Yeast prion physiology

2016 Summer.Includes bibliographical references.Prions, or proteinaceous infections, are caused by proteins that have the unique ability to adopt an alternative, self-replicating structure. These self-replicating structures are the causative agent of a number of mammalian diseases including Bovine spongiform encephalopathy, Creutzfeldt-Jakob disease, and Kuru. More recently, yeast were discovered to carry at least a dozen proteins capable of making this structural conversion. Yeast prions are unique in that their prion-forming domains are intrinsically disordered domains, with unusual compositional biases. This thesis addresses two broad questions about yeast prion physiology. First, a recent mutagenic screen suggested that both aromatic and non-aromatic hydrophobic residues strongly promote prion formation. However, while aromatic residues are common in yeast prion domains, non-aromatic hydrophobics are strongly under-represented. The second chapter of this dissertation explores the effects of hydrophobic and aromatic residues on prion formation. Insertion of even a small number of hydrophobic residues is found to strongly increase prion formation. These data, combined with bioinformatics analysis of glutamine/asparagine-rich domains, suggest a limit on the number of strongly prion-promoting residues tolerated in glutamine/asparagine-rich domains. Recent studies have demonstrated that aromatic residues play a key role in the maintenance of yeast prions during cell division. Taken together, these results imply that non-aromatic hydrophobic residues are excluded from prion domains not because they inhibit prion formation, but instead because they too strongly promote aggregation, without promoting prion propagation. Despite more than 20 years of research, we still don’t know why yeast carry so many prion and prion-like domains. It has been proposed that prions may serve some biological function. Chapter Three presents progress on two lines of investigation designed to resolve this issue First, a novel bioinformatics algorithm (GARRF) is used to screen a wide range of proteomes to find examples of Q/N rich domains outside of Saccharomyces cerevisiae. Identifying other species that carry these unusual regions provides insight into their role in cellular biology. We find a wide range species carry prion-like domains at levels comparable to Saccharomyces cerevisiae, and a small number carry up to an order of magnitude more. Second, currently researchers rely primarily on yeast genetic methods to discover and monitor prions. These methods have a number of drawbacks, including a glacially slow readout time. Chapter Three reports on progress towards the development of a novel fluorescence based prion assay. This assay takes advantage of bi-molecular fluorescence complementation, a technique that uses complementary fragments of a fluorescent protein to indicate when two interacting domains are in proximity to one another. When completed, this assay will provide a means to monitor protein aggregations that is both faster and more sensitive than any existing assay

Multi-rotor with suspended load: System Dynamics and Control Toolbox

There is an increasing demand for Unmanned Aerial Systems (UAS) to carry suspended loads as this can provide significant benefits to several applications in agriculture, law enforcement and construction. The load impact on the underlying system dynamics should not be neglected as significant feedback forces may be induced on the vehicle during certain flight manoeuvres. The constant variation in operating point induced by the slung load also causes conventional controllers to demand increased control effort. Much research has focused on standard multi-rotor position and attitude control with and without a slung load. However, predictive control schemes, such as Nonlinear Model Predictive Control (NMPC), have not yet been fully explored. To this end, we present a novel controller for safe and precise operation of multi-rotors with heavy slung load in three dimensions. The paper describes a System Dynamics and Control Simulation Toolbox for use with MATLAB/SIMULINK which includes a detailed simulation of the multi-rotor and slung load as well as a predictive controller to manage the nonlinear dynamics whilst accounting for system constraints. It is demonstrated that the controller simultaneously tracks specified waypoints and actively damps large slung load oscillations. A linear-quadratic regulator (LQR) is derived and control performance is compared. Results show the improved performance of the predictive controller for a larger flight envelope, including aggressive manoeuvres and large slung load displacements. The computational cost remains relatively small, amenable to practical implementations

College Misconceptions

Researching a topic can never take the place of actually experiencing something, but you can find out a lot about a topic by looking at information online. You can’t research every aspect of college to be completely prepared, but you could still learn a lot so why isn’t the difficulty of adjusting to college a thing of the past? Our group chose to focus on college misconceptions because with so much information readily available online, we want to know what areas students still end up struggling with. We wanted to gain insights on how college students’ expectations of college compared to the reality and where these expectations are coming from

A preferred vision for administering elementary schools: A reflective essay

In this reflective paper I will describe what I believe are the necessary skills, abilities, and effective strategies which educational leaders should possess as they administrate in a school setting. These skills, abilities, and effective strategies include having the ability to lead an organization through constant changes, monitoring societal trends for future organizational expectations, and developing shared values and vision. In addition, administrative educational leaders must be able to empower teachers, praise teachers for their efforts, coach individuals to reach their potential, communicate effectively to members within as well as outside of the organization, and still must possess personal and professional integrity

