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Marek Langner - One of the best experts on this subject based on the ideXlab platform.

  • Fluorescence Techniques for Determination of the Membrane Potentials in High Throughput Screening
    Journal of Fluorescence, 2010
    Co-Authors: Magda Przybylo, Tomasz Borowik, Marek Langner
    Abstract:

    The characterization of small molecules requires identification and evaluation of several predictive parameters, when selecting compounds for pharmacological applications and/or determining their toxicity. A number of them are correlated with the compound interaction with biological membranes and/or capacity to cross them. The knowledge of the extent of adsorption, partition coefficient and permeability along with the compound ability to alter membrane properties are critical for such studies. Lipid bilayers are frequently used as the adequate experimental models of a biological membrane despite their simple structure and a limited number of components. A significant number of the biologically relevant lipid bilayer properties are related to its electrostatics. Three electrostatic potentials were defined for the lipid bilayer; the intrinsic or induced surface electrostatic potential, the dipole potential and the membrane potential. Each of them was measured with dedicated methodologies. The complex measurement protocols and technically demanding instrumentation made the development of efficient HTS approaches for complete characterization of membrane electrostatics practically impossible. However, the rapid development of Fluorescence Techniques accompanied by rapid growth in diversity and number of dedicated fluorescent probes enabled characterization of lipid bilayer electrostatics in a moderately simple manner. Technically advanced, compact and automated workstations, capable of measuring practically all Fluorescence parameters, are now available. Therefore, the proper selection of fluorescent probes with measuring procedures can be designed to evaluate drug candidates in context of their ability to alter membrane electrostatics. In the paper we present a critical review of available Fluorescence methods, useful for the membrane electrostatics evaluation and discuss the feasibility of their adaptation to HTS procedures. The significance of the presented methodology is even greater considering the rapid growth of advanced drug formulations, where electrostatics is an important parameter for production processes and pharmacokinetics of the product. Finally, the potential of the membrane electrostatics to emerge as a viable pharmacological target is indicated and Fluorescence Techniques capable to evaluate this potential are presented.

  • Fluorescence Techniques for Determination of the Membrane Potentials in High Throughput Screening
    Journal of Fluorescence, 2010
    Co-Authors: Magda Przybylo, Tomasz Borowik, Marek Langner
    Abstract:

    The characterization of small molecules requires identification and evaluation of several predictive parameters, when selecting compounds for pharmacological applications and/or determining their toxicity. A number of them are correlated with the compound interaction with biological membranes and/or capacity to cross them. The knowledge of the extent of adsorption, partition coefficient and permeability along with the compound ability to alter membrane properties are critical for such studies. Lipid bilayers are frequently used as the adequate experimental models of a biological membrane despite their simple structure and a limited number of components. A significant number of the biologically relevant lipid bilayer properties are related to its electrostatics. Three electrostatic potentials were defined for the lipid bilayer; the intrinsic or induced surface electrostatic potential, the dipole potential and the membrane potential. Each of them was measured with dedicated methodologies. The complex measurement protocols and technically demanding instrumentation made the development of efficient HTS approaches for complete characterization of membrane electrostatics practically impossible. However, the rapid development of Fluorescence Techniques accompanied by rapid growth in diversity and number of dedicated fluorescent probes enabled characterization of lipid bilayer electrostatics in a moderately simple manner. Technically advanced, compact and automated workstations, capable of measuring practically all Fluorescence parameters, are now available. Therefore, the proper selection of fluorescent probes with measuring procedures can be designed to evaluate drug candidates in context of their ability to alter membrane electrostatics. In the paper we present a critical review of available Fluorescence methods, useful for the membrane electrostatics evaluation and discuss the feasibility of their adaptation to HTS procedures. The significance of the presented methodology is even greater considering the rapid growth of advanced drug formulations, where electrostatics is an important parameter for production processes and pharmacokinetics of the product. Finally, the potential of the membrane electrostatics to emerge as a viable pharmacological target is indicated and Fluorescence Techniques capable to evaluate this potential are presented.

Ismail Yilmaz - One of the best experts on this subject based on the ideXlab platform.

  • In situ monitoring of metallation of metal-free phthalocyanineviaUV-Vis and steady-state Fluorescence Techniques. Thin-layer UV-Vis and Fluorescence spectroelectrochemistry of a new non-aggregating and electrochromic manganese(3+) phthalocyanine
    New Journal of Chemistry, 2008
    Co-Authors: Ismail Yilmaz
    Abstract:

