• Electrophoresis?is an?analytical technique?which separates ions by placing them in an electrical field
  • This method is often used in?biochemical analysis?to?identify?and?purify?proteins
• A sample of amino acids is placed between?two oppositely charged electrodes
  • The positively charged ions will move towards the?negative electrode
  • The negatively charged ions will move towards the?positive electrode
• The?rate?(how fast) at which the ions move towards the electrodes depends on:
  • The?size?of the ions: larger ions move?more?slowly
  • The?charge?of the ions: highly charged ions move?more quickly
• An?electropherogram?is the series of bands which are observed on the paper or gel after?electrophoresis?has occurred
  • Each band in the electropherogram corresponds to a particular species

Separating mixtures of amino acids by varying the pH

• The charge on the?amino acid ions?depends on the pH of the solution
• The movement of the ions to the electrodes during electrophoresis will therefore be affected by the pH
• Consider a sample which consists of a?mixture?of three amino acids at pH 7
  • Amino acid A: lysine, side-chain is?positively charged
  • Amino acid B: glycine, side chain is?neutral
  • Amino acid C: glutamic acid, side chain is?negatively charged

The sample consists of a mixture of three amino acids which are separated using electrophoresis

• The amino acids in this mixture can be separated by electrophoresis
  • Amino acid C will move towards the?positive?electrode
  • Amino acid B will remain in the?well?where the sample is applied to the gel
  • Amino acid A will move towards the?negative?electrode
• Since glutamic acid is?larger?than lysine, it will travel towards the positive electrode at a?slower rate?compared to lysine

Separation of a mixture of amino acids by electrophoresis