Paul W. Chun and coworkers are continuing thermodynamic
studies on the fragment complementation reaction in ribonuclease S’. To investigate the role of Phe 8 and Met
13 in the stabilization of two S-peptides in their interaction with S-protein of RNase S’ system, the group will synthesize 13S and 20S peptides in which both Phe 8 and Met 13 amino acid residues have been replaced by other charged amino acids. The peptides-protein complementation reaction provides a way of delineating the effect of amino acid substitution on the stability of the complex in terms of location in the secondary structure. A two-pronged approach will be taken in the analysis of site-specific S-peptides-S-protein fragment complementation reactions. Experimental data on the Gibbs free energy change as a function of temperature using analytical ultracentrifugation of difference scanning calorimetric will be subject to thermodynamic analysis to determine the innate thermodynamic quantity ( the inherent chemical bond energy). Current studies focus on the
temperature-dependent heat capacity of reaction in biological systems, and its relationship to the recently-identified thermodynamic molecular switch. The Planck-Benzinger methodology can be effectively applied to the thermodynamic analysis of site-directed mutagenesis, and it is the best method for determining the heat of reaction in biological systems.

1967-1970 Assistant Professor, Dept. Of Biochem. & Mol.
Biol. University of Florida
1970-1978 Associate Professor, Dept. Of Biochem. & Mol.
Biol. University of Florida
1978 - present Professor, Dept. of Biochem. & Mol. Biol.
University Of Florida
1984 - 1985 Visiting Professor, Department of Biology,
Johns Hopkins University, MD
1985 Visiting Professor, Dept. of Biochem. Univ.of
Virginia, Charlottesville, VA;
1985 Visiting Professor, Dept. Biological Engineering,
KAIST, Seoul, Korea,