Chaotropic activity
{{Short description|Disordering of biological structures}}
Chaotropicity describes the entropic disordering of lipid bilayers and other biomacromolecules which is caused by substances dissolved in water. According to the original usage{{cite journal|last1=Hamaguchi & Geiduschek|title=The Effect of Electrolytes on the Stability of the Deoxyribonucleate Helix|journal=J. Am. Chem. Soc.|date=1962|volume=84|issue=8|pages=1329–1338|doi=10.1021/ja00867a001}} and work carried out on cellular stress mechanisms and responses,{{cite journal|last1=Hallsworth, J.E.|title=Ethanol-induced water stress in yeast|journal=Journal of Fermentation and Bioengineering|date=1998|volume=85|issue=2|pages=125–137|doi=10.1016/S0922-338X(97)86756-6}}{{cite journal|last1=Hallsworth, J.E., Heim, S. and Timmis, K.|title=Chaotropic solutes cause water stress in Pseudomonas putida|journal=Environmental Microbiology|date=2003|volume=5|issue=12|pages=1270–1280|doi=10.1111/j.1462-2920.2003.00478.x|pmid=14641573}}{{cite journal|last1=Bhaganna, P.|title=Hydrophobic substances induce water stress in microbial cells|journal=Microbial Biotechnology|date=2010|volume=3|issue=6|pages=701–716|doi=10.1111/j.1751-7915.2010.00203.x|display-authors=etal|pmid=21255365|pmc=3815343}} chaotropic substances do not necessarily disorder the structure of water.{{cite journal|author1=Ball, P. |author2=Hallsworth, J.E.|title=Water structure and chaotropicity: their uses, abuses and biological implications |journal=Physical Chemistry Chemical Physics|date=2015|volume=17|issue=13|pages=8297–8305|doi=10.1039/C4CP04564E|pmid=25628033|bibcode=2015PCCP...17.8297B}}
The chaotropic activities of solutes in the aqueous phase (e.g. ethanol, butanol, urea, MgCl2, and phenol) have been quantified using an agar-gelation assay.{{cite journal|last1=Cray, J.A.|title=A universal measure of chaotropicity and kosmotropicity.|journal=Environmental Microbiology|date=2013|volume=15|issue=1|pages=287–296|doi=10.1111/1462-2920.12018|display-authors=etal|pmid=23145833}} Whereas chaotropicity was first applied to studies of ions, it is equally applicable to alcohols, aromatics, ion mixtures, and other solutes.{{cite journal|last1=Hallsworth, J.E.|title=Limits of life in MgCl2-containing environments: chaotropicity defines the window.|journal=Environmental Microbiology|date=2007|volume=9|issue=3|pages=801–813|doi=10.1111/j.1462-2920.2006.01212.x|display-authors=etal|pmid=17298378}}{{cite journal|last1=Alves, F.L.|title=Concomitant osmotic and chaotropicity-induced stresses in Aspergillus wentii: compatible solutes determine the biotic window.|journal=Current Genetics|date=2015|volume=61|issue=3|pages=457–477|doi=10.1007/s00294-015-0496-8|pmid=26055444|s2cid=14826577|display-authors=etal}} Furthermore, hydrophobic substances known to stress cellular systems (including benzene and toluene) can chaotropically disorder macromolecules and induce a chaotrope-stress response in microbial cells, even though they partition into the hydrophobic domains of macromolecular systems.{{cite journal|last1=Cray, J.A.|title=Chaotropicity: a key factor in product tolerance of biofuel-producing microorganisms.|journal=Current Opinion in Biotechnology|date=2015|volume=33|pages=228–259|doi=10.1016/j.copbio.2015.02.010 |pmid=25841213|display-authors=etal}}