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Fig. 2 | BMC Biology

Fig. 2

From: Winter is coming: the future of cryopreservation

Fig. 2

How cryoprotective agents (CPAs) work. A When a sample is cooled, ice first forms in the extracellular space. Ice excludes solutes, so the extracellular solute concentration increases as extracellular water becomes part of the ice crystals. Intracellular water is then drawn out of the cells via osmosis. B In unprotected cells, the intracellular solute concentration increases and causes damage. C Penetrating CPAs permeate the cell membrane and increase the intracellular solute concentration which prevents water loss and dilutes other solutes inside the cell which can cause damage at high concentrations. Ice blockers bind to ice crystals, preventing them from growing, or to nucleators, which prevents heterogenous ice nucleation. D1, D2 Penetrating CPAs interfere with homogenous ice nucleation by colligative interference, which depresses the freezing point of the solution. D1 Water forms a regular ice lattice. D2 A CPA molecule disrupts the hydrogen bonding between water molecules

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