Life Sciences Commons^™

Septin Phosphorylation And Coiled-Coil Domains Function In Cell And Septin Ring Morphology In The Filamentous Fungus Ashbya Gossypii, Rebecca A. Meseroll, Patricia Occhipinti, Amy S. Gladfelter

Dartmouth Scholarship

Septins are a class of GTP-binding proteins conserved throughout many eukaryotes. Individual septin subunits associate with one another and assemble into heteromeric complexes that form filaments and higher-order structures in vivo. The mechanisms underlying the assembly and maintenance of higher-order structures in cells remain poorly understood. Septins in several organisms have been shown to be phosphorylated, although precisely how septin phosphorylation may be contributing to the formation of high-order septin structures is unknown. Four of the five septins expressed in the filamentous fungus, Ashbya gossypii, are phosphorylated, and we demonstrate here the diverse roles of these phosphorylation sites …

A Human Phospholipid Phosphatase Activated By A Transmembrane Control Module, Christian R. Halaszovich, Michael G. Leitner, Angeliki Mavrantoni, Audrey Le, Ludivine Frezza, Anja Feuer, Daniela N. Schreiber, Carlos A. Villalba-Galea, Dominik Oliver

School of Pharmacy Faculty Articles

In voltage-sensitive phosphatases (VSPs), a transmembrane voltage sensor domain (VSD) controls an intracellular phosphoinositide phosphatase domain, thereby enabling immediate initiation of intracellular signals by membrane depolarization. The existence of such a mechanism in mammals has remained elusive, despite the presence of VSP-homologous proteins in mammalian cells, in particular in sperm precursor cells. Here we demonstrate activation of a human VSP (hVSP1/TPIP) by an intramolecular switch. By engineering a chimeric hVSP1 with enhanced plasma membrane targeting containing the VSD of a prototypic invertebrate VSP, we show that hVSP1 is a phosphoinositide-5-phosphatase whose predominant substrate is PI(4,5)P(2). In the chimera, enzymatic activity …

Structural Studies Of Membrane-Assembled Popd And Popb, The Pseudomonas Aeruginosa Type 3 Secretion Translocators, Fabian B Romano Chernac

Doctoral Dissertations 1896 - February 2014

Transport of proteins across membranes is essential during many stages of pathogen infection and colonization of human cells. Many Gram-negative pathogens use a Type 3 Secretion (T3S) system to inject proteins into the target cell during infection. Substantial genetic and biochemical evidence suggest that proteins are translocated across the host plasma membrane through a proteinaceous pore or translocon formed by two bacterial secreted proteins: the T3S translocators. Despite its key role in pathogenesis, virtually nothing is known about the assembly mechanism, structure, and composition of this critical transmembrane complex.

To this end, a cell-free system for the structural and functional …

Plant Calcium Content: Ready To Remodel, Jian Yang, Tracy Punshon, Mary Lou Guerinot, Kendal D. Hirschi

Dartmouth Scholarship

By identifying the relationship between calcium location in the plant cell and nutrient bioavailability, the plant characteristics leading to maximal calcium absorption by humans can be identified. Knowledge of plant cellular and molecular targets controlling calcium location in plants is emerging. These insights should allow for better strategies for increasing the nutritional content of foods. In particular, the use of preparation-free elemental imaging technologies such as synchrotron X-ray fluorescence (SXRF) microscopy in plant biology may allow researchers to understand the relationship between subcellular location and nutrient bioavailability. These approaches may lead to better strategies for altering the location of calcium …

Membrane Properties Involved In Calcium-Stimulated Microparticle Release From The Plasma Membranes Of S49 Lymphoma Cells, Lauryl Elizabeth Campbell

