218 research outputs found
A nuclear magnetic resonance investigation of brine inclusions in Antarctic and artificial sea ice : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Physics at Massey University
Additional images with the print copy held in the library.The aim of this thesis is to use Nuclear Magnetic Resonance (NMR) techniques to examine the brine pockets in sea ice. Both the movement of the brine pockets within the ice, and the movement of the brine within the brine pockets is examined. The experiments are carried out using Earth's field NMR on sea ice in situ in Antarctica, and high field NMR equipment on artificially grown sea ice in New Zealand. The field work involved probe design, construction, and use. Investigations were carried out on brine content, and brine diffusion rates. The laboratory work involved growing realistic artificial sea ice, designing and constructing a temperature control system for the high field NMR machine, and carrying out experiments on the artificial sea ice samples. The brine pockets' morphology and distribution was examined. The brine and brine pocket movements over time, with a controlled temperature gradient, were also investigated. The results from the field work clearly showed multiple diffusion rates in sea ice, both faster and slower than that of water. The lab work showed that realistic sea ice had been grown, and that there was a migration of brine pockets in the direction of the temperature gradient
Chemical tools to investigate inositol pyrophosphate protein interactions
Die Inositol-Pyrophosphate (PP-InsPs) sind eine ubiquitĂ€re Gruppe hochphosphorylierter eukaryotischer SignalmolekĂŒle. Sie werden mit einer Vielzahl zentraler zellulĂ€rer Prozesse in Verbindung gebracht, doch fehlt oft ein detailliertes VerstĂ€ndnis der einzelnen Signalereignisse, was zum Teil auf einen Mangel an chemischen Werkzeugen zurĂŒckzufĂŒhren ist. Diese Arbeit beschreibt die chemische Synthese, Validierung und Anwendung von PP-InsP-AffinitĂ€tsreagenzien zur Identifizierung von Proteinbindungspartnern von Inositolhexakisphosphat (InsP6) und 5-Diphosphoinositol-Pentakisphosphat (5PP-InsP5), zwei wichtigen eukaryotischen Metaboliten. Die AffinitĂ€tsreagenzien wurden entwickelt, um InsP6 und ein metabolisch stabiles 5PP-InsP5-Analogon auf drei verschiedene Arten darzustellen. Die Anwendung dieser triplexierten Reagenzien auf SĂ€ugetier-Lysate lieferte einen ersten umfassenden Datensatz in HCT116- und HEK293T-Zellen. Die Interaktome wurden mittels quantitativer Proteomik annotiert und enthĂŒllten Hunderte von potenziellen Proteinbindungspartnern. Die quantitative Analyse der InsP6- und 5PP-InsP5-bindenden Proteine zeigte Beispiele fĂŒr hochspezifische Protein-Ligand-Interaktionen auf. Biochemische Untersuchungen ergaben, dass Inositol-5-Phosphatasen, PRPS1 und spezifische Phosphatidyl-Inositolphosphat-Kinasen potenziell unentdeckte Zielproteine von PP-InsPs sind.
DarĂŒber hinaus wurde durch die Entwicklung einer neuen Strategie der Myo-Inositol-Desymmetrisierung erstmals die Synthese eines AffinitĂ€tsreagens auf der Basis von 1,5-Bisdiphosphoinositol-Tetrakisphosphat (1,5(PP)2-InsP4) beschrieben. Die AffinitĂ€tsreagenzien und die proteomischen DatensĂ€tze stellen fĂŒr die Gemeinschaft leistungsstarke Ressourcen dar, um kĂŒnftige Untersuchungen zu den vielfĂ€ltigen SignalmodalitĂ€ten von Inositolpyrophosphaten einzuleiten.Inositol pyrophosphates (PP-InsPs) are a ubiquitous group of highly phosphorylated eukaryotic messengers. They have been linked to a panoply of central cellular processes, but a detailed understanding of the discrete signaling events is often missing, which can partially be attributed to a lack of chemical tools. This thesis describes the chemical synthesis, validation and application of PP-InsP affinity reagents to identify protein binding partners of inositol hexakisphosphate (InsP6) and 5-diphosphoinositol pentakisphosphate (5PP-InsP5), two important eukaryotic metabolites. The affinity reagents were developed to display InsP6 and a metabolically stable 5PP-InsP5 analog in three different ways. Application of these triplexed reagents to mammalian lysates provided a first comprehensive data set in HCT116 and HEK293T cells. The interactomes were annotated using quantitative proteomics and uncovered hundreds of potential protein binding partners. Quantitative analysis of InsP6 versus 5PP-InsP5 binding proteins highlighted examples of highly specific protein-ligand interactions. Biochemical studies primed inositol 5-phosphatases, PRPS1 and specific phosphatidyl inositol phosphate kinases as potentially undiscovered targets of PP-InsPs.
