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Franzen Research Group
Physical, Biophysical and Biological Chemistry
       
 
people exploring science
 

The themes of the research in the Franzen group are bioremediation and biomedical applications of chemistry. We use physical techniques to characterize enzymes and plant viruses as tools to carry out the objectives of each project area. We use laser spectroscopy for study of vibrational bands and for time-resolved measurements. We use structural methods of X-ray crystallography and Nuclear Magnetic Resonance to obtain structural information relevant to enzymatic catalysis. With the broad categories stated above there are several specific project areas that have evolved as students have made discoveries. At present, we are focused on three discoveries that have more narrowly defined the research effort.

Discoveries

Perhaps it sounds a little presumptive to call something a discovery. However, the process of scientific investigation involves milestones that help define progress and new directions. For this reason, it is useful to call attention to the new insights that we have contributed.

  1. The internal inhibitor binding site of dehaloperoxidase-hemoglobin. This interesting protein was discovered about 15 years ago and is known as dual function enzyme. It is both a hemoglobin and a peroxidase. Originally, it was thought that a unique internal binding site was the substrate binding site. We have recently discovered that this internal binding site is an inhibitor binding site. It is remarkable that inhibitor binding competes with substrate binding even through the substrate binds on the outside and the inhibitor binds on the inside of the protein. Thus, the is perhaps the first example of two-site competitive inhibition, known in the textbooks as non-classical competitive inhibition.
  2. The reversible opening and closing transition of the plant virus, Red clover necrotic mosaic virus. The transition in this virus permits drugs to be loaded inside a protein shell. The drugs are sequestered inside the virus, which means that they do not leak and they can be delivered to tumors. Recent tumor targeting data show that a virus modified with tumor-targeting peptides can kill tumors. What is most remarkable is that the toxic drugs used to kill the tumor apparently pass through the liver and are excreted without harming the body. The virus is a true targeting agent.
  3. Surface plasmon resonance on conducting metal oxides. Surface plasmon resonance is widely used as an analytical method for determining binding interactions in biological samples. All commerical surface plasmon resonance uses gold surfaces because of the unique optical properties of gold, which can seen by its unusual color as a metal. Gold is not a perfect reflector of visible light and has a yellowish luster due to its plasmon band. We have shown that a similar phenomenon can be used in a range of conducting metal oxides, which paves the way for new materials in this field. Conducting metal oxides are compatible with silicon technology, electrochemistry, and some are optically transparent. While gold will always be an important material, we are exploring a range of new optical phenomena that will expand the field of plasmon resonance sensing.
 
key publications
 
September 10, 2010

Publication of Biophysical Journal article showing the two-site competitive inhibition. read more…

 
September, 15 2009

Publication of our paper in Optics Letters showing the first hybrid plasmon. We layered gold nanoparticle layers onto indium tin oxide to makes a plasmonic material composed of two different conducting layers. The physics of this substrate has ramifications for how we use plasmonic materials in capture of light for solar energy as well as sensing applications. read more…

 
January, 2008

Publication of our paper in Chemical Communications showing the opening-closing transition of the plant virus, RCNMV (Red clover necrotic mosaic virus). This process was demonstrated to permit loading of nearly 1000 molecules of the chemotherapy agent doxorubicin. The loading density is higher than the commercial liposome preparation known as Doxil(TM).read more…

 

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