Measured electron spin relaxation rates in frozen solutions of azurin: Vitamin B12r and nitrosyl ferrous myoglobin
type: CreativeWork
description: Measured electron spin-lattice relaxation rates in frozen glycerin/water solutions at temperatures from 1.4 K to 20 K are reported for a copper-containing protein, azurin, and a cobalt -containing bi omol ecul ar complex, vitamin B 12r, which is the paramagnetic product of the photolysis of coenzyme B 12. The results are interpreted in terms of a spectral dimensianality. Rates are also reported for nitrosyl ferrous myoglobin in frozen water solution, which ex hi bits a dominant one-phonon relaxation process at temperatures up to 20 K and thus provides no data from which to determine the spectral dimensionality. The aim of this study was to determine whether the anomolous variation of the relaxation rate with temperature observed in several iron-containing proteins is also present in proteins and large molecular complexes containing other paramagnetic ions. Within a model involving a two-phonon mechanism of relaxation, the anomalous temperature variations can be conveniently specified by a spectral dimensionality. The spectral dimensionality, m, is a parameter that indicates the variation of the vibrational density of states with frequency, i.e. p(v) ex: vm-1. It is named in analogy with the Debye vibrational density of states of crystalline solids in 1-, 2-, and 3-dimension a 1 space. At sufficiently high temperatures, a non-resonant, two-phonon relaxation mechanism, the Raman process, should dominate the relaxation of a paramagnetic ion unless low-lying (under 70 cm-1) electronic states are present. Low-lying excited states are common among rare earths and high spin ferric complexes, including many ferric proteins. The temperature dependence of a Raman relaxation rate for a Kremers ion (odd number of electrons) is T3+2m H the spectral dimensionality 1s m and the temperature is sufficiently low in comparison wHh E> = h Vmaxlk, the De bye temperature. The maxi mum values of m extracted from relaxation data on heme proteins, iron-sulfur proteins, and one copper-and-ir…
abstract: Measured electron spin-lattice relaxation rates in frozen glycerin/water solutions at temperatures from 1.4 K to 20 K are reported for a copper-containing protein, azurin, and a cobalt -containing bi omol ecul ar complex, vitamin B 12r, which is the paramagnetic product of the photolysis of coenzyme B 12. The results are interpreted in terms of a spectral dimensianality. Rates are also reported for nitrosyl ferrous myoglobin in frozen water solution, which ex hi bits a dominant one-phonon relaxation process at temperatures up to 20 K and thus provides no data from which to determine the spectral dimensionality. The aim of this study was to determine whether the anomolous variation of the relaxation rate with temperature observed in several iron-containing proteins is also present in proteins and large molecular complexes containing other paramagnetic ions. Within a model involving a two-phonon mechanism of relaxation, the anomalous temperature variations can be conveniently specified by a spectral dimensionality. The spectral dimensionality, m, is a parameter that indicates the variation of the vibrational density of states with frequency, i.e. p(v) ex: vm-1. It is named in analogy with the Debye vibrational density of states of crystalline solids in 1-, 2-, and 3-dimension a 1 space. At sufficiently high temperatures, a non-resonant, two-phonon relaxation mechanism, the Raman process, should dominate the relaxation of a paramagnetic ion unless low-lying (under 70 cm-1) electronic states are present. Low-lying excited states are common among rare earths and high spin ferric complexes, including many ferric proteins. The temperature dependence of a Raman relaxation rate for a Kremers ion (odd number of electrons) is T3+2m H the spectral dimensionality 1s m and the temperature is sufficiently low in comparison wHh E> = h Vmaxlk, the De bye temperature. The maxi mum values of m extracted from relaxation data on heme proteins, iron-sulfur proteins, and one copper-and-ir…
author: Muench, Philip James
language: en
keywords: electron spin relaxation, frozen solutions of azurin, vitamin B12, nitrosyl ferrous myoglobin
date published: 2011-06-20T13:57:26Z
date modified: 2026-07-22T22:25:24Z
provider: University of Illinois - Urbana-Champaign
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Illinois - Urbana-Champaign

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property ID: Handle
value: http://hdl.handle.net/2142/25446