The Experts below are selected from a list of 6312 Experts worldwide ranked by ideXlab platform

Gareth R. Eaton - One of the best experts on this subject based on the ideXlab platform.

  • Using rapid-scan EPR to improve the detection limit of quantitative EPR by more than one order of magnitude.
    Journal of magnetic resonance (San Diego Calif. : 1997), 2017
    Co-Authors: J. Möser, Gareth R. Eaton, Sandra S. Eaton, Klaus Lips, Mark Tseytlin, Alexander Schnegg
    Abstract:

    X-band rapid-scan EPR was implemented on a commercially available Bruker ELEXSYS E580 spectrometer. Room temperature rapid-scan and Continuous-Wave EPR spectra were recorded for amorphous silicon powder samples. By comparing the resulting signal intensities the feasibility of performing quantitative rapid-scan EPR is demonstrated. For different hydrogenated amorphous silicon samples, rapid-scan EPR results in signal-to-noise improvements by factors between 10 and 50. Rapid-scan EPR is thus capable of improving the detection limit of quantitative EPR by at least one order of magnitude. In addition, we provide a recipe for setting up and calibrating a conventional pulsed and Continuous-Wave EPR spectrometer for rapid-scan EPR.

  • Imaging thiol redox status in murine tumors in vivo with rapid-scan electron paramagnetic resonance.
    Journal of magnetic resonance (San Diego Calif. : 1997), 2016
    Co-Authors: Boris Epel, Gareth R. Eaton, Sandra S. Eaton, Mark Tseytlin, Subramanian V. Sundramoorthy, Martyna Krzykawska-serda, Matthew C. Maggio, Gerald M. Rosen, Joseph P. Y. Kao, Howard J. Halpern
    Abstract:

    Thiol redox status is an important physiologic parameter that affects the success or failure of cancer treatment. Rapid scan electron paramagnetic resonance (RS EPR) is a novel technique that has shown higher signal-to-noise ratio than conventional Continuous-Wave EPR in in vitro studies. Here we used RS EPR to acquire rapid three-dimensional images of the thiol redox status of tumors in living mice. This work presents, for the first time, in vivo RS EPR images of the kinetics of the reaction of 2H,15N-substituted disulfide-linked dinitroxide (PxSSPx) spin probe with intracellular glutathione. The cleavage rate is proportional to the intracellular glutathione concentration. Feasibility was demonstrated in a FSa fibrosarcoma tumor model in C3H mice. Similar to other in vivo and cell model studies, decreasing intracellular glutathione concentration by treating mice with l-buthionine sulfoximine (BSO) markedly altered the kinetic images.

  • X-Band Rapid-Scan Electron Paramagnetic Resonance of Radiation-Induced Defects in Tooth Enamel.
    Radiation research, 2015
    Co-Authors: Alexander Romanyukha, Sandra S. Eaton, Gareth R. Eaton
    Abstract:

    X-band rapid-scan electron paramagnetic resonance (EPR) spectra from tooth enamel samples irradiated with doses of 0.5, 1 and 10 Gy had substantially improved signal-to-noise relative to conventional continuous wave EPR. The radiation-induced signal in a 60 mg of a tooth enamel sample irradiated with a 0.5 Gy dose was readily characterized in spectra recorded with 34 min data acquisition times. The coefficient of variance of the calculated dose for a 1 Gy irradiated sample, based on simulation of the first-derivative spectra for three replicates as the sum of native and radiation-induced signals, was 3.9% for continuous wave and 0.4% for rapid scan.

  • Improved sensitivity for imaging spin trapped hydroxyl radical at 250 MHz.
    Chemphyschem : a European journal of chemical physics and physical chemistry, 2014
    Co-Authors: Joshua R. Biller, Sandra S. Eaton, Gerald M. Rosen, Joseph P. Y. Kao, Mark Tseitlin, Deborah G. Mitchell, Laura A. Buchanan, Hanan Elajaili, Gareth R. Eaton
    Abstract:

