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Miguel Viveiros - One of the best experts on this subject based on the ideXlab platform.

  • Thioridazine and chlorpromazine inhibition of Ethidium Bromide efflux in Mycobacterium avium and Mycobacterium smegmatis
    2015
    Co-Authors: Liliana Rodrigues, Isabel Couto, Miguel Viveiros, Dirk Wagner, Daniela Sampaio, Martina Vavra, Winfried V Kern, Leonard Amaral
    Abstract:

    Objectives: Therapy of AIDS patients infected with Mycobacterium avium is problematic due to its intrinsic resistance to antibiotics. We have characterized the efflux pump activity of M. avium wild-type strain through an automated fluorometric method and correlated it with intrinsic resistance to antibiotics. Methods: M. avium ATCC 25291T and Mycobacterium smegmatis mc2155 were evaluated for accumulation and efflux of Ethidium Bromide in the presence or absence of the efflux pump inhi-bitors (EPIs) thioridazine, chlorpromazine, verapamil and the proton uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP). For this purpose, a new automated fluorometric method was used that separately assesses accumulation and extrusion of Ethidium Bromide. Results: The automated fluorometric method described in this paper allowed the detection and quantification of Ethidium Bromide transport across M. avium and M. smegmatis cell walls. Accumulation of Ethidium Bromide was found to be temperature-dependent and significantly increased by EPIs thioridazine, chlorpromazine, verapamil and CCCP in a concentration-dependent manner. Efflux of Ethidium Bromide under optimum conditions of temperature and glucose is inhibited by the above agents. At half their intrinsic MICs, both thioridazine and chlorpromazine

  • Ethidium Bromide efflux by salmonella modulation by metabolic energy ph ions and phenothiazines
    International Journal of Antimicrobial Agents, 2011
    Co-Authors: Leonard Amaral, Isabel Couto, Miguel Viveiros, Ana Martins, Pedro Cerca, Gabriella Spengler, Lisa Machado, Séamus Fanning
    Abstract:

    The main efflux pump of Salmonella enterica serotype Enteritidis, which obtains its energy for the extrusion of noxious agents from the proton-motive force, was studied with the aid of an Ethidium Bromide (EtBr) semi-automated method under conditions that define the role of metabolic energy, ions and pH in the extrusion of the universal substrate EtBr. The results obtained in this study indicate that in minimal medium containing sodium at pH 5 efflux of EtBr is independent of glucose, whereas at pH 8 metabolic energy is an absolute requirement for the maintenance of efflux. In deionised water at pH 5.5, metabolic energy is required for the maintenance of efflux. The inhibitory effect of the ionophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) on efflux is shown to be minimised by low pH, and at high pH by metabolic energy. Similarly, thioridazine, an inhibitor of metabolic enzymes, inhibits efflux of EtBr only at pH 8 and the degree of inhibition is lessened by the presence of metabolic energy.

  • identification of efflux pump mediated multidrug resistant bacteria by the Ethidium Bromide agar cartwheel method
    in Vivo, 2011
    Co-Authors: Marta Martins, S S Costa, Teresa Pacheco, Jean-marie Pagès, Isabel Couto, Miguel Viveiros, Séamus Fanning, Leonard Amaral
    Abstract:

    Background/Aim: Bacterial multidrug resistance may be mediated by the overexpression of efflux pumps. Conventional evaluation of efflux activity using efflux pump substrates, such as Ethidium Bromide, requires specialised instrumentation. The agar-based method, previously reported, has been modified to evaluate as many as twelve bacterial strains and has been termed the Ethidium Bromide-agar cartwheel method. Materials and Methods: Agar plates containing different concentrations of Ethidium Bromide were swabbed with bacterial cultures. The cell efflux capacity increased with increasing Ethidium Bromide concentration, which produced fluorescence of the bacterial mass. Results: The method was shown to be useful for the detection of efflux activity among multidrug-resistant Gram-negative and Gram-positive clinical isolates, as confirmed by the determination of minimum inhibitory concentration for several antibiotics in the presence of known efflux pump inhibitors. Conclusion: This method may be adapted to the clinical laboratory for the presumptive identification of multidrug-resistant isolates that overexpress efflux pump systems. Multidrug-resistant (MDR) phenotypes of clinical isolates have been shown to be related to overexpression of efflux pump systems (1-5). These systems are found in Gram- negative and Gram-positive bacteria; however, efflux mediated resistance in Gram-negative bacteria is more complex due to the molecular architecture of the cell

