Form Of Methylene Blue Research Articles

Methylene blue stimulates 2-deoxyglucose uptake in L929 fibroblast cells

Methylene blue (MB), a common cell stain, has been shown to inhibit nitric oxide synthase and guanylate cyclase, which has led to the recent use of MB in nitric oxide signaling studies. This study documents the effects of MB on 2-deoxyglucose (2DG) uptake in L929 fibroblast cells where uptake is controlled by a single glucose transporter, GLUT 1. MB significantly activates cytochalasin B-inhibitable glucose transport in a dose dependent fashion within 10 min. A maximal stimulation of up to 800% was achieved by 50 μM MB after a 45-min exposure. The Vmax of transport increased without a change in the Km, which was accomplished without a significant change in the GLUT 1 content. The reduced form of MB, did not stimulate 2DG uptake and potassium ferricyanide, an extracellular redox agent, prevented both the staining and stimulatory effects of MB suggesting MB is reduced at the cell surface before it enters L929 cells. Phenylarsine oxide did not block cell staining as noted in other cells lines, but it did inhibit both basal and MB-stimulated 2DG uptake. Likewise, methyl-β-cyclodextrin, an agent used to remove membrane cholesterol, blocked both the staining and stimulatory effects of MB. The AMP analog, AICAR, inhibited rather than activated basal 2DG uptake, and it did not alter MB-stimulated uptake suggesting that AMP kinase activation is not critical to the MB effect. Wortmannin, an inhibitor of PI kinase, had no effect on MB-stimulated 2DG uptake. These data provide additional insight into the acute regulation of GLUT 1 transport activity in L929 cells.

Fluorimetric Determination of Ascorbic Acid in Vitamin C Tablets Using Methylene Blue

In this study, a simple and sensitive fluorimetric method was described for the determination of Ascorbic Acid (AA). The procedure is based on the reaction between AA and Methylene Blue (MB). The fluorescence intensity of MB was measured at excitation and emission of 664 and 682 nm, respectively. MB concentration was decreased as a function of decreasing fluorescence intensity due to forming colorless form of MB (Leuco-MB) in the reaction between AA and MB. A linear relationship was obtained between the decreasing fluorescence intensity and the concentration of AA in the range of 3.0 x 10(-7)-6.0 x 10(-6) mol.l(-1). The detection limit was 2.5 x 10(-7) mol.l(-1). The proposed method was applied successfully for the determination of AA in Vitamin C tablets.

A sub-second, time-resolved, linear dichroism measurement system for visible attenuated total reflection spectroscopy with a slab optical waveguide

A sub-second, time-resolved, linear dichroism (LD) measurement system was constructed, fitted with a slab optical waveguide (SOWG), and utilized to observe the adsorption process of methylene blue (MB) onto silica surfaces. In the system, a semiconductor laser (670 nm) was used as the light source and the out-coupled beam from the SOWG was split by a polarizing beam splitter into two polarized beams (TE and TM modes) to allow sequential linear dichroic ratio data to be obtained; the acquisition rate was 11 data sets per second. For an MB solution that contained no sodium dodecylbenzenesulfonate (DBS), in contact with a bare silica surface, a clear decrease occurred in the average orientation angle of adsorbed MB in the initial stages of the adsorption process. This result may correspond to a change in the chemical form of MB from monomer to dimer.

Adsorption of methylene blue onto silylated silica surfaces, studied using visible attenuated total reflection spectroscopy with a slab optical waveguide.

The behavior of methylene blue (MB) molecules at silica/water and silylated silica/water interfaces was examined using visible attenuated total reflection spectroscopy with a slab optical waveguide (SOWG). An alkyl silane coating changed the adsorbed form of MB on the surface from a dimer (lambda max = 600 nm, bare silica surface) to a monomer (lambda max = 670 nm), and the carbon number of the silylation reagent influenced the amount of adsorption and the orientation of the molecule. Moreover, the addition of an anionic surfactant, dodecylbenzenesulfonate (DBS), caused the deposition of MB/DBS ion pairs, which gave an identical attenuated total reflection (ATR) spectrum to that of the dimer. Linear dichroism measurements revealed that the ion pairs were adsorbed onto the silylated silica surface randomly in terms of the orientation angle of MB, while the MB monomer was strongly oriented, i.e., the direction of the transition moment of MB roughly parallels the surface plane. This difference in the orientation angles of the adsorbed species can be utilized for their selective detection using polarization SOWG measurements.

Methylene Blue Interactions with Reduced-Charge Smectites

AbstractThe objective of this work was to prepare series of reduced-charge materials from different parent Li-saturated dioctahedral smectites, to investigate the effects of temperature, chemical composition and charge location in smectites on the charge reduction and to characterize reduced-charge smectites (RCSs) using methylene blue (MB) adsorption. The layer charge decrease, induced by Li fixation, is correlated with the trends in the spectra of MB-RCS dispersions in the visible region (VIS) spectra. Distribution of the negative surface charge of the clay minerals controls the distance between the adsorbed MB cations and thus affects the formation of MB dimers and higher agglomerates. Because each form of MB (monomer, dimer, higher agglomerate, J-aggregates) absorbs light at a different wavelength, the VIS spectra of MB depend sensitively on the charge density at the clay surface. Both cation exchange capacity (CEC) values and spectra of MB-clay dispersions clearly detect extensive reduction of the layer-charge density in reduced-charge montmorillonites (RCMs) upon Li-thermal treatment. The extent of charge reduction depends on the temperature of the thermal treatment, as well as on the octahedral charge of the montmorillonite. Reduction of the layer charge proceeds to a much lesser extent for smectites with mainly tetrahedral charge and high Fe content (Fe-rich beidellite and ferruginous smectite). Both CEC data and MB spectra detect only a slight decrease of the layer charge density, which relates to the low octahedral charge of these minerals. Following heating at higher temperatures (120-160°C), slightly higher Li fixation is indicated by CEC values; however, no charge reduction is confirmed by MB spectra. Release of protons accompanying Li+ fixation in Fe-rich smectites heated at 180 or 200°C was detected in the spectra of MB-clay dispersions and confirmed by potentiometric titrations.

Interaction of Methylene Blue with Reduced Charge Montmorillonite

Interaction of methylene blue (MB) with reduced charge Li−montmorillonites (RCM) in the aqueous suspensions was investigated using visible absorption spectroscopy. Dye cation agglomeration and protonation at the clay surface depended very sensitively on layer charge density. With increasing layer charge reduction, the content of agglomerates of MB cations decreased in favor of monomers and the protonated form of MB. Lower negative charge density on the clay basal surface induces a greater distance between neighboring MB cations sorbed at the clay surfaces, which suppresses dye agglomeration. Since each form of MB absorbs visible light at a different wavelength, different layer charge densities induce different colors of the resulting clay−dye suspension. Therefore, visible spectra of MB−smectite suspensions may be a simple but extremely sensitive method for the detection of layer charge density of smectites.