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Determination of the Isoelectric Points of Casein

Determination of the Isoelectric Points of Casein . Due to its amphoteric nature, the solubilty of casein depends greatly on the PH of the medium. Determination of the Isoelectric Points of Casein. Certain proteins e.g. gelatin are relatively soluble in water even at their I.E.P.

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Determination of the Isoelectric Points of Casein

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  1. Determination of the Isoelectric Points of Casein • Due to its amphoteric nature, the solubilty of casein depends greatly on the PH of the medium.

  2. Determination of the Isoelectric Points of Casein • Certain proteins e.g. gelatin are relatively soluble in water even at their I.E.P. BUT maximum precipitation can be obtained at the the isoelectric point by addition of some reagents such as, ethanol which dehydrates the molecule and allow neutralization of charge.

  3. * Principle • Using acetate buffer of different PH values the approximate position of the isoelectric point of casein can be obtained by determining the PH of minimum solubility. • The PH of any solution can be calculated from Handerson-hasselbalch equation. PH = Pka + log [Sodium acetate] [acetic acid]

  4. Tube # 1 2 3 4 5 6 7 0.05% casein solution in 0.1ml CH3COONa 1 1 1 1 1 1 1 (ml) Distilled Water (ml) 8.4 8 8.8 8.5 8 7 7.4 0.01M acetic acid (ml) 0.6 1 - - - - - 0.1M acetic acid (ml) - - 0.2 0.5 1 2 - 1M acetic acid (ml) - - - - - - 1.6

  5. * Results

  6. * Results PK acetic acid = 4.5 PH = PKa + log [CH3COONa] [CH3COOH] Samar A. Damiati

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