  • Ethidium Bromide transport across mycobacterium smegmatis cell wall correlation with antibiotic resistance
    BMC Microbiology, 2011
    Co-Authors: Liliana Rodrigues, Leonard Amaral, Isabel Couto, Jorge Ramos, Miguel Viveiros
    Abstract:

    Background Active efflux systems and reduced cell-wall permeability are considered to be the main causes of mycobacterial intrinsic resistance to many antimicrobials. In this study, we have compared the Mycobacterium smegmatis wild-type strain mc2155 with knockout mutants for porins MspA (the main porin of M. smegmatis) and MspC, the efflux pump LfrA (the main efflux pump system of M. smegmatis) and its repressor LfrR for their ability to transport Ethidium Bromide (EtBr) on a real-time basis. This information was then correlated with minimum inhibitory concentrations (MICs) of several antibiotics in the presence or absence of the efflux inhibitors chlorpromazine, thioridazine and verapamil.

  • Ethidium Bromide transport across mycobacterium smegmatis cell wall correlation with antibiotic resistance
    BMC Microbiology, 2011
    Co-Authors: Liliana Rodrigues, Leonard Amaral, Isabel Couto, Jorge Ramos, Miguel Viveiros
    Abstract:

    Background Active efflux systems and reduced cell-wall permeability are considered to be the main causes of mycobacterial intrinsic resistance to many antimicrobials. In this study, we have compared the Mycobacterium smegmatis wild-type strain mc2155 with knockout mutants for porins MspA (the main porin of M. smegmatis) and MspC, the efflux pump LfrA (the main efflux pump system of M. smegmatis) and its repressor LfrR for their ability to transport Ethidium Bromide (EtBr) on a real-time basis. This information was then correlated with minimum inhibitory concentrations (MICs) of several antibiotics in the presence or absence of the efflux inhibitors chlorpromazine, thioridazine and verapamil.

Leonard Amaral - One of the best experts on this subject based on the ideXlab platform.

  • Thioridazine and chlorpromazine inhibition of Ethidium Bromide efflux in Mycobacterium avium and Mycobacterium smegmatis
    2015
    Co-Authors: Liliana Rodrigues, Isabel Couto, Miguel Viveiros, Dirk Wagner, Daniela Sampaio, Martina Vavra, Winfried V Kern, Leonard Amaral
    Abstract:

    Objectives: Therapy of AIDS patients infected with Mycobacterium avium is problematic due to its intrinsic resistance to antibiotics. We have characterized the efflux pump activity of M. avium wild-type strain through an automated fluorometric method and correlated it with intrinsic resistance to antibiotics. Methods: M. avium ATCC 25291T and Mycobacterium smegmatis mc2155 were evaluated for accumulation and efflux of Ethidium Bromide in the presence or absence of the efflux pump inhi-bitors (EPIs) thioridazine, chlorpromazine, verapamil and the proton uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP). For this purpose, a new automated fluorometric method was used that separately assesses accumulation and extrusion of Ethidium Bromide. Results: The automated fluorometric method described in this paper allowed the detection and quantification of Ethidium Bromide transport across M. avium and M. smegmatis cell walls. Accumulation of Ethidium Bromide was found to be temperature-dependent and significantly increased by EPIs thioridazine, chlorpromazine, verapamil and CCCP in a concentration-dependent manner. Efflux of Ethidium Bromide under optimum conditions of temperature and glucose is inhibited by the above agents. At half their intrinsic MICs, both thioridazine and chlorpromazine

  • Ethidium Bromide efflux by salmonella modulation by metabolic energy ph ions and phenothiazines
    International Journal of Antimicrobial Agents, 2011
    Co-Authors: Leonard Amaral, Isabel Couto, Miguel Viveiros, Ana Martins, Pedro Cerca, Gabriella Spengler, Lisa Machado, Séamus Fanning
    Abstract:

