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Interplay of Entropy and Enthalpy in Peptide Binding to Zwitterionic Phospholipid Membranes as Revealed from Membrane Thinning

Abstract

Membrane thinning resulted from peptide-binding is observed with temperature dependent small-angle X-ray scattering (SAXS). The result reveals a small thermal thinning rate of 0.038 Å/K for the neat unilamellar vesicle (ULV) of zwitterionic phospholipid of 1,2-dioleoyl-sn-glycero-3-phosphocholine (diC20:1PC) in the temperature range of 286-312 K. The thinning effect promotes greatly the association between a model antimicrobial peptide melittin and the ULV. Scaling the observed isothermal melittin-ULV bilayer thinning to that measured using low-angle X-ray diffraction from the melittin-multilamellar membranes of defined peptide-to-lipid ratios, establishes temperature-dependent binding isotherms Xb of the peptide-ULV as a function of free peptide concentration in solution. From the binding isotherms, temperature-dependent peptide-membrane binding constant K(T) is extracted on the basis of a modified Gouy-Chapman model. Changes of K(T) follow the linearized Van't Hoff equation lnK(T) = -(dH)/T with a constant enthalpy change dH = 9.6 kcal /mol, suggesting an entropy-driven process. Correspondingly, a five-fold enhancement of K is observed in the temperature range studied. The peptide-binding strength is found to follow the growth trend of membrane thermal thinning rate better than the lipid chain length of the three phosphocholine-based ULV of diCn:1PC with n = 18, 20, and 22.

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Publication details

The article was received on 05 May 2018, accepted on 06 Aug 2018 and first published on 07 Aug 2018


Article type: Paper
DOI: 10.1039/C8CP02861C
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Interplay of Entropy and Enthalpy in Peptide Binding to Zwitterionic Phospholipid Membranes as Revealed from Membrane Thinning

    C. Su, M. Lee, K. Liao, O. Shih and U. Jeng, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C8CP02861C

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