Biophys Chem 2010 Nov 29;152(1-3):178-83. Epub 2010 Sep 29.
Department of Chemistry, Occidental College, 1600 Campus Road, Los Angeles, CA 90041, USA.
Differential scanning calorimetry (DSC) was used to analyze the thermotropic phase behavior of dipalmitoylphosphatidylcholine (DPPC) bilayers in the presence of pentanol isomers. The concentration of each pentanol isomer needed to induce the interdigitated phase was determined by the appearance of a biphasic effect in the main transition temperatures, the onset of a hysteresis associated with the main transition from the gel-to-liquid crystalline phase, and the disappearance of the pretransition. Lower threshold concentrations were found to correlate with isomers of greater alkyl chain length while branching of the alkyl chain was found to increase biphasic behavior. The addition of a methyl group to butanol systems drastically decreased threshold concentrations. However, as demonstrated in the DPPC/neopentanol system, branching of the alkyl chain away from the -OH group lowers the threshold concentration while maintaining a biphasic effect.