DESCRIPTION: The response of proteins to sequences of femtosecond infrared pulses provides a multidimensional view into their equilibrium distribution of structures and snapshot pictures of fast-triggered dynamical events. Analyzing these experiments requires advanced computational tools for assigning regions in the resulting multidimensional correlation plots to specific secondary-structure elements and their couplings. A differential sensitivity analysis technique based on a perturbation of the local (real space) Hamiltonian is developed to achieve that goal. Application to the amide I region of a small globular protein reveals regions associated with the -helix, -sheet, and their coupling. Comparison of signals generated in different directions shows that the double-quantumcoherence signal has a higher sensitivity to the couplings compared with the single-quantum-coherence (photon echo) technique.
REFERENCE: W. Zhuang, D. Abramavicius and S. Mukamel ¡°Dissecting Coherent Vibrational Spectra of Small Proteins into Secondary Structural Elements by Sensitivity Analysis¡± Proceedings of National Academy of Sciences, USA.2005, 102, 7443-7448