Detecting the effect of very low amounts of penetrants in lipid bilayers using Raman spectroscopy.

We show that, by the influence on the gauche content in the acyl chains, the effect of very low concentrations (order 10(-2) %) of penetrants (here 2,4-dichlorophenol) in lipid bilayers (here dipalmitoyl-glycerophosphatidylcholine) can be experimentally seen in the Raman spectra. The observed effects suggest increased order and are in accordance with previous X-ray diffraction and calorimetric data. These findings show great promise for studying in situ the effect of low amounts of various small molecules on cell membranes using Raman spectroscopy.