METHODS FOR DEHYDRATION-TOLERANCE - DEPRESSION OF THE PHASE-TRANSITION TEMPERATURE IN DRY MEMBRANES AND CARBOHYDRATE VITRIFICATION

Anhydrobiosis, or life without water, is the remarkable ability of cer tain types of plants and animals to survive almost total dehydration. This phenomenon requires a coordinated series of events within the cel ls of anhydrobiotes that protect their cellular components, particular ly proteins and lipid membranes, from damage caused by the removal of water. Much of what is now understood about preserving biological samp les during drying was learned by studying naturally desiccation-tolera nt organisms and extended using model systems such as phospholipid ves icles. Most anhydrobiotic organisms accumulate disaccharides in their cells and tissues during the dehydration process. These carbohydrates, usually sucrose or trehalose, satisfy two criteria that appear to be necessary for protecting membranes during desiccation and during stora ge in the dry state. These requirements include: (1) depression of the gel-to-liquid crystalline phase transition temperature (T-m) in the d ehydrated lipid to a temperature at or near that of the hydrated lipid , a process that appears to require a direct interaction between the c arbohydrates and the lipid molecules of the membrane; and (2) formatio n of a carbohydrate glass with a relatively high glass transition temp erature, reading to inhibition of fusion between the vesicles.