title: The structure of tri-proline in water probed by polarized Raman, Fourier transform infrared, vibrational circular dichroism, and electric ultraviolet circular dichroism spectroscopy.
abstract: Tripeptidesserve as model systems for understanding the so-called random-coil state of peptides and proteins. While it is well known that polyproline or proline-rich polypeptides adopt the very regular polyproline-II (PPII) or left-handed 3(1)-helix conformation, it was thus far not clear whether this is also the predominant structure adopted by proline-containing tripeptides. To clarify this issue, we have investigated the amide I' band profile in the ir, isotropic, and anisotropic Raman, and vibrational circular dichroism (VCD) spectrum of cationic and zwitterionic tri-proline in D(2)O. The data were analyzed by modifying a recently developed algorithm, which allows one to obtain the central dihedral angles of tripeptides from the amide I' band intensities (R. Schweitzer-Stenner, Biophysical Journal, 2002, Vol. 83, pp. 523-532). Our analysis revealed that the peptide adopts a nearly canonical PPII structure in water with psi and phi values in the range of 175 degrees -165 degrees and -70 degrees -(-80 degrees ), respectively. This is fully confirmed by the respective electronic ultraviolet-CD spectra. Our result indicates that the strong PPII propensity of trans proline results from local interactions between the pyrrolidine ring and the backbone and is not due to any long-range interactions.
authors.affiliation: Department of Chemistry, University of Puerto Rico, Río Piedras Campus, San Juan, Puerto Rico 00931, USA. RSchweitzer-Stenner@drexel.edu
authors.forename: Reinhard
authors.initials: R
authors.lastname: Schweitzer-Stenner
authors.forename: Fatma
authors.initials: F
authors.lastname: Eker
authors.forename: Alejandro
authors.initials: A
authors.lastname: Perez
authors.forename: Kai
authors.initials: K
authors.lastname: Griebenow
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Cao
authors.forename: Laurence A
authors.initials: LA
authors.lastname: Nafie
mesh_terms: D000409:Alanine / Q000737:chemistry; D002942:Circular Dichroism; D006358:Hot Temperature; D009842:Oligopeptides / Q000737:chemistry*; D011392:Proline / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman
chemical_list: D009842:Oligopeptides; D011392:Proline; D000409:Alanine