The impact of pollution on stellar evolution models

An approach is introduced for incorporating the concept of stellar pollution into stellar evolution models. The approach involves enhancing the metal content of the surface layers of stellar models. In addition, the surface layers of stars in the mass range of 0.5-2.0 Solar masses are mixed to an artificial depth motivated by observations of lithium abundance. The behavior of polluted stellar evolution models is explored assuming the pollution occurs after the star has left the fully convective pre main sequence phase. Stellar models polluted with a few Earth masses of iron are significantly hotter than stars of the same mass with an equivalent bulk metallicity. Polluted stellar evolution models can successfully reproduce the metal-rich, parent star tau Bootis and suggest a slightly lower mass than standard evolution models. Finally, the possibility that stars in the Hyades open cluster have accreted an average of 0.5 Earth masses of iron is explored. The results indicate that it is not possible to rule out stellar pollution on this scale from the scatter of Hyades stars on a color-magnitude diagram. The small amount of scatter in the observational data set does rule out pollution on the order of 1.5 Earth masses of iron. Pollution effects at the low level of 0.5 Earth masses of iron do not produce substantial changes in a star's evolution.Comment: 14 pages, 3 figures, AASTeX, to appear in the 10/10/03 issue of Ap

Cinética de imbibición e isotermas de adsorción de humedad de la semilla de jamaica (Hibiscus sabdariffa L.)

La jamaica es un arbusto que se cultiva para comercializar el cáliz de sus flores, pero como subproducto se obtienen las semillas, que por su valor nutritivo y alto rendimiento representan un potencial económico considerable. El objetivo de este trabajo fue describir la cinética de imbibición y las isotermas de adsorción de humedad a 25, 35 y 45ºC en tres variedades cultivadas en México ("Criolla", "China" y "Sudán"). Los resultados mostraron que el proceso de imbibición describe una curva que se ajusta al modelo de Weibull, con coeficientes α de 12.99, 8.81 y 2.21 horas y β de 0.83, 1.70 y 0.72 para las variedades Criolla, China y Sudán, respectivamente. Los modelos de GAB, y de Chung-Pfost describieron adecuadamente las isotermas de adsorción. La humedad de la capa monomolecular (coeficiente a del modelo de GAB) resultó entre 3.97 y 5.71% b.s., lo cual representa una actividad de agua entre 0.1 y 0.30. Los calores isostéricos totales de adsorción obtenidos en el intervalo de humedades de equilibrio de 6 a 22% b.s., oscilaron entre 52.85 y 42.90 .90 kJmּol-1, 60.99 y 43.41 kJmּol-1 y 51.23 y 43.20 kJmּol-1para las variedades Criolla, China y Sudán, respectivamente. A humedades de equilibrio iguales o superiores a 12 % b.s., el calor isostérico fue similar a la entalpía de vaporización del agua, pero a humedades inferiores a 6% b.s., éste alcanzó los valores más elevados

A Search for Ultraviolet Emission from LINERs

We have obtained Hubble Space Telescope WFPC2 2200 A and optical V-band images of 20 low-luminosity active galactic nuclei, most of which are spectroscopically classified as LINERs, in order to search for a possible photoionizing continuum. Six (30%) of the galaxies are detected in the UV. Two of the detected galaxies (NGC 3642 and NGC 4203) have compact, unresolved nuclear UV sources, while the remaining four UV sources (in NGC 4569, NGC 5005, NGC 6500, and NGC 7743) are spatially extended. Combining our sample with that of Maoz et al. (1995), we find that the probability of detection of a nuclear UV source is greatest for galaxies having low internal reddening and low inclination, and we conclude that dust obscuration is the dominant factor determining whether or not a UV source is detected. Large emission-line equivalent widths and the presence of broad-line emission also increase the likelihood of detection of nuclear UV emission. Our results suggest that the majority of LINERs harbor obscured nuclear UV sources, which may be either accretion-powered active nuclei or young star clusters. Under the assumption that the compact UV sources in NGC 3642 and NGC 4203 have nonstellar power-law spectra extending into the extreme ultraviolet, the extrapolated ionizing fluxes are sufficiently strong to photoionize the narrow-line regions of these objects. The V-band images of many galaxies in our sample reveal remarkably strong dust lanes which may be responsible for obscuring some UV sources.Comment: 25 pages, 4 figures, 3 tables, LaTeX, AASTeX v4.0 style file, accepted for publication in The Astrophysical Journal, additional figures available at http://astro.berkeley.edu/~barth/papers/u