Section Highlights

Protein Purification: Highlights

• A buffer is a solution consisting of either a

  weak acid or a weak base

  ---

  that can resist pH changes upon the addition of acidic or basic compounds.
• The buffer range can be devised from the

  pKa and the Ka

  ---

  .
• Physiological buffers work around

  pH 7

  ---

  .
• Activity assays can be used to determine the

  activity units

  ---

  of a protein preparation or a stage in protein purification.
• Activity units are the quantity of enzyme needed to convert one

  micromole

  ---

  of substrate to product per min.
• Specific activity

  ---

  can be determined by dividing the activity units by total protein.
• Gel filtration chromatography

  ---

  (also called size exclusion chromatography) separates proteins based on size.
• Large proteins elute before small proteins.
• Affinity chromatography isolates

  tagged proteins

  ---

  which binds reversibly to the column with great specificity.
• Ammonium sulfate precipitation is a way of reveribly denaturating proteins though increased salt concentration.
• SDS PAGE gels are a way of visualizing proteins.
• SDS binds to proteins and gives them an overall

  negative

  ---

  charge.
• This gel separates just on

  size

  ---

  .