Acridine Orange Cation Research Articles

A Quantitative Model for Using Acridine Orange as a Transmembrane pH Gradient Probe

Monitoring the acidification of the internal space of membrane vesicles by proton pumps can be achieved easily with optical probes. Transmembrane pH gradients cause a blue-shift in the absorbance spectrum and the quenching of the fluorescence of the cationic dye acridine orange. It has been postulated that these changes are caused by accumulation and aggregation of the dye inside the vesicles. We tested this hypothesis using liposomes with transmembrane concentration gradients of ammonium sulfate as model system. Fluorescence intensity of acridine orange solutions incubated with liposomes was affected by magnitude of the gradient, volume trapped by vesicles, and temperature. These experimental data were compared to a theoretical model describing the accumulation of acridine orange monomers in the vesicles according to the inside-to-outside ratio of proton concentrations, and the intravesicular formation of sandwich-like piles of acridine orange cations. This theoretical model predicted quantitatively the relationship between the transmembrane pH gradients and spectral changes of acridine orange. Therefore, adequate characterization of aggregation of dye in the lumen of biological vesicles provides the theoretical basis for using acridine orange as an optical probe to quantify transmembrane pH gradients.

The Determination of Surface Basicity of the Oxygen Planes of Expanding Clay Minerals by Acridine Orange

The surface basicity of the oxygen planes of four Na–smectites and one Na–vermiculite was studied by visible spectroscopy of clay suspensions saturated with the metachromic cationic dye acridine orange. A metachromic band in the spectrum is an indication of π interactions in which the cationic dye is involved. Curves describing the wavelength of the metachromic band in the presence of clay minerals as a function of the degree of saturation showed three regions. X-ray diffractions proved that in the first region monomeric acridine orange cations were located in the interlayer space with the aromatic rings lying parallel to the silicate layers. Thus, metachromasy in the first region was due to π interactions in which atoms from the O-planes donate lone-pair electrons to π antibonding orbitals of the organic cations. From the location of the metachromic band it was concluded that the basic strength of the O-planes decreased in the order: beidellite > vermiculite > montmorillonite > saponite > laponite.

Effects of alkyl chain length on the adsorption of an N-alkylated Acridine Orange cation by colloidally dispersed zirconium phosphate

The adsorption of N-alkylated acridine orange derivatives (AO-C{sub n}; n = the number of carbon atoms in an alkyl group) by colloidally dispersed zirconium phosphate (ZrP) was studied by spectrophotometry and electric dichroism. An AO-C{sub n} cation was bound to ZrP by releasing a proton in the phosphate group of ZrP. The electronic spectrum of bound AO-C{sub n} showed that the dye cations formed an aggregate on the polymer. The reduced linear dichroism of a bound dye molecule, {rho}, was determined as a function of n: {rho} = 1.3-1.0 for n = 0-2, while {rho} = {minus}0.3 to {minus}0.4 for n = 3-9.

Specific interactions between dye cations in premicellar aggregates as revealed by electric dichroism measurements

The electronic absorption and electric dichroism spectra are compared between an SDS solution containing one kind of cationic dye ( D + SDS ) and an SDS solution containing two kinds of cationic dyes (D 1 +/D 2 +/SDS). Here D 1 + and D 2 + are chosen from acridine orange cation (AOH +), N-nonylacridine orange cation (AO +(CH 2) 9H) and thionine cation (Th +). At the investigated SDS concentration (≈5 × 10 −5 M), the aggregate of a 1:1 dye-SDS ion pair is formed, which remains stable in a solution for several hours. In any of the three cases studied, the absorbance and dichroism amplitude for D 1 +/D 2 +/SDS are not expressed by the sum of the ones for D 1 + SDS and D 2 + SDS . The results indicate that the coexistence of two kinds of dyes in the same aggregate induces the rearrangement and orientational change of dye-SDS pairs.

Aliphatic tail effects on adsorption of acridine orange cation on a colloidal surface of montmorillonite

Aliphatic tail effects on adsorption of acridine orange cation on a colloidal surface of montmorillonite

Transient electric dichroism studies on interaction of a cationic dye with sodium dodecylsulfate

Transient electric dichroism is measured on a solution of sodium dodecylsulfate (SDS) and N-alkylated acridine orange cation (AO + —(CH 2 ) n H). The length of the alkyl chain of a dye cation is varied from n = 0 to n = 18. The electric dichroism is observed due to a large mixed aggregate of SDS and dye cation in the concentration ranges of [SDS] = 1–9 × 10 −3 M and [dye] = 1–2 × 10 −5 M . Assuming a rodlike shape for such an aggregate, the length ( l ) of the aggregate is determined from the decay rate of the induced dichroism; l takes a value from 3300A˚( n = 0) to 5100A˚( n = 12). The sign and magnitude of the dichroism provide an angle φ between electric field direction and the transition moment of a bound dye. φ is dependent on the length of the attached alkyl chain to an appreciate extent.

