die Rohdaten der RNA-Seq auszuwerten. Darüber hinaus konnte die Masse des isolierten Proteins von 26963 Da ermittelt werden und aufgrund des Spektrums wurde die Vermutung aufgestellt, dass es sich bei dem isolierten Protein um drei Isoformen handeln könnte. Nach der bioinformatischen Auswertung der RNA-Seq-Rohdaten wurde eine erste Konsen-sussequenz erhalten, die eine Länge von 247 Aminosäuren und eine theoretische Masse von 27140 Da aufzeigte. Anhand dieser Sequenz konnten fünf weitere Peptidfragmente der MALDI-TOF-MS Untersuchung sequenziert werden. Durch einen Vergleich der MALDI-TOF-MS-Sequenzen mit der Konsensussequenz wurde aufgrund von Sequenzunterschieden einzelner Aminosäuren der Verdacht bestätigt, dass es sich bei dem isolierten Protein um drei Isoformen handeln musste. Außerdem wurde die erste Konsensussequenz revidiert und es wurde eine zweite Konsensussequenz erhalten mit einer Länge von 290 Aminosäuren und einer theoretischen Masse von 31900 Da. Durch in silico Untersuchungen konnte ein N-terminales Signalpeptid ausfindig gemacht werden, jedoch konnte die Massedifferenz der zweiten Konsensussequenz und des isolierten Proteins nicht im Detail erklärt werden und stattdessen wurde lediglich der Verdacht aufgestellt, dass bei der Isolierung des Proteins ein Peptid proteolytisch abgespalten wurde. Durch Vergleich der zweiten Konsensussequenz mit den Aminosäuresequenzen von anderen RIPs konnte gezeigt werden, dass die Konsensussequenz die konservierten Aminosäuren enthält, die für die enzymatische N-Glykosidase Aktivität verantwortlich sind. Damit wurde endgültig geklärt, dass es sich bei dem isolierten Protein um das Typ 1 RIP Agrostin handeln musste. Durch eine RACE-PCR konnte gezeigt werden, dass die mRNA für das Agrostin nicht nur in silico durch Auswertung der RNA-Seq-Rohdaten aufgezeigt werden konnte, sondern auch in vitro. Abschließend wurde für zukünftige Untersuchungen nicht nur die zweite, sondern auch die erste Konsensussequenz so weit präpariert, um eine Fremdexpression durchführen zu können. Dadurch soll unter anderem untersucht werden, ob es sich bei der ersten Konsensusse-quenz um eine Isoform des Agrostins handeln könnte.Weniger anzeigen
In biological and other non-isolated systems, an environment is typically coupled to a collective variable that characterizes the physical process of interest. Therefore, effective models are necessary for the description of the collective variable, which is also called the reaction coordinate. If there is no separation of time scales between the dynamics of reaction coordinate and environment, memory effects are present. This thesis investigates several systems in the realm of biological physics where memory effects are relevant. In the first part, we study cyclization kinetics of linear polymers via Langevin simulations of different backbone models, and phantom as well as self-avoiding collapsed chains. We find that while details of bonded interactions do not influence the end-to-end distance dynamics qualitatively, self-avoidance does. All memory kernels for the end-to-end distance and cyclization times extracted from our simulations are explained by scaling arguments based on Flory theory. In the second part, we study the mean first-passage time for barrier crossing for non-Markovian dynamics using Langevin simulations. For single-exponential memory, we recover known asymptotic scalings and identify a new parameter regime where memory effects accelerate barrier crossing. These numerical results are supplemented by a theoretical analysis. We present a heuristic formula for calculating the mean first-passage time and use it to globally characterize the dependence of the barrier crossing time on the system parameters. For bi-exponential memory, we find that the mean first-passage time can be calculated using the single-exponential heuristic formula with effective parameters, which are dominated by the shorter of the two memory times. This dominance is corroborated by an analytical calculation. In the third part, we consider surface waves. We study linear surface waves on a viscoelastic medium bounded by a viscoelastic interface, including the effects of gravitation. We investigate in which parameter regimes the classical Rayleigh, capillary-gravity and Lucassen surface waves exist and how they are related, and identify an additional wave solution which exists on a pure air-water interface. We subsequently derive the nonlinear fractional wave equation that governs compression waves at an elastic interface that is coupled to a viscous bulk medium. The fractional character of the equation constitutes a memory effect and comes from the frequency-dependent effective thickness of the bulk layer that is coupled to the interface. The nonlinearity arises from the dependence of the interface compressibility on the local compression. Numerical solutions of our theory reproduce experimental key features of surface waves in phospholipid monolayers at the air-water interface without freely adjustable fitting parameters.Weniger anzeigen
Network-based feature selection methods on omics data have been developed in recent years. Their performance gain, however, is shown to be affected by the datasets, networks, and evaluation metrics. The reproducibility and robustness of biomarkers await to be improved. In this endeavor, one of the major challenges is the curse of dimensionality.
To mitigate this issue, we proposed the Phenotype Relevant Network-based Feature Selection (PRNFS) framework. By employing a much smaller but phenotype relevant network, we could avoid irrelevant information and select robust molecular signatures. The advantages of PRNFS were demonstrated with the application of lung cancer prognosis prediction. Specifically, we constructed epithelial mesenchymal transition (EMT) networks and employed them for feature selection. We mapped multiple types of omics data on it alternatively to select single-omics signatures and further integrated them into multi-omics signatures. Then we introduced a multiplex network-based feature selection method to directly select multi-omics signatures. Both single-omics and multi-omics EMT signatures were evaluated on TCGA data as well as an independent multi-omics dataset.
The results showed that EMT signatures achieved significant performance gain, although EMT networks covered less than 2.5% of the original data dimensions. Frequently selected EMT features achieved average AUC values of 0.83 on TCGA data. Employing EMT signatures on the independent dataset stratified the patients into significantly different prognostic groups. Multi-omics features showed superior performance over single-omics features on both TCGA data and the independent data.
Additionally, we tested the performance of a few relational and non-relational databases for storing and retrieving omics data. Since biological data have large volume, high velocity, and wide varieties, it is necessary to have database systems that meet the need of integrative omics data analysis. Based on the results, we provided a few advices on building scalable omics data infrastructures.Weniger anzeigen
The aim of the thesis is to investigate the sensitivity of novel NMR outcome measures (OM) aiming to quantify pathological changes in the dystrophic muscle. Muscular dystrophy (MD) refers to a heterogeneous group of diseases with progressive muscle wasting and associated weakness characterized by variable degrees of necrosis, regeneration, ionic homeostasis disturbances, chronic inflamma-tion, and, ultimately, resulting in the replacement of muscles by fibro-fatty tissue. My focus was on the evaluation of 23Na NMR and advanced 1H transverse relaxation time (T2) techniques as early, sensitive OM. 23Na NMR measures the tightly controlled sodium concentrations and distribution in skeletal muscle tissue. This biophysical information can be used to assess ion homeostasis and cell integrity. However, 23Na NMR suffers from a low sensitivity and in vivo concentration compared to 1H. Alterations in the muscle 1H T2, commonly interpreted as an indicator of disease activity, are linked to a variety of non-specific events like oedema, inflammation, or necrosis that precede the actual muscle replacement by fat. Protocols including different 23Na NMR and 1H T2 methods were implemented to evaluate healthy and dystrophic skeletal muscle tissues of animal models and patients. This work provides evidence that 23Na NMR could offer a sensitive outcome measure able to monitor specific alteration of the dystrophic muscle at a very early stage.Weniger anzeigen
Using the theoretical frame of sensemaking, the author analyses empirically how top executives in Germany conduct sensemaking and how they conceptualize the future.