Theses and Dissertations

The mechanism of microparticle shedding from the plasma membrane of calcium-loaded cells has been investigated in erythrocytes and platelets. Recent studies have revealed the physiological and clinical importance of microparticle release from nucleated cells such as lymphocytes and endothelium. The experiments of this study were designed to address whether simple mechanisms discovered in platelets and erythrocytes also apply to the more complex nucleated cells. Four such mechanisms were addressed: potassium efflux, transbilayer phosphatidylserine migration, cytoskeleton degradation, and membrane lipid order. The rate and amount of microparticle release in the presence of a calcium ionophore, ionomycin, was assayed by light scatter …

Enumeration Of Sandy Sediment Bacteria: Search For Optimal Protocol, Slava Epstein, Jeffrey Rossel

Slava Epstein

We examined and compared a variety of existing protocols for enumeration of bacteria from marine sandy sediments. The focus was on how to dislodge bacteria from sediment particles; a commercial blender, an ultrasonic cleaner, and an ultrasonic cell disrupter were tested. The ultrasonic cell disrupter was found to be the most efficient device for bacterial dislodgment. With a 5 mm microtip vibrating at 109 μm amplitude and 20 kHz, the optimal sonication time of small (≤ 0.5 cm³) samples was 180 s. Having identified the optimal dislodgment treatment, we went through other steps of sediment bacteria enumeration (use of surfactants, …

Methodology Of In Situ Grazing Experiments: Evaluation Of A New Vital Dye For Preparation Of Fluorescently Labeled Bacteria, Slava S. Epstein, Jeffrey Rossel

Slava Epstein

A new fluorescent dye, cyanoditolyl tetrazolium chloride (CTC), is suggested for use in grazing studies to prepare fluorescently labeled bacteria (FLB). As food tracers, CTC-stained bacteria appeared to have advantages over FLBs prepared in accordance with previously published protocols. The CTC is a vital dye, non-toxic to the examined bacteria; in our study, the CTC-stained bacteria grew at the same rate as non-stained bacteria. This is an advantage over the commonly used DTAF-employing staining protocol, which results in heat-killed or immobilized prey particles. The CTC-stained bacteria were not toxic to the studied bacterial grazers; a test ciliate grew on FLBs …

Introduction To Nanoscopy Nano-Talk, George Mcnamara

George McNamara

T7-1 is the designation for the LMRG Nanoscopy session at ABRF in Orlando, FL, on March 20, 2012. The PDF file here is a draft of my presentation.

May not be very helpful since (1) would probably help to know what is in my head and each slide will [hopefully] prompt me to say, and (2) 10 minute talk so I am going to push the "next slide" button after saying very little.

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Publisher statement:

The T7-1 Introduction to Nanoscopy Nano Talk is copyrighted (c) George McNamara, 2012. Except for (1) screenshots from research articles (which are copyrighted by …

Heterogeneity In Mitochondrial Morphology And Membrane Potential Is Independent Of The Nuclear Division Cycle In Multinucleate Fungal Cells, John P. Gerstenberger, Patricia Occhipinti, Amy S. Gladfelter

Dartmouth Scholarship

In the multinucleate filamentous fungus Ashbya gossypii, nuclei divide asynchronously in a common cytoplasm. We hypothesize that the division cycle machinery has a limited zone of influence in the cytoplasm to promote nuclear autonomy. Mitochondria in cultured mammalian cells undergo cell cycle-specific changes in morphology and membrane potential and therefore can serve as a reporter of the cell cycle state of the cytoplasm. To evaluate if the cell cycle state of nuclei in A. gossypii can influ

Conformational Properties Of Cardiolipin-Bound Cytochrome C, Jonas Hanske, Jason R. Toffey, Anna M. Morenz, Amber J. Bonilla, Katherine H. Schiavoni;, Ekaterina V. Pletneva

Dartmouth Scholarship

Interactions of cytochrome c (cyt c) with cardiolipin (CL) are important for both electron transfer and apoptotic functions of this protein. A sluggish peroxidase in its native state, when bound to CL, cyt c catalyzes CL peroxidation, which contributes to the protein apoptotic release. The heterogeneous CL-bound cyt c ensemble is difficult to characterize with traditional structural methods and ensemble-averaged probes. We have employed time-resolved FRET measurements to evaluate structural properties of the CL-bound protein in four dansyl (Dns)-labeled variants of horse heart cyt c. The Dns decay curves and extracted Dns-to-heme distance distributions P(r) …

