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Proton Flux (proton + flux)

Distribution by Scientific Domains

Earth and Environmental Science	40%

Selected Abstracts

Imaging Local Proton Fluxes through a Polycarbonate Membrane by Using Scanning Electrochemical Microscopy and Functionalized Alkanethiols

CHEMPHYSCHEM, Issue 1 2009
Norman Baltes Dr.
Abstract A new application of scanning electrochemical microscopy (SECM) to probe the transport of protons through membranes is described. Herein, a probe ultramicroelectrode (UME) is modified with a self-assembled monolayer (SAM) of 11-mercaptoundecanoic acid to qualitatively image areas within different pH regions above a track-etched membrane. The current response of the modified electrode in the presence of potassium hexacyanoferrate as electroactive component is different in acidic and alkaline solutions. Depending on the pH value of the solution, the SAM-covered electrode exposes either a neutral or a negatively charged insulating monolayer at pH 3 or 7, respectively, which leads to an increase/decrease in the faradaic current due to electrostatic interactions between the neutral/charged surface and the charged redox mediator. Therefore, local pH changes in the close vicinity of a membrane-like substrate lead to different current responses recorded at the tip electrode when scanning above the surface. [source]

Physicochemical responses of Pythium porphyrae (Oomycota), the causative organism of red rot disease in Porphyra to acidification

AQUACULTURE RESEARCH, Issue 15 2009
Eun Kyoung Hwang
Abstract Physicochemical responses to acidification in Pythium porphyrae, the causative organism of red rot disease in Porphyra, were investigated. The acid tolerance of P. porphyrae mycelia under pH 4 (acidic condition) condition increased significantly compared with that of the mycelia under pH 8 (condition equivalent to seawater) condition. Free amino acid levels in the mycelia decreased 1.3,8.8-fold under pH 4 condition. However, some free amino acids such as the d -cysteinolic acid-like component, phosphoethanolamine, glutamic acid, aminoadipic acid and methionine increased 2.6,21.7-fold under the same condition. Proton flux on the mycelia exposed to pH 8 increased significantly compared with the mycelia exposed to pH 4. The patterns of proteins present (examined by two-dimensional polyacrylamide gel electrophoresis) differed among the pH conditions. These results suggest that P. porphyrae acquires acid tolerance and is able to adapt to the changing pH conditions. This has significant implications for the use of acidic fungicide treatment for prevention of red rot disease on Porphyra farms. [source]

The impact of metabolic state on Cd adsorption onto bacterial cells

GEOBIOLOGY, Issue 3 2007
K. J. JOHNSON
ABSTRACT This study examines the effect of bacterial metabolism on the adsorption of Cd onto Gram-positive and Gram-negative bacterial cells. Metabolically active Gram-positive cells adsorbed significantly less Cd than non-metabolizing cells. Gram-negative cells, however, showed no systematic difference in Cd adsorption between metabolizing and non-metabolizing cells. The effect of metabolism on Cd adsorption to Gram-positive cells was likely due to an influx of protons in and around the cell wall from the metabolic proton motive force, promoting competition between Cd and protons for adsorption sites on the cell wall. The relative lack of a metabolic effect on Cd adsorption onto Gram-negative compared to Gram-positive cells suggests that Cd binding in Gram-negative cells is focused in a region of the cell wall that is not reached, or is unaffected by this proton flux. Thermodynamic modeling was used to estimate that proton pumping causes the pH in the cell wall of metabolizing Gram-positive bacteria to decrease from the bulk solution value of 7.0 to approximately 5.7. [source]

Transport mechanisms and performance simulation of a PEM fuel cell

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2008
Geng-Po Ren
Abstract A three-dimensional, gas,liquid two-phase flow and transport model has been developed and utilized to simulate the multi-dimensional, multi-phase flow and transport phenomena in both the anode and cathode sides in a proton exchange membrane (PEM) fuel cell and the cell performance with different influencing operational and geometric parameters. The simulations are presented with an emphasis on the physical insight and fundamental understanding afforded by the detailed distributions of velocity vector, oxygen concentration, water vapor concentration, liquid water concentration, water content in the PEM, net water flux per proton flux, local current density, and overpotential. Cell performances with different influencing factors are also presented and discussed. The comparison of the model prediction and experimental data shows a good agreement. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Mechanism of cell death and disease resistance induction by transgenic expression of bacterio-opsin

THE PLANT JOURNAL, Issue 5 2002
Dominique Pontier
Summary One of the earliest signal transduction events that trigger the hypersensitive response (HR) of plants against pathogen attack is thought to be an alteration of proton flux across the plasma membrane (PM). However, no direct genetic evidence for the involvement of PM-localised proton channels or pumps in the induction of this response has been reported. We previously showed that expression of the bacterial proton pump bacterio-opsin (bO) in transgenic plants resulted in the spontaneous activation of the HR. Here we show that the bO protein is likely localised to the PM in transgenic tobacco plants. Furthermore, mutational analysis shows that induction of the HR by bO expression is dependent upon the capability of bO to translocate protons. Although bO functions as a light-driven proton pump in Halobacteria when assembled with retinal, we also show by mutational analysis that this chromophore binding is unnecessary for its in planta activity. Taken together, our results suggest that expression of bO in plants leads to the insertion of a passive proton channel into the PM. The activity of this channel in the PM results in spontaneous activation of cell death and HR-associated phenotypes including enhanced resistance to a broad spectrum of plant pathogens. Our work provides direct molecular evidence to support a working model in which alterations in ionic homeostasis at the level of the PM may work as one of the critical steps in the signalling pathway for the activation of the HR. [source]