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The Role of Diffusion in NMR Proton Relaxation Enhancement by Ferritin

Boss, Michael
http://rave.ohiolink.edu/etdc/view?acc_num=osu1275484465

Abstract Details

2010, Doctor of Philosophy, Ohio State University, Physics.
By using binary solutions of water and glycerol, we controlled diffusion so as to better understand its role in the relaxation rate enhancement of protons in the vicinity of ferritin at 7 tesla. The slower diffusion rates and higher external magnetic field used in these experiments are more consistent with the conditions expected in MRI experiments. New data was obtained on the diffusion coefficients of water and glycerol in binary solutions with relatively dilute amounts of glycerol. The effects of chemical exchange in such systems was also quantified. Two main relaxation mechanisms have been proposed for protons in the vicinity of ferritin: an outer-sphere mechanism (OS) in which spins diffuse past ferritin and experience a changing Larmor frequency by moving through the ferritin’s magnetic field, and a proton exchange dephasing mechanism (PE), where protons temporarily reside on the surface of the ferritin core and sample a single, enhanced, Larmor frequency. At high-field, the OS mechanism becomes increasingly important because of a quadratic dependence on field strength, versus linear for the competing mechanism involving proton exchange. It was found that the relaxation enhancement of protons of both water and glycerol in the presence of ferritin was inversely proportional to their diffusion coefficients, in agreement with the OS model of relaxation enhancement. The strength of the relaxation enhancement on inverse diffusion coefficient was weaker for slow-diffusing glycerol than for water: glycerol molecules spent more time in a weaker magnetic field, indicating that glycerol did not approach the ferritin core as closely as water, potentially answering questions about molecular intake into the ferritin structure. The results of these experiments have important implications for the quantification of brain iron in vivo.
P Chris Hammel (Advisor)
Klaus Honscheid, PhD (Committee Member)
Thomas Lemberger, PhD (Committee Member)
Nandini Trivedi, PhD (Committee Member)
108 p.
Physics
ferritin; relaxation; water; glycerol; diffusion; outer-sphere; chemical exchange; protons; NMR

Recommended Citations

Citations

  • Boss, M. (2010). The Role of Diffusion in NMR Proton Relaxation Enhancement by Ferritin [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275484465

    APA Style (7th edition)

  • Boss, Michael. The Role of Diffusion in NMR Proton Relaxation Enhancement by Ferritin. 2010. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1275484465.

    MLA Style (8th edition)

  • Boss, Michael. "The Role of Diffusion in NMR Proton Relaxation Enhancement by Ferritin." Doctoral dissertation, Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275484465

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.