A superconducting thin film tunnel junction (Sn-Sn0₂ -Sn) of total thickness 4000 Å, area 7 x 10ˉ⁴ cm² and normal (4.2 K) resistance 77 mΩ was prepared on a glass substrate. When cooled to 1.2 K the junction was biased at 0.3 mV where, the Josephson supercurrent having been suppressed with a magnetic field, the junction dynamic resistance had its maximum value of 9.3Ω . The junction was then bombarded with 5.1 MeV alpha particles and the resulting pulses induced in the tunneling current were observed to have amplitudes up to 19 times the preamplifier-dominated rms output noise level. For purposes of analysis, it was assumed that the induced current pulse had the form i(t) = i₀ exp(-t/Ƭ), t ≥ 0. With this form of the current pulse and the known transfer function of the transmission line-amplifier system, it was calculated that for all pulses T = (1.38±.33)xl0ˉ⁷ sec and that for the largest amplitude pulses, corresponding to an energy loss ΔE⍺ ≤2.75 MeV, i₀ lay in the range 20 ≤ i₀ ≤ 26 μA with a most probable value of 22 μA. With this value of i₀ and ΔE⍺ = 2.75 MeV, an upper limit of 8.2 x 10ˉ³ eV has been assigned to the value of w(Sn), the average energy expended by the alpha particle to excite a quasiparticle pair in superconducting tin at 1.2 K. A tentative theory of the superconducting tunnel junction charged particle detector is given and the cryogenic and electronic apparatus required for the measurements are described. Details related to thin film junction fabrication technology and interpretation of dc experimental results are discussed in four appendices. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The alpha-particle reduced widths for the ground state in Po²¹² are calculated on the basis of the nuclear shell model, employing the technique of Harada, but treating the nuclear surface in a more direct manner. It is contended that the calculations of previous authors, who have generally used a square-edge nucleus and a Coulomb barrier rounded-off by the nuclear potential of Igo, have, essentially, used the equivalent square-edge nucleus model of Vogt. Their J.W.K.B. estimate of the barrier penetrabilities is checked by an analytic calculation in Chapter 3 and is found to be reasonable. It is shown in Chapter 4 that, in the scattering of an alpha-particle from the ground state of Pb²⁰⁸, the diffuse nuclear edge considerably enhances the one-body reduced widths and, in a direct manner, that it similarly enhances the one-body differential elastic scattering cross-section. In this manner, it is demonstrated that the radius involved in the equivalent square-edge nucleus model must be considerably larger than that of the diffuse-edge nucleus to which it corresponds. This is shown directly in Chapter 5, where the validity of the equivalent square-edge nucleus model in heavy nuclei is examined. It is contended that this explains the large radii found in previous calculations. This is demonstrated directly by repeating the calculation of Harada with the diffuse nuclear edge being introduced in a direct manner. Although the effects of configuration mixing have not been directly examined, it has been concluded that shell model calculations can explain the major part of rates provided that the nuclear surface is manner. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

No description available.

Introduction: Alpha-2-macroglobulin (α2m) is a plasma glycoprotein serine protease inhibitor. Previous studies have shown that coagulation factor concentrations are highly variable with age and α2m levels have been found to be twice as high in newborns compared to adults. This may contribute to a resistance towards thrombotic events observed in young populations. Protein glycosylation is known to affect protein activity and the glycosylation profile of adult α2m has previously been analyzed. Information regarding glycosylation of α2m in other age groups has yet to be elucidated. Therefore, the purpose of this study is to examine the differences in the glycosylation profiles between newborn and adult α2m. Methods: To evaluate glycan macroheterogeneity, plasma samples were enzymatically deglycosylated by PNGaseF, followed by SDS PAGE and western blotting (WB) to detect α2m. To evaluate microheterogeneity, plasma samples were incubated with Neuraminidase (Clostridium perfringens) followed by native PAGE and WB to determine sialic acid content. To detect non-sialylated terminal galactose residues, plasma samples were incubated with immobilized RCA120, and lectin-bound molecules were separated from unbound molecules. Additionally, the affinity of α2m for ricin was evaluated by eluting bound proteins with increasing concentrations of galactose. All fractions were subjected to SDS-PAGE and WB to detect α2m. 2D gel electrophoresis was completed to examine differences in pI and molecular weight of α2m in both age groups. Purification by immunoprecipitation was also performed and eluted α2m was analyzed by fluorescence-assisted carbohydrate electrophoresis (FACE) to determine the glycan fingerprint in the two populations. Results: Deglycosylation of both newborn and adult α2m with PNGaseF resulted in a change in migration and apparent molecular weight, however no statistically significant difference was found between newborn and adult. On native PAGE following treatment with neuraminidase, newborn α2m exhibited a statistically significant change in migration compared to adult. Additionally, newborn α2m exhibited a higher percentage of molecules bound to RCA120 than adult (no statistical difference) and elution of α2m from RCA120 with a galactose step gradient produced similar profiles for newborn and adult molecules. 2D electrophoresis and WB revealed a difference in pI of α2m in newborns as compared to adults. Finally, purified newborn and adult α2m were analyzed by FACE and quantification of prominent fluorescent bands revealed a higher secondary:primary band ratio in newborns when compared to adults. Conclusions: To our knowledge, this is the first study investigating glycosylation differences between newborn and adult α2m molecules. The results from PNGaseF analyses indicate no significant difference in total N-glycan content. Neuraminidase results suggest significantly greater sialic acid presence on newborn α2m, however there was no significant difference in galactose content. 2D electrophoresis revealed a difference in pI as well as the way in which newborn and adult α2m degrade when exposed to experimental conditions. A2m was successfully purified from both newborn and adult plasma, and FACE results indicate that the proportion of more branched glycans present in the two major fluorescent bands are of higher quantity in newborns than adults. / Thesis / Master of Science (MSc)

