Copper transport into the chloroplast and its implications for copper homeostasis in Arabidopsis thaliana

2012 Fall.Includes bibliographical references.Copper (Cu) is an essential micronutrient for most aerobic organisms including plants. It is present as Cu+ or Cu2+, which makes it an ideal cofactor for enzymes involved in processes such as photosynthesis and respiration. Plant cuproproteins are almost ubiquitously found in every cell compartment. The blue Cu protein plastocyanin (PC) is believed to bind the majority of Cu ions in green tissues and is essential for higher plants. Cu reaches the thylakoid lumen through the activity of two P1B-type ATPases called PAA1/HMA6 and PAA2/HMA8 (P-type ATPase of Arabidopsis/Heavy-metal ATPase), which are located in the inner chloroplast envelope and the thylakoid lumen respectively. Under Cu limiting conditions, plants have been suggested to prioritize cellular Cu to PC to ensure adequate photosynthesis. This process involves the post-transcriptional down-regulation of seemingly less essential cuproproteins through the activity of a single transcription factor called SPL7 (SQUAMOSA promoter binding protein-like7). The first chapter reviews Cu homeostasis in plants. The research presented in the three experimental chapters of this dissertation is aimed to determine the role of the chloroplast in Cu homeostasis of Arabidopsis thaliana. I report a novel SPL7-independent and chloroplast-specific regulation of the thylakoid-localized Cu transporter PAA2/HMA8. The transporter is most abundant in the absence of Cu and is turned over at higher chloroplastic Cu concentrations. PAA2/HMA8 abundance in Cu deficiency is furthermore controlled by the presence of PC, because in a pc mutant PAA2/HMA8 abundance is always low. The regulation of the transporter likely serves as a checkpoint for the Cu requirements of the thylakoid lumen. I identified two components of the stroma-localized Clp protease (Caseinolytic peptidase) which are involved in PAA2/HMA8 turnover. The Cu status of these mutants is not affected, decreasing the likelihood of a secondary affect of Cu on PAA2/HMA8 in these plants. In the last experimental chapter I summarize relevant results that further describe and characterize PAA1 and PAA2. Most notably, Arabidopsis encodes for a splice-form of PAA1. This much smaller fragment is expressed with a chloroplast targeting sequence and could potentially function as a stromal Cu chaperone

Efficient Azimuthal Mode Analysis using Compressed Sensing

A new approach for the Azimuthal Mode Analysis (AMA) of over- and subsampled sound fields in flow ducts of turbomachines using circumferential sensor arrays is presented which is based on Compressed Sensing. Compressed Sensing is a framework to solve underdetermined systems of linear equations under the assumption that the solution vector is sparse. In the context of AMA, such sparse mode spectra often occur in the analysis of tonal sound field components generated by rotor-stator interaction. Important features such as stability and accuracy are investigated by analysis of a wide range of simulated and measured pressure data and comparison with commonly applied methods. Also two different optimisation approaches for the design of circumferential sensor arrays are introduced which allows a reduction of the number of sensors for large modal ranges if only a limited number of modes are dominant. Furthermore, the remaining mode amplitudes are estimated exploiting the deconvolution property of the applied Compressed Sensing algorithm

Modelling and Controlling the Kinetic and Dynamic of a Bicycle

En este trabajo, se presenta el modelado y control posterior de una mini-bicicleta autónoma, que se utilizará para la enseñanza de sistemas de control. El modelo mecánico se construye inicialmente a partir de un diseño CAD y posteriormente se integra en Simulink, conjuntamente con los módulos de control. Se lleva a cabo el modelado del sistema completo, incluyendo las partes mecánicas, sensores, actuadores y la fricción de las ruedas con el suelo, consiguiéndose el mismo comportamiento que con la bicicleta física. A partir de las ecuaciones matemáticas que definen el comportamiento del sistema se diseña un controlador PID y un controlador LQG en el espacio de estados. Para verificar el modelo, los controladores diseñados se prueban también con los mismos parámetros en la mini-bicicleta física, obteniéndose un resultado idéntico.In this work, the modeling and subsequent control of an autonomous mini-bicycle is presented, which will be used for the teaching of control systems. The mechanical model is initially built from a CAD design and then integrated into Simulink, together with the control modules. The modeling of the complete system is carried out, including the mechanical parts, sensors, actuators and the friction of the wheels with the ground, achieving the same behavior as with the physical bicycle. From the mathematical equations that define the behavior of the system, a PID controller and an LQG controller are designed in the state space. To verify the model, the designed controllers are also tested with the same parameters in the physical mini-bicycle, obtaining an identical result.Universidad de Granada: Departamento de Arquitectura y Tecnología de Computadore

