Zhuang Wei, Abramavicius Darius, Mukamel Shaul
Department of Chemistry, University of California, Irvine, CA 92697-2025, USA.
Proc Natl Acad Sci U S A. 2005 May 24;102(21):7443-8. doi: 10.1073/pnas.0408781102. Epub 2005 May 13.
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 multi-dimensional 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 alpha-helix, beta-sheet, and their coupling. Comparison of signals generated in different directions shows that the double-quantum-coherence signal has a higher sensitivity to the couplings compared with the single-quantum-coherence (photon echo) technique.