Model-free analysis of binding at lipid membranes employing micro-calorimetric measurements |
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Authors: | G Schwarz L Damian M Winterhalter |
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Institution: | (1) Biocenter, University of Basel, Basel, Switzerland;(2) International University Bremen, Campusring 1, 28759 Bremen, Germany;(3) Present address: MicroCal Europe, Milton Keynes, UK |
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Abstract: | Based on universal thermodynamic principles (Schwarz in Biophys Chem 86:119–129, 2000) it is shown how measured enthalpy changes can be utilized to determine the relevant binding isotherm as well as the variation
of the molar enthalpy change. This is carried out in a novel way involving multiple titration experiments whose evaluation
requires no beforehand assumptions or models whatever. An appropriate specific model mechanism may be discussed afterwards
and developed in view of the given experimental results. The pertinent procedure is demonstrated using micro-calorimetric
data obtained in the case of the local anesthetic dibucaine as it associates with POPC liposomes. Mutual interactions of the
bound ligand molecules could be described in terms of repulsive enthalpic and entropic activity coefficients. Apparently these
are induced by electrostatic forces and by the finite size of binding sites, respectively. |
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Keywords: | Association isotherm Binding enthalpy Novel approach Dibucaine Molecular interactions Activity coefficients |
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