    The main efflux pump of Salmonella enterica serotype Enteritidis, which obtains its energy for the extrusion of noxious agents from the proton-motive force, was studied with the aid of an Ethidium Bromide (EtBr) semi-automated method under conditions that define the role of metabolic energy, ions and pH in the extrusion of the universal substrate EtBr. The results obtained in this study indicate that in minimal medium containing sodium at pH 5 efflux of EtBr is independent of glucose, whereas at pH 8 metabolic energy is an absolute requirement for the maintenance of efflux. In deionised water at pH 5.5, metabolic energy is required for the maintenance of efflux. The inhibitory effect of the ionophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) on efflux is shown to be minimised by low pH, and at high pH by metabolic energy. Similarly, thioridazine, an inhibitor of metabolic enzymes, inhibits efflux of EtBr only at pH 8 and the degree of inhibition is lessened by the presence of metabolic energy.

  • identification of efflux pump mediated multidrug resistant bacteria by the Ethidium Bromide agar cartwheel method
    in Vivo, 2011
    Co-Authors: Marta Martins, S S Costa, Teresa Pacheco, Jean-marie Pagès, Isabel Couto, Miguel Viveiros, Séamus Fanning, Leonard Amaral
    Abstract:

    Background/Aim: Bacterial multidrug resistance may be mediated by the overexpression of efflux pumps. Conventional evaluation of efflux activity using efflux pump substrates, such as Ethidium Bromide, requires specialised instrumentation. The agar-based method, previously reported, has been modified to evaluate as many as twelve bacterial strains and has been termed the Ethidium Bromide-agar cartwheel method. Materials and Methods: Agar plates containing different concentrations of Ethidium Bromide were swabbed with bacterial cultures. The cell efflux capacity increased with increasing Ethidium Bromide concentration, which produced fluorescence of the bacterial mass. Results: The method was shown to be useful for the detection of efflux activity among multidrug-resistant Gram-negative and Gram-positive clinical isolates, as confirmed by the determination of minimum inhibitory concentration for several antibiotics in the presence of known efflux pump inhibitors. Conclusion: This method may be adapted to the clinical laboratory for the presumptive identification of multidrug-resistant isolates that overexpress efflux pump systems. Multidrug-resistant (MDR) phenotypes of clinical isolates have been shown to be related to overexpression of efflux pump systems (1-5). These systems are found in Gram- negative and Gram-positive bacteria; however, efflux mediated resistance in Gram-negative bacteria is more complex due to the molecular architecture of the cell

  • Ethidium Bromide transport across mycobacterium smegmatis cell wall correlation with antibiotic resistance
    BMC Microbiology, 2011
    Co-Authors: Liliana Rodrigues, Leonard Amaral, Isabel Couto, Jorge Ramos, Miguel Viveiros
    Abstract:

    Background Active efflux systems and reduced cell-wall permeability are considered to be the main causes of mycobacterial intrinsic resistance to many antimicrobials. In this study, we have compared the Mycobacterium smegmatis wild-type strain mc2155 with knockout mutants for porins MspA (the main porin of M. smegmatis) and MspC, the efflux pump LfrA (the main efflux pump system of M. smegmatis) and its repressor LfrR for their ability to transport Ethidium Bromide (EtBr) on a real-time basis. This information was then correlated with minimum inhibitory concentrations (MICs) of several antibiotics in the presence or absence of the efflux inhibitors chlorpromazine, thioridazine and verapamil.

  • Ethidium Bromide transport across mycobacterium smegmatis cell wall correlation with antibiotic resistance
    BMC Microbiology, 2011
    Co-Authors: Liliana Rodrigues, Leonard Amaral, Isabel Couto, Jorge Ramos, Miguel Viveiros
    Abstract:

    Background Active efflux systems and reduced cell-wall permeability are considered to be the main causes of mycobacterial intrinsic resistance to many antimicrobials. In this study, we have compared the Mycobacterium smegmatis wild-type strain mc2155 with knockout mutants for porins MspA (the main porin of M. smegmatis) and MspC, the efflux pump LfrA (the main efflux pump system of M. smegmatis) and its repressor LfrR for their ability to transport Ethidium Bromide (EtBr) on a real-time basis. This information was then correlated with minimum inhibitory concentrations (MICs) of several antibiotics in the presence or absence of the efflux inhibitors chlorpromazine, thioridazine and verapamil.

