Department of Chemistry and Biochemistry

Research Synopsis: Biophysical Chemistry, Physical Chemistry, Analytical Chemistry:

Raman and time-resolved Raman spectroscopy of metalloporphyrins, related macrocycles, and protein systems.

 

Metalloporphyrins are pervasive in nature. They play important, key roles in many processes such as electron transfer, oxygen transport and storage, and conversion of light into chemical energy. They are also coming into prominence as components in alternate energy systems. While it is clear that reactivity of these macrocyclic systems is very sensitive to the immediate environment, this dependence is not well understood.

 

My research interests center around the use of spectroscopic techniques to study the physical properties of metalloporphyrins and related macrocyclic compounds, and how those properties are modulated by the surrounding protein or solvent environment.

My research interests resolve into four basic areas:

1) The excited state behavior of porphyrins and related molecules and the effect of the solvent environment upon their excited states;

 

2) Electron transfer mechanisms in metalloporphyrins, both in and out of protein systems;

 

3) The more difficult and long term question of how a porphyrin's reactivity is modulated by the protein matrix surrounding it in proteins such as myoglobin, hemoglobin, and cytochrome c;

 

4) The application of gathered information to problems such as energy collection and storage, hematoporphyrin photodynamic therapy, and protein structure-function relationships.

 

My group uses many spectroscopic techniques to probe the effects of environment upon metalloporphyrin reactivity. The primary spectroscopic tool used in this research will be resonance Raman spectroscopy. Some of the other techniques which will be employed include Infrared, Electron Spin Resonance, Fluorescence, and Optical Absorption spectroscopies.

 

Resonance Raman spectroscopy is a very sensitive technique which can be used to study the vibrational and electronic response of a chromophore at equilibrium and after perturbation. Often the excited state properties of a molecule like a porphyrin are much more sensitive to environmental factors than those of the ground state molecule. Transient and time resolved resonance Raman spectroscopy can provide detailed information concerning the vibrational and electronic dynamics of a molecular system. Pulsed lasers are used to probe the molecular system at discrete time delays after optical excitation with a pump laser pulse. This laboratory has a Nd:YAG laser system capable of producing high power pulses with either 20 ps or 10 ns wide pulses. Information gained by other time resolved techniques such as transient absorption and time resolved fluorescence spectroscopies. Development of instrumentation, electronics, and techniques to improve the sensitivity, resolution, and applications of Raman spectroscopy are also strong components of the research efforts of this laboratory.