    Radicals, including hydroxyl, superoxide, and nitric oxide, play key signaling roles in vivo. Reaction of these free radicals with a spin trap affords more stable paramagnetic nitroxides, but concentrations in vivo still are so low that detection by electron paramagnetic resonance (EPR) is challenging. Three innovative enabling technologies have been combined to substantially improve sensitivity for imaging spin-trapped radicals at 250 MHz. (i) Spin trapped adducts of BMPO have lifetimes that are long enough to make imaging by EPR at 250 MHz feasible. (ii) The signal-to-noise of rapid scan EPR is substantially higher than for conventional continuous wave EPR. (iii) An improved algorithm permits image reconstruction with a spectral dimension that encompasses the full 50 G spectrum of the BMPO-OH spin-adduct without requiring the very wide sweeps that would be needed for filtered backprojection. A 2D spectral-spatial image is shown for a phantom containing ca. 5 μM BMPO-OH.

  • Basics of Continuous Wave EPR
    Quantitative EPR, 2010
    Co-Authors: Gareth R. Eaton, Sandra S. Eaton, David P. Barr, Ralph T. Weber
    Abstract:

    This chapter is an introduction to the basic theory, practice, and instrumentation for EPR spectroscopy. It is designed to give someone who is new to EPR sufficient background to understand the following chapters. A reader who is already well acquainted with the basics of EPR theory and instrumentation, may skip this chapter. Topics in several sections of this chapter are presented in greater detail in subsequent chapters. This introduction, and much of the book, focuses primarily on molecules with a single unpaired electron, which is denoted as having a spin state of S = 1/2.

Johann P. Klare - One of the best experts on this subject based on the ideXlab platform.

  • In vivo EPR on spin labeled colicin A reveals an oligomeric assembly of the pore-forming domain in E. coli membranes
    Physical chemistry chemical physics : PCCP, 2015
    Co-Authors: Sabrina Dunkel, Heinzjurgen Steinhoff, Lakshmi Padmavathi Pulagam, Johann P. Klare
    Abstract:

    We report on the application of site-directed spin labeling (SDSL) and electron paramagnetic resonance (EPR) spectroscopy to study possible oligomerization of the bacterial toxin colicin A (ColA) upon membrane insertion in vitro and in vivo. We applied SDSL-EPR protocols and optimized experimental conditions to perform continuous wave EPR experiments and double electron–electron resonance distance measurements on intact Escherichia coli cells interacting with nitroxide spin-labeled ColA. Our data suggest that ColA forms dimers upon membrane insertion, thus explaining previously reported pore diameters of about 1 nm, which are unlikely to be formed by a single colicin A monomer.

  • Assembly and Function of the tRNA-Modifying GTPase MnmE Adsorbed to Surface Functionalized Bioactive Glass
    ACS applied materials & interfaces, 2014
    Co-Authors: C. Gruian, Heinzjurgen Steinhoff, S. Boehme, Simion Simon, Johann P. Klare
    Abstract:

    Protein adsorption onto solid surfaces is a common phenomenon in tissue engineering related applications, and considerable progress was achieved in this field. However, there are still unanswered questions or contradictory opinions concerning details of the protein’s structure, conformational changes, or aggregation once adsorbed onto solid surfaces. Electron paramagnetic resonance (EPR) spectroscopy and site-directed spin labeling (SDSL) were employed in this work to investigate the conformational changes and dynamics of the tRNA-modifying dimeric protein MnmE from E. coli, an ortholog of the human GTPBP3, upon adsorption on bioactive glass mimicking the composition of the classical 45S5 Bioglass. In addition, prior to protein attachment, the bioactive glass surface was modified with the protein coupling agent glutaraldehyde. Continuous wave EPR spectra of different spin labeled MnmE mutants were recorded to assess the dynamics of the attached spin labels before and after protein adsorption. The area of ...

  • Structural Information from Spin-Labelled Membrane-Bound Proteins
    Structural Information from Spin-Labels and Intrinsic Paramagnetic Centres in the Biosciences, 2013
    Co-Authors: Johann P. Klare, Heinzjurgen Steinhoff
    Abstract:

    Site-directed spin labelling (SDSL) in combination with electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for the investigation of the structure and conformational dynamics of biomolecules including membrane proteins under native-like conditions. EPR spectroscopy of the spin-labelled molecules provides information about the spin label side chain mobility, its solvent accessibility, the polarity of its immediate environment and intra- or intermolecular distances to another paramagnetic centre or spin label. This chapter provides an overview of the basics as well as recent progress in SDSL and related EPR techniques. Continuous wave EPR spectra analyses and pulse EPR techniques are reviewed with special emphasis on applications to the membrane-embedded sensory rhodopsin–transducer complex mediating the photophobic response of the halophilic archaeum Natronomonas pharaonis, the maltose ABC importer MalFGK2 and the mechanosensitive channel MscS.

