Why nature chose amide bonds for life systems on Earth

Abstract

Our group has been studying the temperature dependence of complex permittivity spectra from sub-GHz to THz of hydrated soft matters, especially biopolymers such as proteins and lipid bilayers, by varying the level of hydration in order to investigate the effects of hydration and thermal excitation on the low-frequency vibrations of these materials. Measurements have been made on globular proteins (lysozyme), membrane proteins (bacteriorhodopsin), and lipid bilayers (DMPC). In this presentation, we will report on the results of these hydrated broadband dielectric spectroscopy measurements and compare them with experimental results obtained by molecular dynamics simulations. Calculations were performed on lysozyme to see if the changes in the complex permittivity spectrum can be reproduced, and the coupling between hydrated water and proteins is discussed. We also performed similar measurements on hydrophilic polymers. The broadband dielectric spectra of the hydrophilic polymers also depend on the hydration level. However, the dependence is quite difference between proteins and hydrophobic polymers. We discuss characteristic aspects of the protein spectra, which may be important of their functions.