INFLUENCE OF THE SHAPE OF PHOSPHOLIPID-VESICLES ON THE MEASUREMENT OFTHEIR SIZE BY PHOTON-CORRELATION SPECTROSCOPY

The influence of shape transformation of large unilamellar vesicles (L UV) on their size measurement by photon correlation spectroscopy (PCS) has been investigated. The experimental size of vesicles after hypero smotic contractions of increasing intensities have been compared to th e theoretical volume decrease determined by applying Boyle Van't Hoff' s law. The main observation is that PCS size measurement gives overest imated values when LUV have been subjected to a volume decrease of mor e than 20% of their initial volume. The PCS size overestimation is rel ated to the influence of the shape transformation of the vesicles on t heir diffusion coefficient (D) as shown by modelling the evolution of D of a sphere which is transformed into an ellipsoid by internal volum e reduction under constant area.