The development of a model of Alpha helix formation for transmembrane peptides

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaf 26).Researchers have studied the folding and binding properties of peptides in water for many years, but only recently has anyone attempted to explore those same tendencies in an environment similar to that of a transmembrane protein incorporated into the phospholipid bilayer of the cell. To this end, we have been working on the synthesis of a group of peptides with the general sequence +H3N-Ala2-Leu3-Ala7-Trp-Ala-X-Ala10-Lys6-COOH, where we will substitute all twenty naturally occurring amino acids into position X. We have successfully synthesized and purified the peptide in which the guest position X is filled by an isoleucine-due to the difficulty of the sequence involved, we have been unable to synthesize and purify eighteen of the remaining nineteen. Peptides, once synthesized, are characterized by MALDI mass spectrometry and HPLC and purified peptides are studied using circular dichroism (CD) spectroscopy to determine the a-helicity. Initial results suggest that the transmembrane environment will indeed alter the propensities of the various amino acid residues to form a-helices, though to what degree still remains to be seen. Once complete, this study should make it possible to determine a system for predicting a-helix formation in membrane proteins and determine the basic rules that guide such helix formation

Dissecting the theories of lanthanide magnetic resonance

The NMR relaxation and chemical shift behaviour of isostructural series of macrocyclic lanthanide(III) complexes has been investigated. The 1H, 31P and 19F longitudinal relaxation rates of multiple series of lanthanide(III) complexes (Tb, Dy, Ho, Er, Tm, Yb) have been measured in solution at five magnetic field strengths in the range 4.7 to 16.5 Tesla. The electronic relaxation time, T1e, is a function of both the lanthanide(III) ion and the local ligand field. Analysis of the field-dependent nuclear relaxation rates, based on Solomon-Bloembergen Morgan theory, describing the paramagnetic enhancement of the nuclear relaxation rates, has allowed reliable estimates of the electronic relaxation times, T1e. It has been shown that in systems of high symmetry, the electronic relaxation times are directly proportional to the ligand field and that in some cases changing the ligand field can have a greater effect on the nuclear relaxation rates than lanthanide selection. The chemical shift data for the series of lanthanide(III) complexes were analysed. The pseudocontact shift of lanthanide(III) complexes is described by Bleaney’s theory of magnetic anisotropy. Most of the assumptions in this theory were shown to be questionable. In particular for systems in low symmetry significant deivations between the experimental chemical shifts and those predicted by theory were found. The low symmetry systems exhibit crystal field splittings of the same order of magnitude as the spin-orbit coupling. The possibility of a mixing of the electronic energy levels of the lanthanide(III) ion has to be considered. The effect of the coordination environment on the magnetic susceptibility was investigated using a variety of methods. Significant deviation (10 – 20%) from the theoretical values was observed in systems of low symmetry. These investigations show that paramagnetic relaxation enhancements and magnetic susceptibility are dependent on the ligand field. Applying this knowledge allows the design of more efficient paramagnetic probes, as needed in PARASHIFT magnetic resonance

Development of a Molecular Genetic Method for Characterizing Amphibian Diets

DEVELOPMENT OF A MOLECULAR GENETIC METHOD FOR CHARACTERIZING AMPHIBIAN DIETS.Alexander Funk* and Todd W. Pierson, Department of Ecology and Evolutionary Biology, University of Tennessee Knoxville, [email protected] Dietary studies can provide key insights into the ecology and behavior of animals. Methods common in dietary studies of amphibians (e.g., gastric lavage, fecal analysis, dissection) often fail to identify prey beyond the level of Order, are time intensive, and can be biased against soft-bodied prey. Here, we are developing a DNA metabarcoding assay to characterize amphibian diets from non-invasive fecal samples. In DNA metabarcoding, barcoding loci from mixed community samples (e.g., feces) are sequenced on a next-generation sequencing platform, and resulting reads are used to identify members of that community (e.g., diet composition). To validate this method, we will prepare COI amplicon libraries from 27 fecal samples collected from wild Blue Ridge two-lined salamander (Eurycea wilderae) during the breeding season. We will sequence these reads on an Illumina MiSeq and compare resulting reads against a reference library of sequences of known identity to characterize invertebrate diet composition. Some of our samples are derived from male E. wilderae with two alternative reproductive tactics-“searching” and “guarding”. Because the latter is more likely to be found in aquatic habitats in the breeding season, we expect to find a great representation of aquatic invertebrates in its diet. We hope that this method will prove to be more accurate and efficient than previous methods, providing a new, versatile tool with which amphibian diets can be characterized and compared

