The Equilibria of Lipid–K+ Ions in Monolayer at the Air/Water Interface

The effect of K+ ion interaction with monolayers of phosphatidylcholine (lecithin, PC) or cholesterol (Ch) was investigated at the air/water interface. We present surface tension measurements of lipid monolayers obtained using a Langmuir method as a function of K+ ion concentration. Measurements were carried out at 22°C using a Teflon trough and a Nima 9000 tensiometer. Interactions between lecithin and K+ ions or Ch and K+ ions result in significant deviations from the additivity rule. An equilibrium theory to describe the behavior of monolayer components at the air/water interface was developed in order to obtain the stability constants and area occupied by one molecule of lipid–K+ ion complex (LK+). The stability constants for lecithin–K+ ion (PCK+) complex, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$K_{{{\text{PCK}}^{ + } }} = { 3}. 2 6\times 10^{ 2} {\text{dm}}^{ 3} \,{\text{mol}}^{ - 1}$$\end{document}, and for cholesterol–K+ ion (ChK+) complex, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$K_{{{\text{ChK}}^{ + } }} = { 1}.00 \times 10^{ 3} {\text{dm}}^{ 3} \,{\text{mol}}^{ - 1}$$\end{document}, were calculated by inserting the experimental data. The value of area occupied by one PCK+ complex is 60 Å2 molecule−1, while the area occupied by one ChK+ complex is 40.9 Å2 molecule−1. The complex formation energy (Gibbs free energy) values for the PCK+ and ChK+ complexes are −14.18 ± 0.71 and −16.92 ± 0.85 kJ mol−1, respectively

Quantitative High-Throughput Screen Identifies Inhibitors of the Schistosoma mansoni Redox Cascade

Schistosomiasis is a tropical disease associated with high morbidity and mortality, currently affecting over 200 million people worldwide. Praziquantel is the only drug used to treat the disease, and with its increased use the probability of developing drug resistance has grown significantly. The Schistosoma parasites can survive for up to decades in the human host due in part to a unique set of antioxidant enzymes that continuously degrade the reactive oxygen species produced by the host's innate immune response. Two principal components of this defense system have been recently identified in S. mansoni as thioredoxin/glutathione reductase (TGR) and peroxiredoxin (Prx) and as such these enzymes present attractive new targets for anti-schistosomiasis drug development. Inhibition of TGR/Prx activity was screened in a dual-enzyme format with reducing equivalents being transferred from NADPH to glutathione via a TGR-catalyzed reaction and then to hydrogen peroxide via a Prx-catalyzed step. A fully automated quantitative high-throughput (qHTS) experiment was performed against a collection of 71,028 compounds tested as 7- to 15-point concentration series at 5 µL reaction volume in 1536-well plate format. In order to generate a robust data set and to minimize the effect of compound autofluorescence, apparent reaction rates derived from a kinetic read were utilized instead of end-point measurements. Actives identified from the screen, along with previously untested analogues, were subjected to confirmatory experiments using the screening assay and subsequently against the individual targets in secondary assays. Several novel active series were identified which inhibited TGR at a range of potencies, with IC50s ranging from micromolar to the assay response limit (∼25 nM). This is, to our knowledge, the first report of a large-scale HTS to identify lead compounds for a helminthic disease, and provides a paradigm that can be used to jump-start development of novel therapeutics for other neglected tropical diseases

Coquillettidia (Culicidae, Diptera) mosquitoes are natural vectors of avian malaria in Africa

