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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 5/1/2004 Publication Date: 9/25/2004 Citation: Walters, C. 2004. The status of water in preserved cells and what it means for long-term viability. 9th International Symposium on the Properties of Water, September 25-30, 2004, Mar del Plata, Argentina. pp. 121. Interpretive Summary: N/A Technical Abstract: Technical Abstract: Despite appropriate drying and even cryogenic storage, desiccated organisms lose viability with time. Time scales vary among diverse species and among individuals within a species. The unexplained variability in life spans is one of the most significant problems of preserving genetic resources in gene banks. Deterioration rates are dependent on the water content and temperature at which the organism is stored. Hence we have focused our research efforts on how properties within aqueous and lipid domains of cells are affected by storage conditions. Most of our research to date uses seeds as the study organism. We find little correspondence between deterioration rates and aqueous glass transition temperatures (Tg), and suggest that the Kauzmann temperature (TK, the point at which molecular mobility of glasses is considered nil) be used as the benchmark for "safe storage." We calculated TK and relaxation rates of aqueous glasses for dried seeds using concepts of configurational entropy and differential scanning calorimetry measurements of heat capacity. Changes in calculated glassy relaxation rates with temperature corresponded to seed aging kinetics at temperatures above TK, and these fit Vogel-Tamman-Fulcher (VTF) behavior. At temperatures near TK (-20 to -40C in seeds containing 0.07 g H2O/g dry mass), the temperature coefficient for seed deterioration rate changed abruptly and became small, reflecting faster than expected deterioration rates of cryogenically-stored seeds. Our analyses confirm that molecular mobility within the aqueous domain of seeds is an important determinant of deterioration kinetics; however, other factors also contribute to loss of viability in storage. Further studies on the effects of water content on molecular mobility and the correlation of molecular mobility and deterioration rates in diverse organisms may reveal these additional factors and provide a mechanistic understanding of why organisms lose viability in dry storage. |