A Syntactic Treatment of Adjectival Non-Intersectivity in English

Natural language has long been observed to be rife with apparently \u27non-intersective\u27 modification constructions (false teeth, huge flea, heavy smoker, etc.), whose apparent non-compositionality poses difficulties for formally-articulated theories of language. Bolinger\u27s (1967) demonstration of the extent and significance of the issue ushered in several lines of investigation, first in semantics (most notably Kamp 1975, Siegel 1976, Partee 2009), but more recently in syntax as well, with the insights of Larson (1998) and Bouchard (2002) informing approaches to the nominal domain such as that in Cinque (2010). However, \u27semantics-only\u27 accounts of non-intersectivity phenomena have limited explanatory capacity given the clear sensitivity of syntax to intersectivity, and recent syntactic proposals leave many questions about non-intersectivity largely unresolved, particularly the implications of non-intersective adnominal modification (NIAM) for the internal structure of the Determiner Phrase (DP), and for fundamental conceptions of category and predication. This thesis articulates the alignment of NIAM intepretation patterns based on an enriched typology of both adjectives and nouns. In particular, it exploits non-lexicalist approaches to syntax--the \u27late insertion\u27 approach of Distributed Morphology (Halle & Marantz 1993, 1994)--as well as non-directional predication structures (den Dikken 2006) to develop an understanding of interpretation and distribution patterns of English NIAM structures which elude explanation in simpler, \u27bivalent\u27 approaches to non-intersectivity. By outlining analyses for reference examples from a wide range of NIAM types, it demonstrates the potential for this line of analysis to capture putative \u27non-intersectivity\u27 intersectively, and to develop a unified understanding of predication and modification

Magnetokalorische Regeneratoren aus (Mn,Fe)2(P,Si)- und La(Fe,(Co),Si)13-Legierungen

Diese Arbeit befasst sich mit unterschiedlichen werkstoffwissenschaftlichen Fragestellungen auf dem Gebiet der magnetokalorischen Kühlung. Magnetokalorische Materialien, z.B. (Mn,Fe)2(P,Si)- oder La(Fe,(Co),Si)13-Legierungen, erwärmen sich bzw. kühlen ab, wenn das Material unter adiabatischer Prozessführung und einer Umgebungstemperatur nahe der magnetischen Phasenübergangstemperatur einem externen Magnetfeld ausgesetzt bzw. daraus entfernt wird. Der magnetokalorische Effekt (MKE) von Materialien kann, bei zyklischer Wiederholung von Magnetisierung und Entmagnetisierung, in einer Wärmepumpe genutzt werden, um Wärme von einer Substanz oder einem Raum abzuführen. Ein Wärmetauscher aus magnetokalorischem Material – der magnetokalorische Regenerator – ist, neben einem Magnet- und Pumpensystem, das essenzielle Bauteil in magnetokalorischen Wärmepumpen und Kältemaschinen. Regeneratoren können aus Schichten unterschiedlicher Pulverchargen eines magnetokalorischen Materials bestehen, dass mit einem Polymer gebunden wird. Der Aufbau von konventionellen (Mn,Fe)2(P,Si)-Pulverschüttungen wird in der vorliegenden Arbeit anhand zerstörungsfreier Röntgencomputertomographie überprüft. Neben individuellen Merkmalen einer Pulvercharge, können entlang der Schichtstapelrichtung auftretende Porositätsvariationen zur Detektion von Schichten genutzt werden. Weiterführend werden magnetische Wechselwirkungen der einzelnen Partikel und Schichten in einem (Mn,Fe)2(P,Si)-Regenerator mittels magneto-optischer Bildgebung untersucht. In La(Fe,(Co),Si)13-Legierungen geht der MKE mit einer zusammensetzungsabhängigen Volumenänderung der Elementarzelle einher, die das Material unter Umständen katastrophal versagen lässt. Die Festigkeit der Legierung spielt sowohl für die Langzeitstabilität als auch die Verarbeitung mit Maschinen eine wesentliche Rolle. Im Rahmen der Arbeit wurde eine intermetallische LaFe10,2Si1,8-Legierung auf unterschiedlichen Längenskalen mechanischen Prüfungen unterzogen. Die Festigkeit ist von inneren Defekten (Mikrorisse, Zweitphasen) beeinflusst, weshalb Druckversuche zur Eigenschaftsbestimmung ungeeignet sind. Lokale Härtemessungen hingegen erlauben eine Abschätzung der intrinsischen Festigkeit der magnetokalorischen Hauptphase von 2GPa. Damit lassen sich Experimente zur Langzeitstabilität unter wiederholt induziertem Phasenübergang erklären. Abschließend wird ein Verfahren demonstriert, dass es ermöglicht magnetokalorische Kompositdrähte mit einem La(Fe,(Co),Si)13-Kern und einer rostfreiem Stahlhülle herzustellen. Drahthalbzeuge sind Geometrien, die bisher nicht für den Aufbau von Regeneratoren in Erwägung gezogen wurden, da sie nicht herstellbar waren. Drähte bieten ein hohes Maß an Anordnungsfreiheit und bereichern die Vielfalt möglicher Regeneratorgeometrien. Das Material wird durch die Stahlhülle sowohl vor chemischen Einflüssen geschützt, als auch mechanisch stabilisiert, und mit Kernvolumenanteilen von bis zu ∼ 60 vol% sind die Drähte für den Einsatz in einer Wärmepumpe geeignet

