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Protein structures are essential elements in every biological system evolved on earth, where they function as stabilizing elements, signaltransducers or replication machin eries. They are consisting of linear-bonded amino acids, which determine the three-dimensional structure of the protein, whereas the structure in turn determines the function. The native and biological active structure ofa protein can be understood as the folding state of a polypeptide chain at the global minimum of free energy.
By means of protein energy profiling, which is an approach derived from statistical physics it is possible to assign a so called energy profile to a protein structure. Such an energy profile describes the local energetic interaction features of every amino acid within the structure and introduces an energetic point of view, instead of a structural or sequential onto proteins.
This work aims to give a perspective to the question of how we may gain pattern information out of energy profiles. The concrete subjects are energy-mapped Pfam family alignments and investigations on finding motifs or patterns indiscretizised energy profile segments.
nicht vorhanden
Proteins are involved in almost every aspect of life, mediating a wide range of cellular tasks. The protein sequence dictates the spatial arrangement of the residues and thus ultimately the function of a rotein. Huge effort is put into cumbersome structure eludication experiments which obtain models describing the observed spatial conformation of a protein, enabling users to predict their function, to understand their mode of action or to design tailored drugs to cure disease caused by misfolded or misregulated proteins.
However, the result of structure determination experiments are merely models of reality, made under simplifying assumptions - sometimes containing major undetected errors. On the other hand, such experiments are resource demanding and they cannot supply the actual demand.
Thus, scientists are predicting the structure of proteins in silico, resulting in models that are even
more prone to error.
In consequence, the structure biologists search after a practicable definition of structure quality and over the last two decades several model quality assessment programs emerged, measuring the local and global quality of peculiar structures. Seven representatives were studied, regarding the paradigms they follow and the features they use to describe the quality of residues. Their predications were compared, showing that there is almost no common ground among the tools.
Is there a way to combine their statements anyway?
Finally, the accumulated knowledge was used to design a novel evaluation tool, addressing problems previously spotted. Thereby, high quality of its predication as well as superior usability was
key. The strategy was compared to existing approaches and evaluated on suitable datasets.
In this work a new method for the prediction of the Xaa-proline (where Xaa is any amino acid) cis/trans isomerization was investigated. By extraction of twelve structural features (real secondary structure, inside/outside classification, properties of the environment around proline and proline itself) a support vector machine (SVM) based prediction approach was evolved. The Java software Xaa-PIPT for structural feature extraction was developed. Based on 4397 (2199 cis and 2198 trans) prolines extracted from non-redundant, globular proteins a classifier was trained using the radial basis function (RBF) kernel. In ten-fold cross-validation it achieved an accuracy of 70.0478 % and a Matthews correlation coefficient (MCC) of 0.4223, a sensitivity of 0.5433 and a specificity of 0.8576. Based on this classifier a lightweight and easy-to-use Java software tool, called m Xaa-PIPT, for the prediction of the Xaa-proline cis/trans isomerization was devel-oped. It was shown that there are correlations between the proline surrounding environment and the isomerization state. m Xaa-PIPT can be used for the evaluation of low-resolution protein structures and theoretical models to improve their quality by the prediction of the Xaa-proline isomerization.
nicht vorhanden
After the expression of the titin-Hsp27-construct with the following purification supplies no satisfied results which makes the realization of the atomic force microscopy not possible. The devel-opment of the structure model by using different bioinformatic methods can establish a model for the protein sequence. As bioinformatic methods the template search by different BLAST runs and free available software like SwissModel, Pcons, ModWeb and other tools are used. Nevertheless, the generated model is not the native conformation and has to be analyzed with other software until a stable conformation of the structure can be predicted. Depending on the time which is provided the generated model is a good approach for the aim this master thesis has.
As widely discussed in literature spatial patterns of amino acids, so-called structural motifs, play an important role in protein function. The functional responsible part of a protein often lies in an evolutionary highly conserved spatial arrangement of only few amino acids, which are held in place tightly by the rest of the structure. In general, these motifs can mediate various functional interactions, such as DNA/RNA targeting and binding, ligand interactions, substrate catalysis, and stabilization of the protein structure.
