Interaction Of Ethidium Research Articles

Interaction of ethidium and tetraphenylphosphonium cations with Salmonella enterica cells

Background and objectiveOne of the main causes of bacterial resistance to antimicrobials is multidrug resistance induced by the increased efficiency of the efflux pumps. In this study we analyzed how the conditions of assay affect the efflux of indicator substrates ethidium (Et+) and tetraphenylphosphonium (TPP+) in Salmonella enterica ser. Typhimurium cells. Impact of the outer membrane permeability barrier, composition and temperature of the medium on accumulation of the indicator compounds also was analyzed. Materials and methodsThe fluorescence of Et+ and Nile Red was measured using 96-well plates and a plate reader. In parallel to traditional studies of fluorescence we applied a constructed selective electrode to follow the accumulation of Et+ in S. enterica cells. Simultaneously with monitoring of Et+ concentration in the cell incubation medium, electrochemical measurements of TPP+ accumulation were performed. Furthermore, Et+ and TPP+ were used within the same sample as agents competing for the interaction with the efflux pumps. An inhibitor phenylalanyl-arginyl-β-naphtylamide (PAβN) was applied to evaluate the input of RND-family pumps in the total efflux of these indicator compounds. ResultsS. enterica cells with the intact outer membrane (OM) bound very low amounts of Et+ or TPP+. Cells with the permeabilized OM accumulate considerably higher amounts of the indicator compounds at pH 8.0, but only Et+ was considerably accumulated at pH 6.5. At conditions of electrochemical monitoring accumulation of Et+ by the permeabilized cells at 37°C was considerably faster than at 23°C, but at the higher temperature most of the cell-accumulated Et+ was extruded back to the medium. The fluorescence of Et+ in suspension of cells incubated in 400mmol/L Tris buffer was about twice higher compared to 100mmol/L one. The inhibitory action of TPP+ on Et+ efflux was evident only in 400mmol/L Tris although PAβN effectively increased Et+ fluorescence at both buffer concentrations. ConclusionsResults of our experiments indicate that ionic strength of the incubation medium influence the selectivity, the medium temperature and the assay conditions impact the kinetics of efflux. The lower accumulated amount and the weaker fluorescence of Et+ registered in slightly acidic medium indicate that ΔΨ plays a role in the accumulation of this indicator cation. The bound amount of Et+ to the de-energized or permeabilized cells considerably varies depending on the conditions and methods of de-energization or permeabilization of cells. Tris/EDTA permeabilization of the cells does not inhibit the efflux.

Binding of ethidium bromide to a DNA triple helix. Evidence for intercalation.

The interaction of ethidium, a DNA intercalator, with the poly(dA).poly(dT) duplex and the poly (dA).2poly(dT) triplex has been investigated by a variety of spectrophotometric and hydrodynamic techniques. The fluorescence of ethidium is increased when either the duplex or triplex form is present. Binding constants, determined from absorbance measurements, indicate that binding to the triple helical form is substantially stronger than to the duplex, with a larger binding site size (2.8 base triplets compared to 2.4 base pairs). Furthermore, while binding to poly(dA).poly(dT) shows strong positive cooperativity, binding to the triplex is noncooperative. Thermal denaturation experiments demonstrate that ethidium stabilizes the triple helix. Binding to either form induces a weak circular dichroism band in the visible wavelength region, while in the region around 310 nm, there is a band that is strongly dependent on the degree of saturation of the duplex, and which is positive for the duplex but negative for the triplex. Both fluorescence energy transfer and quenching studies provide evidence of intercalation of ethidium in both duplex and triplex complexes. Binding of ethidium leads to an initial decrease in viscosity for both the duplex and triplex structures, followed by an increase, which is greater for the duplex. Taken together, these results strongly suggest that ethidium binds to the poly (dA).2poly(dT) triple helix via an intercalative mechanism.