Isabel Couto - One of the best experts on this subject based on the ideXlab platform.

  • Thioridazine and chlorpromazine inhibition of Ethidium Bromide efflux in Mycobacterium avium and Mycobacterium smegmatis
    2015
    Co-Authors: Liliana Rodrigues, Isabel Couto, Miguel Viveiros, Dirk Wagner, Daniela Sampaio, Martina Vavra, Winfried V Kern, Leonard Amaral
    Abstract:

    Objectives: Therapy of AIDS patients infected with Mycobacterium avium is problematic due to its intrinsic resistance to antibiotics. We have characterized the efflux pump activity of M. avium wild-type strain through an automated fluorometric method and correlated it with intrinsic resistance to antibiotics. Methods: M. avium ATCC 25291T and Mycobacterium smegmatis mc2155 were evaluated for accumulation and efflux of Ethidium Bromide in the presence or absence of the efflux pump inhi-bitors (EPIs) thioridazine, chlorpromazine, verapamil and the proton uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP). For this purpose, a new automated fluorometric method was used that separately assesses accumulation and extrusion of Ethidium Bromide. Results: The automated fluorometric method described in this paper allowed the detection and quantification of Ethidium Bromide transport across M. avium and M. smegmatis cell walls. Accumulation of Ethidium Bromide was found to be temperature-dependent and significantly increased by EPIs thioridazine, chlorpromazine, verapamil and CCCP in a concentration-dependent manner. Efflux of Ethidium Bromide under optimum conditions of temperature and glucose is inhibited by the above agents. At half their intrinsic MICs, both thioridazine and chlorpromazine

  • Ethidium Bromide efflux by salmonella modulation by metabolic energy ph ions and phenothiazines
    International Journal of Antimicrobial Agents, 2011
    Co-Authors: Leonard Amaral, Isabel Couto, Miguel Viveiros, Ana Martins, Pedro Cerca, Gabriella Spengler, Lisa Machado, Séamus Fanning
    Abstract:

    The main efflux pump of Salmonella enterica serotype Enteritidis, which obtains its energy for the extrusion of noxious agents from the proton-motive force, was studied with the aid of an Ethidium Bromide (EtBr) semi-automated method under conditions that define the role of metabolic energy, ions and pH in the extrusion of the universal substrate EtBr. The results obtained in this study indicate that in minimal medium containing sodium at pH 5 efflux of EtBr is independent of glucose, whereas at pH 8 metabolic energy is an absolute requirement for the maintenance of efflux. In deionised water at pH 5.5, metabolic energy is required for the maintenance of efflux. The inhibitory effect of the ionophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) on efflux is shown to be minimised by low pH, and at high pH by metabolic energy. Similarly, thioridazine, an inhibitor of metabolic enzymes, inhibits efflux of EtBr only at pH 8 and the degree of inhibition is lessened by the presence of metabolic energy.

  • identification of efflux pump mediated multidrug resistant bacteria by the Ethidium Bromide agar cartwheel method
    in Vivo, 2011
    Co-Authors: Marta Martins, S S Costa, Teresa Pacheco, Jean-marie Pagès, Isabel Couto, Miguel Viveiros, Séamus Fanning, Leonard Amaral
    Abstract:

    Background/Aim: Bacterial multidrug resistance may be mediated by the overexpression of efflux pumps. Conventional evaluation of efflux activity using efflux pump substrates, such as Ethidium Bromide, requires specialised instrumentation. The agar-based method, previously reported, has been modified to evaluate as many as twelve bacterial strains and has been termed the Ethidium Bromide-agar cartwheel method. Materials and Methods: Agar plates containing different concentrations of Ethidium Bromide were swabbed with bacterial cultures. The cell efflux capacity increased with increasing Ethidium Bromide concentration, which produced fluorescence of the bacterial mass. Results: The method was shown to be useful for the detection of efflux activity among multidrug-resistant Gram-negative and Gram-positive clinical isolates, as confirmed by the determination of minimum inhibitory concentration for several antibiotics in the presence of known efflux pump inhibitors. Conclusion: This method may be adapted to the clinical laboratory for the presumptive identification of multidrug-resistant isolates that overexpress efflux pump systems. Multidrug-resistant (MDR) phenotypes of clinical isolates have been shown to be related to overexpression of efflux pump systems (1-5). These systems are found in Gram- negative and Gram-positive bacteria; however, efflux mediated resistance in Gram-negative bacteria is more complex due to the molecular architecture of the cell

