Structures and properties of mixtures of branched chain compounds and lecithin: phytol, α-tocopherol (vitamin E), and phytanic acid

Abstract

Phospholipid bilayers containing branched chain molecules, phytol (1), vitamin E (2), and phytanic acid (3), have been investigated by ³¹P nmr, esr, and differential scanning calorimetry (dsc).A ³¹P lanthanide induced shift study indicated varying permeabilities to Pr³⁺ in the order phytanic acid > vitamin E > phytol > egg yolk lecithin alone; the half-lives (in days) were 0.002, 0.14, 0.83, and 6.5, respectively. The activation energy for Pr³⁺ permeation through the egg yolk lecithin–phytol membrane was found to be 84.9 ± 0.8 kJ.The following esr order parameters, S₃, were obtained using the extrinsic spin label, 5-doxylpalmitic acid, in oriented mixed multibilayers: S₃ (1) = 0.29, S₃ (2) = 0.50, and S₃ (3) = 0.02.Differential scanning calorimetry revealed a lowering of the gel–liquid crystalline phase transition temperature, T_c, as the concentration of incorporated isoprenoid compound increases, with eventual disappearance of the endotherm. Specific entropy, s, calculated for dipalmitoyl lecithin +25 mol% 3 is 126 J kg⁻¹ K⁻¹ compared to s = 114.2 J kg⁻¹ K⁻¹ for 1and s = 85 J kg⁻¹ K⁻¹ for 2.