The thesis builds on the premise that the trends of postmodernity change the context of leadership. With the transition from modernity to postmodernity, technological progress, acceleration, and individualization affect the context of leadership. As a consequence, leaders and in particular top executives are experiencing increasing inconsistency. They have to deal with growing complexity, and they are conducting sensemaking vis-à-vis a more and more uncertain future.
This thesis builds on an analytical framework of sensemaking based on Karl Weick's work. A total of 33 semi-structured interviews with top executives from German-speaking countries are used for the survey, including CEOs of leading companies, federal ministers, mayors of larger cities, constitutional judges, high-ranking church representatives and trade union chairpersons.
The data analysis yields three findings. Firstly, it becomes apparent that the top executives interviewed are constantly exposed to inconsistencies and often fail to recognize them. Not every inconsistency leads to a complexity-reducing sensemaking process. Secondly, the empirical evidence shows that the process of sensemaking can be understood as gauging the stock variable "internal complexity", i.e. the complexity of the cognitive map. The executive does this by adjusting the flow variables "information intake" (which increases complexity) and "complexity reduction". And thirdly: While the first two findings seem to apply equally to all top executives, there are great differences in the conceptualization of future among the group of top executives surveyed. A second differentiating dimension was found along locus of control. The superimposition of both dimensions resulted in five different types of future-oriented sensemaking. Of particular interest is an observed form of sensemaking, which assumes an unpredictable future coupled with a "schizophrenic" locus of control.
In summary, the results of this thesis suggest that the process of sensemaking can be understood as a constant balancing act of the internal complexity of the top executive. A key attribute is the tolerance for complexity of the leader in question. If the internal complexity is too high, sensemaking may be triggered less often than if it is lower. Accordingly, it can be assumed that executives with a high degree of complexity tolerance are more likely to be able to maintain the idea of an unforeseeable future and therefore deal appropriately with the enormous complexity and unpredictability of the future, rather than shielding themselves from it.Weniger anzeigen
The research interest in the field of automated driving has been growing rapidly from the first milestones in the 1980s decade to our days. Actually, this interest keeps growing exponentially. The increasing research effort implies a large number of novel approaches, techniques and solutions. Nevertheless, further research is needed to achieve automated driving systems in all different kind of scenarios. Particularly, automated driving at urban scenarios still represents a very complex challenge for the research community.
This thesis deals with the development of a scenario interpretation module for automated driving at urban intersection. The main objective is to interpret the information from the perception module and guide the ego vehicle along the desired path to complete the maneuver.
The first contribution of this work is focused on the analysis of the problem, which yields to a classification of all scenarios considering the potential conflicts with other road users. Based on this statement, the need of a proper pass permission interpretation becomes crucial. The proposed solution in this thesis consists on calculating the probability that every pass permission state is valid for the ego vehicle. This is done by representing all possible traffic lights and traffic signs in two different probability mass functions, which are consequently combined. The developed approach deals not only with the uncertainty of the received inputs, but also with the fluctuations over time.
The concept of primary situations is presented as the core approach for further contributions. The key idea is to interpret the scenario by breaking down the whole desired maneuver into a sequence of primary situations. Using this concept, the object prediction module is significantly simplified. The movement of other involved road users is estimated, and this estimation is used to calculate the probability that every primary situation is occupied. In this thesis, the concept is presented for vehicles and pedestrians.
Another relevant contribution of this thesis is the use of the generated primary situations to perform the subsequent tactical decision making based on a state machine algorithm. The proposed solution enables to handle occlusions in a simpler manner imitating the human reaction.
The implementation of the developed approaches in a demonstrator vehicle and the consequent evaluation confirms that the presented solution is suitable for interpreting the scenario at urban intersections.Weniger anzeigen
This thesis consists of four different parts of the synthesis and investigation of various porphyrins containing different types of linkers for the connection to substrates, conjugates of these porphyrins with hyperbranched polyglycerol (hPG) in nanoparticles and nanogels, hPG-porphyrin conjugates additionally loaded with mannose and investigation of their antibacterial activity, and cleavable porphyrin-hPG-conjugates: A) The reaction of pentafluorophenyl-substituted A3B-porphyrins with amines has been used to obtain diverse reactive groups which are useful for the further functionalization and/or conjugation to different substrates and/or materials. With this method, porphyrins with alkenyl-, alkynyl-, amino-, azido-, cyclooctyne-, epoxide-, hydroxyl- and maleimido-groups have been obtained. The conjugation of an alkynyl porphyrin to an hPG-azide via the copper(I)-catalyzed 1,3-dipolar cycloaddition (CuAAC) is shown. For a possible application in the photodynamic therapy (PDT) the photocytotoxicity of porphyrin-hPG-conjugates has been demonstrated against human epidermoid carcinoma A-253 and squamous carcinoma CAL-27 cells. To allow cleavage of the porphyrins from a carrier system, examples of porphyrins containing disulfide (for reductive cleavage) and acetal (for pH-triggered cleavage) linkers are presented. B) The multivalency effect has been investigated using hPG loaded with zinc porphyrins as photosensitizer (PS) and a systematically varied number of mannose units as targeting groups. These conjugates have been tested on their antibacterial photodynamic activity. hPG-azide with a core molecular weight (MW) of 19.5 kDa was functionalized with approx. 14 groups of the PS using the CuAAC. Subsequently, the conjugates have been further functionalized with systematically different loadings of mannose in the range of approx. 20 to 110 units. For the conjugates with approx. 58-110 mannose groups with this method the water insoluble zinc-porphyrin have been transformed to water soluble formulation. For these conjugates, the antibacterial phototoxicity against S. aureus was investigated in phosphate-buffered saline (PBS). Conjugates with approx. 69 to 110 mannose groups showed a significantly higher antibacterial activity, whereas conjugates with approx. 20 to 58 groups exhibited no activity at all. These in vitro tests showed promising results shedding light on the multivalency effect in combination with PDT. With the addition of serum, the antibacterial activity is completely quenched. We investigated this behavior with fluorescence studies performed with bovine serum albumin (BSA) suggesting protein-conjugate association as a possible cause for the loss of antibacterial activity. C) Another insight into multivalency effect came from the preparation of hPG with systematically different MW loaded with zinc porphyrins as PS and mannose groups as targeting functionality which have been tested on their antibacterial photodynamic activity. hPG-azides with a core MW between 3.7 and 100 kDa have been functionalized with approx. 4 to 108 groups of the PS [[5,10,15-tris(3-hydroxyphenyl)-20-[4-(prop-2-yn-1-ylamino)tetrafluorophenyl]porphyrinato]]-zinc(II) using the CuAAC. Additionally, polyglycerol based nanogel (nPG) with azide functionalities have been synthesized using a modified inverse nanoprecipitation. With this new method, it was possible to obtain nPGs with excess azide functionalities on the surface. The nPG-azides were further transformed to the porphyrin-nPG-conjugates via CuAAC. Subsequently, the conjugates have been further functionalized with mannose in the range of approx. 14 to 527 units. With this method the complete water insoluble zinc-porphyrin could be transformed into water-soluble formulations. Investigation of the antibacterial phototoxicity of these conjugates against S. aureus has revealed that conjugates with approx. 