Terahertz (THz) spectroscopic investigations of crystalline dipeptide nanotubes are discussed in the frequency region from 0.6 THz (2 cm-1) to 3 THz (100 cm-1). The THz region provides access to collective modes of biomolecular systems and is therefore sensitive to the large scale motions important in understanding the impact of environmental stimuli in biomolecular systems. The focus of this chapter is on THz spectral changes observed in this region when crystals of alanyl isoleucine (AI) and isoleucyl alanine (IA) nanotubes are exposed to water. Of biological significance is the water permeability through hydrophobic pore regions as exemplified in the disparate behavior of these two dipeptide nanotubes. AI is known from x-ray studies and confirmed here to act reversibly to the exchange of water while IA does not accept water into its pore region. Both quantum chemical and classical theoretical calculations are performed to better understand the subtle balance that determines guest water absorption and conduction through these hydrophobic channels. Examination of the vibrational character of the THz modes with and without water suggests water mode decoupling may play an important role.
Citation: METHODS IN NANO CELL BIOLOGY
Publisher Info: Elsevier, New York, NY
Pub Type: Books
Biological water, CHARMM, Crystalline Dipeptides, DFT, Hydration, Nanotubes, THz Spectroscopy, Density Functional Theory