  • Ethidium Bromide transport across mycobacterium smegmatis cell wall correlation with antibiotic resistance
    BMC Microbiology, 2011
    Co-Authors: Liliana Rodrigues, Leonard Amaral, Isabel Couto, Jorge Ramos, Miguel Viveiros
    Abstract:

    Background Active efflux systems and reduced cell-wall permeability are considered to be the main causes of mycobacterial intrinsic resistance to many antimicrobials. In this study, we have compared the Mycobacterium smegmatis wild-type strain mc2155 with knockout mutants for porins MspA (the main porin of M. smegmatis) and MspC, the efflux pump LfrA (the main efflux pump system of M. smegmatis) and its repressor LfrR for their ability to transport Ethidium Bromide (EtBr) on a real-time basis. This information was then correlated with minimum inhibitory concentrations (MICs) of several antibiotics in the presence or absence of the efflux inhibitors chlorpromazine, thioridazine and verapamil.

  • Ethidium Bromide transport across mycobacterium smegmatis cell wall correlation with antibiotic resistance
    BMC Microbiology, 2011
    Co-Authors: Liliana Rodrigues, Leonard Amaral, Isabel Couto, Jorge Ramos, Miguel Viveiros
    Abstract:

    Background Active efflux systems and reduced cell-wall permeability are considered to be the main causes of mycobacterial intrinsic resistance to many antimicrobials. In this study, we have compared the Mycobacterium smegmatis wild-type strain mc2155 with knockout mutants for porins MspA (the main porin of M. smegmatis) and MspC, the efflux pump LfrA (the main efflux pump system of M. smegmatis) and its repressor LfrR for their ability to transport Ethidium Bromide (EtBr) on a real-time basis. This information was then correlated with minimum inhibitory concentrations (MICs) of several antibiotics in the presence or absence of the efflux inhibitors chlorpromazine, thioridazine and verapamil.

Liliana Rodrigues - One of the best experts on this subject based on the ideXlab platform.

  • Thioridazine and chlorpromazine inhibition of Ethidium Bromide efflux in Mycobacterium avium and Mycobacterium smegmatis
    2015
    Co-Authors: Liliana Rodrigues, Isabel Couto, Miguel Viveiros, Dirk Wagner, Daniela Sampaio, Martina Vavra, Winfried V Kern, Leonard Amaral
    Abstract:

    Objectives: Therapy of AIDS patients infected with Mycobacterium avium is problematic due to its intrinsic resistance to antibiotics. We have characterized the efflux pump activity of M. avium wild-type strain through an automated fluorometric method and correlated it with intrinsic resistance to antibiotics. Methods: M. avium ATCC 25291T and Mycobacterium smegmatis mc2155 were evaluated for accumulation and efflux of Ethidium Bromide in the presence or absence of the efflux pump inhi-bitors (EPIs) thioridazine, chlorpromazine, verapamil and the proton uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP). For this purpose, a new automated fluorometric method was used that separately assesses accumulation and extrusion of Ethidium Bromide. Results: The automated fluorometric method described in this paper allowed the detection and quantification of Ethidium Bromide transport across M. avium and M. smegmatis cell walls. Accumulation of Ethidium Bromide was found to be temperature-dependent and significantly increased by EPIs thioridazine, chlorpromazine, verapamil and CCCP in a concentration-dependent manner. Efflux of Ethidium Bromide under optimum conditions of temperature and glucose is inhibited by the above agents. At half their intrinsic MICs, both thioridazine and chlorpromazine

  • Ethidium Bromide transport across mycobacterium smegmatis cell wall correlation with antibiotic resistance
    BMC Microbiology, 2011
    Co-Authors: Liliana Rodrigues, Leonard Amaral, Isabel Couto, Jorge Ramos, Miguel Viveiros
    Abstract:

    Background Active efflux systems and reduced cell-wall permeability are considered to be the main causes of mycobacterial intrinsic resistance to many antimicrobials. In this study, we have compared the Mycobacterium smegmatis wild-type strain mc2155 with knockout mutants for porins MspA (the main porin of M. smegmatis) and MspC, the efflux pump LfrA (the main efflux pump system of M. smegmatis) and its repressor LfrR for their ability to transport Ethidium Bromide (EtBr) on a real-time basis. This information was then correlated with minimum inhibitory concentrations (MICs) of several antibiotics in the presence or absence of the efflux inhibitors chlorpromazine, thioridazine and verapamil.

