The spectral and kinetic properties of Chlorobium thiosulfatophilum cytochrome c-555 have been investigated and are compared to analogous properties of procaryotic and eucaryotic c-type cytochromes. The circular dichroism spectra are similar for c-type cytochromes of a given class and effects arising from specific amino acid substitutions are determined. The oxidation-reduction state dependence of the spectra in the near-ultraviolet region is interpreted in terms of changes in hydrogen bonding and polarity of the environment of aromatic amino acid residues in close proximity to heme iron resulting from small structural changes. An electrostatic model of bimolecular rate constants is developed to adequately describe the electric field effects for accurate computation of intrinsic rate constants. Structural models of bimolecular complexes of cytochrome c and flavodoxin or cytochrome b₅, developed by other investigators, are used to constrain the dielectric coefficients of the electrostatic model. Using these constraints, the relative contributions of ionic and dipolar interactions to the intermolecular electrostatic potential energies are estimated for several c-type cytochrome reactions. The ionic contribution is adequately described by the charged residue interactions in the region of intermolecular contact, and the dipolar contribution is adequately described by the molecular dipole moment. Oxidation-reduction reactions of cytochrome c-555 with small molecule reagents suggest a mechanism of electron transfer that is similar to other c-type cytochromes. In general, electron transfer may be preceded by formation of a bimolecular collision complex or may occur during the collision. Further, the ionic strength dependence of second-order rate constants indicates that molecular electric fields significantly affect the bimolecular reaction rates. Calculated intrinsic rate constants are dependent on the difference between oxidation-reduction potentials of the reactants as predicted by Marcus outer sphere electron transfer theory. The mechanism of reduction of c-type cytochromes by flavodoxin semiquinone is similar to the mechanism of electron transfer reactions involving small molecules. Thus, principles involved in protein-small molecule reactions are also involved in protein-protein reactions.

Thesis (M.S.)--Tennessee Technological University, 2009. / Title from title page screen (viewed on Mar. 12, 2010). Bibliography: leaves 89-95.

No description available.

Cytochrome c was immobilized to several supports to study the effects of immobilization on the molecule and to serve as a model for the in vivo system. Immobilization was accomplished by covalent attachment of cytochrome c to the support surface, either Sepharose 6MB or glassy carbon. The effect of the coupling conditions on the covalent attachment reaction was studied with Sepharose 6MB. The reactive groups were monitored colorimetrically and were highly susceptible to hydrolysis. Correction for hydrolysis indicated that the covalent attachment reaction was first order with respect to reacted groups. Coupling conditions most affecting the amount of attached cytochrome c were the initial cytochrome c concentration, temperature, and pH. A detailed study of the resulting immobilized cytochrome c was conducted based on its three characteristic properties: spectra, oxidation reduction potential, and biological activity. The spectral properties demonstrated that no major conformational changes had occurred upon immobilization since the spectra were essentially the same. The redox potentials for most samples of immobilized cytochrome c loaded with different amounts of protein were found to be 20-25 mV lower than native cytochrome c (+ 270 mV). Two samples, the heaviest loaded, were approximately equal to the native protein suggesting that they may be least affected by immobilization. The biological activity measurements provide an indication of the ability of the molecule to function properly. The Michaelis constant (K(m)) for cytochrome oxidase and reductase with immobilized cytochromes c were significantly higher (20-400X) than the K(m) for soluble cytochrome c. The higher K(m)s reflect that about 1% of the immobilized cytochrome c is availble for reaction in agreement with distribution and exclusion studies. Correction of the immobilized cytochrome c K(m)s for available protein results in values similar to the soluble cytochrome c K(m). Immobilization of cytochrome c to glassy carbon was performed by two procedures employing a carbodiimide or 4-vinylpyridine as the coupling reagents. The former resulted in electrodes with higher specific activities and lower protein loadings than the latter. In both cases up to 60% of the immobilized protein was held by adsorption on the surface. Protein coverages were approximately 10⁻⁸ to 10⁻⁹ moles/cm² which corresponds to 100-800 layers.

Thesis (M.Sc.) --University of Adelaide, 1946. / Typewritten copy.

Thesis (B.S.) Magna Cum Laude--Butler University, 2008. / Includes bibliographical references (76-77).

No description available.

by Chu Wing Fai. / Parallel title in Chinese characters. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1988. / Bibliography: leaves 89-92.

Thesis--Leiden. / Summaries in English and Dutch. Includes reprints of papers previously published in various journals. Includes bibliographical references.

published_or_final_version / Chemistry / Master / Master of Philosophy