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" EPR investigations of anisotropic interaction and Cole-Davidson parameters, novel phospholipids, and newly synthesized buckminsterfullerenes using nitroxide spin probes "
Y. T. A. Al-Janabi
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Latin Dissertation
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English
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| Record Number
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1112879
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TLpq304431755
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| Main Entry
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Y. T. A. Al-Janabi
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| Title & Author
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EPR investigations of anisotropic interaction and Cole-Davidson parameters, novel phospholipids, and newly synthesized buckminsterfullerenes using nitroxide spin probes\ Y. T. A. Al-Janabi
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| College
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King Fahd University of Petroleum and Minerals (Saudi Arabia)
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| Date
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1997
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1997
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| Degree
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Ph.D.
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| Page No
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292
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| Abstract
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This study can he divided into three major parts. In the first part, the dynamics, represented by the anisotropic interaction parameter usd\kappausd and the anisotropy of rotational reorientation N, of two nitroxide spin probes in toluene were thoroughly investigated by Electron Paramagnetic Resonance (EPR) spectroscopy at the four microwave bands L (1 GHz), S (4 GHz), X (9.5 GHz), and Q (35 GHz). The relatively small and large probes are perdeuterated-2,2,6,6-tetramethyl-4-piperidone-N-oxide (abbreviated as PD-Tempone) and 4-N(p-n-butylbenzilidine) amino 2,2,6,6-tetramethylpiperidine 1-oxide (abbreviated as BBTMPO), respectively. PD-Tempone was consequently used in the second part to study the magnetic arrangement of phospholipid bilayer in the presence of the rare earth metal ions ytterbium(III), Yb and yttrium(III), Y by the EPR technique. The phospholipid bilayer consisted of the long chain 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), the short chain 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC), and KCl aqueous solution. In the third part, buckminsterfullerene (C{60}) adducts of nitric oxide (NO) and nitroxide spin probes were synthesized and investigated by EPR spectroscopy. For PD-Tempone, values of the usd\kappausd parameter were similar at the four microwave bands: 0.40 at L-Band and 0.44 at S-, X-, and Q-Bands. The Cole-Davidson parameter usd\betausd was introduced successfully to the spectral densities for the first time. A usd\betausd value of 0.55 was used at L-Band to unify the results of usdN,\ \kappausd and the magnetic alignment of PD-Tempone in toluene. To determine the usd\kappausd values for BBTMPO in toluene at the four microwave bands, the solute hydrodynamic radius was determined at room temperature by the capillary translational diffusion experiment. Assuming a slip boundary condition, a value of 5.6 A was obtained. Lineshape analysis of the EPR spectra of BBTMPO was performed for the first time to account for inhomogeneous broadening resulting from the twelve protons adjacent to the NO-moiety. Values of usd\kappausd at L-, S-, and X-Bands were similar and were equal to 0.23, 0.24, and 0.25, respectively. The usd\kappausd value at Q-Band was much smaller (0.08) which indicated reduced coupling between the spin probe BBTMPO and the solvent toluene. The X-band EPR results of PD-Tempone in DMPC/DHPC (I), DMPC/DHPC + Yb (II), and DMPC/DHPC + Y (III) were typical of lyotropic smectic mesophases, i.e., the g-factor increased with temperature whereas the hyperfine splitting a decreased with temperature. Ordering parameters usdS\sbusd and usdS\sb{22}usd indicated 90 flipping of the bilayer after adding Yb and exposing the system to a static magnetic field of one Tesla. In the third part of this study, the adduct of C{60} and NO gave six transient EPR peaks which were attributed to gaseous NO molecules interacting with the twelve pentagons in the solid C{60}. Adsorbed NO2 molecules, which produced a single EPR line at the center of the six peaks, reduced the symmetry of C{60} resulting in six different sets of two equivalent pentagons. (Abstract shortened by UMI.)
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Chemistry
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Pure sciences
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