Thermal Analyses of Phospholipid Mixtures by Differential Scanning Calorimetry and Effect of Doping with a Bolaform Amphiphile

Abstract

Abstract Morphological phases of DMPC/DHPC mixtures have already been investigated by using SANS, SAXS, NMR, and fluorescence-based techniques, as well as cryo-TEM, in which the manner of temperature is changed stepwise. We continuously monitored temperature-dependent phase transitions of DMPC/DHPC mixtures by DSC. We observed four significant transitions, two of which (transitions 1 and 4) were newly discovered in our current study. It was shown that bicelles have phase transitions similar to vesicles, and we proposed a phase diagram of DMPC/DHPC mixtures based on a continuous temperature change method. Such a phase diagram, in which transition temperatures are shown clearly, has never been reported to our knowledge. Moreover, we studied the doping effect of a synthetic bolaform amphiphile, which is used to construct stable model membranes, and found that the temperature range of the magnetically aligned state shifted to a higher temperature. This result indicates that doping synthetic phospholipids, which is done to create a thermostable membrane, is useful for stabilizing bicelles, worm-like micelles, or perforated lamellae. Such applications might be relevant to a variety of experiments, including those that utilize DMPC/DHPC mixtures as model membranes or alignment media.