  • Spin labeling EPR
    Photosynthesis Research, 2009
    Co-Authors: Johann P. Klare, Heinzjurgen Steinhoff
    Abstract:

    Site-directed spin labeling in combination with electron paramagnetic resonance spectroscopy has emerged as an efficient tool to elucidate the structure and conformational dynamics of biomolecules under native-like conditions. This article summarizes the basics as well as recent progress of site-directed spin labeling. Continuous wave EPR spectra analyses and pulse EPR techniques are reviewed with special emphasis on applications to the sensory rhodopsin-transducer complex mediating the photophobic response of the halophilic archaeum Natronomonas pharaonis and the photosynthetic reaction center from Rhodobacter sphaeroides R26.

Sandra S. Eaton - One of the best experts on this subject based on the ideXlab platform.

  • Using rapid-scan EPR to improve the detection limit of quantitative EPR by more than one order of magnitude.
    Journal of magnetic resonance (San Diego Calif. : 1997), 2017
    Co-Authors: J. Möser, Gareth R. Eaton, Sandra S. Eaton, Klaus Lips, Mark Tseytlin, Alexander Schnegg
    Abstract:

    X-band rapid-scan EPR was implemented on a commercially available Bruker ELEXSYS E580 spectrometer. Room temperature rapid-scan and Continuous-Wave EPR spectra were recorded for amorphous silicon powder samples. By comparing the resulting signal intensities the feasibility of performing quantitative rapid-scan EPR is demonstrated. For different hydrogenated amorphous silicon samples, rapid-scan EPR results in signal-to-noise improvements by factors between 10 and 50. Rapid-scan EPR is thus capable of improving the detection limit of quantitative EPR by at least one order of magnitude. In addition, we provide a recipe for setting up and calibrating a conventional pulsed and Continuous-Wave EPR spectrometer for rapid-scan EPR.

  • Imaging thiol redox status in murine tumors in vivo with rapid-scan electron paramagnetic resonance.
    Journal of magnetic resonance (San Diego Calif. : 1997), 2016
    Co-Authors: Boris Epel, Gareth R. Eaton, Sandra S. Eaton, Mark Tseytlin, Subramanian V. Sundramoorthy, Martyna Krzykawska-serda, Matthew C. Maggio, Gerald M. Rosen, Joseph P. Y. Kao, Howard J. Halpern
    Abstract:

    Thiol redox status is an important physiologic parameter that affects the success or failure of cancer treatment. Rapid scan electron paramagnetic resonance (RS EPR) is a novel technique that has shown higher signal-to-noise ratio than conventional Continuous-Wave EPR in in vitro studies. Here we used RS EPR to acquire rapid three-dimensional images of the thiol redox status of tumors in living mice. This work presents, for the first time, in vivo RS EPR images of the kinetics of the reaction of 2H,15N-substituted disulfide-linked dinitroxide (PxSSPx) spin probe with intracellular glutathione. The cleavage rate is proportional to the intracellular glutathione concentration. Feasibility was demonstrated in a FSa fibrosarcoma tumor model in C3H mice. Similar to other in vivo and cell model studies, decreasing intracellular glutathione concentration by treating mice with l-buthionine sulfoximine (BSO) markedly altered the kinetic images.

  • X-Band Rapid-Scan Electron Paramagnetic Resonance of Radiation-Induced Defects in Tooth Enamel.
    Radiation research, 2015
    Co-Authors: Alexander Romanyukha, Sandra S. Eaton, Gareth R. Eaton
    Abstract:

    X-band rapid-scan electron paramagnetic resonance (EPR) spectra from tooth enamel samples irradiated with doses of 0.5, 1 and 10 Gy had substantially improved signal-to-noise relative to conventional continuous wave EPR. The radiation-induced signal in a 60 mg of a tooth enamel sample irradiated with a 0.5 Gy dose was readily characterized in spectra recorded with 34 min data acquisition times. The coefficient of variance of the calculated dose for a 1 Gy irradiated sample, based on simulation of the first-derivative spectra for three replicates as the sum of native and radiation-induced signals, was 3.9% for continuous wave and 0.4% for rapid scan.

