59 research outputs found
The Effects of Cholera Toxin on Cellular Energy Metabolism
Multianalyte microphysiometry, a real-time instrument for simultaneous measurement of metabolic analytes in a microfluidic environment, was used to explore the effects of cholera toxin (CTx). Upon exposure of CTx to PC-12 cells, anaerobic respiration was triggered, measured as increases in acid and lactate production and a decrease in the oxygen uptake. We believe the responses observed are due to a CTx-induced activation of adenylate cyclase, increasing cAMP production and resulting in a switch to anaerobic respiration. Inhibitors (H-89, brefeldin A) and stimulators (forskolin) of cAMP were employed to modulate the CTx-induced cAMP responses. The results of this study show the utility of multianalyte microphysiometry to quantitatively determine the dynamic metabolic effects of toxins and affected pathways
Use of Gold Nanoparticles To Enhance Capillary Electrophoresis
We describe here the use of gold nanoparticles to manipulate the selectivity between solutes in capillary electrophoresis. Two different gold-based nanoparticles were added to the run buffer. In one case, the nanoparticles were stabilized with citrate ions, but in another study, the gold nanoparticles were capped with mercaptopropionate ions (thiol-stablized). Citrate-stabilized gold nanoparticles were used in conjunction with capillaries treated with poly(diallyldimethylammonium chloride) (PDADMAC). The positively charged PDADMAC layer on the capillary walls adsorbs the negatively charged gold nanoparticles. The model solutes that were used to study the effect of the presence of the citrate-stabilized gold nanoparticles are structural isomers of aromatic acids and bases. The presence of the PDADMAC layer and the PDADMAC plus the gold nanoparticles changes both the electroosmotic mobility and the observed mobility of the solutes. These changes in the mobilities influence the observed selectivities and the separations of the system. Thiol-stabilized gold nanoparticles were used without PDADMAC in the capillary. The model solutes studied in this part are various aromatic amines. In this case as well, the presence of the gold nanoparticles modifies the electroosmotic mobility and the observed mobility of the solutes. These changes in the mobilities are manifested in selectivity alterations. The largest change in the selectivities occurs at low concentrations of the gold nanoparticles in the run buffer. The presence of nanoparticles improves the precision of the analysis and increases the separation efficiency. Nanodispersions have attracted extensive attention in various fields of physics, biology, and chemistry. [1][2][3][4][5] Physicists and chemists are intrigued by the gradual transition of the nanomaterial properties from molecule-like to those of solid-state properties by a change of a single variable, the particle size. This property has practical and future applications for nonlinear optics and electronics. The large surface area of nanomaterials intrigues chemical engineers and catalysis scientists. Surprisingly, very little research has been devoted to the application of nanoparticles for chemical separation. In this work, we demonstrate the utility and versatility of organically modified gold nanoparticles in capillary electrophoresis (CE) separations. The nanoparticles serve as large surface area platforms for organofunctional groups that interact with the capillary surface, the analytes, or both. Thus, the apparent mobilities of target analytes, as well as the electroosmotic flow, can be altered leading to enhanced selectivities. Separation of various benzene derivatives demonstrates these capabilities. Metallic nanodispersions can be prepared in aqueous and organic solvents using diverse procedures. 1,2,6-9 Nanodispersions can be stabilized in organic solvents by the solvent itself, 10 by the addition of long chain surfactants, 11,12 or by specific ligands. 13 Stabilization of metal nanodispersions in aqueous solutions is somewhat more complicated. Several successful stabilization methods are available that are based on capping of the metal nanoparticles (e.g., citrate, 6 3-mercaptopropionate, 1
Single-Step Biofriendly Synthesis of Surface Modifiable, Near-Spherical Gold Nanoparticles for Applications in Biological Detection and Catalysis
Mercaptoammonium-Monolayer-Protected, Water-Soluble Gold, Silver, and Palladium Clusters
A Pt−Ru/Graphitic Carbon Nanofiber Nanocomposite Exhibiting High Relative Performance as a Direct-Methanol Fuel Cell Anode Catalyst
Prostaglandin E<sub>2</sub> Regulation of Macrophage Innate Immunity
Globally,
maternal and fetal health is greatly impacted by extraplacental
inflammation. Group B <i>Streptococcus</i> (GBS), a leading
cause of chorioamnionitis, is thought to take advantage of the uterine
environment during pregnancy in order to cause inflammation and infection.
In this study, we demonstrate the metabolic changes of murine macrophages
caused by GBS exposure. GBS alone prompted a delayed increase in lactate
production, highlighting its ability to redirect macrophage metabolism
from aerobic to anaerobic respiration. This production of lactate
is thought to aid in the development and propagation of GBS throughout
the surrounding tissue. Additionally, this study shows that PGE<sub>2</sub> priming was able to exacerbate lactate production, shown
by the rapid and substantial lactate increases seen upon GBS exposure.
These data provide a novel model to study the role of GBS exposure
to macrophages with and without PGE<sub>2</sub> priming
Metabolic Discrimination of Select List Agents by Monitoring Cellular Responses in a Multianalyte Microphysiometer
sensor
Real-Time Monitoring of Cellular Bioenergetics with a Multianalyte Screen-Printed Electrode
Photoactive Films of Photosystem I on Transparent Reduced Graphene Oxide Electrodes
Photosystem I (PSI) is a photoactive
electron-transport protein found in plants that participates in the
process of photosynthesis. Because of PSI’s abundance in nature
and its efficiency with charge transfer and separation, there is a
great interest in applying the protein in photoactive electrodes.
Here, we developed a completely organic, transparent, conductive electrode
using reduced graphene oxide (RGO) on which a multilayer of PSI could
be deposited. The resulting photoactive electrode demonstrated current
densities comparable to that of a gold electrode modified with a multilayer
film of PSI and significantly higher than that of a graphene electrode
modified with a monolayer film of PSI. The relatively large photocurrents
produced by integrating PSI with RGO and using an opaque, organic
mediator can be applied to the facile production of more economic
solar energy conversion devices
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