Applications of a Medium Bandwidth (100 MHz) Chirped-Pulse Fourier Transform Microwave Spectrometer for the study of Model Peptide Systems


Kevin O. Douglass, Francis Lovas, David F. Plusquellic



         The current research is focused on determining the conformational structure of peptides and peptide analogues in the gas phase.  The system we have studied is acetylphenylalanine methyl ester (Ac-Phe-OMe), which has two peptide bonds structurally characterized by the Ramachandran angles φ (Cα-N) and ψ (Cα-C).  The Ramachandran angles determine the secondary structure of the peptide.  Some examples of secondary structures are alpha helix, beta turn, and gamma linkage.  A large protein may contain many types of secondary structures, which interact to form the three dimensional structure of the peptide.  Microwave spectroscopy is used to record the rotational spectrum of the peptide.  Fitting of the rotational spectrum is used to determine the structure of the molecule.  We have recently built a Chirped-Pulse Broadband Fourier Transform Microwave (CP-FTMW) spectrometer that improves acquisition speed and analysis.  A laser desorption/ablation source is being developed that will provide the tools needed to investigate peptides and peptide analogues of increasing size and complexity.  Due to the small size of these molecules, high level quantum chemical calculations are possible and the results may be compared directly to the experimental data.  The calculations are used to correlate the experimentally determined parameters to a specific conformational form(s).  These results also serve as benchmark data for validation of predictions from classical force field programs such CHARMm or Amber used to model much larger biomolecular systems.  By performing precise measurements on model peptide systems we aim to understand the formation of secondary structures and potentially use these building blocks to gain insight into protein folding.  



Author Kevin O. Douglass

Mentor David F. Plusquellic

Physics Laboratory

Biophysics Group

Division 844.06

Building 216

Room B227

Mail Stop 8443

Phone 301-975-6489

Fax     301-975-6991

Sigma Xi members No