Vesicle shapes and shape transformations: a systematic study

In our contribution we report a systematic experimental and theoretical study on shape transformations. In order to avoid the above mentioned complications we have investigated vesicles which consist of electrically neutral lipids (that is phosphatidylcholine) in Millipore water. We find, that even for such a simple system a change in temperature can lead to three different types of shape transformations. Theoretically, we discuss shape transformations within two well established curvature models, (i) the bilayer coupling model of Svetina and Zeks and (ii) the spontaneous curvature model of Helfrichs.A comparison leads to the conclusion that the observed shape transformations can well be explained within the bilayer coupling model provided a small asymmetry in the thermal expansivities of both monolayers is assumed. In some cases, such an asymmetry is not required