14 to 108 mannose groups exhibit an increasing antibacterial activity, whereas conjugates with approx. 108 to 527 groups exhibit a complete eradication of the bacteria. It has been shown that the increasing size of the porphyrin-mannose-hPG conjugates has a direct effect of antibacterial phototoxicity. With the results of the conjugates with a fixed polymer size and systematically varied mannose loadings from part B these in vitro tests show another aspect of the multivalency effect in combination with PDT. D) Porphyrin-hPG-conjugates connected via reductive and acid-cleavable linkers have been synthesized for application in PDT using CuAAC and strain-promoted alkyne-azide cycloaddition (SPAAC). Employing nucleophilic aromatic substitution (SNAr), a pentafluorophenyl substituted porphyrin has been functionalized with 1,6-diaminohexane and cystamine. In the next step, these porphyrins have been further reacted with propiolic acid or bicycle[6.1.0]non-4-yn-9-ylmethyl(4-nitrophenyl)carbonate. Porphyrin-hPG-conjugates with hPG-azide and/or hPG with acid-labile benzacetal linkers have been obtained using CuAAC or SPAAC and the previously synthesized porphyrins. With this method, the final porphyrin-hPG conjugates with acidic and/or reductive cleavable linkers were synthesized. The successful cleavage of the PS from these conjugates has been shown in different release studies. To illustrate the possible application of these conjugates selected compounds have been tested for their phototoxicity in four tumor cell lines and on the typical Gram-positive germ S. aureus.Weniger anzeigen
Phosphinine galten lange Zeit als „chemische Kuriositäten“, da sich ihre Eigenschaften deutlich von sowohl klassischen Phosphor(III)-Verbindungen als auch von ihren niederen Homologen, den Pyridinen, unterscheiden. Jedoch gewinnen Phosphinine und allgemein phosphorhaltige Heterozyklen in den letzten Jahrzehnten immer mehr an Bedeutung und finden zudem Anwendung in vielen interessanten Bereichen der modernen Molekülchemie. In der Arbeit wird die Synthese und Charakterisierung zweier neuartiger P,N-Hybridliganden, Phosphinine NPN und PN‘, beschrieben. Die Darstellung erfolgt dabei über die Pyryliumsalz-Route. Zudem konnte das in der Vergangenheit nur schwer zu synthetisierende Phosphinin PNP durch Änderung und Optimierung der ursprünglichen Synthesevorschrift darstellt werden. Zu Vergleichszwecken ist es gelungen, die drei analogen Pyridinderivate ebenfalls erfolgreich zu synthetisieren. Die erfolgreich synthetisierten Phosphinine und Pyridine wurden als Liganden in Koordinationsverbindungen mit Übergangsmetallen wie Wolfram, Rhodium, Kupfer, Silber und Gold in den Oxidationsstufen zwischen 0 und +I eingesetzt. Die Komplexe wurden durch NMR-Spektroskopie und Massenspektrometrie nachgewiesen. Einige Koordinationsverbindungen konnten darüber hinaus röntgenkristallographisch eindeutig charakterisiert werden. Zudem konnte ein leicht zugänglicher und gut umsetzbarer Syntheseweg zu Trimethylsilyl-substituierten Phosphininen gezeigt werden. Diese [4+2]-Cycloadditionsreaktionen mit TMS-Phosphaalkin als Phosphorquelle ermöglichen durch geeignete Substituenten am Edukt eine regioselektive Darstellung von 2-TMS-Phosphininen. Dieses konnte in bestimmten Fällen mittels Röntgenkristallstrukturanalyse der korrespondierenden W(0)-, Cu(I), und Ag(I)-Komplexe bestätigt werden. Bei der Silber(I)-Verbindung handelt es sich um den ersten kristallographisch charakterisierten Phosphinin-Ag(I)-Komplex. Die erhaltenen TMS-Phosphinine zeigen erstaunlicherweise eine hohe kinetische Stabilität gegenüber Luft und Wasser im Gegensatz zu der in der Literatur beschriebenen Hydrolyse- und Luftempfindlichkeit der Stammverbindung Phosphinin. Durch sterisch weniger anspruchsvolle Reste in 6-Position von 2-Pyronen ließen sich erste Informationen über die Regioselektivität dieser Reaktion sammeln sowie die Bildung von zwei Regioisomeren demonstrieren. Durch Pd-katalysierte Negishi-Kreuzkupplungsreaktionen ließ sich das bromsubstituierte Phosphinin leicht weiter funktionalisieren. Zudem konnte gezeigt werden, dass sowohl die Stammverbindung Phosphinin als auch weitere niedersubstituierte 2-Phosphinine mittels Protodesilylierung mit HCl sauber erhalten werden können. Sowohl eine erfolgreiche Negishi-Kreuzkupplung als auch die Protodesilylierung konnten im Falle eines Phosphinin-W(0)-Komplexes und eines Phosphinin-Cu(I)-Komplexes kristallographisch bewiesen werden. Zuletzt haben durchgeführte DFT-Rechnungen zeigen können, dass die TMS-Gruppe in ortho-Position am Phosphinin-Heterozyklus eine starke Erhöhung der σ-donierenden Eigenschaften des Phosphoratoms bewirkt.Weniger anzeigen
Many eukaryotic proteins are attached to the cell membrane via Glycosylphosphatidyl-inositol (GPI) anchors that are added post-translationally to the C-terminus of proteins. These complex structures contain a highly conserved carbohydrate core, variable number of phosphate residues and lipid chains. The functions of GPI-anchored proteins (GPI-APs) are widespread, including participation in signal transduction, immune response regulation, lipid raft partitioning and prion disease pathogenesis. However, the effect of the GPI-anchor itself in these processes still remains unclear. Due to their high complexity and metabolic expense, a function beyond membrane anchoring has been anticipated. GPI-APs are not accessible in a homogeneous form and high amounts by isolation from natural sources, making investigation of the GPI effects on the function and structure of the protein difficult. Some progress has been made in the field of total GPI synthesis and small GPI-anchored peptides are now accessible by chemical synthesis, but these strategies are limited regarding peptide length by the scope of solid-phase peptide synthesis (SPPS). So far, no method is available for the routine generation of homogeneous GPI-APs for structural or biological studies. In this work, different semi-synthetic, intein-based methods have been investigated and established for the generation of homogeneous GPI-anchored proteins, Figure 1. The first method, Expressed Protein Ligation (EPL, a), utilizes the GyraseA intein from Mycobacterium xenopi for the generation of protein α-thioesters which are then ligated to cysteine-containing GPI-anchors. The second method, Protein Trans-Splicing (PTS, b) uses the naturally split DnaE intein from Nostoc punctiforme. For PTS, proteins of interest are expressed in E. coli as fusion proteins with the larger N-terminal split intein fragment NpuN, whereas the shorter (39 amino acids) C-terminal fragment NpuC is synthesized by SPPS and ligated to a cysteine-containing GPI-anchor. Subsequently both fragments are combined and trans-splicing takes place initiated by association of the fragments and folding into a full intein structure, ligating both exteins together with a native peptide bond. This method requires the introduction of some extra amino acid residues which are essential for the splicing reaction. Both EPL and PTS were successfully established for the anchoring of eGFP as a model protein to biotin and a GPI anchor containing the full pseudo-pentasaccharide core structure, phosphates, and a simplified monolipid chain. Application of these strategies to the semi-synthesis of the naturally GPI-anchored proteins Thy-1 and prion protein (PrP) showed, however, that thioester generation is inefficient under denaturing conditions, making the EPL strategy less useful for our purpose. PTS on the other hand was efficient under denaturing conditions, although slower. In comparison to the natural conditions, this strategy suffered from insufficient availability of the synthetic GPI-coupled peptide due to a high synthetic effort required for its synthesis. Therefore, a third semi-synthetic, intein-based method was developed: One-Pot-Ligation (OPL, c). In OPL, the same fusion proteins required for PTS can be used, but they are combined with a mutated C-terminal fragment, NpuC(AA), in which two essential amino acid residues are exchanged for alanines, rendering the C-terminus of the split intein function-less. Instead, with this system, a protein intermediate can be captured and protein thioesters can be generated in situ by the additions of external thiol reagents, with subsequent ligation of Cys-GPI in a one-pot manner. This strategy was successfully applied for anchoring both soluble and denatured proteins (eGFP, Thy-1, PrP and IL-2) to biotin, dimannose and mono- and bilipidated GPI-anchors. It is more versatile towards the generation of GPI-AP libraries, however exhibited some immature protein thioester hydrolysis which could largely be overcome by the use of more stable thiols. Additional challenges arose from characterization of these highly complex protein-carbohydrate-lipid conjugates, carrying multiple charges, in LC-MS. Although progress could be made towards this goal, a complete characterization was not achieved for each protein. Initial structural characterization of the obtained GPI-APs was performed for eGFP-GPI using circular dichroism (CD). This study showed that using any of the three methods investigated, anchoring to GPIs does not affect the structure of eGFP.Weniger anzeigen
