Abstract

During the past several years, we have developed a fluorescence technique to study the disorder of the protein structure. The method is based on the determination of the fluorescence lifetime of tryptophan. It is now well established that the fluorescence lifetime of the tryptophan residues in proteins is not single exponential and that the value of the lifetime can span several orders of magnitudes in different proteins. The study of proteins containing a single tryptophan residue has shown, in the majority of cases, that the decay requires several exponential terms to be satisfactorily described. Each component in the multiexponential decay has been attributed to different protein conformations. An alternative viewpoint is to describe the decay using a continuous distribution of decay rates. Using this approach, it is possible to quantify the "disorder" in the protein's structure by the width of the lifetime distribution. It has been found that at lower temperatures the width of the distribution is always larger than at higher temperatures.

© 1992 Optical Society of America