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| The '''Hofmeister series''' or '''lyotropic series''' is a classification of [[ion]]s in order of their ability to salt out or salt in proteins. The effects of these changes were first worked out by [[Franz Hofmeister]], who studied the effects of cations and anions on the solubility of [[protein]]s.<ref>F.Hofmeister Arch. Exp. Pathol. Pharmacol. 24, (1888) 247-260.</ref>
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| Hofmeister discovered a series of salts that have consistent effects on the solubility of proteins and (it was discovered later) on the stability of their [[secondary structure|secondary]] and [[tertiary structure]]. Anions appear to have a larger effect than cations, and are usually ordered
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| :<math>
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| \mathrm{F^{-} \approx SO_{4}^{2-} > HPO_{4}^{2-} > acetate > Cl^{-} > NO_{3}^{-} > Br^{-} > ClO_{3}^{-} > I^{-} > ClO_{4}^{-} > SCN^{-}}
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| </math>
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| (This is a partial listing; many more salts have been studied.)
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| The order of cations is usually given as | |
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| :<math>
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| \mathrm{NH_{4}^{+} > K^{+} > Na^{+} > Li^{+} > Mg^{2+} > Ca^{2+} > guanidinium}
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| </math>
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| The mechanism of the Hofmeister series is not entirely clear, but does not seem to result from changes in general water structure, instead more specific interactions between ions and proteins and ions and the water molecules directly contacting the proteins may be more important.<ref>{{cite journal |author=Zhang Y, Cremer PS |title=Interactions between macromolecules and ions: The Hofmeister series |journal=Current Opinion in Chemical Biology |volume=10 |issue=6 |pages=658–63 |year=2006 |pmid=17035073 |doi=10.1016/j.cbpa.2006.09.020}}</ref>
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| Early members of the series increase solvent [[surface tension]] and decrease the solubility of nonpolar molecules ("[[salting out]]"); in effect, they ''strengthen'' the [[hydrophobic interaction]]. By contrast, later salts in the series increase the solubility of nonpolar molecules ("[[salting in]]") and decrease the order in water; in effect, they ''weaken'' the [[hydrophobic effect]]. The salting out effect is commonly exploited in [[protein purification]] through the use of [[ammonium sulfate precipitation]].
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| However, these salts also interact directly with proteins (which are charged and have strong dipole moments) and may even bind specifically (e.g., phosphate and sulfate binding to [[ribonuclease A]]). Ions that have a strong 'salting in' effect such as I<sup>-</sup> and SCN<sup>-</sup> are strong denaturants, because they salt in the peptide group, and thus interact much more strongly with the unfolded form of a protein than with its native form. Consequently, they shift the [[chemical equilibrium]] of the unfolding reaction towards unfolded protein.<ref name="baldwin">{{cite journal |author=Baldwin RL. |title=How Hofmeister ion interactions affect protein stability |journal=Biophys J |volume=71 |issue=4 |pages=2056–63 |year=1996 |pmid=8889180 |doi=10.1016/S0006-3495(96)79404-3 |pmc=1233672|bibcode = 1996BpJ....71.2056B }}</ref>
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| ==References==
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| {{reflist}}
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| *{{cite book |title=H<sub>2</sub>O - A Biography of Water|last=Ball |first=Philip |authorlink=Philip Ball |coauthors= |year=1999 |publisher=Phoenix |location=London |isbn=0-7538-1092-1 |page=239 }}
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| * [http://www.cendigital.org/cendigital/20120716?sub_id=FNQ5wyPIC7Sq&folio=42#pg46 Hofmeister Still Mystifies, ''Chemical & Engineering News'', July 16, 2012.]
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| [[Category:Solutions]]
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| [[Category:Physical chemistry]]
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| [[Category:Laboratory techniques]]
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Hi there, I am Alyson Pomerleau and I believe it seems fairly great when you say it. My wife and I reside in Mississippi but now I'm contemplating other choices. The preferred pastime for him and his kids is to play lacross and he'll be starting some thing else along with it. I am currently a travel agent.
Also visit my site: online reader (Highly recommended Webpage)