In this thesis, functionalized graphene sheets were synthesized and their cellular uptake features, drug release properties, and anti-MDR ability were investigated and some significant conclusions were obtained. Hyperbranched polyglycerol (hPG) was successfully conjugated to the graphene backbone that was functionalized by nitrene through a [2+1] cycloaddition reaction. The resulting hPG-coating graphene sheets showed high polymer coverage, controllable size, good water dispersibility, excellent biocompatibility and can be easily post-functionalized. Amination and sulfation was applied to obtain positively charged and negatively charged graphene sheets, respectively. Furthermore, functionalized graphene sheets could be broken down into smaller sizes by horn sonication with corresponding time frames. In my first project, the cellular uptake characteristics of these graphene derivatives with similar polymer content, but different size and surface charges were investigated. It was found that large functionalized graphene sheets (1 μm) were preferable taken up via a phagocytic pathway, regardless of their surface charges. However, surface charge is a dominant factor for their small analogs (200 nm size). Small graphene sheets with positive charges mainly entered into the cells through clathrin-mediated endocytosis (CME), while this pathway did not play a significant role for the small ones with negative charge. Because of the surface charge, the negatively charged and positively charged graphene derivatives displayed size-independent and sizedependent uptake efficacy. Moreover, our results also revealed the cellular internalization of hPG-conjugated graphene sheets is negligible for all the sizes, which is attributed to the protein-resistant feature of hPG and low nonspecific interactions with biointerfaces. In the next project, we prepared graphene sheets with similar polymer content, size (around 150 nm), but different functionalities and surface charges according to our established protocol of the first project. The hydrophobic anticancer drug, DOX, was loaded onto these graphene derivatives and a pH-sensitive dye was connected onto their surface and employed as an antenna to receive strong signals from the acidic cell compartments. It was found that these functionalized graphene sheets with different functionalities underwent the same cellular uptake and acidification process, while their intracellular release properties were fundamentally different. The protonation of DOX in acidic conditions decreased their hydrophobic and π-π stacking interaction with graphene backbone and facilitated its release from both sheets with different surface charges. However, protonated DOX was positively charged and exhibited attractive and repulsive electrostatic interactions with negatively charged and positively charged hPG-conjugated graphene derivatives, respectively. While the release of DOX was accelerated by repulsive electrostatic force in the case of positive sheets, many of them were trapped on the surface of negative sheets via attractive electrostatic interactions. Therefore, the overall release rate and therapeutic effect was much higher in the first case. This study revealed that intracellular location and release features of the therapeutic agents are a function of their hydrophobic and electrostatic interactions with the graphene-based nanocarriers. In the third project, a graphene-based delivery nanoplatforms was introduced to overcome the newly-emerging MDR in tumor cells. Triphenylphosphonium and 2,3- dimethylmaleic anhydride were conjugated onto the hPG-covered nanographene sheets to achieve mitochondria targeting and charge-convention properties. The average size of these functionalized nanographene sheets were around 75 nm with a narrow sizedistribution, which was favorable for their accumulation in tumor site owning to the widely confirmed EPR effect. After internalization, these nanosheets targeted the mitochondria and finally disrupted them under laser irradiation, leading to the plunge of adenosine triphosphate (ATP) synthesis. Without enough “biological fuel,” the P-gP lost its function and the MDR was successfully reversed. Both of the in vitro and in vivo antitumor results confirmed these functionalized graphene sheets could effectively surmount the troublesome MDR tumors and remarkably promote the synergic antitumor theranostic efficacy. Moreover, serious side effects caused by chemotherapy agents could also be avoided with these graphene-based nanocarriers. During the doctoral studies, my work focused on the biological behavior of graphene derivatives and their potential application for antitumor therapy. Many promising results were obtained and several critical problems were addressed, including the cellular uptake properties, intracellular release features, and anti-MDR theranostic. These outcomes revealed that the biological behaviors of functionalized graphene sheets could be adjusted by their physiochemical characteristics and MDR reversal therapy could be achieved though the rational design of graphene-based nanoplatforms, which is of great significance for the future development of graphene-based nanomaterials for bioapplications.Weniger anzeigen
Cu(In,Ga)Se2 (CIGS) is applied as absorber layer for thin ﬁlm solar cells. An industrially relevant approach for low cost and fast preparation of CIGS is the sequential processing. The sequential process applied in this work is based on sputtering a Cu-In-Ga precursor, which is then heated in Se vapor to form a CIGS layer (selenization) within minutes. However, sequential processing typically leads to Ga segregation at the back contact. The observed Ga segregation inhibits the adjustment of the effective band gap energy to achieve more efficient solar cells. Up to now, a sufficient adjustment of the Ga in-depth proﬁle during fast selenization in Se vapor has not been achieved. Identifying pathways to prevent strong Ga segregation within a fast sequential process is the aim of this thesis. A possible parameter for an additional control of kinetics during growth of CIGS is the Se supply, whose inﬂuences are investigated here. This can mean a control of i) the time of starting the Se supply and ii) the Se partial pressure. It is found, that i) a delayed Se supply can lead to lateral phase segregation and dewetting. The results show how to enable and widen the parameter space for a delayed selenization with a prior annealing step at a temperature of up to 580 °C by fast heating rates or NaF addition on top of the precursor. ii) The control of the Se supply was achieved by evaporation of Se from an external source. For a better understanding of the growth of CIGS, the evolution of phases and their depth distributions were investigated by a simultaneous in situ EDXRD/EDXRF method. By comparing the measured with numerically calculated ﬂuorescence intensities, a schematic model of the evolution of the phase depth distribution during selenization was obtained. With this approach, two different growth paths, one with strong Ga segregation and one with Ga homogenization were analyzed. For the former, it was possible to experimentally observe the formation and period of presence of Cu2−xSe with this method for the ﬁrst time and to conﬁrm the position to be near the surface of the ﬁlm. Decreasing the Se source temperature corresponds to a lower Se supply for the CIGS formation and was the key for preventing Ga segregation in the absorber. The growth without Ga segregation was observed via an in situ method the ﬁrst time. A different evolution of the phase formation and depth proﬁle was observed. A consequence of the low Se supply was a longer presence of the intermediate phases InSe and γ-Cu9(In,Ga)4. At 500 °C, Ga and Cu quickly move towards the surface and the minimum band gap of the resulting absorber ﬁlm is widened. A schematic model of growth is presented. This processing is considered to play an important role for a forthcoming industrially relevant technology. By utilizing the CIGS formation with a higher Ga concentration close to the absorber surface and optimizing the precursor architecture towards a multilayer precursor consisting of 22 In/CuGa/In layers, solar cells with a conversion efficiency of up to 15.5 % were achieved (active area, in-house measured, no anti reﬂective coating). This is the highest reported efficiency for sulfur free CIGS-based solar cells utilizing fast atmospheric processes and elemental Se.Weniger anzeigen
1. Lipid-drug-conjugate (LDC) solid lipid nanoparticles (SLN®) for the delivery of nicotine to the oral cavity – optimization of nicotine loading efficiency.
