FTIR and turbidity studies of fish oil-dipalmitoylphosphatidylcholine model membrane interactions

The temperature induced effects of fish oil on dipalmitoyl phosphatidylchol ine (DPPC) model membranes (fish oil/lipid ratio: 2% w/w) were investigated by Fourier transform infrared (FTIR) smd UV/Visible spectroscopic techniqu es. In FTIR study the C-H and C=O stretching modes were investigated. The r esults of the FTIR study reveals that fish oil changes the physical propert ies of the DPPC multilamellar liposomes by broadening the phase transition profile and increasing the bandwidth of the CH2 stretching bands. Those res ults imply respectively that fish oil interacts with the cooperativity regi on (C2-C8) of the fatty acyl chain and increases the dynamics of the acyl c hains. At this fish oil/lipid ratio, fish oil decreases the main phase tran sition temperature to lower degrees. No significant change in the frequency of the CH2 stretching bands is observed implying that fish oil does not ch ange the number of gauche conformers, i.e., does not make any significant e ffect on the order of the membrane. Investigation of the C=O band reveals t hat fish oil does not make hydrogen bonding with the C=O group of phospholi pid. Turbidity studies were performed at 550 nm. With the addition of fish oil, main phase transition temperature shifts to lower degrees and a dramat ic decrease in absorbance values were observed indicating that fish oil inc reases the fluidity of the membrane. The results of turbidity studies are c onsistent with the FTIR study. (C) 1999 Elsevier Science B.V. All rights re served.