Double Well Potential Energy Surfaces in Biological Molecules

Jessica is currently studying two very different molecules that have similar potential energy surfaces.  1,3-Benzodioxole is a double ring system consisting of a benzene ring and a constrained five-membered ring containing two oxygen atoms.  Low frequency vibrations in this molecule include the pucker of the 5-membered ring and the flapping motion of one ring with respect to the other.  Each of these motions is symmetrical about the planar configuration leading to a ground state potential energy surface with a double well and split energy levels.

The second molecule is 1-phenylpyrrole.  Here the benzene ring and five-membered ring, which contains a nitrogen atom, are separated by a single bond.  The lowest frequency vibration is the twisting of one ring with respect to the other again causing a double well in the ground state.

Using rotationally resolved high resolution electronic spectroscopy, Jessica is characterizing the excited state of these molecules and confirming vibrational assignments.  Is the molecule more or less planar in the excited state?  Is splitting observed in the spectra? 

                   

 

Intramolecular Interactions in the Folding Nucleus of a Protein

Within the last decade, folding nuclei (sometimes called foldons) have been identified in some proteins. These are short sequences of amino acids that initiate folding and consistently fold in the same way.  By determining the shape of the protein backbone in the area of folding nuclei, interactions causing that shape can be identified.  This will lead to an understanding of why folding nuclei fold in the way that they do and why they do so consistently.

In 2008 Jessica worked under Michel Mons and François Piuzzi in Saclay, France studying a folding nucleus found in β-lactoglobulin using IR-UV double resonance spectroscopy.  Molecules studied include capped TrpTyr, TrpTyrSer, and TrpTyrSerLys.  She thanks the CEA in France and the University of Pittsburgh for funding for this project.  

            Based on the device used by Mons and Piuzzi, Jessica has added a laser ablation source to the low res (vibrationally resolved) lab.  Laser ablation produces gas phase samples of biologically relevant molecules with reduced decomposition compared to vaporization by heating.

 

      Jessica is a senior member of the Pratt Group.  She is originally from West Chester, PA and received her BSED in Chemistry and General Science Education from Indiana University Pennsylvania where she was a member of the Robert E. Cook Honors College.  After graduation, she taught several courses in chemistry, physics, and environmental science at Eastern York High School.  After graduation she plans to teach physical chemistry at a primarily undergraduate institution.