Phycoerythrin-Specific Bilin Lyase-Isomerase Controls Blue-Green Chromatic Acclimation In Marine Synechococcus, Wendy M. Schluchter, Avijit Biswas, Frédéric Partensky, J. A. Karty, Laurence Garczarek, A. Gutu, David M. Kehoe, A. Shukla, N. Blot, L. A. Hammad

Biological Sciences Faculty Publications

The marine cyanobacterium Synechococcus is the second most abundant phytoplanktonic organism in the world's oceans. The ubiquity of this genus is in large part due to its use of a diverse set of photosynthetic light-harvesting pigments called phycobiliproteins, which allow it to efficiently exploit a wide range of light colors. Here we uncover a pivotal molecular mechanism underpinning a widespread response among marine Synechococcus cells known as type IV chromatic acclimation (CA4). During this process, the pigmentation of the two main phycobiliproteins of this organism, phycoerythrins I and II, is reversibly modified to match changes in the ambient light color …

The Role Of Cax1 And Cax3 In Elemental Distribution And Abundance In Arabidopsis Seed, Tracy Punshon, Kendall Hirschi, Jian Yang, Antonio Lanzirotti, Barry Lai, Mary Lou Guerinot

Dartmouth Scholarship

The ability to alter nutrient partitioning within plants cells is poorly understood. In Arabidopsis (Arabidopsis thaliana), a family of endomembrane cation exchangers (CAXs) transports Ca²⁺ and other cations. However, experiments have not focused on how the distribution and partitioning of calcium (Ca) and other elements within seeds are altered by perturbed CAX activity. Here, we investigate Ca distribution and abundance in Arabidopsis seed from cax1 and cax3 loss-of-function lines and lines expressing deregulated CAX1 using synchrotron x-ray fluorescence microscopy. We conducted 7- to 10-μm resolution in vivo x-ray microtomography on dry mature seed and 0.2-μm resolution x-ray …

Synchrotron Radiation Spectroscopic Techniques As Tools For The Medicinal Chemist: Microprobe X-Ray Fluorescence Imaging, X-Ray Absorption Spectroscopy, And Infrared Microspectroscopy, Carolyn Therese Dillon

Faculty of Science - Papers (Archive)

This review updates the recent advances and applications of three prominent synchrotron radiation techniques, microprobe X-ray fluorescence spectroscopy/imaging, X-ray absorption spectroscopy, and infrared microspectroscopy, and highlights how these tools are useful to the medicinal chemist. A brief description of the principles of the techniques is given with emphasis on the advantages of using synchrotron radiation-based instrumentation rather than instruments using typical laboratory radiation sources. This review focuses on several recent applications of these techniques to solve inorganic medicinal chemistry problems, focusing on studies of cellular uptake, distribution, and biotransformation of established and potential therapeutic agents. The importance of using these …

Growth And Photochemical Responses Of Three Crop Species Treated With Textile Azo Dyes, Nuran Çi̇çek, Banu Efeoğlu, Deni̇z Tanyolaç, Yasemi̇n Ekmekçi̇, Reto Jörg Strasser

Turkish Journal of Botany

The present study was conducted to investigate the impact of textile dye on the early seedling stage of 3 crops: barley, maize, and wheat. Seeds were imbibed in different concentrations of textile dye for 12 h and were then grown in a controlled growth room for 8 days with a related dye solution. Some growth and polyphasic chlorophyll fluorescence parameters were measured and analysed to appraise the effect of textile dye on the 3 crops. Although different crop species showed differences in response to different concentrations, textile dye generally affected almost all radicle growth parameters more adversely than coleoptile growth …