Titration calorimetric and differential scanning calorimetric studies of the interactions of n-butanol with several phases of dipalmitoylphosphatidylcholine

Abstract

The interactions of n-butanol with dipalmitoylphosphatidylcholine (DPPC) were studied using titration calorimetry and differential scanning calorimetry (DSC). DSC results indicated that n-butanol induces the interdigitated phase in DPPC above 10 mg/mL butanol. A new application of titration calorimetry for measuring partition coefficients of nonsaturating solutes into lipids was developed. The partition coefficients and the heat of binding of n-butanol into DPPC were measured for the L beta', P beta', L alpha, and L beta I phases of DPPC. The partition coefficients were temperature dependent and ranged from 70 to 110 for the L beta I phase, from 170 to 183 for the L alpha phase, and similar to that for the L beta I phase in the P beta' phase. The binding to the L beta' phase could not be detected, giving an upper limit for this partition coefficient of 23. The enthalpies for binding to the L beta I and L alpha phases were 1.0 and 1.5 kcal/mol, respectively. The van't Hoff enthalpy was in good agreement with the calorimetric enthalpy for the partitioning into the L alpha phase; however, it was greater than the calorimetric enthalpy for the L beta I phase, suggesting that the interaction of n-butanol with this phase is cooperative in some way.

Effects of butanol isomers on dipalmitoylphosphatidylcholine bilayer membranes

“…Comparatively, the n-butanol system exhibited "stunted" biphasic behavior. From this data it was concluded that the threshold concentration for n-butanol is 0.16 M, in agreement with previous studies on the DPPC system [6,14,15].…”

Effects of a short length alcohol on the dimyristoylphosphatidylcholine system

“…It's worth emphasizing that the occurrence of the interdigitated phase is expected at alcohol concentrations above a threshold value equal to 2:1 alcohol/lipid ratio, as it has been observed for DPPC/n-butanol system [6]. This is just the concentration of the lipid/alcohol samples which have been investigated in this paper.…”

“…More precisely, experiments on phospholipid membranes have shown that alcohol can induce the interdigitated phase [3,4,5] that, at high alcohol concentrations, replaces the ripple gel phase [5,6]. The interdigitated phase is characterized by a greater order compared to the ripple phase [7].…”

A review on the ligand binding studies by isothermal titration calorimetry

“…The principal of these methods is to fit the experimental data in an equation relating equilibrium constant, molar enthalpy of binding and reactants concentration. The Wiseman method [45] for data analysis has extensively used for ligand binding studies by ITC and a computer program is needed for using this method [61][62][63][64][65][66][67].…”