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Osmoprotectants or compatible solutes are small molecules that act as osmolytes and help organisms survive extreme osmotic stress.[1] In plants, their accumulation can increase survival under stress e.g. drought.[2] Examples of compatible solutes include betaines, amino acids, and the sugar trehalose. These molecules accumulate in cells and balance the osmotic difference between the cell's surroundings and the cytosol. In extreme cases, such as in bdelloid rotifers, tardigrades, brine shrimp, and nematodes, these molecules can allow cells to survive being completely dried out and let them enter a state of suspended animation called cryptobiosis.[3] In this state the cytosol and osmoprotectants become a glass-like solid that helps stabilize proteins and cell membranes from the damaging effects of desiccation.[4]

Compatible solutes have also been shown to play a protective role by maintaining enzyme activity through freeze-thaw cycles and at higher temperatures. Their specific action is unknown but is thought that they are preferentially excluded from the proteins interface due to their propensity to form water structures.

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  1. ^ Lang F (October 2007). "Mechanisms and significance of cell volume regulation". J Am Coll Nutr 26 (5 Suppl): 613S–623S. doi:10.1080/07315724.2007.10719667. PMID 17921474. 
  2. ^ Ogbaga, Chukwuma C.; Stepien, Piotr; Johnson, Giles N. (October 2014). "Sorghum ( ) varieties adopt strongly contrasting strategies in response to drought". Physiologia Plantarum 152 (2): 389–401. doi:10.1111/ppl.12196. 
  3. ^ Sussich F, Skopec C, Brady J, Cesàro A (August 2001). "Reversible dehydration of trehalose and anhydrobiosis: from solution state to an exotic crystal?". Carbohydr. Res. 334 (3): 165–76. doi:10.1016/S0008-6215(01)00189-6. PMID 11513823. 
  4. ^ Crowe JH, Carpenter JF, Crowe LM (1998). "The role of vitrification in anhydrobiosis". Annu. Rev. Physiol. 60: 73–103. doi:10.1146/annurev.physiol.60.1.73. PMID 9558455.