Mixed lipid aggregates containing gangliosides impose different ²H-NMR dynamical parameters on water environment depending on their lipid composition

Abstract

Water dynamics in samples of ceramide tetrasaccharide (G_g4Cer) vesicles and G_M1 ganglioside micelles at 300:1 water/lipid mole ratio were studied by using deuterium nuclear magnetic resonance (²H-NMR). G_M1 imposes a different restriction on water dynamics that is insensitive to temperatures either above or below its phase transition temperature or below the freezing point of water. The calculated correlation times are in the range of 10⁻¹⁰ s, typical of water molecules near to the polar groups. Pure G_M1 micelles have two distinct water microenvironments dynamically characterized. Their dynamic parameters remain constant with temperature ranging from −18 to 32°C, but the amount of strongly associated water is modified. By contrast, a mixture of single soluble carbohydrates corresponding to G_M1 polar head group does not preserve the dynamic parameters of water hydration when the temperature is varied. Incorporation of cholesterol or lysophosphatidylcholine into G_M1 micelles substantially increases the mobility of water molecules compared with that found in pure G_M1 micelles. The overall results indicate that both the supramolecular organization and the local surface quality (lipid–lipid interaction) strongly influence the interfacial water mobility and the extent of hydration layers in glycosphingolipid aggregates.

• Glycosphingolipid
• cholesterol, hydration
• 2H-NMR
• water–lipid interface

²H-NMR, Nuclear Magnetic Resonance of Deuterium; FFT, Fast Fourier Transform; FID, Free Induction Decay; T₁, spin–lattice relaxation time; T₂, spin–spin relaxation time; G_M1, Gal(β1–3)GalNac(β1–4)Gal(3-2α)NeuAc(β1–4)Glc(β1-1′)N-acylsphingosine; Gg₄Cer, Gal((β1–3)GalNac(β1–4)Gal(β1–4)Glc(β1-1′)N-acylsphingosine; Chol, cholesterol; LPC, egg lysophosphatidylcholine; T_m, gel→liquid lipid phase transition temperature (temperature of maximal excess heat capacity; T_1/2 of endothermic peak means the temperature width at half height of excess heat capacity trace; τ_c, correlation time

²H-NMR, Nuclear Magnetic Resonance of Deuterium; FFT, Fast Fourier Transform; FID, Free Induction Decay; T₁, spin–lattice relaxation time; T₂, spin–spin relaxation time; G_M1, Gal(β1–3)GalNac(β1–4)Gal(3-2α)NeuAc(β1–4)Glc(β1-1′)N-acylsphingosine; Gg₄Cer, Gal((β1–3)GalNac(β1–4)Gal(β1–4)Glc(β1-1′)N-acylsphingosine; Chol, cholesterol; LPC, egg lysophosphatidylcholine; T_m, gel→liquid lipid phase transition temperature (temperature of maximal excess heat capacity; T_1/2 of endothermic peak means the temperature width at half height of excess heat capacity trace; τ_c, correlation time