Lipid reorganization in biological membranes: a study by Fourier transform infrared difference spectroscopy

The first application of infrared difference spectroscopy to the study of a natural biological membrane is described. Perdeuterated palmitic acid was incorporated biosynthetically into the lipids of the plasma membrane of Acholeplasma laidlawii and the temperature-induced structural rearrangement of the endogenous lipids monitored via their C--2H vibrational modes. Changes in infrared parameters were studied between 0 and 50 degrees C and contrasted with those occurring in the model membrane system of 1,2-diperdeuteropalmitoyl-sn-glycero-3-phosphocholine. The phase transition of the biomembrane occurs over a 20 degrees C range with the temperature of the maximum rate of change of absorbance coinciding with that of the sharp phase transition of the model membrane.