title: UV resonance Raman investigation of a 3(10)-helical peptide reveals a rough energy landscape.
abstract: We used UVRRS at 194 and 204 nm excitation to examine the backbone conformation of a 13-residue polypeptide (gp41(659-671)) that has been shown by NMR to predominantly fold into a 3(10)-helix. Examination of the conformation sensitive AmIII(3) region indicates the peptide has significant populations of beta-turn, PPII, 3(10)-helix, and pi-helix-like conformations but little alpha-helix. We estimate that at 1 degree C on average six of the 12 peptide bonds are in folded conformations (predominantly 3(10)- and pi-helix), while the other six are in unfolded (beta-turn/PPII) conformations. The folded and unfolded populations do not change significantly as the temperature is increased from 1 to 60 degrees C, suggesting a unique energy landscape where the folded and unfolded conformations are essentially degenerate in energy and exhibit identical temperature dependences.
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
authors.forename: Zeeshan
authors.initials: Z
authors.lastname: Ahmed
authors.forename: Sanford A
authors.initials: SA
authors.lastname: Asher
mesh_terms: D015700:HIV Envelope Protein gp41 / Q000737:chemistry*; D010446:Peptide Fragments / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013696:Temperature; D013816:Thermodynamics
chemical_list: D015700:HIV Envelope Protein gp41; D010446:Peptide Fragments