Hence, characterizing and identifying such conserved structural motifs can contribute to understanding of structurefunction relationships in diverse protein families. Therefore and because of the rapidly increasing number of solved protein structures, it is highly desirable to identify, understand and moreover to search for structural scattered amino acid motifs. The aim of this work was the development and the implementation of a matching algorithm to search for such small structural motifs in large sets of target structures. Furthermore, motif matches were extensively analyzed, statistically assessed and functionally classified. Following a novel approach, hierarchical clustering was combined with functional classification and used to deduce evolutionary structure-function relationships. The proposed methods were combined and implemented to a feature-rich and easy-to-use command line software tool, which is freely available and contributes to the field of structural bioinformatic research.
The bachelor thesis is about cis-trans isomerization of Xaa-Pro (Xaa = any amino acid), their quantitative acquisition and the selection of 3D structure information for the prediction with a support vector machine (SVM). The quantitative detection of occurrence of cis-, trans- and cis/trans conformation in membrane proteins will be examined and evaluated. The 3D structure informa-tions include 12 features, the amino acids around proline and are including of proline. These include the inside/outside classification, the real secondary structure, energy consideration, as well as five further amino acid occur properties within a defined radius of the proline. From this information, a data set was created for the SVM. This program is used for the prediction of unknown and known Xaa Pro Isomerisms. The methods for the analysis were implemented with the platform independent programming language Java. Two programs have emerged from the work to a Xaa PIPT for the quantitative detection and extracting structural information and m Xaa-PIPT to the pure prediction of Xaa-Pro isomerism in protein structures. 389 Membrane proteins from the PDB (Protein Data Bank) served as a basis. The data were also statistically analysed and evaluated.
The study “Proteomic and systems biological database analysis of changed proteins from rat brain tissue after diving “ is about system biological testing of proteomic data obtained by rat brain after experimental diving in a pressure chamber. Basically, brain tissue from animal decompression sickness (DCS) was analyzed by mass spectrometry and has given two larger sets of modified proteins. Thereupon, the resulting up- and down-regulated proteins wereidentified and later compared by means of systems of biological databases, in this case GeneGo MetaCoreTM, in order to find similar or various affected cell biological signaling pathways when two different mass-spectrometry methods were compared.
This thesis investigated the generation of laser induced periodic surface structures (LIPSS) using femtosecond laser irradiation at a central wavelength of 775 nm.
The metals stainless steel and copper as well as a semiconducting thin film, ITO on glass substrate were investigated. The impact of the processing parameters was studied for single and multiple pulse irradiation to determine the ablation threshold of the materials
and the different types of LIPSS. These observations allowed the optimisation of area structuring with regards to processing speed and LIPSS quality.
The feasibility of the LIPSS generation in dynamic, real time polarisation control was then explored. By using a fast response, liquid-crystal polarisation rotation device, the direction of the linear polarisation of the laser beam could be dynamically controlled and synchronised to the scanning during laser processing. As a result, a range of complex micro- and nano-scale patterns with orthogonal direction of LIPSS were created. The samples were analysed using optical and electron microscopy. The orientation of the LIPSS was determined also from detection of light diffracted by the LIPSS.
Finally, two applications of large area LIPSS patterning were demonstrated, information encoding on metals and periodic structuring of a thin film conducting oxide for solar cells.
A number of real time PCR approaches have been published in the literature. In this thesis, the suitability of different real time PCR approaches using hydrolysis probes have been evaluated regarding PCR performance, cost effectiveness as well as handling. The effect of double-quenched probes as well as the impact of the increase of relative Flap endonuclease amount in quantitative real time PCR has been examined. In terms of genotyping a TaqMan™ assay, considered to be the gold-standard in this application, has been tested and compared to phosphorothioate modified probes, allele specific primers, SNAKE primers, an allele specific probe and primer assays as well as an assay using minor groove binder probes. Promising observations have been made in the case of double-quenched probes, phosphorothioate modified probes, SNAKE primers as well as minor groove binder probes.
