Wize University Biochemistry Textbook > Protein Purification and Identification

Activity Assays
Every enzyme catalyzes a reaction
These reactions can be measured (eg. spectrophotometer)
Monitor UV absorption as decrease in substrate or increase in product
Or monitor the change in a cofactor
Activity units:
The amount of enzyme required to convert one micromol of substrate to product per min.

https://commons.wikimedia.org/wiki/File:LDH_reaction.svg. Yikrazuul. Public Domain.
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Specific Activity:
Used to monitor the protein purification process
Calculated by total activity units divided by total protein in solution
Protein purification table:

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Ammonium Sulfate Precipitation
A reversible method of denaturing and precipitating proteins
Every protein will precipitate at a different ammonium sulfate concentration
Highest concentration of of ammonium sulfate depends on temperature
Maximum temperature at room temp is about 4.4M
Increasing the % of ammonium sulfate within that range will precipitate more proteins
Reducing the % of ammonium sulfate within the range will re-solubilize the proteins
Salting in and Salting out

https://commons.wikimedia.org/wiki/File:Saltin_in_%26_Salting_out.png. Michel Awkal. Creative Commons Attribution-Share Alike 4.0 International license.