Nicotine lipid-drug-conjugates (LDC) were prepared by mixing nicotine with a fatty acid (Kolliwax® S or stearic acid). Hydrogenated sunflower oil (HSO) combined with the LDC were used as the lipid matrix in the LDC-containing SLN® system, whereas non-LDC SLN® were produced as a reference using HSO and pure nicotine. Both LDC-containing SLN® and non-LDC SLN® were successfully produced using a hot high-pressure homogenization method. Following production, photon correlation spectroscopy (PCS) confirmed all formulations were in the submicron size range (150 to 350 nm diameter) with narrow size distributions (PDI around 0.25). The laser diffractometry (LD) results showed 90% of the particles had a diameter lower than 1,000 nm. Light microscopy images show no aggregation of the particles, which is good agreement with the LD result. Differential scanning calorimetry (DSC) was used to investigate the thermal behavior of the system, and showed the thermal response of the four formulations was dominated by the HSO. The onset temperature of the melting process (> 39 °C) was higher than mouth temperature (37 °C), showing good applicability for buccal delivery. The nicotine-loaded particles could be successfully separated from the water phase using Amicon® Ultra-4 centrifugal filter devices, and the encapsulation efficiency of nicotine in LDC-containing SLN® was about 50% w/w. This is an almost fivefold increase compared to the conventional nicotine loaded SLN® (around 10% w/w). The high degree of encapsulation makes the LDC-containing SLN® a promising system for buccal delivery of nicotine with low side effects, and incorporating the SLN® into nicotine chewing gum or lozenges has the potential to be an innovative nicotine replacement therapy.
2. smartLipids® as third solid lipid nanoparticle generation – stabilization of retinol for dermal application.
Following a screening of several stabilizers, Tween® 20 proved most suitable for smartLipids® production. smartLipids® were successfully produced by a hot high-pressure homogenization method, and loaded with different amounts of retinol (5%, 15%, 20% w/w). The mean diameter of smartLipids® formulations was about 200 nm, and remained unchanged during a storage period of two months as determined by PCS. DSC results showed an absence of polymorphic transitions, an indication of good physical stability. Furthermore, the onset temperatures of melting peaks were above 38 °C, ensuring the particles maintain their solid state during the skin penetration process (skin temperature is 32 °C). Results showed that after 60 days of storage, 37%, 59% and 75% w/w of retinol remained in the particle suspensions loaded with 5%, 15% and 20% retinol, respectively. Thus, the degradation of loaded retinol was reduced significantly by incorporating it into smartLipids® when compared to other studies. Since the loading capacity was superior to other studies as well, two major advantages characteristic for smartLipids®¬ were combined. Dispersing the smartLipids® suspension into a gel base as a dermal formulation did not change the particle size, and the same chemical stability was observed as for the lipid nanoparticle suspension. Thus, the concept of smartLipids® worked efficiently for retinol, improving not only the encapsulation efficiency but also physical and chemical stability, as well as showing good performance in a gel base.
3. The influencing factors of producing stable smartLipids®: lipids, surfactants and production parameters.
Although smartLipids® provide a more universal delivery approach owing to the possibility of stabilizing a wide spectrum of different actives, the stability of the lipid nanoparticle suspensions strongly depends on a variety of influencing factors, and developing stable formulations is generally a resource- and time-intensive process. This study investigated in more detail the influences of the lipid compositions, the type and concentration of the surfactants and the production parameters on the stability. Most of the produced formulations instantly gelated after production, or showed macroscopic particle growth. The investigated lipid composition 2 and 4 - combinations of low melting range lipids - showed nano-ranged particle sizes, narrow particle size distributions and were stable for 180 days. The addition of a liquid lipid increased the stability in lipid composition 2, 3 and 4, due to the enhanced miscibility of the lipid matrix. Formulations stabilized by surfactants with a high hydrophilic-lipophilic balance (HLB) showed better physical stability. On the contrary, increasing the concentration of surfactants did not successfully suppress aggregation when surfactants with a lower HLB value are used, likely owing to increased Ostwald ripening. Furthermore, the zeta potential value did not reliably predict the long-term stability of smartLipids®. Both stable lipid nanoparticle suspensions with low zeta potential were encountered as well as unstable formulations with a high zeta potential were encountered, showing that steric effects are important. Additionally, the most stable formulations were achieved by performing only 1 or 2 homogenization cycles.
4. Solid lipid nanoparticles (SLN®) for the delivery of α-tocopherol – an efficient method for improving the drug loading capability.
