Modeling the Conductance of the Peptide Alamethicin With and Without Ion Gradients

2011 ◽  
Author(s):  
M. Austin Creasy ◽  
Donald J. Leo
Keyword(s):  
Ion Channels ◽  
Probabilistic Model ◽  
Transmembrane Potential ◽  
Trichoderma Viride ◽  
Ion Concentration ◽  
Voltage Source ◽  
Ion Currents ◽  
Individual Ion ◽  
Ion Gradients ◽  
Ion Gradient

Alamethicin is an antibiotic peptide from the fungus Trichoderma viride that forms ion channels in bilayer lipid membranes. Each peptide consists of 20 amino acids that can form larger channels with the congregation of multiple monomers of the peptide. These formed ion channels have some voltage dependent characteristics when a potential is induced across the bilayer. This potential can be from an applied voltage source or from an ion concentration gradient inducing a transmembrane potential across the membrane. The peptide alamethicin can be modeled as a conductor that allows the flow of ions through the membrane. The formed channels have distinct conductance level states caused by accumulation of additional alamethicin monomers being added to an individual ion channel. The voltage dependence of the accumulation of multiple ion channels can be modeled for the average response. A probabilistic model is used to capture the statistics of the state changes of individual channels. This type of model can be summed to simulate the conductance of multiple channels within a bilayer. This work focuses on obtaining the statistic for individual ion channels and using those statistics to show that a probabilistic model of the peptide’s conductance can capture some of the dynamics seen in aggregated responses. The Nernst equation is used to estimate the transmembrane potential caused by an ion gradient of a bilayer in equilibrium. This potential is used in the model to assist in determining the current conductance states of an individual channel of the peptide in the presence of an ion gradient. This paper will show the experimental results of ion currents across a bilayer induced by membrane potentials and the ion currents induced by ion gradients. The statistics of the measurements are used in a probabilistic conductance model of the peptide alamethicin.

COMPARATIVE RESPONSE OF TWO SAPROPHYTIC AND TWO PLANT PARASITIC SOIL FUNGI TO TEMPERATURE, HYDROGEN-ION CONCENTRATION, AND NUTRITIONAL FACTORS

1961 ◽  
Vol 39 (1) ◽  
pp. 65-79 ◽  
Author(s):  
E. W. B. Ward ◽  
A. W. Henry
Keyword(s):  
Soil Fungi ◽  
Inorganic Nitrogen ◽  
Synthetic Medium ◽  
Trichoderma Viride ◽  
Nitrogen Sources ◽  
Ion Concentration ◽  
Good Growth ◽  
Hydrogen Ion Concentration ◽  
Nutritional Factors ◽  
Ph Values

The behavior of two soil saprophytes, Trichoderma viride and Trichocladium asperum, and two root-infecting fungi, Ophiobolus graminis and Fomes annosus, was compared under various conditions in laboratory culture.On an agar-solidified organic medium optimum temperatures for growth were approximately: T. viride 25–30 °C, T. asperum 20–25 °C, O. graminis 20–25 °C, F. annosus 25 °C. T. viride rapidly outgrew the other fungi in the optimum range but this relationship changed at lower temperatures, its growth rate being equalled by that of O. graminis at 10 °C. T. viride was the only fungus to grow at 35 °C. In a synthetic liquid medium adjusted to pH values from 3.0–7.0 with a citrate–phosphate buffer, growth of O. graminis and F. annosus was sharply reduced at pH values below 5.0. T. viride made good growth at pH 3.1 and reduction in growth of T. asperum occurred only below pH 4.0. Both parasites required thiamine for growth in a synthetic medium and O. graminis also required biotin; in addition they showed a preference for organic as opposed to inorganic nitrogen sources. T. viride and T. asperum grew well with KNO3 as nitrogen source and neither required vitamins. D-Glucose, D-fructose, and D-mannose were readily utilized, and D-arabinose poorly utilized, by all four fungi. Utilization of other hexoses, pentoses, disaccharides, and polysaccharides varied considerably between the fungi.The relationship of the results obtained to the observations of others on the ecology of soil fungi is discussed and the possibility that combinations of physical and nutritional factors may favor specific fungi in the soil is considered.