<p>Abstract</p> <p>Background</p> <p>The mosquito vectors of <it>Plasmodium </it>spp. have largely been overlooked in studies of ecology and evolution of avian malaria and other vertebrates in wildlife.</p> <p>Methods</p> <p><it>Plasmodium </it>DNA from wild-caught <it>Coquillettidia </it>spp. collected from lowland forests in Cameroon was isolated and sequenced using nested PCR. Female <it>Coquillettidia aurites </it>were also dissected and salivary glands were isolated and microscopically examined for the presence of sporozoites.</p> <p>Results</p> <p>In total, 33% (85/256) of mosquito pools tested positive for avian <it>Plasmodium </it>spp., harbouring at least eight distinct parasite lineages. Sporozoites of <it>Plasmodium </it>spp. were recorded in salivary glands of <it>C. aurites </it>supporting the PCR data that the parasites complete development in these mosquitoes. Results suggest <it>C. aurites</it>, <it>Coquillettidia pseudoconopas </it>and <it>Coquillettidia metallica </it>as new and important vectors of avian malaria in Africa. All parasite lineages recovered clustered with parasites formerly identified from several bird species and suggest the vectors capability of infecting birds from different families.</p> <p>Conclusion</p> <p>Identifying the major vectors of avian <it>Plasmodium </it>spp. will assist in understanding the epizootiology of avian malaria, including differences in this disease distribution between pristine and disturbed landscapes.</p

Hardware considerations for preclinical magnetic resonance of the kidney

Magnetic resonance imaging (MRI) is a noninvasive imaging technology that offers unparalleled anatomical and functional detail, along with diagnostic sensitivity. MRI is suitable for longitudinal studies due to the lack of exposure to ionizing radiation. Before undertaking preclinical MRI investigations of the kidney, the appropriate MRI hardware should be carefully chosen to balance the competing demands of image quality, spatial resolution, and imaging speed, tailored to the specific scientific objectives of the investigation. Here we describe the equipment needed to perform renal MRI in rodents, with the aim to guide the appropriate hardware selection to meet the needs of renal MRI applications.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This chapter on hardware considerations for renal MRI in small animals is complemented by two separate publications describing the experimental procedure and data analysis

P3HT-Based Solar Cells: Structural Properties and Photovoltaic Performance

Each year we are bombarded with B.Sc. and Ph.D. applications from students that want to improve the world. They have learned that their future depends on changing the type of fuel we use and that solar energy is our future. The hope and energy of these young people will transform future energy technologies, but it will not happen quickly. Organic photovoltaic devices are easy to sketch, but the materials, processing steps, and ways of measuring the properties of the materials are very complicated. It is not trivial to make a systematic measurement that will change the way other research groups think or practice. In approaching this chapter, we thought about what a new researcher would need to know about organic photovoltaic devices and materials in order to have a good start in the subject. Then, we simplified that to focus on what a new researcher would need to know about poly-3-hexylthiophene:phenyl-C61-butyric acid methyl ester blends (P3HT: PCBM) to make research progress with these materials. This chapter is by no means authoritative or a compendium of all things on P3HT:PCBM. We have selected to explain how the sample fabrication techniques lead to control of morphology and structural features and how these morphological features have specific optical and electronic consequences for organic photovoltaic device applications

Purification of Legionella pneumophila major outer membrane protein and demonstration that it is a porin.

We have purified the major outer membrane protein (MOMP) of Legionella pneumophila, determined that it is associated with peptidoglycan, and characterized it as a porin. To purify the MOMP, we used a simple, rapid, three-step procedure that gave us the protein in high yield. The first step of the purification procedure involved selectively extracting the MOMP from whole bacterial cells with calcium and zwitterionic detergent. The second and third steps achieved purification by ion-exchange and molecular-sieve chromatography. The dissociation of the MOMP into monomers was dependent upon the presence of a reducing agent and was enhanced by treatment at 100 degrees C. To study the relationship of the MOMP to peptidoglycan, we extracted the protein by a modification of the Rosenbusch procedure. Like the Escherichia coli porins, the MOMP was peptidoglycan associated. The MOMP was at least partially dissociated from peptidoglycan in sodium dodecyl sulfate and a high salt concentration. To study the ion channel-forming properties of the MOMP, we reconstituted the MOMP in planar lipid membranes. The MOMP formed ion-permeable channels with a single-channel conductance size of 100 picoSiemens. The MOMP channels exhibited a fourfold selectivity for cations over anions and voltage-independent gating. These findings demonstrate that the MOMP is a porin with properties similar to those of E. coli porins