Faculty Page

 

 

 

 

 

 

Watson J. Lees

Associate Professor
Department of Chemistry and Biochemistry
Florida International University
11200 SW 8th St.
Miami, FL, 33199
Tel: 305-348-3993
Fax: 305-348-3772
email: leeswj@fiu.edu

Open postdoctoral position

Individuals interested in studying the folding of disulfide containing proteins in the presence of small molecules should apply. The position will involve the development and application of biochemical assays for protein folding and the use of HPLC and UV-vis spectroscopy and will be funded by an NSF grant

Research Activities

Folding of disulfide containing proteins in vitro

Disulfide bonds are essential for the activity of many extracellular proteins including almost all pharmaceutically relevant proteins, e.g. insulin. The formation of these essential bonds can occur either in vitro or in vivo. In vivo, the process is catalyzed by various chaperones including protein disulfide isomerase (PDI). Unfortunately, in many cases when proteins are overexpressed or produced in foreign organisms, the in vivo chaperones are not sufficient to allow the formation of the correct disulfide bonds and the proteins precipitate as aggregates. These protein aggregates, however, can be resolubilized and then folded in vitro to produce active protein. The in vitro folding process is slow but the rate can be increased by the addition of a redox buffer containing a small molecule thiol and its corresponding disulfide. Traditionally, the small molecule thiol is glutathione (GSH), mercaptoethanol (ME), or dithiothreitiol (DTT)

A dimer of insulin with the disulfide bonds expanded and highlighted in green

Protein Disulfide Isomerase (PDI)

The group is interested in gaining a greater understanding of the protein foldin process and in increasing the slow rate of in vitro protein folding. We investigate the folding of the disulfide containing protein, ribonuclease A (RNase A),in the presence of non-traditional thiols. Using these non-traditional thiols we have increased the rate of protein folding by up to a factor of 20 over that using the traditional thiol glutathione. In addition, we have gained information about the folding process. We plan to investigating the generality of our approach by applying it to the folding of other disulfide containing proteins. Also, we would like to improve upon our the already enhanced folding rates by examining additional non-traditional thiols.

Ribonuclease A(RNase A) with the four disulfide bonds enlarged and highlighted in green

 

Photochromic organic compounds

An additional research area pursued by the group involves photochromic organic compounds. Photochromic organic compounds exist in at least two forms that possess different absorption spectra and can be interconverted with light. One example would be Transition Lenses, which are incorporated in eyeglasses and darken upon exposure to outside light. In the case of Transition Lenses form A (clear compound) is converted to form B (dark compound) with UV light and then form B is converted back to form A thermally. We are interested in compounds that are thermally stable in both forms, c be interconverted in both directions with wavelength specific light and can be used for optical information storage (form A = 0 and form B = 1) or as optical switches. Several attributes are required for thes applications including readily distinguishable absorption spectra for each form, efficient photoreactions and both thermal and photochemical stability. As the availability of photons generally increases with increasing wavelength, it is also desirable to utilize materials that absorb light well into the visible region. The focus of our work has been on improving the hydrolytic, thermal and photochemical stabilities of the fulgide class of compounds by performing structure-activity relathionships. We have synthesized over twenty novel fulgides using our improved synthetic sequence and analyzed them for their photochemical and physical properties. Using this knowledge we are currently preparing improved photochromic organic materials.