Synthese und biologische Evaluierung von 4H-Pyrido[1,2-a]pyrimidinen

Ziel der Arbeit war die Untersuchung des Potentials der Synthese von Pyrido[1,2-a]pyrimidinen zur Darstellung biologisch aktiver Substanzen. Der Synthesebaustein PCNiB wurde durch Azolierung modifiziert, um für die Synthese von Pyrido[1,2-a]pyrimidinen eingesetzt werden zu können. Nach Optimierung der Reaktionsbedingungen konnten unterschiedlich substituierte Pyrido[1,2 a]pyrimidine im Multigrammmaßstab, im Weiteren durch Veränderung der Reaktion und durch den Einsatz von Natriumhydrid auch sterisch anspruchsvolle und elektronenarme 2 Aminopyridine für die Synthese des Heterocyclus zugänglich gemacht werden. Diese Bedingungen konnten ebenfalls für Pyrazino[1,2 a]pyrimidine angewendet werden. Oligonukleophile Aminopyridine führten zur Darstellung ungewöhnlicher Heterocyclen wie Oxazolen oder das als einkristalline Faser ausfallende Thiadiazinon. Ausgehend von den Benzotriazolylderivaten wurde die Möglichkeit einer Substitution in 2 Position mit unterschiedlichen Nukleophilen untersucht. Es gelang die Substitution mit N Nukleophilen wie primären und sekundären Aminen sowie Hydraziden, S-Nukleophilen wie Thiolen, dem O Nukleophil Methanol und C Nukleophilen durch Umpolung von Aroylen durch ein Carben als Katalysator. An der 3-Position gelang die Reduktion der Nitrogruppe zum primären Amin und weiter durch Diazotierung die Darstellung verschiedener Triazole. Die erhöhte Löslichkeit der primären Amine und Triazole wurde zur NMR-spektroskopischen Untersuchung der Stickstoffatome und einer Diskussion der Aromatizität des Systems genutzt. Die Aromatizität des Systems konnte dank der Vielzahl an vermessenen Röntgenstrukturen weiter untersucht und diskutiert werden. Die Dichlormethylengruppe des Systems konnte zur Methylgruppe reduziert oder durch Addition mit Aminen und Alkoholen zur Bildung eines chiralen Zentrums umgesetzt werden. Weiterhin gelang die erste SONOGASHIRA Reaktion mit einer Dichlormethylengruppe, wobei eine Folgereaktion mit der Nitrogruppe zur Bildung eines betainischen N-Pyrroloxids führte. Der Pyridinring des Bicyclus konnte durch Wahl des Aminopyridins als auch durch C-C-Kupplungsreaktionen wie der SUZUKI-MIYAURA und der SONOGASHIRA Reaktionen modifiziert werden. Mit chiralen Aminen konnte die Atropisomerie, die durch die Dichlormethylengruppe und die Nitrogruppe induziert wird, nachgewiesen und untersucht werden. Ausgehend von den Diethern erfolgte mit Hilfe von Natriumazid der Aufbruch des Systems, was zur Darstellung von Azinsäuren führte. Diese konnten zur Darstellung von Betainen verwendet werden. Die photokatalytische Reaktion der Indazolylderivate führte zur Bildung von N-Oxiden. Es konnten für jede Position des bicyclischen Systems Strategien und Synthesen entwickelt werden, die eine zielgerichtete Modifikation erlauben. Außerdem wurden weitere heterocyclische Systeme aufbauend auf den Pyrimidinen entdeckt und beschrieben. Insgesamt konnten in dieser Arbeit 147 neue Verbindungen dargestellt und charakterisiert werden. Der Großteil der dargestellten Verbindungen konnte am Helmholtz-Zentrum für Infektionsforschung in Braunschweig auf ihre biologische Aktivität hin untersucht werden. Es konnten Erkenntnisse gewonnen werden wie die Möglichkeit, die Bioaktivität von sekundären Aminen durch Alkylierung wie auch durch Oxidation des Schwefels von Thioethern zum Sulfoxid zu erhöhen. Die dargestellten Thioether zeigten durchweg eine erhöhte Zytotoxizität und die dargestellten Aminderivate eine erhöhte Aktivität gegen verschiedene Bakterienstämme. Ausgehend von diesen Leitstrukturen kann die Entwicklung neuer Wirkstoffe gegen Tumore oder gegen resistente Bakterienstämme fortgeführt werden. Es konnte somit eine Vielzahl vielversprechender, biologisch aktiver Verbindungen der Klasse bicyclischer Pyrimidine identifiziert und beschrieben werden. Durch weitere Optimierung ihres chemischen Aufbaus sollten zukünftig Heterocyclen mit einem noch besseren Wirkspektrum zugänglich gemacht werden können.Goal of this work was to investigate the potential of the synthesis of pyrido[1,2-a]pyrimidines for the preparation of biologically active substances. The synthesis building block PCNiB was modified by azolation in order to be able to be used for the synthesis of pyrido[1,2-a]pyrimidines. After optimization of the reaction conditions, differently substituted pyrido[1,2-a]pyrimidines could be synthesized on a multigram scale. By changing the reaction and by using sodium hydride also sterically demanding and electron-poor 2-aminopyridines could be used as starting material. These newly developed conditions could also be used to synthesize pyrazino[1,2-a]pyrimidines. Oligonucleophilic aminopyridines led to the preparation of unusual heterocycles such as oxazoles or the thiadiazinone which precipitates out as a single-crystalline fiber. Starting from the benzotriazolyl derivatives, the possibility of substitution in the 2-position with different nucleophiles was investigated. The substitution with N-nucleophiles such as primary and secondary amines and hydrazides, S-nucleophiles such as thiols, the O-nucleophile methanol and C nucleophiles by umpolung of aroyls with a carbene as a catalyst was successful. At the 3-position, the nitro group was reduced to the primary amine and various triazoles were further prepared by diazotization. The increased solubility of the primary amines and triazoles was used for the NMR spectroscopic investigation of the nitrogen atoms and a discussion of the aromaticity of the system. The aromaticity of the system could be further investigated and discussed thanks to the large number of measured X-ray structures. The dichloromethylene group of the system could be reduced to a methyl group or converted by addition with amines and alcohols to form a chiral center. Furthermore, the first SONOGASHIRA reaction with a dichloromethylene group was successful, with a subsequent reaction with the nitro group leading to the formation of a betainic N-pyrrole oxide. The substitution of the pyridine ring of the bicyclic molecule could be modified by choosing the aminopyridine as well as by C-C coupling reactions such as the SUZUKI-MIYAURA and the SONOGASHIRA reactions. With chiral amines, the atropisomerism induced by the dichloromethylene group and the nitro group could be detected and investigated. Starting from the diethers, with the help of sodium azide a ring opening reaction occured, which led to the preparation of azinic acids. These could be used to synthesize betaines. The photocatalytic reaction of the indazolyl derivatives led to the formation of N-oxides. For every position of the bicyclic system strategies and syntheses could be developed that allow a targeted modification. In addition, other heterocyclic systems based on the pyrimidines have been discovered and described. A total of 147 new compounds could be synthesized and characterized in this work. The majority of the compounds shown could be examined for their biological activity at the Helmholtz Center for Infection Research in Braunschweig. Insights could be gained such as the possibility of increasing the bioactivity of secondary amines by alkylation as well as by oxidation of the sulfur from thioethers to sulfoxide. The thioethers shown consistently had increased cytotoxicity and the amine derivatives showed increased activity against various bacterial strains. Based on these lead structures, the development of new active substances against tumors or against resistant bacterial strains can be continued. A large number of promising, biologically active compounds of the class of bicyclic pyrimidines could be identified and described. By further optimizing their chemical structure, it should be possible in the future to make heterocycles with an even better spectrum of activity accessible