    A new non-aggregating and electrochromic manganese(3+) phthalocyanine, (acetato)[2(3),9(10),16(17),23(24)-tetrakis(4-(1-naphthoxy-4-sulfonic acid sodium salt))phthalocyaninato]manganese(3+) [NhtMn(3+)PcL] (where Nht and L indicate naphthoxy-4-sulfonic acid sodium salt and acetate ion, respectively), was synthesized by reaction of the metal-free phthalocyanine (NhtH2Pc) and manganese(2+) acetate (Mn(OAc)2) in methanol. The formation of the complex was monitored by both in situUV-Vis and Fluorescence Techniques based on the change of the symmetry and the quenching of the Fluorescence-probe molecule as a result of the insertion of the metal into the cavity of the macrocycle. The electro-spectrochemical behavior of [NhtMn(3+)PcL] was investigated with thin-layer UV-Vis and Fluorescence spectroelectrochemical methods in DMSO solution. The electrochemical studies revealed that [NhtMn(3+)PcL] exhibited two reversible one-electron reductions which were assigned to Mn(2+)Pc(2–)/Mn(3+)Pc(2–) and Mn(2+)Pc(3–)/Mn(2+)Pc(2–) reversible couples based on the metal and phthalocyanine ring reductions, respectively. All redox processes were accompanied with a change of color from dark green to green and purple which are clearly monitored on the surface of the light transparent platinum gauze working electrode in the thin-layer cell. In situUV-Vis and Fluorescence spectroelectrochemical methods were also applied to determine the E1/2 (half-wave potential) and n (number of electrons) of the first reduction process, both of which confirmed the reversible one-electron [Mn(3+)Pc(2–)L] + e → [Mn(2+)Pc(2–)L]–reduction process.

Magda Przybylo - One of the best experts on this subject based on the ideXlab platform.

  • Fluorescence Techniques for Determination of the Membrane Potentials in High Throughput Screening
    Journal of Fluorescence, 2010
    Co-Authors: Magda Przybylo, Tomasz Borowik, Marek Langner
    Abstract:

    The characterization of small molecules requires identification and evaluation of several predictive parameters, when selecting compounds for pharmacological applications and/or determining their toxicity. A number of them are correlated with the compound interaction with biological membranes and/or capacity to cross them. The knowledge of the extent of adsorption, partition coefficient and permeability along with the compound ability to alter membrane properties are critical for such studies. Lipid bilayers are frequently used as the adequate experimental models of a biological membrane despite their simple structure and a limited number of components. A significant number of the biologically relevant lipid bilayer properties are related to its electrostatics. Three electrostatic potentials were defined for the lipid bilayer; the intrinsic or induced surface electrostatic potential, the dipole potential and the membrane potential. Each of them was measured with dedicated methodologies. The complex measurement protocols and technically demanding instrumentation made the development of efficient HTS approaches for complete characterization of membrane electrostatics practically impossible. However, the rapid development of Fluorescence Techniques accompanied by rapid growth in diversity and number of dedicated fluorescent probes enabled characterization of lipid bilayer electrostatics in a moderately simple manner. Technically advanced, compact and automated workstations, capable of measuring practically all Fluorescence parameters, are now available. Therefore, the proper selection of fluorescent probes with measuring procedures can be designed to evaluate drug candidates in context of their ability to alter membrane electrostatics. In the paper we present a critical review of available Fluorescence methods, useful for the membrane electrostatics evaluation and discuss the feasibility of their adaptation to HTS procedures. The significance of the presented methodology is even greater considering the rapid growth of advanced drug formulations, where electrostatics is an important parameter for production processes and pharmacokinetics of the product. Finally, the potential of the membrane electrostatics to emerge as a viable pharmacological target is indicated and Fluorescence Techniques capable to evaluate this potential are presented.

  • Fluorescence Techniques for Determination of the Membrane Potentials in High Throughput Screening
    Journal of Fluorescence, 2010
    Co-Authors: Magda Przybylo, Tomasz Borowik, Marek Langner
    Abstract:

    The characterization of small molecules requires identification and evaluation of several predictive parameters, when selecting compounds for pharmacological applications and/or determining their toxicity. A number of them are correlated with the compound interaction with biological membranes and/or capacity to cross them. The knowledge of the extent of adsorption, partition coefficient and permeability along with the compound ability to alter membrane properties are critical for such studies. Lipid bilayers are frequently used as the adequate experimental models of a biological membrane despite their simple structure and a limited number of components. A significant number of the biologically relevant lipid bilayer properties are related to its electrostatics. Three electrostatic potentials were defined for the lipid bilayer; the intrinsic or induced surface electrostatic potential, the dipole potential and the membrane potential. Each of them was measured with dedicated methodologies. The complex measurement protocols and technically demanding instrumentation made the development of efficient HTS approaches for complete characterization of membrane electrostatics practically impossible. However, the rapid development of Fluorescence Techniques accompanied by rapid growth in diversity and number of dedicated fluorescent probes enabled characterization of lipid bilayer electrostatics in a moderately simple manner. Technically advanced, compact and automated workstations, capable of measuring practically all Fluorescence parameters, are now available. Therefore, the proper selection of fluorescent probes with measuring procedures can be designed to evaluate drug candidates in context of their ability to alter membrane electrostatics. In the paper we present a critical review of available Fluorescence methods, useful for the membrane electrostatics evaluation and discuss the feasibility of their adaptation to HTS procedures. The significance of the presented methodology is even greater considering the rapid growth of advanced drug formulations, where electrostatics is an important parameter for production processes and pharmacokinetics of the product. Finally, the potential of the membrane electrostatics to emerge as a viable pharmacological target is indicated and Fluorescence Techniques capable to evaluate this potential are presented.

