Gasdetektor

Mann kann Karbon-Nanoröhrchen für eine empfindliche Detektion der Konzentration gewisser Gase einsetzen. Die Einführung dieser Nanoröhren in einem Feldeffekttransistor erlaubt ein gassensitiven Element zu erhalten. In Kontakt mit dem Gas wird die Kennlinie des Transistors nach links verschoben. Die Größe der Verschiebung ist ein Maß für die Konzentration des Gases. Dieser Bericht ist eine Fortsetzung des Semesterprojekts. Er beschreibt die verschiedenen Schritte, um ein funktionsfähiges Softwaresystem zu erreichen. Ein erster Analyse Schritt ist, um die Bedürfnisse zu erkennen und das notwendig Wissen erwerben, um das Projekt durchzuführen. Dann kommt ein Entwicklungsphase. In dieser Phase werden die Elemente der Analyse wieder gefasst und für dem Projekt erarbeitet. Schließlich wird eine Reihe von Tests durchgeführt und dokumentiert werden, um den Betrieb des Systems zu überprüfen

Distance sensing via magnetic resonance coupling

The goal is to understand how the principle of distance determination via resonant magnetic coupling based on the researches of Hashimoto laboratory works and to perform measurements

Commande pour MEMS électrostatique

Objectif: Le but de ce travail de diplôme est de concevoir et tester une commande programmable pour une matrice de micro-miroirs afin de réaliser un cache du soleil qui éblouit une caméra prenant une image du ciel les jours de beau temps Résultats: Les tests effectués permettent d’affirmer que le système de commande conçu est fonctionnel. La partie concernant l'alimentation est à améliorer.Ziel: In dieser Diplomarbeit geht es darum, eine programmierbare Ansteuerung für eine Matrix von Mikro-Spieglen zu entwerfen und zu testen, mit welcher eine Blende der Sonne in einer Tageshimmels-Kamera verwirklicht werden soll. Resultate: Aufgrund der durchgeführten Versuche stellen wir fest, dass die entworfene Ansteuerung funktioniert. Die Speiseschaltung muss noch weiter verbessert werden

Installation d’instrument par drone (InstalloDrone)

Les instruments de mesure environnementaux doivent souvent être installés dans des zones à risque. Ce projet cherche à développer un concept d'installation d'un appareil sur un rocher, avec un drone, pour réduire les risques et les coûts

Synthesis of DNA fragments in yeast by one-step assembly of overlapping oligonucleotides

Here it is demonstrated that the yeast Saccharomyces cerevisiae can take up and assemble at least 38 overlapping single-stranded oligonucleotides and a linear double-stranded vector in one transformation event. These oligonucleotides can overlap by as few as 20 bp, and can be as long as 200 nucleotides in length. This straightforward scheme for assembling chemically-synthesized oligonucleotides could be a useful tool for building synthetic DNA molecules

Murine Transporter Associated with Antigen Presentation (TAP) Preferences Influence Class I–restricted T Cell Responses

The transporter associated with antigen presentation (TAP) complex shuttles cytosolic peptides into the exocytic compartment for association with nascent major histocompatibility complex class I molecules. Biochemical studies of murine and human TAP have established that substrate length and COOH-terminal residue identity are strong determinants of transport efficiency. However, the existence of these specificities in the intact cell and their influences on T cell responses have not been demonstrated. We have devised a method for studying TAP- mediated transport in intact cells, using T cell activation as a readout. The approach makes use of a panel of recombinant vaccinia viruses expressing peptides containing the Kd-restricted nonamer influenza nucleoprotein residues 147–155. The COOH terminus of each construct was appended with a dipeptide composed of an internal threonine residue followed by a varying amino acid. Synthetic peptide versions of these 11-mers exhibit vastly different transport capabilities in streptolysin O–permeabilized cells, in accordance with the predicted influence of the COOH-terminal residues. Presentation of the endogenously expressed version of each construct requires TAP-mediated transport and cooexpression with a vac-encoded exocytic COOH-terminal dipeptidase, angiotensin converting enzyme, to allow liberation of the minimal epitope. Recognition by epitope-specific CTLs therefore signifies TAP-mediated transport of a complete 11-mer within the target cell. Under normal assay conditions no influences of the COOH-terminal residue were revealed. However, when T cell recognition was limited, either by blocking CD8 coreceptor interactions or by decreasing the amount of transport substrate synthesized, significant COOH-terminal effects were revealed. Under such conditions, those peptides that transported poorly in biochemical assays were less efficiently presented. Therefore, TAP specificity operates in the intact cell, appears to reflect previously defined rules with regard to the influence of the COOH-terminal residue, and can strongly influence T cell responses

