The N-H vibrational modes of peptides at ca. 3( are essentially localized oscillators. They undergo Fermi resonance with N-H bends. The anharmonicity of these N-H vibrations allows them to be seen in the third order nonlinear response and hence in two-dimensional spectroscopy. Since the modes are local the assembly of peptide N-H vibrators can be considered to be a set of N coupled oscillators. The 2D experiments can yield couplings between the various oscillators. The couplings can be used to establish the three-dimensional structure of the peptide. The data obtained in these experiments will be complimentary to those found for amide couplings. With both sets of couplings the determination of peptide structure will be greatly enabled. The goal is top obtain structures at high time resolution and data acquisition rate. The research underway involves the construction of a 3( based nonlinear IR spectrometer. Three methods will be possible with this new apparatus (1) pump/probe where the two dimensions arise from a Fabry-Perot interferometer setting and the array detector dispersion (2) transient grating, which uses three beams (3) spectrally resolved heterodyned photon echo which utilizes two time delays.
Showing the most recent 10 out of 128 publications