Recent studies suggest that Adenosine Triphosphate (ATP) can either enhance or inhibit the aggregation of amyloid proteins, depending on the interaction mechanism as well as specific protein properties. The connection between ATP and protein solubility is particularly important in Parkinson’s Disease (PD), where the aggregation of alpha-synuclein (αS) is closely linked to pathology. Since the greatest risk factor for PD is aging, and ATP levels decline dramatically with age and are greatly reduced in the brains of patients with early PD, it is possible that the modulating effect of ATP on protein solubility is a factor in PD onset. However, the driving mechanism behind the interaction of ATP and αS is currently unclear, as is the effect of physiologically-relevant ATP concentrations on early- and late-stage αS aggregation. Here, we determine using NMR spectroscopy that the triphosphate moeity of ATP drives its electrostatic interaction primarily with the N-terminal pseudo-apolipoprotein repeats of αS monomers. These interactions are modulated by magnesium and disrupt long-range N- to C-terminal contacts in αS monomers, causing a concentration-dependent enhancement of initial αS aggregation. We also show by Thioflavin T fluorescence as well as electron microscopy that ATP inhibits late-stage αS β-sheet fibril formation in a phosphate-dependent manner. Our NMR data reveals that ATP inhibits αS monomer-fibril interactions, suggesting that ATP attenuates αS secondary nucleation. Lastly, we show that the effects of ATP are different in the presence of PD-related αS mutations E46K and A53T. Overall, our study contributes a thorough characterization of the biologically- and pathologically-relevant interactions between ATP and αS, while also proposing a role for ATP in the age-related development of PD pathology. / Thesis / Master of Science (MSc) / Alpha-synuclein (αS) is a protein whose abnormal aggregation is characteristic of Parkinson’s Disease (PD). Adenosine Triphosphate (ATP) is a molecule that has recently been shown to reduce the aggregation of select disease-causing proteins. Therefore, the aim of this study is to characterize the interaction mechanism between ATP and αS, to explore how this interaction influences αS structural dynamics and to determine the effect of ATP on early- and late-stage αS aggregation. Another overall aim of this study is to characterize how the ATP-αS interaction is influenced by PD-related mutations in αS. To accomplish these aims, we will rely primarily on NMR spectroscopy as well as fluorescence and microscopy techniques. Our goal is to determine the role of ATP in αS aggregation as well as potentially connect the age-related decrease in ATP levels with PD, an age-related disease.

No / ¿-Ketophosphonates are prepared by a [3,3]-sigmatropic shift of enolphosphonates.

L’alpha-foetoprotéine (AFP) est la protéine majoritaire du sérum fœtal de mammifère. C’est une glycoprotéine produite et sécrétée par l’endoderme viscéral du sac vitellin, les hépatocytes fœtaux et dans une moindre mesure, par l’intestin fœtal. Son profil d’expression est onco-fœtal : la synthèse de cette protéine chute fortement après la naissance mais peut reprendre en cas de régénération hépatique ou en cas de tumeurs diverses. Cette protéine est capable de fixer les oestrogènes et jouerait un rôle dans la différenciation sexuelle du cerveau femelle. Deux invalidations du gène de l’AFP ont été réalisées au Laboratoire de Biologie du Développement afin de comprendre la fonction de cette protéine. Dans les deux cas, des souris homozygotes pour l’allèle invalidé (souris AFP KO) ont été obtenues. Elles sont viables et apparemment phénotypiquement normales, mais les femelles sont stériles, suite à une anovulation. Il a été démontré que l’absence d’ovulation provient d’un mauvais fonctionnement de l’axe hypothalamo-hypopysaire. Nous avons démontré au cours de cette thèse que l’ARN messager d’une série de gènes était sous-représenté au sein de l’hypophyse des souris femelles invalidées pour le gène Afp. Nous trouvons parmi ces gènes, ceux d’une cascade particulièrement importante pour l’ovulation, la cascade du récepteur de la GnRH. La fertilité des souris femelles AFP KO, ainsi que le taux d’expression des gènes testés dans l’hypophyse, sont restaurés si ces souris se développent dans un environnement appauvri en oestrogènes. Nous avons donc pu corriger le phénotype des souris femelles invalidées pour le gène de l’AFP. Nous avons en ce faisant démontré que l’AFP, par sa capacité de fixer les oestrogènes, protégeait le cerveau femelle en développement des effets masculinisants de ces hormones

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Thesis (M.Sc.). / Written for the Dept. of Neurology and Neurosurgery. Title from title page of PDF (viewed 2008/05/14). Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 238-308).