  • Improved sensitivity for imaging spin trapped hydroxyl radical at 250 MHz.
    Chemphyschem : a European journal of chemical physics and physical chemistry, 2014
    Co-Authors: Joshua R. Biller, Sandra S. Eaton, Gerald M. Rosen, Joseph P. Y. Kao, Mark Tseitlin, Deborah G. Mitchell, Laura A. Buchanan, Hanan Elajaili, Gareth R. Eaton
    Abstract:

    Radicals, including hydroxyl, superoxide, and nitric oxide, play key signaling roles in vivo. Reaction of these free radicals with a spin trap affords more stable paramagnetic nitroxides, but concentrations in vivo still are so low that detection by electron paramagnetic resonance (EPR) is challenging. Three innovative enabling technologies have been combined to substantially improve sensitivity for imaging spin-trapped radicals at 250 MHz. (i) Spin trapped adducts of BMPO have lifetimes that are long enough to make imaging by EPR at 250 MHz feasible. (ii) The signal-to-noise of rapid scan EPR is substantially higher than for conventional continuous wave EPR. (iii) An improved algorithm permits image reconstruction with a spectral dimension that encompasses the full 50 G spectrum of the BMPO-OH spin-adduct without requiring the very wide sweeps that would be needed for filtered backprojection. A 2D spectral-spatial image is shown for a phantom containing ca. 5 μM BMPO-OH.

  • Basics of Continuous Wave EPR
    Quantitative EPR, 2010
    Co-Authors: Gareth R. Eaton, Sandra S. Eaton, David P. Barr, Ralph T. Weber
    Abstract:

    This chapter is an introduction to the basic theory, practice, and instrumentation for EPR spectroscopy. It is designed to give someone who is new to EPR sufficient background to understand the following chapters. A reader who is already well acquainted with the basics of EPR theory and instrumentation, may skip this chapter. Topics in several sections of this chapter are presented in greater detail in subsequent chapters. This introduction, and much of the book, focuses primarily on molecules with a single unpaired electron, which is denoted as having a spin state of S = 1/2.

Heinzjurgen Steinhoff - One of the best experts on this subject based on the ideXlab platform.

  • In vivo EPR on spin labeled colicin A reveals an oligomeric assembly of the pore-forming domain in E. coli membranes
    Physical chemistry chemical physics : PCCP, 2015
    Co-Authors: Sabrina Dunkel, Heinzjurgen Steinhoff, Lakshmi Padmavathi Pulagam, Johann P. Klare
    Abstract:

    We report on the application of site-directed spin labeling (SDSL) and electron paramagnetic resonance (EPR) spectroscopy to study possible oligomerization of the bacterial toxin colicin A (ColA) upon membrane insertion in vitro and in vivo. We applied SDSL-EPR protocols and optimized experimental conditions to perform continuous wave EPR experiments and double electron–electron resonance distance measurements on intact Escherichia coli cells interacting with nitroxide spin-labeled ColA. Our data suggest that ColA forms dimers upon membrane insertion, thus explaining previously reported pore diameters of about 1 nm, which are unlikely to be formed by a single colicin A monomer.

  • Assembly and Function of the tRNA-Modifying GTPase MnmE Adsorbed to Surface Functionalized Bioactive Glass
    ACS applied materials & interfaces, 2014
    Co-Authors: C. Gruian, Heinzjurgen Steinhoff, S. Boehme, Simion Simon, Johann P. Klare
    Abstract:

    Protein adsorption onto solid surfaces is a common phenomenon in tissue engineering related applications, and considerable progress was achieved in this field. However, there are still unanswered questions or contradictory opinions concerning details of the protein’s structure, conformational changes, or aggregation once adsorbed onto solid surfaces. Electron paramagnetic resonance (EPR) spectroscopy and site-directed spin labeling (SDSL) were employed in this work to investigate the conformational changes and dynamics of the tRNA-modifying dimeric protein MnmE from E. coli, an ortholog of the human GTPBP3, upon adsorption on bioactive glass mimicking the composition of the classical 45S5 Bioglass. In addition, prior to protein attachment, the bioactive glass surface was modified with the protein coupling agent glutaraldehyde. Continuous wave EPR spectra of different spin labeled MnmE mutants were recorded to assess the dynamics of the attached spin labels before and after protein adsorption. The area of ...

