Study of supported phospholipid bilayers by THz-TDS

摘要

Terahertz Time-Domain Spectroscopy (THz-TDS) is a new technique in studying the conformational state of molecules. Cell membranes are important structures in the interaction with extra cellular entities. Their principal building blocks are lipids, amphiphilic molecules that spontaneously self-assemble when in contact with water. In this work we report the use of THz-TDS in transmission mode to examine the behavior of supported phospholipid bilayers (SPBs) within the frequency range of 0.2 THz to 3 THz. SPBs were obtained by vesicle adsorption method involving the spread of a suspension (50-100 μl) of small unilamellar vesicles (SUVs) or multilamellar vesicles (MLVs) dissolved in PBS (phosphate buffer solution) on a support of silicon wafers. Both SUVs and MLVs were obtained from dipalmitoyl phosphatidylcholine (DPPC) and lecithin by using the thin-film hydration method. Broadband THz pulses are generated and detected using photoconductive antennas optically excited by a femtosecond laser pulse emitted from a self-mode locked fiber laser at a wavelength of 780 nm with a pulse widths of 150 fs. THz-TDS was proven to be a useful method in studying SPBs and their hydration states. The absorption coefficient and refractive index of the samples were calculated from THz measurements data. The THz absorption spectra for different lipids in SPBs indicate specific absorption frequency lines. A difference in the magnitude of the refractive index was also observed due to the different structure of supported lipid bilayers. The THz spectrum of DPPC was obtained by using theoretical simulations and then the experimental and theoretical THz spectra were compared.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.