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Exposure of insect cells to subzero temperatures typically leads to cell membrane disruption and lethal intracellular ice formation. This study seeks to examine the cryoprotective value of trangenically expressing a bacterial ice nucleation protein (INP) in Spodoptera frugiperda (Sf-21) cells. The bacterium Pseudomonas syringae naturally produces a membrane-bound INP (inaZ), capable of structuring water and initiating ice formation at temperatures as high as -2 °C. I hypothesized that intracellular expression of a genetically altered form of inaZ (PsINP) in Sf-21 cells will mediate highly regulated ice nucleation when cells are cooled to -80 °C in a slow, controlled manner. I also predicted that cells expressing PsINP (Sf-21-PsINP) will maintain cell membrane integrity in greater proportions than wildtype cells (Sf-21-WT). Following one freeze-thaw cycle, 60% of Sf-21-WT cell membranes remained intact, while 72% of Sf-21-PsINP cells maintained membrane integrity. This difference is statistically significant, and indicates that PsINP expression helps to prevent cryoinjury during freezing, and positively impacts cell viability following thawing.

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