Untersuchung von Metallionen induzierten Konformationsänderungen in Proteinkinasen mittels Surface Plasmon Resonance

Surface Plasmon Resonance (SPR) kann benutzt werden, um Protein/Protein Wechselwirkungen aber auch Nukleotid/Protein-Wechselwirkungen kinetisch genau zu charakterisieren. Unser Modellsystem für Proteinkinasefunktion ist die cAMP-abhängige Proteinkinase (cAPK), die das g-Phosphat von ATP auf Serin oder Threoninreste von Substratmolekülen überträgt. Zwei Typen von Inhibitoren der katalytischen Untereinheit (C) der cAPK sind bekannt: die regulatorischen Untereinheiten Typ I und Typ II und die sog. hitzestabilen Proteinkinaseinhibitoren, PKIs. Die Aktivität der cAPK scheint durch die Bindung von ATP, ein oder zwei Metallionen und die Freisetzung von ADP reguliert zu werden. Diese Regulation beruht vermutlich auf der Überführung der C-Untereinheit von einer offenen, thermodynamisch instabilen katalytisch aktiven (?) Form zu einer, geschlossenen, thermodynamisch stabilen, katalytisch inaktiven (?) Form. Die Bindung der physiologischen Inhibitoren PKI und der regulatorischen Untereinheiten hängt von der Konzentration der Nukleotide und der Metallionen ab (1, 2). Mittels SPR wurden die Assoziations- und Dissoziationsgeschwindigkeitskonstanten der Bindung dieser Inhibitoren an die C-Untereinheit in Abhängigkeit von Metallionen und Nukleotiden analysiert, um den Mechanismus der Bindung mit den aus der Kristallstruktur (3) abgeleiteten Konformationsänderungen zu korrelieren

Formation of nitrous oxide over Pt-Pd oxidation catalysts: Secondary emissions by interaction of hydrocarbons and nitric oxide

The interaction of hydrocarbons (HC) and nitric oxide (NO) over noble metal catalysts for exhaust gas after-treatment of lean-operated combustion engines can lead to secondary emissions, namely the formation of nitrous oxide (N$_2$O), which is a strong greenhouse gas calling for N$_2$O reduction concepts. By means of a series of light-off tests over state-of-the-art Pt-Pd oxidation catalysts, this study identifies the most critical catalyst operation regimes that should be avoided in order to minimize N$_2$O levels. Especially unsaturated HCs react with NO to form significant amounts of N$_2$O between 150 °C and 350 °C; an increasing HC/NOx ratio generally promotes N$_2$O formation, whereas the NO oxidation reaction is increasingly inhibited. Since low space velocities and fast catalyst heating allow for minimizing N$_2$O levels, active heating of catalytic converters during cold start and phases of low exhaust gas temperatures may efficiently reduce the formation of N$_2$O in real-world applications

Isolation of the phe-operon from G. stearothermophilus comprising the phenol degradative meta-pathway genes and a novel transcriptional regulator

<p>Abstract</p> <p>Background</p> <p><it>Geobacillus stearothermophilus </it>is able to utilize phenol as a sole carbon source. A DNA fragment encoding a phenol hydroxylase catalyzing the first step in the <it>meta</it>-pathway has been isolated previously. Based on these findings a PCR-based DNA walk was performed initially to isolate a catechol 2,3-dioxygenase for biosensoric applications but was continued to elucidate the organisation of the genes encoding the proteins for the metabolization of phenol.</p> <p>Results</p> <p>A 20.2 kb DNA fragment was isolated as a result of the DNA walk. Fifteen open reading frames residing on a low-copy megaplasmid were identified. Eleven genes are co-transcribed in one polycistronic mRNA as shown by reverse transcription-PCR. Ten genes encode proteins, that are directly linked with the <it>meta</it>-cleavage pathway. The deduced amino acid sequences display similarities to a two-component phenol hydroxylase, a catechol 2,3-dioxygenase, a 4-oxalocrotonate tautomerase, a 2-oxopent-4-dienoate hydratase, a 4-oxalocrotonate decarboxylase, a 4-hydroxy-2-oxovalerate aldolase, an acetaldehyde dehydrogenase, a plant-type ferredoxin involved in the reactivation of extradiol dioxygenases and a novel regulatory protein. The only enzymes missing for the complete mineralization of phenol are a 2-hydroxymuconic acid-6-semialdehyde hydrolase and/or 2-hydroxymuconic acid-6-semialdehyde dehydrogenase.</p> <p>Conclusion</p> <p>Research on the bacterial degradation of aromatic compounds on a sub-cellular level has been more intensively studied in gram-negative organisms than in gram-positive bacteria. Especially regulatory mechanisms in gram-positive (thermophilic) prokaryotes remain mostly unknown. We isolated the first complete sequence of an operon from a thermophilic bacterium encoding the <it>meta</it>-pathway genes and analyzed the genetic organization. Moreover, the first transcriptional regulator of the phenol metabolism in gram-positive bacteria was identified. This is a first step to elucidate regulatory mechanisms that are likely to be distinct from modes described for gram-negative bacteria.</p

Transfer after process-based object-location memory training in healthy older adults

A substantial part of age-related episodic memory decline has been attributed to the decreasing ability of older adults to encode and retrieve associations among simultaneously processed information units from long-term memory. In addition, this ability seems to share unique variance with reasoning. In this study, we therefore examined whether process-based training of the ability to learn and remember associations has the potential to induce transfer effects to untrained episodic memory and reasoning tasks in healthy older adults (60-75 years). For this purpose, the experimental group (n = 36) completed 30 sessions of process-based objectlocation memory training, while the active control group (n = 31) practiced visual perception on the same material. Near (spatial episodic memory), intermediate (verbal episodic memory), and far transfer effects (reasoning) were each assessed with multiple tasks at four measurements (before, midway through, immediately after, and 4 months after training). Linear mixed-effects models revealed transfer effects on spatial episodic memory and reasoning that were still observed 4 months after training. These results provide first empirical evidence that process-based training can enhance healthy older adults' associative memory performance and positively affect untrained episodic memory and reasoning abilities

Evidence behind the use of molecular tests in melanocytic lesions and practice patterns of these tests by dermatopathologists

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146490/1/cup13327_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146490/2/cup13327-sup-0001-AppendixS1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146490/3/cup13327.pd