Ulrich S. Schubert - One of the best experts on this subject based on the ideXlab platform.

Craig S. T. Daughtry - One of the best experts on this subject based on the ideXlab platform.

  • Measuring crop residue cover using remote sensing Techniques
    Theoretical and Applied Climatology, 1996
    Co-Authors: Craig S. T. Daughtry, J. E. Mcmurtrey, Emmett W. Chappelle, W. J. Hunter, J. L. Steiner
    Abstract:

    Crop residues are managed under conservation tillage programs to leave as much as possible on the surface for minimization soil erosion and for improving water quality. Because current methods for measuring crop residue cover are tediuous and somewhat subjective, there is a need for new methods to measure residue cover that are rapid, accurate, and objective. We discuss the potential for discriminating crop residues from soils using reflectance and Fluorescence Techniques and examine experimentally the changes in wheat residue Fluorescence during weathering. The Fluorescence of crop residue was a board band phenomenon with emissions extending from 420 to 600 nm for excitation of 350–420 nm. Soils had low intensity broad band emissions over the 400–690 nm region for excitations of 300–600 nm. We found that the Fluorescence intensities for the crop residues were much greater than the Fluorescence of the soils, but as the crop residues decompose, their blue-green Fluorescence intensities approach the Fluorescence of the soils. We conclude that Fluorescence Techniques are less ambiguous and better suited for discriminating crop residues from soils than the reflectance methods. However, the potential problems, that must be addressed to implement the Fluorescence technique, are (i) adequate excitation energy must be supplied to induce Fluorescence and (ii) the Fluorescence signal is small relative to normal, ambient sunlight. Nevertheless, if properly implemented, we believe that the Fluorescence Techniques can be used to quantify crop residue cover in the field.

  • Potential for Discriminating Crop Residues from Soil by Reflectance and Fluorescence
    Agronomy Journal, 1995
    Co-Authors: Craig S. T. Daughtry, J. E. Mcmurtrey, Emmett W. Chappelle, Wayne Dulaney, J. R. Irons, M. B. Satterwhite
    Abstract:

    Crop residues left in the field after harvest can be important in controlling soil erosion. Current methods for quantifying percent crop residue cover are tedious and somewhat subjective. There is a need for new methods to quantify residue cover that are rapid, accurate, and objective. We evaluated reflectance and Fluorescence Techniques for discriminating crop residues from a wide range of soils. Reflectance and Fluorescence spectra of 37 agricultural soils (wet and dry) and of recently harvested and weathered corn (Zea mays L.), soybean [Glycine max (L.) Merr.] sorghum [Sorghum bicolor (L.) Moench], and wheat (Triticum aestivum L.) residues were measured in the lab. Reflectance factors in the visible or near-infrared wavelengths did not uniquely distinguish all soils from all crop residues. Crop residues may be brighter or darker than a given soil, depending on soil moisture and residue age. When illuminated with ultraviolet radiation, however, the crop residues fluoresced more than most of the soils. Fluorescence of crop residues was a broad-band phenomenon centered between 420 to 520 nm and induced by a relatively broad range of excitation wavelengths centered between 350 to 400 nm. More than 90 % of the crop residues < 2 yr old could be discriminated from 33 of 37 dry soils and 36 of 37 wet soils using Fluorescence. The threshold for discrimination can be optimized for classification accuracy for each soil. Fluorescence Techniques are less ambiguous than reflectance methods and are better suited for discriminating crop residues on soils. Futhermore, if properly implemented, Fluorescence Techniques can be used to quantify crop residue cover in the field

  • Discriminating crop residues from soil by reflectance and Fluorescence Techniques
    Proceedings of IGARSS '93 - IEEE International Geoscience and Remote Sensing Symposium, 1
    Co-Authors: Craig S. T. Daughtry, J. E. Mcmurtrey, Emmett W. Chappelle, Wayne Dulaney, J. R. Irons, M. B. Satterwhite
    Abstract:

    Crop residues, the portion of the crop left in the field after harvest, can be an important factor in controlling soil erosion. Current methods for quantifying percent crop residue cover are tedious and somewhat subjective. There is a need for new methods to quantify residue cover that are rapid, accurate, and objective. Reflectance and Fluorescence spectra of recently-harvested and weathered corn, soybean, sorghum, and wheat residues plus 36 agricultural soils were measured. The reflectance data showed that no single wavelength appears capable of uniquely distinguishing all soils from all crop residues. Crop residues may be brighter or darker than a given soil. The Fluorescence of most of the crop residues was consistently greater than the Fluorescence of most of the soils. The authors' studies indicate that a Fluorescence method may be less ambiguous and better suited for detecting crop residues on soils than reflectance methods. >