Moreover, by developing a novel strategy of myo-inositol desymmetrization, the synthesis of an affinity reagent based on 1,5-bisdiphosphoinositol tetrakisphosphate (1,5(PP)2-InsP4) was described for the first time. The affinity reagents and the proteomic data sets constitute powerful resources for the community, to help launching future investigations into the multiple signaling modalities of inositol pyrophosphates
Ăberversorgte StĂ€dte, unterversorgtes Land? Regionale Selektionsprozesse im Bereich der Daseinsvorsorge
LÀndliche RÀume können nicht generell als unterversorgt gelten. Dort, wo der
Staat mit seinen Instrumenten steuern kann, gelingt meist auch die Versorgung in
dĂŒnn besiedelten lĂ€ndlichen und peripheren Regionen. In diesem Beitrag wird daher das Problem einer systematischen generellen Unterversorgung der lĂ€ndlichen RĂ€ume gegenĂŒber den verstĂ€dterten RĂ€umen differenzierter betrachtet. Zuerst wird gefragt, ob die Betrachtung Stadt versus Land im Hinblick auf die Daseinsvorsorge angemessen oder eine GegenĂŒberstellung von Zentrum versus Peripherie zielfĂŒhrender ist. Es ist darĂŒber hinaus auch notwendig, zwischen privatwirtschaftlich organisierten und staatlich geplanten und finanzierten Einrichtungen der Daseinsvorsorge zu unterscheiden. An konkreten Beispielen werden dann spezifische Facetten der Ăber- und Unterversorgung aufgezeigt. Den Mittelzentren kommt zur Versorgung der Bevölkerung sowohl in stĂ€dtischen als auch in lĂ€ndlichen Regionen eine hohe Bedeutung zu. Zuletzt wird kurz repliziert, wie Politik und Verwaltung den Herausforderungen einer möglichen Unterversorgung in TeilrĂ€umen begegnen wollen
The growth exponent for planar loop-erased random walk
We give a new proof of a result of Kenyon that the growth exponent for
loop-erased random walks in two dimensions is 5/4. The proof uses the
convergence of LERW to Schramm-Loewner evolution with parameter 2, and is valid
for irreducible bounded symmetric random walks on any two-dimensional discrete
lattice.Comment: 62 pages, 7 figures; fixed typos, added reference
Differences in signal activation by LH and hCG are mediated by the LH/CG receptorâs extracellular hinge region
The human lutropin (hLH)/choriogonadotropin (hCG) receptor (LHCGR) can be
activated by binding two slightly different gonadotropic glycoprotein
hormones, choriogonadotropin (CG) â secreted by the placenta, and lutropin
(LH) â produced by the pituitary. They induce different signaling profiles at
the LHCGR. This cannot be explained by binding to the receptorâs leucine-rich-
repeat domain (LRRD), as this binding is similar for the two hormones. We
therefore speculate that there are previously unknown differences in the
hormone/receptor interaction at the extracellular hinge region, which might
help to understand functional differences between the two hormones. We have
therefore performed a detailed study of the binding and action of LH and CG at
the LHCGR hinge region. We focused on a primate-specific additional exon in
the hinge region, which is located between LRRD and the serpentine domain. The
segment of the hinge region encoded by exon10 was previously reported to be
only relevant to hLH signaling, as the exon10-deletion receptor exhibits
decreased hLH signaling, but unchanged hCG signaling. We designed an advanced
homology model of the hormone/LHCGR complex, followed by experimental
characterization of relevant fragments in the hinge region. In addition, we
examined predictions of a helical exon10-encoded conformation by block-wise
polyalanine (helix supporting) mutations. These helix preserving modifications
showed no effect on hormone-induced signaling. However, introduction of a
structure-disturbing double-proline mutant LHCGR-Q303P/E305P within the
exon10-helix has, in contrast to exon10-deletion, no impact on hLH, but only
on hCG signaling. This opposite effect on signaling by hLH and hCG can be
explained by distinct sites of hormone interaction in the hinge region. In
conclusion, our analysis provides details of the differences between hLH- and
hCG-induced signaling that are mainly determined in the L2-beta loop of the
hormones and in the hinge region of the receptor
Endothelin potentiates TRPV1 via ETA receptor-mediated activation of protein kinase C
© 2007 Plant et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens
IP7-SPX Domain Interaction Controls Fungal Virulence by Stabilizing Phosphate Signaling Machinery
In the human-pathogenic fungus Cryptococcus neoformans, the inositol polyphosphate signaling pathway is critical for virulence. We recently demonstrated the key role of the inositol pyrophosphate IP7 (isomer 5-PP-IP5) in driving fungal virulence; however, the mechanism of action remains elusive. Using genetic and biochemical approaches, and mouse infection models, we show that IP7 synthesized by Kcs1 regulates fungal virulence by binding to a conserved lysine surface cluster in the SPX domain of Pho81. Pho81 is the cyclin-dependent kinase (CDK) inhibitor of the phosphate signaling (PHO) pathway. We also provide novel mechanistic insight into the role of IP7 in PHO pathway regulation by demonstrating that IP7 functions as an intermolecular "glue" to stabilize Pho81 association with Pho85/Pho80 and, hence, promote PHO pathway activation and phosphate acquisition. Blocking IP7-Pho81 interaction using