The temperature-dependent hydrogen-bonding signature of lipids monitored in the far-infrared domain.

Phospholipids are studied by means of Fourier transform infrared (FTIR) spectroscopy in the mid- and far-infrared spectral ranges, thereby establishing the hydrogen-bonding continuum as a function of the temperature. The well-known mid-infrared spectrum of the phospholipid layer clearly shows a temperature-dependent phase transition. In the far-infrared region (from 300 to 50 cm(-1)), an alternation of the interaction between the phospholipids and water molecules is found. The hydrogen-bonding network ensemble and bound water molecules can be monitored in this spectral region. The lipid structure is found to strongly influence the intermolecular hydrogen-bonding interplay. Thus, studies in the far-infrared region provide significant information--at the molecular level--about the intermolecular hydrogen-bonding signature of self-assembled phospholipids.