Monitoring the effect of three humic acids on a model membrane system using 31P NMR

被引:16
作者
Elayan, Naser M. [1 ]
Treleaven, W. Dale [3 ]
Cook, Robert L. [1 ,2 ,3 ]
机构
[1] So Univ Baton Rouge, Dept Environm Toxicol, Baton Rouge, LA 70813 USA
[2] So Univ Baton Rouge, Dept Chem, Baton Rouge, LA 70813 USA
[3] Louisiana State Univ, Dept Chem, Baton Rouge, LA 70803 USA
关键词
D O I
10.1021/es7024142
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
The sorption of three humic acids to 1,2-dipalmitoyl-sn-glycero3-phosphocholine multilamellar vesicle model membrane systems was studied by phosphorus nuclear magnetic resonance (P-31 NMR). The effects of temperature and pH were investigated. The gel -> bilayer transition did not appear to be affected by any of the humic acids at pH 7; however, all three humic acids induced a perturbation to this transition and to the bilayer structure at pH 4. On the basis of the findings from this and other work, a conceptual adsorption/absorption model for the sorption of humic acid (HA) to biomembranes has been put forward. The model requires an initial adsorption step initiated at an acidic pH by hydrogen bridging and electrostatic interactions between the functional groups of the HAS and the head groups of the phospholipids. Once the HA material is adsorbed, its hydrophobic domains can further seek a more thermodynamically favorable environment within the bilayer using hydrophobic interactions. These interactions lead to the HA being absorbed into the membrane, which subsequently induces the observed perturbation by disturbing the ordered packing of the phospholipid tail groups. This model is also related to other humic substances/biomembrane observations in the literature.
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收藏
页码:1531 / 1536
页数:6
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