title: Two-dimensional infrared spectroscopy of peptides by phase-controlled femtosecond vibrational photon echoes.
abstract: Two-dimensional infrared spectra of peptides are introduced that are the direct analogues of two- and three-pulse multiple quantum NMR. Phase matching and heterodyning are used to isolate the phase and amplitudes of the electric fields of vibrational photon echoes as a function of multiple pulse delays. Structural information is made available on the time scale of a few picoseconds. Line narrowed spectra of acyl-proline-NH(2) and cross peaks implying the coupling between its amide-I modes are obtained, as are the phases of the various contributions to the signals. Solvent-sensitive structural differences are seen for the dipeptide. The methods show great promise to measure structure changes in biology on a wide range of time scales.
authors.affiliation: Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Asplund
authors.forename: M T
authors.initials: MT
authors.lastname: Zanni
authors.forename: R M
authors.initials: RM
authors.lastname: Hochstrasser
mesh_terms: D000081:Acetamides / Q000032:analysis; D010455:Peptides / Q000737:chemistry*; D017785:Photons; D013055:Spectrophotometry, Infrared / Q000379:methods
chemical_list: D000081:Acetamides; D010455:Peptides; C018595:N-methylacetamide