The cultivation of mammalian cells in the third dimension has a great potential for a
wide application in regenerative medicine, pharmaceutical industry or cancer research.
An overview about actual 3-D cultivation techniques like hydrogels and porous scaffolds as well as their various materials and modifications is given in this thesis. Also different products and their implementation for a new application of 3-D cell
culture in a laboratory are described.
The primary objective of this work and the research at the “Helmholtz-Zentrum für Umweltforschung” was to gain a deeper understanding of the basically transformation processes, especially for nitrogen species, in constructed wetlands. Therefore two different types of laboratory scale model systems, run with two different artificial wastewaters, had been observed for about 4 months. Data about the situation of three nitrogen species (ammonium, nitrate, nitrite), the physical condition of the pore water and the carbon sources contained by the water had been collected and compared. The present work will provide a summary about the actual knowledge of the microbial processes in constructed wetlands and the general character of such constructions. It will explain the different methods used to gain the data which will be later wards discussed with the aid of the created graphs in the final argumentation.
Different small molecule kinase inhibitors, which have an influence on cell growth, proliferation and cell survival were tested alone and in combination with Erlotinib in the Erlotinib-resistant non-small cell lung cancer cell line PC-9ER and Cisplatin in the K-Ras mutant cell line H358. The aim was to find out, which combinations produce the best antiproliferative effects in non-small cell lung cancer cell lines.
For the first time it was discovered that ultraviolet radiation with a wavelength of 200 to 400 nm (maximum 365 nm) radiated from a distance of 40 cm (intensity: 3500 mW/cm²) to PMMA altered its surface wettability as well as a roughness at the nanoscale that was observed with an atomic force microscope (AFM). The roughness rises and falls again in a short time ( 1-2days ) after 75 min and 180 min irradiation time. However , during the next 10 days roughness became stabilized and there was no influence of UV if PMMA was stored in air or in a Petri dish out of glass.
The main purpose of this Bachelor thesis was to find and to compile comprehensive information on barley genes expressed in the context of pollen embryogen esis. In the present study, this approach was confined to genes that were previously known to be associated with the initiation of embryogenesis in different plant species. First, candidate transcript sequences were identified in barley. Second, transcript and associated genomic sequences were analyzed in silico to provide suitable structural and functional annotations. Finally, the results of one representative example are presented and interpreted in detail. This work aims to contribute to a significantly improved understanding of pollen embryogenesis - a biological phenomenon broadly used for haploid technology in crop improvement.
In this work a novelty detection framework provided by M. Filippone and G. Sanguinetti is considered, which is useful especially when only few training samples are available. It is restricted to Gaussian mixture models and makes use of information theory, applying the Kullback-Leibler divergence. In this work two variations of the framework are presented, applying the symmetric Hellinger divergence and a statistical likelihood approach.
This master thesis investigates a new method for the feature extraction of gray scale images, the so called „Non-Euclidean Principal Component Analysis“ 1. Thereby the standard inner product of the Euclidean space is substituted by a semi inner product in the well known learning rule of Oja and Sanger. The new method is compared with the standard principal component analysis (PCA) by extracting features (feature vectors) of different databases with class labels and judged regarding the accuracies of „Border Sensitive Generalized Learning Vector Quantization“ (BSGLVQ), „Feed Forward Neural Networks“ (FFNN) and the „Support Vector Machines“ (SVM).
This Bachelor thesis provides an experimental validation of the “si-Fi” software, which was designed for RNAi off-target searches and silencing efficiency predictions. The experimental approach is based on using synthetic DNA as RNAi-target as well as RNAi-trigger sequence. The data was generated by two different types of experiments using a transient gene silencing system in bombarded barley epidermal cells. The efficiency of RNAi was estimated by scoring the effect of silencing of the susceptibility-related gene Mlo on resistance of transformed cells to the powdery mildew fungus Blumeria graminis f. sp. hordei by observing reduction of fluorescent signals coming from an RNAi target fused to the green fluorescent protein. The aim of this work was a comparison between in silicio prediction of RNAi efficiency and off-target effects in barley and experimental data.