E Organic chemistry experiment The isolation of casein(from milk) Experimental center of chemical education Fudan University
The isolation of casein (from milk) Organic chemistry experiment Experimental center of chemical education Fudan University
Target 1. Comprehend the concept of pI 2. Isolate the protein by adjusting the ph 3. Identify the protein through biuret test
Target 1.Comprehend the concept of pI 2.Isolate the protein by adjusting the pH 3.Identify the protein through biuret test
NIV Background C asein NH/HO GOLD STANDARD CASEIN Ho.∠NH 4.8
Background pI=4.8 Casein
迫 Experimental principle 1. Casein is a kind of complex phosphoprotein, and due to its nature of being amphoteric compound, the acid-base property of the solution will obviously affect the charge on protein. When the ph of milk adjusted close to the pl of casein (pl=4.8), the protein becomes neutral. Since its lowest solubility, sediment will form, which could be separated through centrifugation NH NH2 H salt high solubility low solubility salt( high solubility)●
1.Casein is a kind of complex phosphoprotein, and due to its nature of being amphoteric compound, the acid-base property of the solution will obviously affect the charge on protein. When the pH of milk adjusted close to the pI of casein (pI=4.8), the protein becomes neutral. Since its lowest solubility, sediment will form, which could be separated through centrifugation. salt （ high solubility ） low solubility salt （ high solubility ） Experimental principle
NIV 迫 Experimental principle 2. Biuret test: The compound with polypeptide skeleton can react with Cu2+ under basic condition which will form purple complex A"9人° Protein or polypeptide urple complex
2. Biuret test ：The compound with polypeptide skeleton can react with Cu2+ under basic condition, which will form purple complex. Protein or polypeptide Purple complex Experimental principle