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Effects of lipid membrane curvature on lipid packing state evaluated by isothermal titration calorimetry.

Langmuir : the ACS journal of surfaces and colloids (2012-12-29)
Hirokazu Yokoyama, Keisuke Ikeda, Masaki Wakabayashi, Yasushi Ishihama, Minoru Nakano
ABSTRACT

In this report, we present a novel approach for the elucidation of the physicochemical properties of lipid membranes by isothermal titration calorimetry (ITC) to quantify the heat absorbed during the solubilization of vesicles into TritonX-100 micelles. By using large and small unilamellar vesicles for comparison, this method provides calorimetric data on the gel-to-liquid-crystalline phase transition and its curvature effects and, in particular, the enthalpy change upon membrane deformation from a planar to a curved shape, which cannot be obtained by the conventional approach using differential scanning calorimetry. The results showed quantitatively that the increase in membrane curvature increases the enthalpy of 1,2-dimyristoyl-sn-glycero-3-phosphocholine membranes both below and above the phase-transition temperature, and that the effect is more significant for the former condition. The calorimetric data obtained are further discussed in relation to the elastic bending energy of the membranes and membrane-peptide interaction.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Triton X-100 solution, BioUltra, for molecular biology, ~10% in H2O
Octoxinol 10, European Pharmacopoeia (EP) Reference Standard
Sigma-Aldrich
Triton X-305 solution, 70% in H2O
Sigma-Aldrich
Triton X-102
Sigma-Aldrich
Triton X-100, for molecular biology
Sigma-Aldrich
Triton X-100, peroxide- and carbonyl-free
Sigma-Aldrich
Triton X-100, laboratory grade
Sigma-Aldrich
Triton X-100, BioXtra
Sigma-Aldrich
Triton X-45