Solid lipid nanoparticle suspensions loaded with 5% and 10% α-tocopherol (w/w) were successfully developed. The mean particle sizes of these lipid nanoparticle suspensions remained in the nano-range following production, and their size distributions narrowed with an increasing number of homogenization cycles. After storing all suspensions at room temperature for 7 days, the SLN® suspensions produced with carnauba wax did not remain stable, except for the formulation produced with 10% α-tocopherol and 3 homogenization cycles. On the contrary, all SLN® suspensions produced with cetyl palmitate showed great physical stability. Zeta potential values of the produced lipid nanoparticle suspensions measured in original medium were higher than |40 mV|, and in conductivity water were higher than |60 mV|, a sign of potentially good physical stability. The thermal analysis of SLN® suspensions showed very weak peaks in 10% α-tocopherol-loaded SLN® produced with cetyl palmitate, indicative of an only slightly ordered matrix. Therefore, 10% α-tocopherol-loaded SLN® produced with carnauba wax and 3 homogenization cycles were recommended for further practical usage. Furthermore, the onset of the melting behavior of this SLN® suspension occurs above skin temperature, making it suitable for dermal application. Using carnauba wax and producing the formulation with 3 homogenization cycles, the loading of α-tocopherol could be increased to 10% w/w. Aside from increased drug loading, this formulation has a suitable particle size, narrow size distribution, good physical stability as well as a desirable thermal profile, making it highly promising for dermal application.Weniger anzeigen
Effective cancer therapy relies on early diagnosis and treatment decisions based on patient-specific tumor profile and biology. Peptide receptor targeting proved to be a pivotal tool for imaging, staging and therapy of neuroendocrine tumors, which frequently express G protein-coupled somatostatin receptors (SSTRs) on their cell surface. Optimized somatostatin analogs such as octreotide are successfully utilized for the clinical management of these tumors. However, it is estimated that around 30 % of patients do not profit from SSTR-based approaches, making the characterization of alternative cell surface targets necessary. Previous cell-based screening assays conducted in our group had shown a clear response of human NET cell lines to angiotensin II. In the presented study, expression analyses of the cognate angiotensin II receptor type 1 (AGTR1) revealed an upregulation of both mRNA and protein levels in patient NET tissues compared to healthy controls. To assess the applicability of AGTR1 for in vivo imaging, the receptor ligands saralasin and valsartan were coupled to the near-infrared dye ITCC and tested for their biodistribution in a mouse model bearing receptor-positive and -negative xenograft tumors. Both probes showed promising results and represent a good basis for further development to optimize their physicochemical profile as well as tumor accumulation. Functional assays evaluating signaling cascades and processes such as proliferation and secretion upon receptor stimulation complemented this project. Diagnostic imaging selects eligible patients with SSTR-positive tumors for following peptide receptor radionuclide therapy (PRRT). For this purpose, somatostatin analogs are coupled to therapeutic radionuclides like lutetium-177, which are specifically bound and uptaken by NETs after injection. Although PRRT can deliver radiation doses of up to 250 Gy to the tumors, complete remission is very rare. The additional use of established NET therapies such as targeted mTOR inhibition can be a promising approach. Therefore, the second part of this study assessed a potential radiosensitizing effect of temsirolimus and everolimus in five NET cell line models. Treatment with these mTOR inhibitors alone resulted in antiproliferative effects, modulation of downstream signaling and G1 cell cycle arrest. On the other hand, undirected external beam irradiation induced a G2/M arrest in all tested cell lines. In combination, mTOR inhibitors abrogated the radiation-induced G2/M arrest with further reduction of cell viability and survival. As the investigated NET cell lines revealed a lack of SSTR2 expression, two receptor-positive cell lines were established for further SSTR2-targeted PRRT studies. Although the combination of mTOR inhibitors with the agonistic 177Lu-DOTATOC did not reveal any beneficial effect, the superiority of the recently developed antagonist 177Lu-DOTA-JR11 was demonstrated. This work contributes to the understanding of NET-specific target expression and treatment response. The obtained insights might be further refined by preclinical studies to pave the way for a significant increase of the diagnostic and therapeutic efficacy.Weniger anzeigen
As oral administration of pharmaceutical drugs in patients is the preferred route, special interest is given to predict the ability of a new compound to be absorbed in man. During the last 60 years, a vast number of in vitro, in vivo and in silico absorption models have been developed in order to estimate human intestinal permeability and eventually the fraction of dose absorbed of a compound administered. These were comprehensively characterised and discussed with regards to their strengths and limitations in this thesis. Depending on the stage of the pharmaceutical development process different models can be suitable. Furthermore, two common absorption models were challenged on their ability to investigate the extent of drug absorption.
Firstly, the in vitro Ussing chamber technique using rat jejunal tissue was experimentally established and successfully validated using the reference compounds 14C-mannitol, 3H terbutaline, 3H-propranolol, 3H-verapamil and 14C fexofenadine. Bidirectional permeability studies were conducted, determining the apparent permeability (Papp) of the compounds and the ability to display absorption mechanisms was investigated. Furthermore, reasons for variability found when comparing several reported permeability values in literature was examined, focusing on studying non-specific binding (NSB) of the compound to the experimental equipment. Also, the influence of two tissue preparation techniques (“stripped” or full-thickness tissue) was investigated. Results from the Ussing chamber experiments revealed that NSB can have a crucial influence on the Papp especially for lipophilic compounds. The tissue preparation technique showed a greater influence on the transcellularly absorbed compounds rather than the paracelullarly permeating ones. The route of absorption for each compound could be identified, showing paracellular absorption for mannitol and terbutaline, transcellular absorption for propranolol and verapamil and active uptake of fexofenadine. To ensure comparable results for all compounds, determination of NSB prior to permeability experiments should be mandatory and “stripping” of the rat jejunum is recommended.
Secondly, the in silico physiologically based absorption software GastroPlus™ was challenged, on the ability to predict fraction absorbed (fa) and the absorption rate constant (ka) for eight compounds under development at Bayer Pharma AG, in a retrospective analysis with preclinical and clinical data, using the basic default settings of the software. The influence of the input parameters (physicochemical, physiological and formulation properties) were investigated via parameter sensitivity analysis and predictability for different species was compared. Results from GastroPlus™ simulations showed good predictability of fa with 77 % within a 2 fold error. The tendential overprediction of fa for the species dog, suggested lowering the species-specific Peff converting factor from 3.3 to about 2. The parameter sensitivity analysis for one compound (C5) suggested that an increase of stomach pH in the dog from 3.0 to 4.3 could lead to a distinct decrease (by 64 %) in fraction absorbed. Adjusting the stomach pH prior to in vivo pharmacokinetic studies in the dogs should be considered for compounds with pH-dependent solubility to reduce variability. The general underprediction of ka for simulations with a fast absorption phase in vivo, recommends improvement of the solubility input data. The parameters permeability and solubility were identified as critical input properties. It was suggested, to use the Ussing chamber absorption model to generate a reliable permeability input parameter (Peff). Furthermore, the use of biorelevant buffer systems that mimic the in vivo situation should be used for solubility tests to improve predictability of the in silico tool.Weniger anzeigen
This dissertation is about applications and properties of lattice polytopes. In the second chapter, we briefly review the necessary background material.
In Chapter 3, we examine proper colorings of a special family of graphs. This family is described by the Cartesian graph product of an arbitrary graph and a path (cycle) graph. It is important to note that there are two independent parameters, the size of the path (cycle) graph and the number of colors. In order to determine the number of proper colorings, we combine transfer-matrix methods with Ehrhart theory. Furthermore, we use group actions to limit the size of the transfer matrix. We describe an explicit formula for the chromatic polynomial of the product with a path graph. Moreover, we describe the asymptotic behavior in the case of the product with a cycle graph.
In Chapter 4, we examine and fully characterize the level property of order polytopes, where levelness is a generalization of the Gorenstein property. We use weighted, directed graphs to describe this characertization. This enables us to give construct an infinite class of level order polytopes. In addition, we characterize the level property of alcoved polytopes.
In Chapter 5, both the Gorenstein and the level property of s-lecture hall polytopes are described. We use the results from the literature about the Gorenstein property of s-lecture hall cones to describe and characterize the Gorenstein property of s-lecture hall polytopes. Furthermore, we give a characterization of the level property in terms of inversion sequences. This characterization can explicitly be applied in lower dimensions, which is illustrated while we prove that every 2-dimensional s-lecture hall polygon is level.
In Chapter 6, we examine the holes of affine semigroups. Based on a publication by Hemmecke, Takemura, and Yoshida, we develop a software that describes the set of holes. We use this software to examine the holes of semigroups coming from the common diagonal effect model. Based on explicit computations we conjecture and then prove the structure of these holes. Furthermore, we show that the 7th linear ordering polytope has the integer-decomposition property.
