Heme proteins spectroscopic characterization

The study of model compounds or simply, models of heme proteins is very helpful in elucidating structure-function relationships. Models are compounds with low molecular weight that imitate struetural, spectroscopic, or functional details of the original enzymes. The latter are macromolecules and hence more difficult to study. Synthetic models for states 7-5 must be thiolate-ligated. Such models have been prepared and extensively characterized. The models from several laboratories have recently been reviewed [22]. A model system having a ferric-peroxide composition, as is present in 6, has also been described [40]. Relevant models are listed in the tables (see Sects. 3.1 and 4.1.1). Model chemistry has been extremely important in characterizing these intermediates. 

Spectroscopic Methods to Characterize Metal Centers in Non-heme Iron Proteins... 

Cytochrome c (cyt. c) has become a major protein for testing new approaches and techniques in protein science.1 This is partly due to the venerable position that cytochrome c holds in the field of biochemistry since it was isolated and characterized more than 70 years ago. Cyt. c was one of the first proteins to be sequenced,2 and to have its X-ray structure determined in 1967.3 Cyt. c also has the advantage of stability and a spectroscopically distinct heme group. More than 23,000 articles mentioning cyt. c were published between 1945-2002 (ISI Web of Science). Here, we describe an approach to tetraphenylporphyrin-based protein surface receptors and the characterization of their interactions with the principal target cyt. c. 

Cytochrome c oxidase is the terminal member of the respiratory chain in all animals and plants, aerobic yeasts, and some bacteria." " This enzyme is always found associated with a membrane the inner mitochondrial membrane in higher organisms or the cell membrane in bacteria. It is a large, complex, multisubunit enzyme whose characterization has been complicated by its size, by the fact that it is membrane-bound, and by the diversity of the four redox metal sites, i.e., two copper ions and two heme iron units, each of which is found in a different type of environment within the protein. Because of the complexity of this system and the absence of detailed structural information, spectroscopic studies of this enzyme and comparisons of spectral properties with 02-binding proteins (see Chapter 4) and with model iron-porphyrin and copper complexes have been invaluable in its characterization. 

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