TY - JOUR

T1 - Calorimetric and theoretical studies of the effects of lindane on lipid bilayers of different acyl chain length

AU - Sabra, Mads C.

AU - Jørgensen, Kent

AU - Mouritsen, Ole G.

PY - 1995/1/26

Y1 - 1995/1/26

N2 - The effects of the insecticide lindane on the phase transition in multilamellar bilayers of saturated diacylphosphatidylcholines of different acyl chain length (DC14PC, DC16PC, and DC18PC) have been studied by means of differential scanning calorimetry (DSC), as well as computer-simulation calculations on a molecular interaction model. The calorimetric data show that increasing concentrations of lindane lower the transition temperature and lead to a broadening of the specific heat in a systematic way depending on the lipid acyl chain length. Kinetic effects in the observed calorimetric traces indicate that the incorporation of lindane into multilamellar lipid bilayers is slow, but faster for the shorter lipid species. Large unilamellar vesicles do not show such kinetic effects. The transition enthalpy is for all three lipid species found to be independent of the lindane concentration which implies that the entropy of mixing is vanishingly small. This lends support to a microscopic molecular interaction model which assigns the absorbed lindane molecules to interstitial sites in the bilayer. Computer-simulation calculations on this model, which assumes a specific interaction between lindane and certain excited acyl chain configurations, lead to predictions of the lipid-water partition coefficient in qualitative agreement with experimental measurements (Antunes-Madeira and Madeira (1985) Biochim. Biophys. Acta 820, 165-172). The partition coefficient has a peak near the phase transition which is a consequence of enhanced interfacial adsorption of lindane at lipid-domain interfaces.

AB - The effects of the insecticide lindane on the phase transition in multilamellar bilayers of saturated diacylphosphatidylcholines of different acyl chain length (DC14PC, DC16PC, and DC18PC) have been studied by means of differential scanning calorimetry (DSC), as well as computer-simulation calculations on a molecular interaction model. The calorimetric data show that increasing concentrations of lindane lower the transition temperature and lead to a broadening of the specific heat in a systematic way depending on the lipid acyl chain length. Kinetic effects in the observed calorimetric traces indicate that the incorporation of lindane into multilamellar lipid bilayers is slow, but faster for the shorter lipid species. Large unilamellar vesicles do not show such kinetic effects. The transition enthalpy is for all three lipid species found to be independent of the lindane concentration which implies that the entropy of mixing is vanishingly small. This lends support to a microscopic molecular interaction model which assigns the absorbed lindane molecules to interstitial sites in the bilayer. Computer-simulation calculations on this model, which assumes a specific interaction between lindane and certain excited acyl chain configurations, lead to predictions of the lipid-water partition coefficient in qualitative agreement with experimental measurements (Antunes-Madeira and Madeira (1985) Biochim. Biophys. Acta 820, 165-172). The partition coefficient has a peak near the phase transition which is a consequence of enhanced interfacial adsorption of lindane at lipid-domain interfaces.

KW - Calorimetry

KW - Computer simulation

KW - Kinetic effect

KW - Lindane

KW - Partition coefficient

KW - Phospholipid bilayer

UR - http://www.scopus.com/inward/record.url?scp=0028936275&partnerID=8YFLogxK

U2 - 10.1016/0005-2736(94)00244-J

DO - 10.1016/0005-2736(94)00244-J

M3 - Journal article

C2 - 7530493

AN - SCOPUS:0028936275

VL - 1233

SP - 89

EP - 104

JO - B B A - Biomembranes

JF - B B A - Biomembranes

SN - 0005-2736

IS - 1

ER -