Date of Award

1-1-2016

Document Type

Dissertation

Degree Name

Ph.D.

Department

Chemistry and Biochemistry

First Advisor

Sandra S. Eaton

Abstract

Pulsed and continuous wave electron spin resonance were used to characterize the relaxation rates of selected paramagnetic metals at 5 to 15 K or 80 K, measure the impact of these rapidly relaxing metals on the relaxation rates of nitroxide radicals in glassy mixtures and in discrete complexes, and characterize novel iron-sulfur proteins.

Spin echoes were observed at 5 to 7 K in 1:1 water:glycerol for Er(diethylenetriamine pentaacetic acid)2- (Er(DTPA)2-), Co(DTPA)3- and aquo Co2+ with relaxation times that are strongly temperature dependent. Deep proton modulation was present on spin echo decays (Ch. 3). For Gd3+ and Gd(DTPA)2- in 1:1 water:glycerol at 80 K T1 is 1.5 to 2 mu sub-s and T2 is about 0.5 mu sub-­s. When Gd3+ is loaded into P22 viral capsids with local concentrations up to about 180 mM the relaxation rates at 80 K are dramatically increased (Ch. 6).

Relaxation rates for 0.2 mM nitroxide radical in mixtures with rapidly relaxing metal ions in 1:1 water:glycerol glasses were measured at temperatures between 20 and 200 K (Ch. 4). The enhancement of the relaxation rate of the nitroxide increases in the order Co2+ < Er3+ < Dy3+ < Tm3+. The maximum spin-lattice relaxation enhancement occurs at about 35 K for Dy3+, 40 K for Er3+, and 80 K for Co2+. Changes in T1 are a much larger fraction of the non-interacting values than for T2.

Complexes were prepared in which an ethylenediamine tetraacetic acid (EDTA) metal binding site was separated via linkers of varying lengths from a nitroxide radical. Energy minimization calculations found distances of 1.6, 2.4, and 3.4 nm between the metal binding and nitroxide N-O groups. The interaction between a paramagnetic metal bound to the EDTA and the nitroxide were characterized by measuring relaxation times and continuous wave power saturation.

The temperature dependence of the electron spin-lattice relaxation rates for iron-sulfur clusters from Pyruvate Formate Lyase- Activating Enzyme, hydrogenase and Mycofactin C protein were studied (Ch. 7). Compared to other iron-sulfur proteins the relaxation rates were relatively slow.

Provenance

Recieved from ProQuest

Rights holder

Priyanka Aggarwal Aggarwal

File size

211 p.

File format

application/pdf

Language

en

Discipline

Chemistry

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