  • Ethidium Bromide transport across mycobacterium smegmatis cell wall correlation with antibiotic resistance
    BMC Microbiology, 2011
    Co-Authors: Liliana Rodrigues, Leonard Amaral, Isabel Couto, Jorge Ramos, Miguel Viveiros
    Abstract:

    Background Active efflux systems and reduced cell-wall permeability are considered to be the main causes of mycobacterial intrinsic resistance to many antimicrobials. In this study, we have compared the Mycobacterium smegmatis wild-type strain mc2155 with knockout mutants for porins MspA (the main porin of M. smegmatis) and MspC, the efflux pump LfrA (the main efflux pump system of M. smegmatis) and its repressor LfrR for their ability to transport Ethidium Bromide (EtBr) on a real-time basis. This information was then correlated with minimum inhibitory concentrations (MICs) of several antibiotics in the presence or absence of the efflux inhibitors chlorpromazine, thioridazine and verapamil.

  • fluorometric determination of Ethidium Bromide efflux kinetics in escherichia coli
    Journal of Biological Engineering, 2009
    Co-Authors: Laura Paixao, Leonard Amaral, Marta Martins, Isabel Couto, Liliana Rodrigues, Pedro Fernandes, Carla C C R De Carvalho, Gabriel A Monteiro, Filipe Sansonetty, Miguel Viveiros
    Abstract:

    Background Efflux pump activity has been associated with multidrug resistance phenotypes in bacteria, compromising the effectiveness of antimicrobial therapy. The development of methods for the early detection and quantification of drug transport across the bacterial cell wall is a tool essential to understand and overcome this type of drug resistance mechanism. This approach was developed to study the transport of the efflux pump substrate Ethidium Bromide (EtBr) across the cell envelope of Escherichia coli K-12 and derivatives, differing in the expression of their efflux systems.

  • thioridazine and chlorpromazine inhibition of Ethidium Bromide efflux in mycobacterium avium and mycobacterium smegmatis
    Journal of Antimicrobial Chemotherapy, 2008
    Co-Authors: Liliana Rodrigues, Isabel Couto, Miguel Viveiros, Dirk Wagner, Daniela Sampaio, Martina Vavra, Winfried V Kern, Leonard Amaral
    Abstract:

    Received 24 October 2007; returned 13 December 2007; revised 21 December 2007; accepted 30 January 2008 Objectives: Therapy of AIDS patients infected with Mycobacterium avium is problematic due to its intrinsic resistance to antibiotics. We have characterized the efflux pump activity of M. avium wildtype strain through an automated fluorometric method and correlated it with intrinsic resistance to antibiotics. Methods: M. avium ATCC 25291 T and Mycobacterium smegmatis mc 2 155 were evaluated for accumulation and efflux of Ethidium Bromide in the presence or absence of the efflux pump inhibitors (EPIs) thioridazine, chlorpromazine, verapamil and the proton uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP). For this purpose, a new automated fluorometric method was used that separately assesses accumulation and extrusion of Ethidium Bromide. Results: The automated fluorometric method described in this paper allowed the detection and quantification of Ethidium Bromide transport across M. avium and M. smegmatis cell walls. Accumulation of Ethidium Bromide was found to be temperature-dependent and significantly increased by EPIs thioridazine, chlorpromazine, verapamil and CCCP in a concentration-dependent manner. Efflux of Ethidium Bromide under optimum conditions of temperature and glucose is inhibited by the above agents. At half their intrinsic MICs, both thioridazine and chlorpromazine, similarly to verapamil and CCCP, significantly increased the susceptibility of M. avium to erythromycin, suggesting an effect upon an efflux pump with Ethidium Bromide and erythromycin as substrates. A similar effect was observed for M. smegmatis with verapamil only.

Guowen Zhang - One of the best experts on this subject based on the ideXlab platform.

