Polarization Modulation Infrared Reflection−Absorption Spectroscopy Studies of the Influence of Perfluorinated Compounds on the Properties of a Model Biological Membrane

Abstract

A combination of the Langmuir-Blodgett and Langmuir-Schaefer techniques has been used to build a 1,2-dimyristoyl- sn-glycero-3-phosphocholine (DMPC) bilayer at a Au(111) electrode surface with hydrogen-substituted acyl chains in the top leaflet (solution side) and deuterium-substituted acyl chains in the bottom leaflet (gold side). Polarization modulation infrared reflection-absorption spectroscopy was used to determine changes in the conformation and orientation of the acyl chains of DMPC caused by the incorporation of two selected perfluorinated compounds, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), into the top leaflet of the bilayer. The incorporation of perfluorinated compounds into the DMPC bilayer caused a broadening of the methylene peaks and a shift in the methylene band positions toward higher frequencies. In addition, the tilt angle of the acyl chains decreased in comparison to the tilt angle of a pure DMPC bilayer. The reported tilt angles were smaller upon insertion of PFOS ( approximately 24 degrees ) than in the presence of PFOA ( approximately 30 degrees ). Overall, the results show that the incorporation of the perfluorinated acids has an effect on the bilayer similar to that of cholesterol by increasing the membrane fluidity and thickness due to a decrease in the tilt angle of the acyl chains.

Effect of PFOA/PFOS pre-exposure on the toxicity of the herbicides 2,4-D, Atrazine, Diuron and Paraquat to a model aquatic photosynthetic microorganism

“…Both PFOA and PFOS resulted in an increase of cell membrane permeability to PI, however, the effect of PFOA 25 mg/L was the strongest. These results are in agreement with previous reports which have found that PFOA and PFOS are able to provoke membrane damage (Nobels et al, 2010), and to alter membrane permeability (Hu et al, 2003;Matyszewska et al, 2007Matyszewska et al, , 2008Matyszewska et al, , 2012Liu et al, 2008;Latała et al, 2009). Kleszczynski and Skladanowski (2009) found that PFOA as other perfluorinated aliphatic acids (PFAs) interacted rapidly with membranes, quickly causing membrane depolarization.…”

Perfluorooctanoic acid rigidifies a model lipid membrane

“…As a consequence of their chemical stability, these compounds exhibit an environmental stability and are transmitted into the mammal food chain [3]. Due to their tendency to bioaccumulate, the compounds affect properties of cell membranes, causing developmental and reproductive disorders [2,4]. It is of particular interest to understand the effect of perfluorinated compounds not only on cellular membranes [5,6], but also on their biomimetic counterparts [7].…”

“…Several studies have addressed the insertion of perfluorinated compounds into binary model membranes. Oriented mono-and bilayers were investigated by Matyszewska et al using methods including surface pressure and potential measurements, infrared spectroscopy (IR), nuclear magnetic resonance (NMR) techniques, and molecular dynamics (MD) simulations [4,10,11]. While the phospholipid head group tilt against the bilayer normal decreases with rising amounts of inserted perfluorooctanoic acid (PFOA), the lipid acyl chain order increases.…”

Changes in the structure of model biological membranes in the presence of perfluorooctanesulphonic acid – Electrochemical and EC-STM study

“…1) and transferred onto gold electrodes [19,20]. We showed that perfluorinated compounds may both be incorporated into model membranes during their formation [21] and transfer onto solid support.…”

“…Different nature of the changes occurring for different electroactive probes were attributed to electrostatic interactions, which play a very important role in this system. Moreover, PM-IRRAS studies revealed that the presence of these chemicals in DMPC layer induces changes in the orientation and conformation of the acyl chains of DMPC molecules [20]. A decrease in the tilt angles observed when PFCAs were present in the DMPC layers resulted in the increase in membrane fluidity and thickness.…”