Title
Synthesis, characterization, and determination of critical micellar concentration and thermotropic phase transition of taurolipids
Author
Sengan Megarajan, Pothiappan Vairaprakash, Veerappan Anbazhagan
Year
2017
Journal
Journal of Molecular Liquids
Abstract
Taurolipids (NAT) are a newer class of fatty acid amides (FAA) identified in the central nervous system, liver, and kidney of fatty acid amide hydrolase knockout mice. In this study, we reported a convenient method to synthesize NATs in fair yield and characterized using FTIR, 1H NMR and 13C NMR. Fluorescence spectroscopy study showed that NATs form micelles in an aqueous environment and the critical micellar concentration (CMC) follows a linear trend with respect to fatty acid acyl chain length. Differential scanning calorimetry reveals that NATs undergoes broad endothermic transition with transition temperatures increases with increasing fatty acid acyl chain length though the magnitude of change from one chain length to another chain length decreases as the acyl chain length increase. The transition enthalpy (ΔHt) and transition entropy (ΔSt) corresponding to the chain-melting phase transition depends linearly on the acyl chain length and fitted to a linear equation, which yielded the incremental values, ΔHinc (1.09 ± 0.03 kcal·mol− 1) and ΔSinc (2.96 ± 0.16 cal·mol− 1·K− 1), contributed by each methylene unit to ΔHt and ΔSt. The end contributions arising from the head group and the terminal methyl group were calculated to be ΔH0 = − 7.28 ± 0.46 kcal·mol− 1 and ΔS0 = − 17.36 ± 2.11 cal·mol− 1·K− 1. Thermodynamic parameters, incremental values of ΔHinc and ΔSinc suggest that the acyl chains in NATs are tightly packed and the obtained larger negative ΔS0 suggest that the hydration of polar sulfonate group of NATs also play an important role in the self-assembly of NATs.
Instrument
FP-8200
Keywords
Fluorescence, Membrane structure, Biochemistry