  • spectroscopic studies of cyanazine binding to calf thymus dna with the use of Ethidium Bromide as a probe
    Sensors and Actuators B-chemical, 2013
    Co-Authors: Guowen Zhang, Yepeng Zhang, Yue Zhang, Yu Li
    Abstract:

    Abstract The interaction between cyanazine and calf thymus DNA (ctDNA) in physiological buffer (pH 7.4) was investigated with the use of Ethidium Bromide (EB) as a spectral probe by UV–vis absorption, fluorescence, circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopy, as well as viscosity measurements. The results revealed that intercalation binding should be the interaction mode of cyanazine to ctDNA and the binding constant was obtained to be 2.65 × 10 4  L mol −1 at 298 K. Analysis of the FT-IR spectra suggested that cyanazine mainly bound to guanine and cytosine of ctDNA bases and led to ctDNA duplex aggregation at higher cyanazine concentrations. The thermodynamic parameters, enthalpy change (Δ H °) and entropy change (Δ S °) suggested that hydrophobic interactions and hydrogen bonds played a predominant role in the binding of cyanazine to ctDNA. Furthermore, a chemometrics approach, the alternate least squares (ALS) algorithm, was applied to resolve the measured absorption spectral data array of the competitive reaction between cyanazine and EB with ctDNA, and the results provided simultaneously the concentration information and corresponding pure spectra for the three reaction components, cyanazine, EB and ctDNA–EB. The results obtained from the ALS analysis indicated that cyanazine intercalated into ctDNA by substituting for EB in the ctDNA–EB complex.

  • spectroscopic studies of dna interactions with food colorant indigo carmine with the use of Ethidium Bromide as a fluorescence probe
    Journal of Agricultural and Food Chemistry, 2012
    Co-Authors: Guowen Zhang, Junhui Pan
    Abstract:

    The interaction of indigo carmine (IC) with calf thymus DNA in physiological buffer (pH 7.4), using Ethidium Bromide (EB) dye as a fluorescence probe, was investigated by ultraviolet–visible absorption, fluorescence, and circular dichroism (CD) spectroscopy, coupled with viscosity measurements and DNA-melting studies. Hypochromicity of the absorption spectra of IC and enhancement in fluorescence polarization of IC were observed with the addition of DNA. Moreover, the binding of IC to DNA was able to decrease iodide and single-stranded DNA (ssDNA) quenching effects, increase the melting temperature and relative viscosity of DNA, and induce the changes in CD spectra of DNA. All of the evidence indicated that IC interacted with DNA in the mode of intercalative binding. Furthermore, the three-way synchronous fluorescence spectra data obtained from the interaction between IC and DNA–EB were resolved by parallel factor analysis (PARAFAC), and the results provided simultaneously the concentration information and...

  • spectroscopic studies on the interaction between carbaryl and calf thymus dna with the use of Ethidium Bromide as a fluorescence probe
    Journal of Photochemistry and Photobiology B-biology, 2012
    Co-Authors: Guowen Zhang
    Abstract:

    Abstract The interaction between carbaryl and calf thymus DNA (ctDNA) was investigated under simulated physiological conditions (Tris–HCl buffer of pH 7.4) using Ethidium Bromide (EB) dye as a probe by UV–vis absorption, fluorescence and circular dichroism (CD) spectroscopy, as well as DNA melting studies and viscosity measurements. It can be concluded that carbaryl molecules could intercalate into the base pairs of DNA as evidenced by hyperchromic effect of absorption spectra, decreases in iodide fluorescence quenching effect, induced CD spectral changes, and significant increases in melting temperature and relative viscosity of DNA. The binding constants and thermodynamic parameters of carbaryl with DNA were obtained by the fluorescence quenching method. Furthermore, a chemometrics approach, parallel factor analysis (PARAFAC), was applied to resolve the measured three-way synchronous fluorescence spectral data matrix of the competitive interaction between carbaryl and EB with DNA, and the results provided simultaneously the concentration profiles and corresponding pure spectra for three reaction components (carbaryl, EB and DNA–EB complex) of the kinetic system at equilibrium. This PARAFAC analysis demonstrated the intercalation of carbaryl to the DNA helix by substituting for EB in the DNA–EB complex.