Date : Wednesday, January 30, 2002

Time : 4:30 PM

Location: Willet Science Center Room 109

**Professor Jeff Denny**

Department of Mathematics

Mercer University

**"PISEMA Powder Patterns and PISA
Wheels"**

**Abstract:** Solid-state NMR experiments have proven to be powerful tools for
investigating structures of membrane proteins, which are difficult to study using solution NMR or x-ray crystallography. Resonance patterns
observed in 2D solid-state PISEMA (polarization inversion spin exchange at magic angle) spectra have been
shown to yield structural details of the protein. This talk presents a mathematical discussion of the PISEMA
powder spectrum as the image in the frequency plane of a quadratic function from
the sphere of unit vectors. Based on this analysis of powder patterns, a method will be discussed for solving systems of quadratic
equations to determine possible structures of a protein. Parametric equations for PISA
wheels will also be presented, which are specific patterns observed in PISEMA spectra of oriented peptides. These wheels are
useful both in assigning resonances and in determining the orientation of a peptide with
respect to the magnetic field.

Please join us for light refreshments at 4:15. We hope to see you there!