Ly alpha emission galaxies in the FORS Deep Field

VLT/FORS-Spektren mit einer Aufloesung von A = 2000 von 18 Galaxien mit einer Rotverschiebung von z = 2.7 bis 5 werden praesentiert. Die Sternentstehungsraten der 18 Galaxien reichen von 2 bis 60 Msun/yr und ihre effektiven Radien von r < 0.2 bis 1.8 kpc. Der Vergleich mit synthetischen Spektren ergibt, dass die Galaxien jung sind und ungefaehr SMC/LMC-Metallizitaet haben. Die breiten, blauverschobenen, niedrig-angeregten interstellaren Absorptionslinien weisen darauf hin, dass die Galaxien Superwinde besitzen. Die Staerke dieser Absorptionslinien ist bestimmt durch die Geschwindigkeitsdispersion des ausstroemenden Mediums und nicht durch dessen Abdeckungsgrad. Alle Spektren enthalten die Lyman-alpha-Linie, welche von reiner Absorption bis zu starker Emission (Emissions-EW = -20 bis 270 Å) reicht. Die meisten Emissionslinien sind asymmetrisch, drei Galaxien besitzen ein Lyman-alpha-Profil mit zwei Emissionskomponenten. Die asymmetrischen als auch die komplexeren Profile koennen mit einem kompakten Starburst erklaert werden, der von einer neutralen Schale umgeben ist. Die Staerke der Lyman-alpha-Emissionslinie wird durch die Entweichwahrscheinlichkeit der Lyman-alpha-Photonen bestimmt, welche wiederum durch die mittlere Geschwindigkeit, die Geschwindigkeitsdispersion und den Ionisationsgrad des austroemenden Mediums bestimmt wird. Die moegliche Existenz einer zusaetzlichen Galaxien-Population mit ausserordentlich starker Lyman-alpha-Emissionsline wird diskutiert