Chapter 7 can be seen as a manual of this software. The source code can be found in the appendix.Weniger anzeigen
Dynamic molecular processes in aqueous solutions are essential for biological life, and their fundamental timescale is determined by molecular friction. In this thesis, several basic dynamic phenomena relevant for aqueous biological systems are studied by a combination of molecular dynamics simulations and stochastic models. First, we show by ab initio molecular dynamics simulations that the polarization of continuum bands in infrared spectra of small protonated water clusters allows us to deduce their shape and orientation. The molecular origin of continuum bands of protonated water wires is elucidated. Based on these results and recently recorded, experimental polarization-resolved infrared spectra, we reveal the orientation of a protonated water cluster in the transmembrane protein bacteriorhodopsin. Secondly, the friction of an externally confined, water-solvated methane molecule is extracted from molecular dynamics simulations using a newly developed method to parametrize a generalized Langevin equation. We show that the friction increases by up to 60% with increasing confinement strength, which is accompanied by a slowing down of the translational and rotational water dynamics in the hydration shell. This previously unknown effect is relevant for the interpretation of spectroscopy experiments as well as for trapped particles in viscous solvents. Thirdly, the mass dependence of the methane friction in water is studied by a similar method. We demonstrate that the friction increases with solute mass by up to 70%, which goes along with a slowing down of the hydration shell dynamics by a factor of three. We characterize the scaling behavior of mass-dependent friction and show that the often applied power-law relation holds only for an intermediate regime. Next, we compute the friction memory kernel of the dihedral angle of water-solvated butane by another newly developed method for the parametrization of generalized Langevin equations in the presence of arbitrary, non-linear potentials. This method is applied to a free butane molecule as well as to a constrained butane with the dihedral angle as the only positional degree of freedom, in both cases for different solvent viscosities. The results allow us to answer a long-lasting question by showing that dihedral angle isomerization reactions are dominated by internal friction. Finally, we show that the ensemble properties of so-called transition paths, which connect an initial starting position without return to a target state, deviate significantly from equilibrium. The deviation can be quantified by an effective temperature, which reaches several times the ambient temperature for systems with low friction. All of these results constitute significant advancements to the respective subfields, and together they shed light on the complex and subtle interplay of friction, inertial and non-Markovian effects on the molecular scale.Weniger anzeigen
The utilization of silver nanoparticles in consumer related products has significantly increased over the last decade, especially due to their antimicrobial properties. Today they are used in a plethora of products ranging from cosmetics and textiles to medical instruments. Thus, investigations on nanoscale silver are attracting increasing interest in many fields, such as biomedicine or catalysis. Unfortunately, the results of these studies are diverse and do not lead to a consistent evaluation of the toxicity of silver nanoparticles. A major flaw is the usage of non-uniform and inadequate characterized particles with broad size distributions. To elucidate this problem this thesis deals with the synthesis and thorough characterization of a versatile silver nanoparticle system in a size at the lower end of the nanoscale. Poly(acrylic acid) (PAA)-stabilized silver nanoparticles with a nominal radius of 3 nm are synthesized using two methods. Firstly, they are produced in a classical batch synthesis and secondly in a microwave-assisted synthesis. The comparison of these two routes applying the same reaction conditions provides the opportunity to reveal whether non-thermal microwave effects, which are still under debate in literature, are present. The synthesized particles exhibit a high stability and are used in an inter-laboratory comparison proving their suitability for application in nanometrology, such as determination of nanoparticle sizes, size distribution widths, and particle concentrations. Furthermore, the high versatility of the silver nanoparticle system enables an easy ligand exchange to tune the surface of the particles on demand and improve their biocompatibility. Exemplarily, transfunctionalizations with albumin, glutathione, and tyrosine are performed and characterized by small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), UV/Vis and IR spectroscopy. These differently coated silver nanoparticles are used firstly in a catalytic application: the reduction of 4-nitrophenol. Therein, a dependence of the catalytic activity on the corresponding coating is observed and reveals that the PAA-stabilized silver nanoparticles exhibit an exceptionally high activity. As a preliminary study for future biological applications the binding behavior, especially the adsorption and desorption, of biocompatible, fluorescent ligands is investigated. It is demonstrated that a fluorescent labelling with appropriate binding properties can be provided, which is subsequently used in an initial investigation on lung and intestinal cells regarding particle transport. Subsequently, the PAA-stabilized particles are employed in an artificial digestion. The monitoring of the size and size distribution throughout the three steps of digestion (saliva, stomach, intestine) shows that the silver nanoparticles pass the digestion under transformation in size, but still remain nano-sized. Since silver is known for the continuous release of silver ions, the digestion of silver nanoparticles leads naturally to the question of the behavior of ionic silver in an artificial digestion. The investigation of this topic with the help of small and wide-angle X-ray scattering and IR spectroscopy reveals that silver thiocyanate nanoparticles are formed during in vitro digestion. The release of silver ions from the surface of silver nanoparticles is a crucial point in the risk assessment of silver nanoparticles, since the ions can undergo complex transformations in biological environments. In this work, enhanced ion release was observed for the interaction of PAA-stabilized silver nanoparticles with glutathione. New small silver clusters were formed during this process. The diverse applications of the silver nanoparticle system in this work demonstrate the high versatility and stability of the system, which is a promising candidate for further comparable biological and catalytic applications.Weniger anzeigen
