We study the binding of phenylalanine, (Phe) with dipalthitoylphosphocholirie (DPPC) vesicles in gel (25 degrees C)- and in liquid crystalline states (50 degrees C) and in gel large unilarnellar vesicles (LL/Vs) subjected to osmotic dehydration with merocyanine (MC 540) as a fluorescent surface Membrane marker. Phe does not produce significant changes in MC 540 rnoriorner concentration in DPPC LUVs at 50 degrees C. In contrast, it significantly decreases the monomer adsorption in defects present it DPPC LINs at 25 degrees C. When DPPC LUVs were subjected to hypertonic stress, dehydration caused more defects, Mcl in this case phenylalanine is also able to block such defects.