ABSTRACT

Basic Information

Abstract Number: 1230 - 4
Author Name: Sanford A Asher - University of Pittsburgh
Session Title: Pittsburgh Spectroscopy Award
Event Type: Awards
Event Title: UV Raman Studies of Protein and Peptide Structure and Folding Studies

Presider Name:Singh Manocha
Affiliation:The Pittsburgh Conference

Date: Tuesday, March 19, 2013
Start Time: 02:45 PM (Slot #4)
Location: 114

Abstract Content

We developed a powerful method to follow the evolution of secondary structure in peptides and proteins. UV Raman excitation into the ~200 nm peptide bond electronic transitions enhance peptide bond amide vibrations of the backbone. A particular band (the amide III[sub]3[/sub]) reports on the Ramachandran psi angle and peptide bond hydrogen bonding. This band is Raman scattered independently by each peptide bond with insignificant coupling between adjacent peptide bonds. Isotope editing of a peptide bond (by replacing the C[sub]alpha-[/sub] H with C[sub]alpha-[/sub] D) allows us to determine the frequency of individual peptide bonds within a peptide or protein to yield their psi angles. Consideration of the Boltzmann equilibria allows us to determine the psi angle Gibbs free energy landscape along the psi (un)folding coordinate that connects secondary structure conformations. The psi angle coordinate is the most important reaction coordinate necessary to understand mechanism(s) of protein folding.

We examine the details of peptide folding conformation dynamics with laser T-jumps where the water temperature is elevated by an 1.9 [micro]M IR nsec laser pulse and we monitor the ~200 nm UV Raman spectrum as a function of time. These spectra show the time evolution of conformation. We will discuss the role of salts on stabilizing conformations in solution.