scholarly journals Effective Biosorption of Nickel(II) from Aqueous Solutions UsingTrichoderma viride

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
P. Sujatha ◽  
V. Kalarani ◽  
B. Naresh Kumar
Keyword(s):  
Aqueous Solutions ◽  
Metal Ion ◽  
Low Cost ◽  
Trichoderma Viride ◽  
Toxic Metal ◽  
Freundlich Isotherm ◽  
Recovery Process ◽  
Primary Objective ◽  
Ion Concentration ◽  
Isotherm Models

The primary objective of the present study is to evaluate the optimization conditions such as kinetic and equilibrium isotherm models involved in the removal of Ni(II) from the aqueous solutions byTrichoderma viride. The biosorbent was characterized by FTIR and SEM. The optimum biosorption conditions were determined as a function of pH, biomass dosage, contact time, initial metal ion concentration, and temperature. The maximum Ni(II) biosorption was obtained at pH 4.5. The equilibrium data were better fit by the Langmuir isotherm model than by the Freundlich isotherm. The kinetic studies indicate that the biosorption process of the metal ion Ni(II) has followed well the pseudo-second-order model. The sum of the square errors (SSE) and chi-square (χ2) tests were also carried out to find the best fit kinetic model and adsorption isotherm. The maximum biosorption capacity (qm) ofT.viridebiomass was found to be 47.6 mg/g for Ni(II) ion. Therefore, it can be concluded thatT.viridebiomass was effective and low-cost potential adsorbent to remove the toxic metal Ni(II) from aqueous solutions. The recovery process of Ni(II) fromT.viridebiomass was found to be higher than 98% by using 0.25 M HNO3. Besides the application of removal of toxic metal Ni(II) from aqueous solutions, the biosorbentT.viridecan be reused for five consecutive sorption-desorption cycles was determined.

Charge transport of ion pumps on lipid bilayer membranes

1993 ◽  
Vol 26 (1) ◽  
pp. 1-25 ◽  
Author(s):  
E. Bamberg ◽  
H.-J. Butt ◽  
A. Eisenrauch ◽  
K. Fendler
Keyword(s):  
Amino Acids ◽  
Ion Channels ◽  
Ion Transport ◽  
Charge Transport ◽  
Cell Types ◽  
Ion Pumps ◽  
Lipid Bilayer Membranes ◽  
Bilayer Membranes ◽  
Ion Gradients ◽  
Cotransport Systems

Ion pumps create ion gradients across cell membranes while consuming light energy or chemical energy. The ion gradients are used by the corresponding cell types for passive-ion transport via ion channels or carriers or for accumulation of nutrients like sugar or amino acids via cotransport systems or antiporters.

Interrelation of potassium and hydrogen ion gradients in metabolic alkalosis

1965 ◽  
Vol 208 (6) ◽  
pp. 1114-1118 ◽  
Author(s):  
Jared J. Grantham ◽  
Paul R. Schloerb
Keyword(s):  
Skeletal Muscle ◽  
Gastric Juice ◽  
Metabolic Alkalosis ◽  
Hydrogen Ion ◽  
Ion Gradients ◽  
Chloride Depletion ◽  
Ion Gradient ◽  
K Concentration ◽  
K Depletion

To study the interrelationships of potassium and hydrogen ion intra- and extracellularly, as an extension of previous investigations on gastric alkalosis, metabolic alkalosis was produced in dogs by dietary K depletion, NaHCO3 loading, and deoxycorticosterone administration, with and without chloride depletion. Analysis of skeletal muscle and measurement of intracellular pH confirmed the development of cellular K depletion, with increases of intracellular sodium and hydrogen ion associated with extracellular alkalosis and hypokalemia. These changes were not influenced by concomitant dietary chloride restriction. The intracellular K concentration was linearly and inversely related to the intra-extracellular hydrogen ion gradient. The intra-extracellular K gradient was about 10 times greater than the corresponding hydrogen ion gradient. These respective gradients were linearly related, in this proportion, over the range of K depletion studied in this type of metabolic alkalosis as well as that resulting from gastric juice loss. Deviation from this relationship occurred only with the most severe K depletion. These experimental observations demonstrate in vivo that the potassium and hydrogen ion gradients change in the same direction and are nearly constantly related in at least two types of metabolic alkalosis.

