The Study of Conformational Fluctuations in Proteins by Use of Optical Probes.
Final technical rept. Sep 80-Sep 83,
HEBREW UNIV JERUSALEM (ISRAEL)
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The purpose of this research was to ascertain the existence and to study the configurational fluctuations in proteins, fluctuations which enable small molecules to penetrate the protein structure. To this end the quenching of the tryptophan phosphorescence in Liver Alcohol Dehydrogenase by oxygen and by iodide ions was studied. The quenching could be interpreted in terms of diffusion of the quenchers through the protein network while its temperature dependence measured the activation energy necessary for the above fluctuations to take place. In addition to using tryptophan also the study of porphyrins as potential optical probes in proteins was undertaken. The excited state electron transfer reactions of the model compound Zn octoethylporphyrin, which constitute the main pathway for its deexcitation, were investigated with a view of using a similar redox systems to quench the Zn porphyrin luminescence when incorporated in apomyoglobin or apohemoglibin instead of the non luminescent heme group. Zn substituted myoglobin was prepared and its optical properties studied. Author