The fragility of vitrified glasses correlates with their protective capacity during desiccation.

Abstract

Water is essential for active life processes and metabolism. Despite this, a number of diverse organisms distributed across the kingdoms of life are able to survive near-complete desiccation. How organisms survive extreme water loss is one of the enduring mysteries of organismal physiology. Increases in intracellular viscosity, leading to the formation of a vitrified (glassy) state has been implicated as being necessary, but not sufficient, for conferring desiccation tolerance. What properties of a vitrified system make it desiccation-tolerant or -sensitive are unknown. Here we examine the property of ‘glass fragility.’ Specifically, we look at the glass fragility of different mixtures made from two well-characterized mediators of desiccation tolerance, the non-reducing disaccharide trehalose, and the polyol glycerol. We find that different weight-by-weight mixtures of these two desiccation protective molecules result in glasses with distinct glass fragilities. We test the capacity of these mixtures to preserve the function of a desiccation-sensitive enzyme, lactate dehydrogenase, during drying and find that strong glass formation correlates with increased protective capacity. We also rule out two other competing hypotheses, plasticization/anti-plasticization and water retention as possible mechanisms driving protection of dry trehalose-glycerol mixtures. These data suggest that the strength/fragility of a glass is a property influencing its ability to preserve biological material during drying. Understanding the underpinnings of desiccation tolerance not only advances our understanding of organismal physiology but provides avenues for the development of technologies to reduce our dependence on the cold-chain as well as for increasing food security.