  • Structural Information from Spin-Labelled Membrane-Bound Proteins
    Structural Information from Spin-Labels and Intrinsic Paramagnetic Centres in the Biosciences, 2013
    Co-Authors: Johann P. Klare, Heinzjurgen Steinhoff
    Abstract:

    Site-directed spin labelling (SDSL) in combination with electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for the investigation of the structure and conformational dynamics of biomolecules including membrane proteins under native-like conditions. EPR spectroscopy of the spin-labelled molecules provides information about the spin label side chain mobility, its solvent accessibility, the polarity of its immediate environment and intra- or intermolecular distances to another paramagnetic centre or spin label. This chapter provides an overview of the basics as well as recent progress in SDSL and related EPR techniques. Continuous wave EPR spectra analyses and pulse EPR techniques are reviewed with special emphasis on applications to the membrane-embedded sensory rhodopsin–transducer complex mediating the photophobic response of the halophilic archaeum Natronomonas pharaonis, the maltose ABC importer MalFGK2 and the mechanosensitive channel MscS.

  • Spin labeling EPR
    Photosynthesis Research, 2009
    Co-Authors: Johann P. Klare, Heinzjurgen Steinhoff
    Abstract:

    Site-directed spin labeling in combination with electron paramagnetic resonance spectroscopy has emerged as an efficient tool to elucidate the structure and conformational dynamics of biomolecules under native-like conditions. This article summarizes the basics as well as recent progress of site-directed spin labeling. Continuous wave EPR spectra analyses and pulse EPR techniques are reviewed with special emphasis on applications to the sensory rhodopsin-transducer complex mediating the photophobic response of the halophilic archaeum Natronomonas pharaonis and the photosynthetic reaction center from Rhodobacter sphaeroides R26.

Gary A Lorigan - One of the best experts on this subject based on the ideXlab platform.

  • Probing Structural Properties of KCNE1 Membrane Protein: A Site-Directed Spin Labeling EPR Study
    Biophysical Journal, 2014
    Co-Authors: Megan M. Dunagan, Indra D Sahu, Andrew F Craig, Rongfu Zhang, Robert M Mccarrick, Gary A Lorigan
    Abstract:

    KCNE1 is a single-transmembrane protein found in heart that modulates the activity of the KCNQ1 voltage-gated potassium channel. KCNE1 is very important for proper cardiac function. However, the structure of KCNE1 in a more native membrane environment is not completely understood. Site-directed spin labeling (SDSL) electron paramagnetic resonance (EPR) spectroscopy has emerged as a well-established method to study the structural properties of membrane proteins. In this study we have used continuous wave EPR and pulsed EPR techniques in combination with the SMA-Lipodisq nanoparticles based sample preparation to obtain more accurate and precise EPR data to answer pertinent structural questions on KCNE1. CW-EPR and DEER data were collected on several single and double spin labeling sites on KCNE1 in micelles, proteoliposomes and lipodisqs. We obtained a significant improvement in the quality of EPR measurements in lipodisq samples compared to proteoliposomes. The structural and dynamic properties of KCNE1 will be discussed.

  • The g = 2 multiline EPR signal of the S2 state of the photosynthetic oxygen-evolving complex originates from a ground spin state.
    Biochimica et biophysica acta, 1992
    Co-Authors: R. David Britt, Gary A Lorigan, Kenneth Sauer, Melvin P. Klein, Jean-luc Zimmermann
    Abstract:

    Abstract The amplitude of the g = 2 Mn ‘multiline’ EPR signal of the S 2 state of the photosynthetic oxygen-evolving complex varies inversely with temperature, indicating that this signal arises from a ground spin state. Electron spin echo experiments at temperatures of 4.2 K and 1.4 K show such Curie-law behavior of the g = 2 multiline EPR signal, as do Continuous-Wave EPR experiments performed at a non-saturating microwave power in the range from 15.0 K to 4.2 K.