Modified bases enable high-efficiency oligonucleotide-mediated allelic replacement via mismatch repair evasion

Genome engineering using single-stranded oligonucleotides is an efficient method for generating small chromosomal and episomal modifications in a variety of host organisms. The efficiency of this allelic replacement strategy is highly dependent on avoidance of the endogenous mismatch repair (MMR) machinery. However, global MMR inactivation generally results in significant accumulation of undesired background mutations. Here, we present a novel strategy using oligos containing chemically modified bases (2′-Fluoro-Uridine, 5-Methyl-deoxyCytidine, 2,6-Diaminopurine or Iso-deoxyGuanosine) in place of the standard T, C, A or G to avoid mismatch detection and repair, which we tested in Escherichia coli. This strategy increases transient allelic-replacement efficiencies by up to 20-fold, while maintaining a 100-fold lower background mutation level. We further show that the mismatched bases between the full length oligo and the chromosome are often not incorporated at the target site, probably due to nuclease activity at the 5′ and 3′ termini of the oligo. These results further elucidate the mechanism of oligo-mediated allelic replacement (OMAR) and enable improved methodologies for efficient, large-scale engineering of genomes.Synthetic Biology Engineering Research CenterNational Science Foundation (U.S.) (Grant #SA5283-11210)United States. Dept. of Energy (Genomes to Life Center) (Grant #DE-FG02-03ER6344)Wyss Institute for Biologically Inspired Engineerin

The involvement of replication in single stranded oligonucleotide-mediated gene repair

Targeted gene repair mediated by single-stranded oligonucleotides (SSOs) has great potential for use in functional genomic studies and gene therapy. Genetic changes have been created using this approach in a number of prokaryotic and eukaryotic systems, including mouse embryonic stem cells. However, the underlying mechanisms remain to be fully established. In one of the current models, the ‘annealing-integration’ model, the SSO anneals to its target locus at the replication fork, serving as a primer for subsequent DNA synthesis mediated by the host replication machinery. Using a λ-Red recombination-based system in the bacterium Escherichia coli, we systematically examined several fundamental premises that form the mechanistic basis of this model. Our results provide direct evidence strongly suggesting that SSO-mediated gene repair is mechanistically linked to the process of DNA replication, and most likely involves a replication intermediate. These findings will help guide future experiments involving SSO-mediated gene repair in mammalian and prokaryotic cells, and suggest several mechanisms by which the efficiencies may be reliably and substantially increased

The +4G Site in Kozak Consensus Is Not Related to the Efficiency of Translation Initiation

The optimal context for translation initiation in mammalian species is GCCRCCaugG (where R = purine and “aug” is the initiation codon), with the -3R and +4G being particularly important. The presence of +4G has been interpreted as necessary for efficient translation initiation. Accumulated experimental and bioinformatic evidence has suggested an alternative explanation based on amino acid constraint on the second codon, i.e., amino acid Ala or Gly are needed as the second amino acid in the nascent peptide for the cleavage of the initiator Met, and the consequent overuse of Ala and Gly codons (GCN and GGN) leads to the +4G consensus. I performed a critical test of these alternative hypotheses on +4G based on 34169 human protein-coding genes and published gene expression data. The result shows that the prevalence of +4G is not related to translation initiation. Among the five G-starting codons, only alanine codons (GCN), and glycine codons (GGN) to a much smaller extent, are overrepresented at the second codon, whereas the other three codons are not overrepresented. While highly expressed genes have more +4G than lowly expressed genes, the difference is caused by GCN and GGN codons at the second codon. These results are inconsistent with +4G being needed for efficient translation initiation, but consistent with the proposal of amino acid constraint hypothesis