site-directed mutagenesis led to a dramatic loss of fungal virulence in a mouse infection model, and the effect was similar to that observed following PHO81 gene deletion, highlighting the key importance of Pho81 in fungal virulence. Furthermore, our findings provide additional evidence of evolutionary divergence in PHO pathway regulation in fungi by demonstrating that IP7 isomers have evolved different roles in PHO pathway control in C. neoformans and nonpathogenic yeast.IMPORTANCE Invasive fungal diseases pose a serious threat to human health globally with >1.5 million deaths occurring annually, 180,000 of which are attributable to the AIDS-related pathogen, Cryptococcus neoformans Here, we demonstrate that interaction of the inositol pyrophosphate, IP7, with the CDK inhibitor protein, Pho81, is instrumental in promoting fungal virulence. IP7-Pho81 interaction stabilizes Pho81 association with other CDK complex components to promote PHO pathway activation and phosphate acquisition. Our data demonstrating that blocking IP7-Pho81 interaction or preventing Pho81 production leads to a dramatic loss in fungal virulence, coupled with Pho81 having no homologue in humans, highlights Pho81 function as a potential target for the development of urgently needed antifungal drugs
Mass-spectrometric identification of a novel angiotensin peptide in human plasma
Objectiveâ Angiotensin peptides play a central role in cardiovascular physiology and pathology. Among these peptides, angiotensin II (Ang II) has been investigated most intensively. However, further angiotensin peptides such as Ang 1-7, Ang III, and Ang IV also contribute to vascular regulation, and may elicit additional, different, or even opposite effects to Ang II. Here, we describe a novel Ang II-related, strong vasoconstrictive substance in plasma from healthy humans and end-stage renal failure patients. Methods and Resultsâ Chromatographic purification and structural analysis by matrix-assisted laser desorption/ionisation time-of-flight/time-of-flight (MALDI-TOF/TOF) revealed an angiotensin octapeptide with the sequence Ala-Arg-Val-Tyr-Ile-His-Pro-Phe, which differs from Ang II in Ala1 instead of Asp1. Des[Asp1]-[Ala1]-Ang II, in the following named Angiotensin A (Ang A), is most likely generated enzymatically. In the presence of mononuclear leukocytes, Ang II is converted to Ang A by decarboxylation of Asp1. Ang A has the same affinity to the AT1 receptor as Ang II, but a higher affinity to the AT2 receptor. In the isolated perfused rat kidney, Ang A revealed a smaller vasoconstrictive effect than Ang II, which was not modified in the presence of the AT2 receptor antagonist PD 123319, suggesting a lower intrinsic activity at the AT1 receptor. Ang II and Ang A concentrations in plasma of healthy subjects and end-stage renal failure patients were determined by matrix-assisted laser desorption/ionisation mass-analysis, because conventional enzyme immunoassay for Ang II quantification did not distinguish between Ang II and Ang A. In healthy subjects, Ang A concentrations were less than 20% of the Ang II concentrations, but the ratio Ang A / Ang II was higher in end-stage renal failure patients. Conclusionâ Ang A is a novel human strong vasoconstrictive angiotensin-derived peptide, most likely generated by enzymatic transformation through mononuclear leukocyte-derived aspartate decarboxylase. Plasma Ang A concentration is increased in end-stage renal failure. Because of its stronger agonism at the AT2 receptor, Ang A may modulate the harmful effects of Ang II. In this study, a new angiotensin-peptide of human plasma is described, which is characterized as a strong AT2-receptor agonist
Characterization of BU09059:A novel potent selective Îș-receptor antagonist
[Image: see text] Kappa-opioid receptor (Îș) antagonists are potential therapeutic agents for a range of psychiatric disorders. The feasibility of developing Îș-antagonists has been limited by the pharmacodynamic properties of prototypic Îș-selective antagonists; that is, they inhibit receptor signaling for weeks after a single administration. To address this issue, novel trans-(3R,4R)-dimethyl-4-(3-hydroxyphenyl) piperidine derivatives, based on JDTic, were designed using soft-drug principles. The aim was to determine if the phenylpiperidine-based series of Îș-antagonists was amenable to incorporation of a potentially metabolically labile group, while retaining good affinity and selectivity for the Îș-receptor. Opioid receptor binding affinity and selectivity of three novel compounds (BU09057, BU09058, and BU09059) were tested. BU09059, which most closely resembles JDTic, had nanomolar affinity for the Îș-receptor, with 15-fold and 616-fold selectivity over ÎŒ- and ÎŽ-receptors, respectively. In isolated tissues, BU09059 was a potent and selective Îș-antagonist (pA(2) 8.62) compared with BU09057 (pA(2) 6.87) and BU09058 (pA(2) 6.76) which were not Îș-selective. In vivo, BU09059 (3 and 10 mg/kg) significantly blocked U50,488-induced antinociception and was as potent as, but shorter acting than, the prototypic selective Îș-antagonist norBNI. These data show that a new JDTic analogue, BU09059, retains high affinity and selectivity for the Îș-receptor and has a shorter duration of Îș-antagonist action in vivo
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