The adsorption of divalent cations to phosphatidylcholine bilayer membranes

doi:10.1016/0005-2736(78)90203-1

Biochimica et Biophysica Acta (BBA) - Biomembranes

Volume 513, Issue 3, 16 November 1978, Pages 338-357

https://doi.org/10.1016/0005-2736(78)90203-1 Get rights and content

Abstract

Electrophoretic mobility and ³¹P NMR measurements were combined to test whether the combination of the Henry, Boltzmann and Grahame equations is capable of describing the adsorption of divalent cations to phosphatidylcholine membranes. Cobalt was chosen for this study because, of all the common divalent cations, its effects on the ³¹P NMR spectrum of phosphatidylcholine membranes are easiest to interpret. Both the ³¹P NMR data on the adsorption of cobalt and the zeta potential data calculated from the electrophoretic mobility in the presence of cobalt are well described by the combination of these three equations. Electrophoretic mobility measurements were also performed with a number of other divalent cations and the zeta potentials were, in all cases, well described by the combination of these three equations. The binding deduced from such measurements decreases in the sequence: Mn²⁺, Mg²⁺, Ca²⁺, Co²⁺, Ni²⁺, Sr²⁺, Ba²⁺. If we assume that a lipid molecule occupies an area of 60 Å² and that there is a 1: 1 stoichiometry for the binding of the divalent ions to phosphatidylcholine, the dissociation constants are, respectively: 0.3, 1.0, 1.0, 1.2, 1.2, 2.8, 3.6 M.

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The higher metal concentrations used may explain the observed binding to DMPC. However, a weak binding interaction of Mn with PC agrees with previously-reported binding constants (Table 1) [130]. The authors suggested that the small ionic radius of Mn2+ may allow it to bypass the positively charged choline and access the negative phosphate allowing metal lipid binding.
Anthropogenic activity has increased human exposure to metals and resulted in metal induced toxicity. Essential trace elements like cobalt (Co), nickel (Ni), and manganese (Mn) are best known for their roles as important cofactors in many enzymes involved in signalling, metabolism, and response to oxidative stress. However, deficiencies as well as long-term overexposure to these metals can result in negative health effects.
Co has been associated with cardiomyopathy, lung disease, and hearing damage, while Ni is a known carcinogen, as well as a common sensitizing metal. Mn is best classified as a neurotoxicant that causes a disorder alike to idiopathic Parkinson's disease known as Manganism.
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The adsorption of divalent cations to phosphatidylcholine bilayer membranes

Abstract

Biophys. J.

Biochim. Biophys. Acta

Biochim. Biophys. Acta

J. Theor. Biol.

Chem. Phys. Lipids

Biochim. Biophys. Acta

Biochim. Biophys. Acta

Biochim. Biophys. Acta

Biophys. Chem.

Biochem. Biophys. Res. Commun.

J. Coll. Interface Sci.

J. Theor. Biol.

J. Magn. Res.

Biochim. Biophys. Acta

Biochim. Biophys. Acta

Biochim. Biophys. Acta

Chem. Phys. Lipids

Biochim. Biophys. Acta

Biochim. Biophys. Acta

Biochim. Biophys. Acta

J. Magn. Res.

J. Physiol.

J. Gen. Physiol.

Acta Physiol. Scand.

J. Physiol.

J. Gen. Physiol.

Pflugers Arch.

J. Physiol.

J. Gen. Physiol.

Phil. Trans. Roy. Soc. Lond.

J. Physiol.

Biochemistry