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Adsorption of Ca2+ and La3+ to bilayer membranes : measurement of the adsorption enthalpy and binding constant with titration calorimetry

Lehrmann, R. and Seelig, J.. (1994) Adsorption of Ca2+ and La3+ to bilayer membranes : measurement of the adsorption enthalpy and binding constant with titration calorimetry. Biochimica et biophysica acta, Vol. 1189, H. 1. pp. 89-95.

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Official URL: http://edoc.unibas.ch/dok/A5257447

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Abstract

The adsorption of Ca2+ and La3+ ions to the surface of lipid bilayer membranes was studied with high sensitivity titration calorimetry. Ca2+ adsorbs to mixed phosphatidylcholine/phosphatidylglycerol membranes with a reaction enthalpy of delta H approximately 0.1-0.2 kcal/mol. La3+ binds to sonified phosphatidylcholine vesicles with a reaction enthalpy of delta H approximately +1.8 kcal/mol. Adsorption of La3+ to phosphatidylcholine bilayers imparts a net positive charge to the membrane surface which makes the binding of further La3+ increasingly more difficult. From the decreasing amplitudes in the calorimetric titration experiment a La3+ adsorption constant of K approximately (4.1 +/- 1.1) x 10(3) M-1 was evaluated. Electrostatic effects were corrected for by means of the Gouy-Chapman theory. The adsorption constant of Ca2+ was determined previously as K approximately 10-20 M-1 using the same binding model. Since the reaction enthalpies of Ca2+ and La3+ adsorption are endothermic, the adsorption of both metal ions to the membrane surface is driven by a distinct change in entropy.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Former Organization Units Biozentrum > Biophysical Chemistry (Seelig J)
UniBasel Contributors:Seelig, Joachim
Item Type:Article, refereed
Article Subtype:Research Article
Bibsysno:Link to catalogue
Publisher:Elsevier
ISSN:0006-3002
Note:Publication type according to Uni Basel Research Database: Journal article
Last Modified:22 Mar 2012 14:19
Deposited On:22 Mar 2012 13:18

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