Our research group is interested in the development and application of fast spectroscopic techniques to study problems of electron, proton, and energy transfer on a fundamental level as well as in systems of biological relevance. Investigation of the chemistry and dynamics of biological systems is a major focus of our research group. The principle tool in our laboratory is ultrafast spectroscopy. The development and use of fast spectroscopic techniques is central to our research since most of the phenomena that we investigate occur in the femtosecond (1 x 10-15 s) and picosecond (1 x 10-12
s) time domains.
One problem we are addressing is the characterization and exploitation of optical probes of protein structure and dynamics. A central theme of our efforts is to understand the dynamic aspects of proteins that are involved in their function. We have discovered that the nonnatural amino acid, 7-azatryptophan, is amenable to peptide synthesis and that bacteria can be grown on media containing it and produce functional protein. Furthermore, 7-azatryptophan is spectroscopically distinguishable from its natural counterpart, tryptophan, which to date has been used as an optical probe of proteins. Equally important is that the excited-state photophysics of 7-azatryptophan lend themselves much more easily to interpretation than those of tryptophan. A feature of 7-azatryptophan that renders it a powerful probe is its enormous sensitivity to the molecules responsible for its solvation. Understanding this solute-solvent interplay is a major part of our program.
We are developing light-induced antiviral and antitumor agents and trying to understand the physical-chemical basis of their action. The naturally occurring polycyclic quinone, hypericin, can deactivate the human immunodeficiency virus (HIV) in the presence of light. Exciting results from our laboratory are that hypericin executes an excited-state intramolecular proton transfer reaction on the picosecond time scale, and that it is capable of acidifying the surrounding medium in the presence of light. We currently are working to elucidate the excited-state processes in terms of current theories of proton transfer, to clarify the mechanism or mechanisms of antiviral activity, and to develop antiviral and antitumor therapies based on the light-induced properties of hypericin and its analogs such as hypocrellin . We are also investigating the behavior of hypericin in complex with biologically significant molecules, such as GST.
We have designed and constructed spectroscopic apparatus for the real-time detection of fecal contamination on animal carcasses. We are extending this technology to develop real-time techniques for detecting factors responsible for transmissible spongiform encephalopathies (TSEs), e.g., mad cow disease and Creutzfeldt-Jakob disease (CJD).
Our program encourages and requires collaboration with other research groups on the Iowa State University campus and makes much use of synthetic organic chemistry, molecular biology, and virology. We have numerous collaborations with other research groups in the United States and in other countries.