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Issue 42, 2018
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Interplay of entropy and enthalpy in peptide binding to zwitterionic phospholipid membranes as revealed from membrane thinning

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Abstract

Membrane thinning that resulted from peptide-binding is observed via temperature dependent small-angle X-ray scattering (SAXS). The result reveals a mean thermal thinning rate of 0.038 Å K−1 for the neat unilamellar vesicles (ULVs) of a zwitterionic phospholipid of 1,2-dieicosenoyl-sn-glycero-3-phosphocholine (diC20:1PC) in the temperature range of 285–312 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 χb 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 in K(T) follow the linearized van’t Hoff equation ln K(T) ∝ −ΔHT−1 with a constant enthalpy change ΔH = 9.6 kcal mol−1, suggesting an entropy-driven binding process prior to membrane pore formation. 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 the membrane thermal thinning rate better than the lipid chain length of the three phosphocholine-based ULVs of diCn:1PC with n = 18, 20, and 22.

Graphical abstract: Interplay of entropy and enthalpy in peptide binding to zwitterionic phospholipid membranes as revealed from membrane thinning

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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., 2018,20, 26830-26836
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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, 20, 26830
    DOI: 10.1039/C8CP02861C

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