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The chemical toxic benzo[ a ]pyrene perturbs the physical organization of phosphatidylcholine membranes
Author(s) -
Jiménez María,
Aranda Francisco J.,
Teruel J. Antonio,
Ortiz Antonio
Publication year - 2002
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620210415
Subject(s) - dipalmitoylphosphatidylcholine , chemistry , bilayer , phospholipid , pyrene , phosphatidylcholine , membrane , differential scanning calorimetry , lipid bilayer , benzo(a)pyrene , analytical chemistry (journal) , biological membrane , swelling , infrared spectroscopy , crystallography , chromatography , organic chemistry , chemical engineering , biochemistry , physics , engineering , thermodynamics
The interaction of the chemical carcinogen benzo[ a ]pyrene (B a P) with phosphatidylcholine membranes has been investigated by using various physical techniques. Differential scanning calorimetry showed that B a P, at concentrations as low as 2 mol% in mixtures with dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine, and distearoylphosphatidylcholine, abolished the pretransition and broadened and shifted to lower temperatures the main gel‐to‐liquid crystalline phase transition. The effect was stronger as the lipid acyl chain length decreased. Infrared spectroscopy indicated that inclusion of B a P had a strong influence on the carbonyl (C=O) stretching band. Fitting of this band resulted in the presence of three components in the case of samples containing B a P, centered at 1,742, 1,727, and 1,704 cm −1 (only two components, at 1,742 and 1,727 cm −1 , were observed for pure DMPC). The component at 1,704 cm −1 corresponded to a disolvate and strongly supported the notion that inclusion of B a P increases hydration of the bilayer C=O. Small‐angle x‐ray diffraction showed that incorporation of 10 mol% B a P into DMPC increased bilayer thickness from 66.7 to 71 A in the gel state and from 58.9 to 60.9 A in the fluid phase. It is proposed that, when B a P is incorporated into a phospholipid bilayer, it locates in the most apolar region of the phospholipid palisade, resulting in expansion and swelling of the membrane. These two effects will facilitate water penetration into the polar region of the membrane, as observed by the increased hydration of the C=O groups, and thus perturb both membrane integrity and functionality.