Saturday, October 25, 2014

Abstract-Terahertz Chiroptical Spectroscopy of α-Helical Polypeptide: Molecular Dynamics Simulation Study.

Choi JHCho M.

Vibrational spectroscopy has provided incisive information on structures of biological molecules. Here, using molecular dynamics simulation method, the infrared, vibrational circular dichroism, and vibrational optical rotatory dispersion spectra of right-handed α-helix in the terahertz (THz) frequency range are calculated. Both the auto-correlation function of electric dipole moment and the cross-correlation function of electric dipole and magnetic dipole moments of the -helix are calculated and Fourier-transformed to obtain the THz absorption and optical activity spectra, which reveal characteristic features of helical polypeptide structure. The anharmonicity and delocalized nature of low-frequency modes in the THz frequency domain are taken into account to obtain statistically convergent results on the THz optical activity spectra. In addition, the magnitude of THz vibrational optical activity signal of the α-helix is directly compared with those of mid-infrared and near-infrared optical activities of typical chiral molecules studied before. We anticipate that the THz chiroptical spectroscopy that has not been experimentally demonstrated yet would provide highly important and complementary information on protein structure and dynamics.

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