Protein Stabilization and Enzyme Activation in Ionic Liquids: Specific Ion Effects.

Area of Science:

• Biochemistry
• Physical Chemistry
• Chemical Biology

Background:

• The Hofmeister effect's influence on protein stability and water structure remains debated.
• The term 'specific ion effect' is proposed as a more accurate descriptor.
• Ionic liquids (ILs) are increasingly used as solvents in enzymatic reactions.

Purpose of the Study:

• To review the specific ion effect of inorganic ions and ionic liquids on protein stability.
• To evaluate the structural properties and molecular interactions of ionic liquids.
• To compare the effects of ionic liquids on enzyme stability and activity in various concentrations.

Main Methods:

• Literature review of inorganic ion effects on water structure and protein stability.
• Analysis of structural properties and molecular interactions in neat and aqueous ionic liquids.
• Systematic comparison of specific ion effects of ionic liquids on enzyme stability and activity.

Main Results:

• Inorganic ion effects on water structure are controversial.
• Enzyme specificity in diluted aqueous IL solutions generally follows the Hofmeister series.
• In concentrated or neat ILs, enzyme specificity deviates due to factors like hydrogen-bond basicity and hydrophobicity.

Conclusions:

• The specific ion effect is a more precise term for ion-induced changes in protein stability.
• Ionic liquids exhibit concentration-dependent effects on enzyme activity and stability.
• Biocatalysis in ionic liquids can be guided by empirical specificity rules.