Die vorgestellten Arbeiten untersuchen die funktionelle und strukturelle Integrität von zentralen (prägangionären) und peripheren (postganglionären) Anteilen des autonomen Nervensystems bei neurodegenerativen Erkrankungen. Die quantitative Bewertung und der statistische Vergleich klinischer und autonomer Parameter (Erkrankungs- / Symptomschwere, Progressionsgeschwindigkeit, etc.) offenbart zwar signifikante Unterschiede zwischen den diagnostischen Subgruppen der Parkinsonsyndrome, auf individueller Ebene ist die Diagnostische Sicherheit jedoch deutlich geringer. In einer der hier vorgestellten Arbeit versuchen wir die Nachteile einer quantitativen Analyse durch die qualitative Bestimmung eines hoch spezifischen Biomarkers zu überwinden. Durch den Nachweis von phosphoryliertem alpha-Synuclein (P-α-Syn) in dermalen Nervenfasern konnten wir die klinische Diagnose eines M. Parkinson bereits in-vivo mit histopathologischer Sicherheit bestätigen. Der Nachweis von P-α-Syn in peripheren Nervenfasern, die dermale autonome Zielstrukturen innervieren (Schweißdrüse, M. arector pili und Arteriolen) belegt bestätigt die Läsion postganglionärer autonomer Nervenfasern bei M. Parkinson. Das vollständige Fehlen eine anti-P-α-Syn Immunoreaktivität in dermalen autonomen Nervenfasern bei MSA und Patienten ohne neurodegenerative Erkrankung erlaubt eine sichere Differenzierung der einzelnen Parkinsonsyndrome MSA und M. Parkinson in vivo.Weniger anzeigen
Zur Beurteilung der Körperkondition von Milchkühen wird das BCS-System nach Edmonson et al. (1989) angewandt. Für wachsende Jungrinder hingegen steht noch kein eigenes Bewertungsschema zur Verfügung. Das Ziel der vorliegenden Untersuchung bestand daher darin, ein für die Färsenaufzucht angepassten BCS-Beurteilungsschlüssel zu erarbeiten. Im ersten Teil der Untersuchung wurden Erhebungen zum Wachstumsverlauf und zum Fettansatzverlauf wachsender Färsen durchgeführt. Im zweiten Teil der Untersuchung galt es die Aussage der neu entwickelten Methode zur Körperkonditionsbewertung zu prüfen. Zeitraum für die Bewertung war der Aufzuchtzeitraum von 6 Lebensmonaten bis 9 Trächtigkeitsmonaten. Da gerade in diesem Lebensabschnitt mit Eintritt in die Pubertät im zweiten Lebenshalbjahr und weiter fortsetzend in der Trächtigkeit eine starke Zunahme des Fettansatzes eintritt, gilt es in dieser Zeit ein optimales Wachstum zu gewährleisten und dabei einer Verfettung mit Hilfe der Konditionsbeurteilung entgegenzuwirken. Innerhalb eines Untersuchungszeitraumes von zwei Jahren wurden in drei Herden mit unterschiedlichen Aufzuchtverfahren bei insgesamt 1936 zufällig ausgewählten Holstein-Friesian-Zuchtfärsen die Untersuchungsgrößen Rückenfettdicke (RFD), Lebendmasse (LM) und Kreuzbeinhöhe (KBH) erfasst und die Körperkondition nach einem speziell für die Anwendung bei Färsen neu entwickelten Beurteilungsverfahren geschätzt. Es wurden Altersgruppen gebildet bestehend aus 6 bis 9 Monate alten, 9 bis 11 Monate alten, 12 bis 16 Monate alten Färsen, 1 bis 4 Monate tragenden, 5 bis 7 Monate tragenden und 8 bis 9 Monate hochtragenden Färsen. Pro Untersuchungsgang wurden jeweils 30 Färsen beurteilt. Die mit Ultraschall objektiv gemessene Rückenfettdicke diente als Referenzmethode zur Beurteilung der Körperkondition einer Altersgruppe. Nach dem neuen BCS-System wird die Rückenfettdicke in mm Fettauflage durch visuelle Betrachtung und Palpation am Tier geschätzt. Als Beurteilungskriterien für den BCS bei Aufzuchtfärsen dienen die Fettfüllung der Schwanzfalte und der Bereich zwischen Hüfthöcker und Sitzbeinhöcker. In der Auswertung zum Wachstumsverlauf zeigen sich Unterschiede in der Lebendmasse und der Rückenfettdickenentwicklung. In der Kreuzbeinhöhe besteht ausgenommen des Altersabschnittes von 6 bis 8 Lebensmonaten ein einheitlicher Verlauf zwischen den unterschiedlich aufgezogenen Färsen in den drei Untersuchungsbetrieben. Die Lebendmassekurve der sehr intensiv aufgezogenen Färsen im Betrieb 1 zeigt im Abschnitt von 6 bis 12 Lebensmonaten einen steileren Verlauf, gefolgt von einer Abnahme der Wachstumsintensität im zweiten Lebensjahr. Im Unterschied dazu zeigen die Färsen in den Betrieben 2 und 3 einen gleichmäßig ansteigenden Verlauf der Lebendmassekurve. Im Fettansatz treten starke Veränderungen ab einem Alter von 8 bis 9 Lebensmonaten auf. Die Nutzung der RFD als Maß für die Körperkondition ist erst ab diesem Alter nach Eintritt in die Pubertät sinnvoll. In der Trächtigkeit realisieren die Färsen in den Untersuchungsbetrieben noch einen Zuwachs in der KBH von 6 bis 7 cm. Die für das Erreichen eines EKA von 22 Monaten im ersten Lebensjahr sehr intensiv aufgezogenen Färsen im Betrieb 1 zeigen ab 7 Trächtigkeitsmonaten eine signifikante Abnahme RFD. Die RFD-Abnahme ist die Folge des Haltungs-, Fütterungs- und Aufzuchtmanagements des Betriebes. Die für ein EKA von 24 Monaten ebenfalls intensiv aufgezogenen Aufzuchtfärsen im Betrieb 3 zeigen im gleichen Beobachtungszeitraum eine geringe Zunahme der Rückenfettdicke. Die in den Untersuchungsbetrieben erreichten Lebendgewichte der Färsen vor dem Abkalben betragen 583 kg (Betrieb 1) und 600 kg (Betrieb 3). Die hochtragenden Färsen weisen eine RFD von 15 mm (Betrieb 1) und 18 mm (Betrieb 3) auf. Die mittlere KBH liegt bei 144,3 cm (Betrieb 1) und 145,7 cm (Betrieb 3). Hinsichtlich des Einsatzes der Messmethoden ist festzustellen, dass die RFD immer als Ergebnis unterschiedlich intensiver Wachstumsverläufe zu betrachten ist und nicht getrennt von diesen bewertet werden darf. Auch die Lebendmasse lässt die Differenzierung durch die RFD der Färsen nicht erkennen. Zur zuverlässigen Kontrolle des Wachstumsverlaufes sind daher ab einem Alter von 9 Lebensmonaten sowohl die Lebendmasse als auch die Rückenfettdicke heranzuziehen. Methoden zur Überwachung des Wachstumsverlaufes sind: – Lebendmassewägung – Messung der Widerristhöhe / Kreuzbeinhöhe – Körperkonditionsbeurteilung
Aus den Ergebnissen zur Schätzgenauigkeit der Körperkondition wachsender Färsen geht hervor, dass sowohl durch ausschließliche Betrachtung der Schwanzfaltengrube (visuelle Methode S1) als auch des Bereiches zwischen Hüft- und Sitzbeinhöcker (visuelle Methode S3) sowie durch Betrachten plus zusätzliches Betasten der Fettfüllung der Schwanzfalte (palpatorische Methode S2) der Mittelwert für die mit Ultraschall objektiv gemessene RFD für eine Altersgruppe von Färsen mit hoher Übereinstimmung geschätzt werden kann. Anhand der Schätzung der RFD über ausschließlich visuelle Betrachtung nach Methode S1 können 49% und nach Methode S3 55% der Variabilität der Körperkondition der Färsen erklärt werden. Durch zusätzliches Betasten der Schwanzfalte steigt das Bestimmtheitsmaß (R2) auf 64%. Damit verbessert sich die Schätzung der RFD durch das zusätzliche Betasten. Bei den Methoden wurden hohe Korrelationskoeffizienten in den verschiedenen Altersabschnitten für wiederholte Beurteilungen erzielt (r= 0,75 bis 0,85). Daher kann von einer sicheren Merkmalserfassung anhand der Beurteilungsmethoden ausgegangen werden. Die Aussagekraft der BCS-Methode beim Einzeltier ist relativ begrenzt. Für Herdenuntersuchungen bei der Beurteilung von Tiergruppen stellt diese Methode jedoch ein wichtiges Instrument zur Kontrolle des Wachstumsverlaufes und zur Korrektur der Fütterung dar. Durch die Schätzung der RFD kann der Messaufwand im Rahmen von Herdenuntersuchungen minimiert werden. Zur Überprüfung und zur Sicherung der Schätzgenauigkeit der Konditionsbeurteilung sollten bei einem Anteil an Tieren zusätzlich in bestimmten Zeitabständen die Schätzwerte mit den Ultraschallmesswerten verglichen und der Bewertungsmaßstab justiert werden. Bei schwerer zu beurteilenden Tieren, wie den hochtragenden Färsen, sollten die Schätzwerte bei einem Teil der Tiere durch die RFDMessung überprüft werden. Der bei Milchkühen bekannte BCS kann nicht auf wachsende Färsen direkt übertragen werden. Es wird vorgeschlagen, die im Ergebnis der Untersuchung erarbeiteten Beurteilungskriterien für die Konditionsbewertung bei Aufzuchtfärsen heranzuziehen. Darüber hinaus sollte keine Note vergeben werden, sondern die Kondition mittels der konkreten RFD in mm geschätzt werden.Weniger anzeigen