title: Terahertz and far infrared spectroscopy of alanine-rich peptides having variable ellipticity.
abstract: Terahertz spectra of four alanine-rich peptides with known secondary structures were studied by terahertz time domain spectroscopy (THz-TDS) and by Fourier transform infrared spectroscopy (FTIR) using a synchrotron light source and a liquid-helium cooled bolometer. At ambient temperatures the usable bandwidth was restricted to 0.2-1.5 THz by the absorbance of water. The existence of a solvation shell around the peptide in solution was observed and its size estimated to be between 11 and 17 Å. By cooling the peptide solution to 80 K in order to reduce the water absorbance the bandwidth was increased to 0.1-3.0 THz for both THz-TDS and FTIR. Spectra were consistent with monotonic absorbance of the peptide and the existence of a solid amorphous low density solvation shell.
authors.affiliation: Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Tao
authors.initials: T
authors.lastname: Ding
authors.forename: Ruoyu
authors.initials: R
authors.lastname: Li
authors.forename: J Axel
authors.initials: JA
authors.lastname: Zeitler
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Huber
authors.forename: Lynn F
authors.initials: LF
authors.lastname: Gladden
authors.forename: Anton P J
authors.initials: AP
authors.lastname: Middelberg
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Falconer
mesh_terms: D000409:Alanine / Q000032:analysis / Q000737:chemistry*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D010455:Peptides / Q000032:analysis / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000379:methods*; D017356:Synchrotrons / Q000295:instrumentation*; D055068:Terahertz Spectroscopy / Q000379:methods*
chemical_list: D010455:Peptides; D000409:Alanine