Mixing of perfluorooctanesulfonic acid (PFOS) potassium salt with dipalmitoyl phosphatidylcholine (DPPC)

Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky, United States
Colloids and surfaces B: Biointerfaces (Impact Factor: 4.15). 09/2006; 51(1):25-9. DOI: 10.1016/j.colsurfb.2006.05.013
Source: PubMed


Perfluorooctane-1-sulfonic acid (PFOS) is emerging as an important persistent environmental pollutant. To gain insight into the interaction of PFOS with biological systems, the mixing behavior of dipalmitoylphosphatidylcholine (DPPC) with PFOS was studied using differential scanning calorimetry (DSC) and fluorescence anisotropy measurements. In the DSC experiments the onset temperature of the DPPC pretransition (Tp) decreased with increasing PFOS concentration, disappearing at XDPPC < or = 0.97. The main DPPC phase transition temperature showed a depression and peak broadening with increasing mole fraction of PFOS in both the DSC and the fluorescence anisotropy studies. From the melting point depression in the fluorescence anisotropy studies, which was observed at a concentration as low as 10 mg/L, an apparent partition coefficient of K = 5.7 x 10(4) (mole fraction basis) was calculated. These results suggest that PFOS has a high tendency to partition into lipid bilayers. These direct PFOS-DPPC interactions are one possible mechanism by which PFOS may contribute to adverse effects, for example neonatal mortality, in laboratory studies and possibly in humans.

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Available from: Hans-Joachim Lehmler,
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    • "Dipalmitoylphosphatidylcholine (DPPC) is one of the main phospholipid components in surfactant. Lehmler et al. [51] used DPPC model bilayer membranes to evaluate the effects of PFOS on membrane stability using differential scanning calorimetry and fluorescence anisotropy measurements. PFOS was found to partition into and affect the model membranes, changing membrane fluidity at concentrations as low as 10 mg/L. "
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    • "n . The rescuing agents also failed to mitigate the extent of PFOS - induced neonatal mortality . These investigators surmised that the labored breathing and subsequent mortality observed in the PFOS - exposed newborns might not be related to immaturity of the lung per se . This contention , in fact , is consistent with recent findings reported by Lehmler et al . ( 2006 ) . These researchers examined the mixing behavior of dipalmitoylphos - phatidylcholine ( DPPC ) , a major component of pulmonary surfactant , with PFOS by differential scanning calorimetry and fluorescence anisotropy measurements . They noted that PFOS had a high tendency to partition into lipid bilayers . Such PFOS – DPPC physical int"
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    ABSTRACT: Perfluorooctanesulfonic acid (PFOS) is a persistent environmental pollutant that may cause adverse effects by inhibiting pulmonary surfactant. To gain further insights in this potential mechanism of toxicity, we investigated the interaction of PFOS potassium salt with dipalmitoylphosphatidylcholine (DPPC) - the major component of pulmonary surfactant - using steady-state fluorescence anisotropy spectroscopy and DSC (differential scanning calorimetry). In addition, we investigated the interactions of two structurally related compounds, perfluorooctanoic acid (PFOA) and octanesulfonic acid (OS) potassium salt, with DPPC. In the fluorescence experiments a linear depression of the main phase transition temperature of DPPC (T(m)) and an increased peak width was observed with increasing concentration of all three compounds, both using 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene p-toluenesulfonate (TMA-DPH) as fluorescent probes. PFOS caused an effect on T(m) and peak width at much lower concentrations because of its increased tendency to partition onto DPPC bilayers, i.e., the partition coefficients decrease in the K(PFOS)>K(PFOA)>K(OS). Similar to the fluorescence anisotropy measurements, all three compounds caused a linear depression in the onset of the main phase transition temperature and a significant peak broadening in the DSC experiments, with PFOS having the most pronounced effect of the peak width. The effect of PFOS and other fluorinated surfactants on DPPC in both mono- and bilayers may be one mechanism by which these compounds cause adverse biological effects.
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