Base specificity in the interaction of ethidium with synthetic polyribonucleotides

Base specificity in the interaction of ethidium with double stranded synthetic RNA homopolymers has been studied by means of spectroscopic (UV-visible absorption and fluorescence), microcalorimetric and dilatometric techniques. The results show a strong base specificity in this interaction, the association constant with poly A:poly U being more than three order of magnitude higher than with poly O:poly C. The interaction is mainly enthalpy driven, the differences in affinity being essentially entropic in origin. These evidences along with the dilatometric data suggest that the observed base specificity may arise from the different extent of water release upon intercalation.

ChemInform Abstract: THEORETICAL STUDIES OF DRUG‐DINUCLEOTIDE INTERACTIONS. EMPIRICAL ENERGY FUNCTION CALCULATIONS ON THE INTERACTION OF ETHIDIUM, 9‐AMINOACRIDINE, AND PROFLAVIN CATIONS WITH THE BASE‐PAIRED DINUCLEOTIDES GPC AND CPG

Chemischer InformationsdienstVolume 10, Issue 21 Article ChemInform Abstract: THEORETICAL STUDIES OF DRUG-DINUCLEOTIDE INTERACTIONS. EMPIRICAL ENERGY FUNCTION CALCULATIONS ON THE INTERACTION OF ETHIDIUM, 9-AMINOACRIDINE, AND PROFLAVIN CATIONS WITH THE BASE-PAIRED DINUCLEOTIDES GPC AND CPG M. E. NUSS, M. E. NUSSSearch for more papers by this authorF. J. MARSH, F. J. MARSHSearch for more papers by this authorP. A. KOLLMAN, P. A. KOLLMANSearch for more papers by this author M. E. NUSS, M. E. NUSSSearch for more papers by this authorF. J. MARSH, F. J. MARSHSearch for more papers by this authorP. A. KOLLMAN, P. A. KOLLMANSearch for more papers by this author First published: May 22, 1979 https://doi.org/10.1002/chin.197921095AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume10, Issue21May 22, 1979 RelatedInformation

Theoretical studies of drug-dinucleotide interactions. Empirical energy function calculations on the interaction of ethidium, 9-aminoacridine, and proflavin cations with the base-paired dinucleotides GpC and CpG

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTheoretical studies of drug-dinucleotide interactions. Empirical energy function calculations on the interaction of ethidium, 9-aminoacridine, and proflavin cations with the base-paired dinucleotides GpC and CpGMerrill E. Nuss, Frederick J. Marsh, and Peter A. KollmanCite this: J. Am. Chem. Soc. 1979, 101, 4, 825–833Publication Date (Print):February 1, 1979Publication History Published online1 May 2002Published inissue 1 February 1979https://doi.org/10.1021/ja00498a008RIGHTS & PERMISSIONSArticle Views90Altmetric-Citations73LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

The interaction of ethidium with synthetic double-stranded polynucleotides at low ionic strength.

The interaction of ethidium with synthetic DNA and RNA double-stranded polymers at 0.01 M ionic strength, pH 7.0, has been studied by fluorimetry at low drug to nucleotide ratios. Binding constants have been calculated assuming an excluded-neighbouring site model for the interaction of ethidium with double-stranded polymers. The values obtained are poly d(AT).poly d(AT), 9.5 X 10(6) M-1; poly dA.poly dT, 6.5 X 10(5) M-1; poly d(GC).poly d(GC), 9.9 X 10(6) M-1; poly dG,poly dC, 4.5 X 1-(6) M-1; poly d(AC); poly d(GT), 9.8 X 10(6) M-1; poly d(AG).poly d(CT), 1.3 X 10(6) M-1; poly rA.poly rU, 4.1 X 10(7) M-1. The displacement of ethidium from poly d(AT).poly d(AT) by 9-aminoacridine and an acridine-containing antitumor agent (NSC 156303; 4'-(9-acridinylamino)methanesulphon-m-anisidide) has also been examined.

Interaction of ethidium with the mitochondrial membrane: Cooperative binding and energy-linked changes

Summary Binding of ethidium, a cationic dye, to mitochondrial membranes occurs at a site of low polarity, and has the characteristics of a homotropic cooperative interaction. Energy conservation induces in increase in the affinity of the membrane for the dye.