Salting in: Difference between revisions
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{{Short description|Effect where increased ionic strength results in increased solubility}} |
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'''Salting in''' refers to the effect where increasing the [[ionic strength]] of a [[solution]] increases the [[solubility]] of |
'''Salting in''' refers to the effect where increasing the [[ionic strength]] of a [[Solution (chemistry)|solution]] increases the [[solubility]] of a solute, such as a [[protein]]. This effect tends to be observed at lower [[ionic strength]]s.{{Citation needed|date=November 2015}} |
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| ⚫ | Protein solubility is a complex function of |
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| ⚫ | Protein solubility is a complex function of [[physical chemistry|physicochemical]] nature of the protein, pH, temperature, and the concentration of the salt used. It also depends on whether the salt is [[kosmotropic]], whereby the salt will stabilize water. The solubility of proteins usually increases slightly in the presence of salt, referred to as "salting in". However, at high concentrations of salt, the solubility of the proteins drop sharply and proteins can precipitate out, referred to as "salting out".<ref>{{cite journal |last1=Hassan |first1=Sergio A. |title=Amino Acid Side Chain Interactions in the Presence of Salts |journal=The Journal of Physical Chemistry B |date=1 November 2005 |volume=109 |issue=46 |pages=21989–21996 |doi=10.1021/jp054042r |pmid=16479276 |pmc=1366496 }}</ref> |
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| ⚫ | Initial salting in at low concentrations is explained by the [[ |
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| ⚫ | Initial salting in at low concentrations is explained by the [[Debye–Huckel theory]]. Proteins are surrounded by the salt [[counterion]]s (ions of opposite net charge) and this screening results in decreasing electrostatic free energy of the protein and increasing activity of the solvent, which in turn leads to increasing solubility. This theory predicts that the logarithm of solubility is proportional to the square root of the ionic strength.{{fact|date=April 2022}} |
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| ⚫ | where S is the solubility of the protein, B is a constant (function of protein, pH and temperature), K is the salting out constant (function of pH, mixing and salt), and I is the ionic strength of the salt. This expression is an approximation to that proposed by Long and McDevit.<ref>F.A. |
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| ⚫ | where S is the solubility of the protein, B is a constant (function of protein, pH and temperature), K is the salting out constant (function of pH, mixing and salt), and I is the ionic strength of the salt. This expression is an approximation to that proposed by Long and McDevit.<ref>{{cite journal |last1=Long |first1=F. A. |last2=McDevit |first2=W. F. |title=Activity Coefficients of Nonelectrolyte Solutes in Aqueous Salt Solutions. |journal=Chemical Reviews |date=1 August 1952 |volume=51 |issue=1 |pages=119–169 |doi=10.1021/cr60158a004 }}</ref> |
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Here you could plot the log of protein solubility versus the salt concentration, and it would look like this: |
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==See also== |
==See also== |
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{{Reflist}} |
{{Reflist}} |
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==Further reading== |
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* {{cite journal |last1=Perron |first1=Gérald |last2=Joly |first2=Daniel |last3=Desnoyers |first3=Jacques E. |last4=Avédikian |first4=Lévon |last5=Morel |first5=Jean-Pierre |title=Thermodynamics of the salting effect; free energies, enthalpies, entropies, heat capacities, and volumes of the ternary systems electrolyte–alcohol–water at 25 °C |journal=Canadian Journal of Chemistry |date=15 February 1978 |volume=56 |issue=4 |pages=552–559 |doi=10.1139/v78-089 |doi-access=free }} |
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* {{cite journal |last1=Kramer |first1=Ryan M. |last2=Shende |first2=Varad R. |last3=Motl |first3=Nicole |last4=Pace |first4=C. Nick |last5=Scholtz |first5=J. Martin |title=Toward a Molecular Understanding of Protein Solubility: Increased Negative Surface Charge Correlates with Increased Solubility |journal=Biophysical Journal |date=18 April 2012 |volume=102 |issue=8 |pages=1907–1915 |doi=10.1016/j.bpj.2012.01.060 |pmid=22768947 |pmc=3328702 |bibcode=2012BpJ...102.1907K }} |
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[[Category:Separation processes]] |
[[Category:Separation processes]] |
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Latest revision as of 17:17, 14 December 2023
 | This article needs additional citations for verification. (April 2021) |
Salting in refers to the effect where increasing the ionic strength of a solution increases the solubility of a solute, such as a protein. This effect tends to be observed at lower ionic strengths.[citation needed]
Protein solubility is a complex function of physicochemical nature of the protein, pH, temperature, and the concentration of the salt used. It also depends on whether the salt is kosmotropic, whereby the salt will stabilize water. The solubility of proteins usually increases slightly in the presence of salt, referred to as "salting in". However, at high concentrations of salt, the solubility of the proteins drop sharply and proteins can precipitate out, referred to as "salting out".[1]
Anionic interactions
[edit]Initial salting in at low concentrations is explained by the Debye–Huckel theory. Proteins are surrounded by the salt counterions (ions of opposite net charge) and this screening results in decreasing electrostatic free energy of the protein and increasing activity of the solvent, which in turn leads to increasing solubility. This theory predicts that the logarithm of solubility is proportional to the square root of the ionic strength.[citation needed]
The behavior of proteins in solutions at high salt concentrations is explained by John Gamble Kirkwood. The abundance of the salt ions decreases the solvating power of salt ions, resulting in the decrease in the solubility of the proteins and precipitation results.[citation needed]
At high salt concentrations, the solubility is given by the following empirical expression.[citation needed]
- log S = B − KI
where S is the solubility of the protein, B is a constant (function of protein, pH and temperature), K is the salting out constant (function of pH, mixing and salt), and I is the ionic strength of the salt. This expression is an approximation to that proposed by Long and McDevit.[2]
See also
[edit]References
[edit]- ^ Hassan, Sergio A. (1 November 2005). "Amino Acid Side Chain Interactions in the Presence of Salts". The Journal of Physical Chemistry B. 109 (46): 21989–21996. doi:10.1021/jp054042r. PMC 1366496. PMID 16479276.
- ^ Long, F. A.; McDevit, W. F. (1 August 1952). "Activity Coefficients of Nonelectrolyte Solutes in Aqueous Salt Solutions". Chemical Reviews. 51 (1): 119–169. doi:10.1021/cr60158a004.
Further reading
[edit]- Perron, Gérald; Joly, Daniel; Desnoyers, Jacques E.; Avédikian, Lévon; Morel, Jean-Pierre (15 February 1978). "Thermodynamics of the salting effect; free energies, enthalpies, entropies, heat capacities, and volumes of the ternary systems electrolyte–alcohol–water at 25 °C". Canadian Journal of Chemistry. 56 (4): 552–559. doi:10.1139/v78-089.
- Kramer, Ryan M.; Shende, Varad R.; Motl, Nicole; Pace, C. Nick; Scholtz, J. Martin (18 April 2012). "Toward a Molecular Understanding of Protein Solubility: Increased Negative Surface Charge Correlates with Increased Solubility". Biophysical Journal. 102 (8): 1907–1915. Bibcode:2012BpJ...102.1907K. doi:10.1016/j.bpj.2012.01.060. PMC 3328702. PMID 22768947.
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