Preservation of structural and functional activity in lyophilized sarcoplasmic reticulum

Ca-transporting microsomes isolated from abdominal muscle of lobster were lyophilized in the presence and absence of trehalose. The dry membranes appeared with freeze fracture to collapse into cup-shaped structures embedded in a matrix of trehalose when lyophilized in the presence of trehalose. Upon rehydration, the dry membranes yielded vesicles that were morphologically indistinguishable from freshly prepared ones. These rehydrated vesicles also showed ATPase activity and Ca transport only slightly different from those activities in freshly prepared vesicles. The concentration of trehalose required to achieve this degree of stabilization is about 0.3 g trehalose/g membrane. When the membranes were dried at lower trehalose concentrations extensive fusion occurred between vesicles, along with lateral phase separations of membrane proteins and lipids. The rehydrated vesicles showed poor Ca uptake and coupling between ATPase activity and Ca uptake. The membranes may also be stabilized in the dry state by lyophilizing them in sucrose, but about three times as much sucrose is required as trehalose.