Thermodynamic phase transition parameters of human lens dihydrosphingomyelin

Dihydrosphingomyelin (DHS) is the major phospholipid in the human lens. The influence of this phospholipid on membrane structure and function is not known. In this study we used infrared spectroscopy to determine the thermodynamic and molecular structural properties of the hydrocarbon chains of DHS membranes isolated from human lenses. The phase transition temperature of human lens DHS was 9 degrees C higher than for bovine brain sphingomyelin membranes and 14 and 7 degrees C higher than human lens cortical and nuclear membranes, respectively. This increase in the phase transition temperature results in 20% increase in lipid order at 36 degrees C in comparison to that of native membranes and bovine brain sphingomyelin. DHS is likely to provide structural order to the hydrocarbon chain region and upholds the integrity of native membranes under oxidative conditions.