MadSci Network: Cell Biology |
Question: How DMSO protects cells upon freezing? Hello, The quick and dirty answer is: As the suspension of cells freezes, ice crystals form. These ice crystals can puncture the plasma membrane, leading to cell death. DMSO protects the cells by 1) partially solublizing the membrane so that it is less prone to puncture, and 2) interrupting the lattice of the ice, so that fewer crystals form. (Unfortunately, DMSO is also toxic for the cells (it partially solublizes the membrane, after all), so when you thaw cells, it's important to do it quickly and get them out of DMSO as soon as possible). You can also substitute glycerol for DMSO, and bacteria are often stored in glycerol at -80C (you have probably heard these stocks refered to as "glycerol stocks"). Substances like glycerol and DMSO are generally called cryoprotectants. If you're interested in a more rigorous explanation for the various factors contributing to cell damage during freezing, here is a very extensive and thorough review on cryopreservation: Mazur, P. Cryobiology: The Freezing of Biological Systems. Science, 168: 939-949 (1970). The following are two classic papers: Lovelock, J. E. and Bishop, M. W. H. Prevention of Freezing Damage to Living Cells by Dimethyl Sulphoxide. Nature, 183: 1394-1395 (1959). Discovery that DMSO can be used as a cryoprotectant. Polge, C., Smith, A. U., and Parkes, A. S. Nature 184, 666 (1949). The original, famous trio who (serendipitously) discovered that glycerol can be used as a cryoprotectant. And there is also an online textbook on cryobiology available here: http://www.ucalgary.ca/~kmuldrew/cryo_course/course_outline.html Kathy Xie
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