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CAIE A-Level Chemistry 34.4.3 Electrophoresis of Amino Acids and Dipeptides

Practise predicting spot direction and distance from buffer pH, isoelectric point, net charge and Mr.

Syllabus
2028–2030
Course
Chemistry 9701
Level
A2

Exam points

  • below pI, move cations to the negative electrode; above pI, move anions to the positive electrode
  • leave a species at the origin when buffer pH equals its pI and its net charge is zero
  • for equally charged species, move the lower-Mr particle farther while accounting for charge magnitude when unequal

34.4.3—And predict the results of electrophoresis question 1

[Maximum number: 3]

The isoelectric point of lysine, lys, is at pH 9.8.
lysine

Fig. 6.2

Fig. 6.2

A mixture of the dipeptide lys-asn and its two constituent amino acids, asparagine and lysine, is analysed by electrophoresis using a buffer at pH 5.0 . The results obtained are shown in Fig. 6.3.

Fig. 6.3

Fig. 6.3

Suggest identities for the species responsible for spots E, F and G. Explain your answers.

Table for Question 34.4.3—And predict the results of electrophoresis question 1 — CAIE A-Level Chemistry A2
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