Red-Sequence Galaxies at High Redshift by the COMBO-17+4 Survey

We investigate the evolution of the galaxy population since redshift 2 with a focus on the colour bimodality and mass density of the red sequence. We obtain precise and reliable photometric redshifts up to z=2 by supplementing the optical survey COMBO-17 with observations in four near-infrared bands on 0.2 square degrees of the COMBO-17 A901-field. Our results are based on an H-band-selected catalogue of 10692 galaxies complete to H=21.7. We measure the rest-frame colour (U_280-V) of each galaxy, which across the redshift range of our interest requires no extrapolation and is robust against moderate redshift errors by staying clear of the 4000A-break. We measure the colour-magnitude relation of the red sequence as a function of lookback time from the peak in a colour error-weighted histogram, and thus trace the galaxy bimodality out to z~1.65. The (U_280-V) of the red sequence is found to evolve almost linearly with lookback time. At high redshift, we find massive galaxies in both the red and the blue population. Red-sequence galaxies with log M_*/M_sun>11 increase in mass density by a factor of ~4 from z~2 to 1 and remain nearly constant at z<1. However, some galaxies as massive as log M_*/M_sun=11.5 are already in place at z~2.Comment: 18 pages, 11 figures, accepted for publication in Ap

Modelling high redshift Lyman-alpha Emitters

We present a new model for high redshift Lyman-Alpha Emitters (LAEs) in the cosmological context which takes into account the resonant scattering of Ly-a photons through expanding gas. The GALICS semi-analytic model provides us with the physical properties of a large sample of high redshift galaxies. We implement a gas outflow model for each galaxy based on simple scaling arguments. The coupling with a library of numerical experiments of Ly-a transfer through expanding or static dusty shells of gas allows us to derive the Ly-a escape fractions and profiles. The predicted distribution of Ly-a photons escape fraction shows that galaxies with a low star formation rate have a f_esc of the order of unity, suggesting that, for those objects, Ly-a may be used to trace the star formation rate assuming a given conversion law. In galaxies forming stars intensely, the escape fraction spans the whole range from 0 to 1. The model is able to get a good match to the UV and Ly-a luminosity function (LF) data at 3 < z < 5. We find that we are in good agreement with both the bright Ly-a data and the faint population observed by Rauch et al. (2008) at z=3. Most of the Ly-a profiles of our LAEs are redshifted by the diffusion in the outflow which suppresses IGM absorption. The bulk of the observed Ly-a equivalent width (EW) distribution is recovered by our model, but we fail to obtain the very large values sometimes detected. Predictions for stellar masses and UV LFs of LAEs show a satisfactory agreement with observational estimates. The UV-brightest galaxies are found to show only low Ly-a EWs in our model, as it is reported by many observations of high redshift LAEs. We interpret this effect as the joint consequence of old stellar populations hosted by UV-bright galaxies, and high HI column densities that we predict for these objects, which quench preferentially resonant Ly-a photons via dust extinction.Comment: 17 pages, 12 figures, 3 tables, accepted for publication in MNRA

The nature of the Lyman-alpha emission region of FDF-4691

In order to study the origin of the strong Lyman-alpha emission of high-redshift starburst galaxies we observed and modeled the emission of the z = 3.304 galaxy FDF-4691 (rest-frame EW = 103 Angstroem). The observations show that FDF-4691 is a young starburst galaxy with a (for this redshift) typical metallicity. The broad, double-peaked profile of the Lyman-alpha emission line can be explained assuming a highly turbulent emission region in the inner part of the starburst galaxy, and a surrounding extended shell of low-density neutral gas with a normal dust/gas ratio and with Galactic dust properties. The detection of the Lyman-alpha emission line is explained by the intrinsic broad Lyman-alpha emission and a low HI column density of the neutral shell. A low dust/gas ratio in the neutral shell is not needed to explain the strong Lyman-alpha line.Comment: Accepted for publication in A&A Letter