Thermisches Phasenverhalten homologer α- und β-methylverzweigtkettiger Lecithine im wassergesättigten Zweiphasengebiet

1. By means of differential scanning calorimetry the phase transition temperatures (T _u) and phase transition enthalpies (ΔH _u) ofα- andβ-branched lecithins were determined. The lecithin samples contained 50% water per weight.
2. The occurrence of the pre-transition was dependent on the position of the methyl group in the acid residue as well as on the length of the carbon chains. TheΔH _u values of the pre-transition were about 2.5 kJ·mol^?1.
3. The hydration number (HZ) (number of water molecules per lecithin headgroup) was independent on the position of the methyl group and the length of the acyl group. The average HZ-values for all the lecithins studied is about HZ=14+-1.
4. The influence of the chain length of theα- andβ- branched acyl groups affects the thermodynamical parameters of the main transitions (gel→L _α). TheΔH _m andT _m-values increased as the chain length increases.