LAT Perspectives in Detection of High Energy Cosmic Ray Electrons

The GLAST Large Area Telescope (LAT) science objectives and capabilities in the detection of high energy electrons in the energy range from 20 GeV to approx. 1 TeV are presented. LAT simulations are used to establish the event selections. It is found that maintaining the efficiency of electron detection at the level of 30% the residual hadron contamination does not exceed 2-3% of the electron flux. LAT should collect approx. ten million of electrons with the energy above 20 GeV for each year of observation. Precise spectral reconstruction with high statistics presents us with a unique opportunity to investigate several important problems such as studying galactic models of IC radiation, revealing the signatures of nearby sources such as high energy cutoff in the electron spectrum, testing the propagation model, and searching for KKDM particles decay through their contribution to the electron spectrum

Getting magnetocaloric materials into good shape: Cold-working of La(Fe, Co, Si)13 by powder-in-tube-processing

The powder-in-tube (PIT) technology was applied to La(Fe, Co, Si)13 powder cladded by a thin seamless austenitic steel jacket. Wires appear to be promising in the search for alternative regenerator geometries, since they offer various possibilities of arrangements allowing to optimise heat transfer and pressure loss within the boundaries set by parallel plate and sphere beds. Here, pre-alloyed La(Fe, Co, Si)13 powder was filled in a AISI 316L austenitic steel tube and swaged to wires with an outer diameter of 1 mm. By mechanical deformation, the steel jacket thickness was reduced to about 100 μm surrounding the magnetocaloric core. A post-annealing of only 10 min at 1050 °C is sufficient to form the magnetocaloric NaZn13-type phase resulting in an entropy change close to the value of a pure reference sample. The presented technology is not limited to La(Fe, Co, Si)13/steel combination but can be extended to material pairs involving wire core materials with a first order transition, such as Fe2P-type or Heusler alloys

Desenvolvimento de um condicionador de sinal para eletroantenografia

O objetivo principal que motivou este trabalho foi o de construir um condicionador de sinal para medição da resposta elétrica das antenas de insetos devido à receção de sinais químicos (Eletroantenografia). O estudo da resposta das antenas dos insetos é particularmente relevante para o estudo das pragas de insetos, para a sua monitorização, e também para a descodificação dos mecanismos olfativos nas relações planta-inseto, com consequências para o desenvolvimento de dispositivos biossensores. O trabalho desenvolvido enquadra-se numa área interdisciplinar da física, química, fisiologia, ecologia aplicada e saúde pública. O inseto usado nesta experiência foi o gorgulho do eucalipto (Gonipterus Platensis), que tem vindo a dizimar as plantações de eucalipto em Portugal, provocando graves perdas económicas aos proprietários. O condicionador desenvolvido consiste num sistema de “interface” com a antena do inseto e um amplificador operacional de baixo ruído e ganho variável, que permite amplificar o sinal elétrico da antena para níveis adequados à aquisição e tratamento de sinal. A vantagem do aparelho construído é o fácil manuseamento do material biológico e químico,comparado com ensaios de Eletroantenografia tradicionais com recurso a pipetas de “Pasteur”. Este projeto indicou que o sistema desenvolvido poderá ser capaz da medição da resposta da antena do gorgulho a estímulos olfativos de eucalipto

Synthesis, stereocontrol and structural studies of highly luminescent chiral tris-amidepyridyl-triazacyclononane lanthanide complexes

The configuration of the remote amide chiral moiety determines the helicity of the metal complex in Ln(III) complexes of nonadentate N6O3 ligands based on triazacyclononane. Solution NMR studies revealed the presence of a dominant isomer whose proportion varies from 9 : 1 to 4 : 1 from Ce to Yb and X-ray crystallographic studies at 120 K of the Yb and two enantiomeric Eu complexes confirmed the configuration as S-Δ-λ in the major isomer. Global minimisation methods allowed magnetic susceptibility and electronic relaxation times of the lanthanide ions to be estimated by analysis of variable field longitudinal relaxation rate (R1) data sets. A set of four europium complexes, containing different para-substituted pyridinyl-aryl groups, exist as one major isomer (15 : 1), and absorb light strongly via an ICT transition in the range 320 to 355 nm (ε = 55 to 65 000 M−1 cm−1). The two examples absorbing light at 332 nm, possess overall emission quantum yields of 35 and 37% in aerated water, making these systems as bright as any Eu complex in solution