Dynamic monitoring of transmembrane potential changes: a study of ion channels using an electrical double layer-gated FET biosensor

Lab on a Chip ◽  
2018 ◽  
Vol 18 (7) ◽  
pp. 1047-1056 ◽  
Author(s):  
Anil Kumar Pulikkathodi ◽  
Indu Sarangadharan ◽  
Yi-Hong Chen ◽  
Geng-Yen Lee ◽  
Jen-Inn Chyi ◽  
...  
Keyword(s):  
Ion Channels ◽  
Double Layer ◽  
Electron Mobility ◽  
Electrical Double Layer ◽  
Transmembrane Potential ◽  
High Electron Mobility Transistor ◽  
Dynamic Monitoring ◽  
High Electron ◽  
High Electron Mobility ◽  
Biosensor Array

In this research, we have designed, fabricated and characterized an electrical double layer (EDL)-gated AlGaN/GaN high electron mobility transistor (HEMT) biosensor array to study the transmembrane potential changes of cells.

Membrane Ion Channels and Ion Currents

The Neuron ◽  
2015 ◽  
pp. 63-84
Author(s):  
Irwin B. Levitan ◽  
Leonard K. Kaczmarek
Keyword(s):  
Plasma Membrane ◽  
Ion Channels ◽  
Patch Clamp ◽  
Ion Currents ◽  
Action Potential Firing ◽  
Current Passing ◽  
Essential Properties ◽  
Potential Firing ◽  
Neuronal Plasma Membrane

Electrical activity in neurons (and other kinds of cells) results from the movement of ions across the plasma membrane through specialized membrane proteins known as ion channels. Exquisitely sensitive patch clamp techniques are available to measure the current passing through single ion channels, as well as the macroscopic membrane current carried by a population of ion channels. These techniques have enabled the detailed characterization of various essential properties of ion channels, including their selectivity for particular ions, their pharmacology, and the way their activity is regulated by membrane voltage and other factors. There are many different kinds of ion channels in the neuronal plasma membrane, and their activities sum to generate action potentials and complex patterns of action potential firing.

scholarly journals Automated Patch Clamp on mESC-Derived Cardiomyocytes for Cardiotoxicity Prediction

2011 ◽  
Vol 16 (8) ◽  
pp. 910-916 ◽  
Author(s):  
Sonja Stoelzle ◽  
Alison Haythornthwaite ◽  
Ralf Kettenhofen ◽  
Eugen Kolossov ◽  
Heribert Bohlen ◽  
...  
Keyword(s):  
Stem Cell ◽  
Ion Channels ◽  
Patch Clamp ◽  
Cell Model ◽  
Single Type ◽  
Ion Currents ◽  
Drug Induced ◽  
Cardiovascular Side Effects ◽  
Automated Patch Clamp

Cardiovascular side effects are critical in drug development and have frequently led to late-stage project terminations or even drug withdrawal from the market. Physiologically relevant and predictive assays for cardiotoxicity are hence strongly demanded by the pharmaceutical industry. To identify a potential impact of test compounds on ventricular repolarization, typically a variety of ion channels in diverse heterologously expressing cells have to be investigated. Similar to primary cells, in vitro–generated stem cell–derived cardiomyocytes simultaneously express cardiac ion channels. Thus, they more accurately represent the native situation compared with cell lines overexpressing only a single type of ion channel. The aim of this study was to determine if stem cell–derived cardiomyocytes are suited for use in an automated patch clamp system. The authors show recordings of cardiac ion currents as well as action potential recordings in readily available stem cell–derived cardiomyocytes. Besides monitoring inhibitory effects of reference compounds on typical cardiac ion currents, the authors revealed for the first time drug-induced modulation of cardiac action potentials in an automated patch clamp system. The combination of an in vitro cardiac cell model with higher throughput patch clamp screening technology allows for a cost-effective cardiotoxicity prediction in a physiologically relevant cell system.

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