Temperature Phase Profile by Raman Spectroscopy of Dipalmitoylphosphatidylcholine

Emily Miller

One of the key components of biological cells are the phospholipids that compose the membrane. Dipalmitoylphosphatidylcholine (DPPC) is one of the phospholipid that forms the lipid bilayer. Phospholipids change conformations by rotation of the hydrocarbon tail. The gel-like solid state and the liquid-crystalline state conformations were both previously known; however, the conformation of the molecule throughout the transition and how those conformations were achieved was not known. Raman spectroscopy is one of the most useful methods of spectroscopy to study biological molecules. The temperature dependent phase transition of DPPC was analyzed by dispersive Raman spectroscopy, focusing on the shoulder height to peak height ratio of the CH stretch at approximately 2900 cm1 for the hydrocarbon chain. A 488 nm Argon ion laser was used with a 2252 x 3350 pixel charge-coupled device (CCD) camera within a 0.5 m spectrometer, along with the KestrelSpec software (v. 5.4). The temperature phase profile was then used to determine the conformational changes of DPPC throughout the transition by plotting the shoulder to peak height ratio of the CH stretch versus temperature.