Thermodynamics of mucopolysaccharide–dye binding. III. Thermodynamic and cooperativity parameters of acridine orange–heparin system

AbstractBinding isotherms for acridine orange (AO)–heparin systems can be evaluated solely on the basis of quantitative fluorescence spectroscopic measurements. The evaluation of thermodynamic parameters indicates that the interactions of AO with heparins from several animal sources are similar to each other in magnitude. Binding is highly exothermic (ΔH = −6 kcal mol−1) and is stabilized by dye–polymer and dye–dye (coopertive) interactions, as well as by entropic factors (ΔS = +7 e.u.). The predominant stabilizing factor appears to be the electrostatic attraction between the AO cation and the heparin polyanion, although the other factors are important as well. At 24°C the value of the cooperative binding constants for the various heparins range from 8.8 to 11.3 × 105M−1, corresponding to a free energy of −8 kcal mol−1. The degree of cooperativity, which is a direct measure of dye–dye interaction, varies with polymer:dye ratio; the theoretical basis for this variation remains to be elucidated. Electrophoretic data indicate that each heparin sample consists of a mixture of species, each with its own charge density. This precludes definitive interpretation of observed small differences in the values of the thermodynamic parameters among the various samples until each sample can be resolved into its components.

THE ENERGY TRANSFER FOR AN ORIENTED DYE MOLECULES IN STRETCHED POLY(VINYL ALCOHOL) FILMS

Abstract For various stretch ratios, the degrees of polarization(P) of Acridine Orange(AO) cations in stretched poly(vinyl alcohol) (PVA) films has been measured as a function of the concentration of AO cations. The plots of 1/P versus concentration are linear with the slope dependent on the stretching ratio, for concentrations ranging from 4×10−5to 10−4M. This has been interpreted as the results of energy transfer between partially oriented like molecules.

Concentration Depolarization of the Fluorescence and Phosphorescence of Acridine Orange Cations

Abstract Concentration depolarization of fluorescence and phosphorescence has been studied for Acridine Orange cations in PVA films. Depolarization can be observed with concentrations above 10−6 M. For concentrations ranging from 10−6 M to 10−4 M both depolarization of fluorescence and of phosphorescence obey the Weber equation. The results indicate that singlet-singlet energy transfer is responsible for depolarization of fluorescence, as well as of phosphorescence. Above 10−4 M, the effect of the exchange interaction cannot be ignored due to the formation of higher aggregates.

Neutral Salt Effect on the Interaction of Poly-α, l-glutamic Acid with Acridine Orange

Abstract The effect of potassium chloride on the absorption and optical rotatory properties of the poly-α,l-glutamic acid-acridine orange system in an aqueous solution was studied under various conditions. The stability of the helical conformation of poly-α,l-glutamic acid in this system was examined at different potassium chloride concentrations by estimating the helix fraction of the polymer. At pH 4.5, where poly-α,l-glutamic acid exists in the helix, it was found that the added potassium chloride raised the stability of the helical conformation of the polymer in this system. In this case, it was assumed that the added potassium chloride lowers the disturbance of helix formation by the bound acridine orange cation. However, when the solution’s pH was raised, the added potassium chloride lowered the extent of the helix fraction in this system. These phenomena were discussed on the basis of several experimental findings on the circular dichroism of the systems. Furthermore, from the change in the intensities of the circular dichroism with the variation in the potassium chloride concentration, it was presumed that the positive circular dichroism band at about 520 nm was due to the binding of dimeric acridine orange molecules to the polymer.

On the Dimerization of the Acridine Orange Cation. A Potentiometric and a Spectrophotometric Proof that the Dimerization Does Not Involve Counterions.

On the Dimerization of the Acridine Orange Cation. A Potentiometric and a Spectrophotometric Proof that the Dimerization Does Not Involve Counterions.

The electronic structures and spectra of proflavine, acridine orange, and their DNA complexes

AbstractThe electronic structure of the proflavine cation is studied by the SCF–ASMO–CI method using the Pariser–Parr–Pople approximations. It is shown that the band at 445 mμ may be assigned to the 1A1 → 1B1, transition polarized along the long axis of the molecule. The bands in the neighbourhood of 260 mμ, which are composed of three absorption bands, are tentatively assigned to the 1A1 → 1B1, 1A1 → 1B1, and 1A1 → 1A1 transitions, respectively, in order of decreasing wavelength. The spectrum of the acridine orange cation may be understood to have the same assignment as that of the proflavine cation.The acridine dye cations are well known for their dimerization with concentration. The intermolecular distances in these dimers are estimated from the band shifts due to the formation of dimers, using the exciton theory. The main contribution to the molecular interaction is shown to be the electrostatic dipole–dipole interaction.Since the first excitation band of the dye molecule which exhibits a remarkable change due to the formation of the DNA–acridine dye complex, is suggested to be polarized along the long axis, preference of the outside stacking or the intercalation model is qualitatively discussed from the spectral shift of the acridine dye bound to the DNA, assuming simple models.