Abstract
Fluorescence quenching is a simple method to determine the amount of molecules trapped inside phospholipid bilayer vesicles. It utilizes a fluorescent dye, calcein, the fluorescence of which can be quenched by chilate formation with cobalt (II) ions. The amount of calcein trapped inside POPC vesicles before and after freezing in presence and absence of saccharides was compared by this method. Leakage of the interior due to the damage caused by freeze-thaw process was detected. Three sacchrides were examined and sucrose exhibited the strongest protective ability while glucose exhibited the weakest. Trehalose was not very effective when it was added only in the exterior. However, the protective ability became comparable to that of sucrose when it was added to both interior and exterior of the vesicle.
